@article{cho_microstructure_and_2023, 
author={Cho, J.-H. and Rha, J.-J. and Lee, G.-Y. and Jeon, H. and Kim, J.Y.},
title={Microstructure and mechanical properties of open-cell Ni-foams with hollow struts and NiO oxide layers},
year={2023},
journal = {Materials Science and Engineering: A},
volume = {863},
pages = {144519},
doi = {10.1016/j.msea.2022.144519},
abstract = {Based on electron backscatter diffraction (EBSD) and energy dispersive spectroscopy (EDS), open-cell Ni foams fabricated by electroplating on a removable template were investigated. Hollow struts or cavities inside the Ni foams were observed, implying traces of a removable template. The crystallographic orientations and grain structures of the Ni foam struts were also examined. Individual grains of Ni foams covered the struts completely through the thickness direction. The crystallographic orientations of the Ni foam struts display a random distribution. twinning boundaries were also observed in the Ni matrix. During a two-hour heat treatment at 1273 K under atmospheric condition, refined NiO layers clearly formed on the surface of the Ni matrix. The overall grain sizes of the NiO are smaller than those of the Ni matrix. The obvious crystallographic relationship between the Ni matrix and the NiO layers was observed at the high misorientation angles. Ni foams with high porosity revealed a stress drop and NiO layers that formed during atmospheric annealing caused a predominant stress drop. Young’s modulus and the hardness of the Ni matrix and NiO layers were measured from a Ni foam cell structure consisting of nodes, by means of nano-indentation tests.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.msea.2022.144519} (DOI). Cho, J.-H.; Rha, J.-J.; Lee, G.-Y.; Jeon, H.; Kim, J.Y.: Microstructure and mechanical properties of open-cell Ni-foams with hollow struts and NiO oxide layers. In: Materials Science and Engineering: A. Vol. 863 (2023) 144519. (DOI:  /10.1016/j.msea.2022.144519)}}
@article{bernardi_fatigue_behaviour_2023, 
author={Bernardi, M. and Suhuddin, U. and Fu, B. and Gerber, J. and Bianchi, M. and Ostrovsky, I. and Sievers, B. and Faes, K. and Maawad, E. and Lazzeri, L. and dos Santos, J. and Klusemann, B.},
title={Fatigue behaviour of multi-spot joints of 2024-T3 aluminium sheets obtained by refill Friction Stir Spot Welding with polysulfide sealant},
year={2023},
journal = {International Journal of Fatigue},
volume = {172},
pages = {107539},
doi = {10.1016/j.ijfatigue.2023.107539},
abstract = {The aeronautical industry is looking with interest at friction-based welding for many years due to weight-saving capacities, where fusion-based welding problems can be avoided, allowing also the joining of materials considered complicated to weld with other technologies. Refill Friction Stir Spot Welding (refill FSSW) is a solid-state joining process that shows great potential to be a substitute for single-point joining processes like riveting. The main objective of this study is to investigate the mechanical behaviour of multi-spot joints of AA 2024-T3 obtained by refill FSSW with the addition of a sealant commonly used in riveted joints by the aviation industry. A fatigue test campaign was carried out on the joints with and without sealant to evaluate the possible synergy between the refill FSSW and sealant. The fatigue data obtained are statistically analyzed and compared. According to the comprehensive study including macro- and micro-structure, deformation strain field, residual stress distribution as well as the fatigue crack growth behaviour, the underlying history of multi-spot joints fatigue damage is revealed. The overall results prove that producing lap-joints by refill FSSW with sealant improves considerably the fatigue performance.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.ijfatigue.2023.107539} (DOI). Bernardi, M.; Suhuddin, U.; Fu, B.; Gerber, J.; Bianchi, M.; Ostrovsky, I.; Sievers, B.; Faes, K.; Maawad, E.; Lazzeri, L.; dos Santos, J.; Klusemann, B.: Fatigue behaviour of multi-spot joints of 2024-T3 aluminium sheets obtained by refill Friction Stir Spot Welding with polysulfide sealant. In: International Journal of Fatigue. Vol. 172 (2023) 107539. (DOI:  /10.1016/j.ijfatigue.2023.107539)}}
@article{taghipour_strengthening_mechanisms_2023, 
author={Taghipour, A. and Mazaheri, Y. and McDavid, J. and Sheikhi, S. and Braun, M. and Shen, J. and Klusemann, B. and Ehlers, S.},
title={Strengthening Mechanisms and Strain Hardening Behavior of 316L Stainless Steel Manufactured by Laser-Based Powder Bed Fusion},
year={2023},
journal = {Advanced Engineering Materials},
volume = {25},
number = {4},
pages = {2201230},
doi = {10.1002/adem.202201230},
abstract = {The microstructure–properties relations and strengthening mechanisms of additively manufactured 316L stainless steel are comprehensively investigated in this work. The orientation dependency and the strain hardening are studied by tensile testing of as-built specimens fabricated by laser-based powder bed fusion (LPBF) in different directions. The results are compared with those obtained for wrought material. The microstructure of the wrought and the LPBF materials are also comprehensively investigated. Equiaxed grains with random orientation and relatively uniform size (≈30 μm) are observed in the wrought material, where the LPBF samples show columnar grains inside as well as fine equiaxed grains in the bottom of the molten pool. A bimodal grain size distribution, higher values of geometrically necessary dislocations density (≈25–32%), and lower fractions of high-angle grain boundaries (≈24–28%) are observed in LPBF 316L. A significant yield strength and considerable ultimate strength improvement without remarkable elongation decrease are obtained for the LPBF tensile specimens, resulting in a high strength-elongation balance (up to 26 122 MPa%). Two-stage strain hardening is depicted in both wrought and LPBF samples. This is successfully predicted with two-stage Hollomon analysis. However, the LPBF samples illustrate lower strain hardening exponents in comparison with the wrought ones.},
note = {Online available at: \url{https://dx.doi.org/10.1002/adem.202201230} (DOI). Taghipour, A.; Mazaheri, Y.; McDavid, J.; Sheikhi, S.; Braun, M.; Shen, J.; Klusemann, B.; Ehlers, S.: Strengthening Mechanisms and Strain Hardening Behavior of 316L Stainless Steel Manufactured by Laser-Based Powder Bed Fusion. In: Advanced Engineering Materials. Vol. 25 (2023) 4, 2201230. (DOI:  /10.1002/adem.202201230)}}
@article{gomezgomez_unraveling_the_2023, 
author={Gomez-Gomez, A. and Winhard, B. and Lilleodden, E. and Huber, N. and Furlan, K.P.},
title={Unraveling the role of shell thickness and pore size on the mechanical properties of ceramic-based macroporous structures},
year={2023},
journal = {Journal of the American Ceramic Society},
volume = {106},
number = {2},
pages = {1273 - 1286},
doi = {10.1111/jace.18811},
abstract = {Macroporous structures are of interest for several technological applications such as catalysis, sensors, filters, membranes, batteries, energy conversion devices, structural colors, and reflective thermal barrier coatings. Ceramic-based inverse opal macroporous structures are especially interesting for high-temperature applications. However, the interrelation between the structural parameters, mechanical properties, and thermal stability of such structures is not yet clarified. In this work, we analyzed the mechanical properties as well as the thermal stability of aluminum oxide inverse opal three-dimensional macroporous structures with different macropore sizes and shell thicknesses produced by atomic layer deposition. Our results show that the structures’ thermal stability increased with increasing shell thickness and macropore size, however, their higher stability was not linked to their mechanical properties. To be able to explain this unexpected behavior, finite element modeling simulations were performed, showing that bending stresses became more pronounced with increasing shell thickness, potentially creating additional critical sites for crack initiation and consequent structural failure.},
note = {Online available at: \url{https://dx.doi.org/10.1111/jace.18811} (DOI). Gomez-Gomez, A.; Winhard, B.; Lilleodden, E.; Huber, N.; Furlan, K.P.: Unraveling the role of shell thickness and pore size on the mechanical properties of ceramic-based macroporous structures. In: Journal of the American Ceramic Society. Vol. 106 (2023) 2, 1273 - 1286. (DOI:  /10.1111/jace.18811)}}
@article{jin_heatpattern_induced_2023, 
author={Jin, F. and Rao, H. and Wang, Q. and Wen, G. and Liu, P. and Liu, J. and Shen, J. and Li, J. and Xiong, J. and Ma, N.},
title={Heat-pattern induced non-uniform radial microstructure and properties of Ti-6Al-4V joint prepared by rotary friction welding},
year={2023},
journal = {Materials Characterization},
volume = {195},
pages = {112536},
doi = {10.1016/j.matchar.2022.112536},
abstract = {Heat-pattern (HP) induced non-uniform radial microstructure and properties of rotary friction welded Ti-6Al-4 V joint was focused in this study, the formation mechanism of which was clarified by β-reconstruction. The results show that Ti-6Al-4 V friction welded heat-pattern at different rotational speeds can be generally separated into ‘glass-like’ HP and ‘scissor-like’ HP. According to the results of β-reconstruction, the radial microstructures of ‘glass-like’ HP and ‘scissor-like’ HP are deformed α grains → deformed α grains and lamellar α’ laths → lamellar α’ laths corresponding to center→1/2R → periphery respectively, where lamellar α’ laths at periphery of ‘scissor-like’ HP have similar orientations to form α’ colony. Deformed α grains at center zone make the strength higher than that of base metal (BM) and share the similar morphology of BM compared with the lamellar α’ laths, to get the highest elongation among the three regions of center, 1/2R and periphery, reaching near 80% of BM. Whereas, lamellar α’ laths at periphery share a coarser size than that of the center zone, the strength of which is reduced and close to the BM. Compared with the deformed α grains, lamellar α’ laths are quite different from BM in morphology, which causes a significant reduction in elongation to only 62.1% of BM. Aggravating the issue further, the elongation of ‘scissor - like’ HP is reduced to only 50.3% of BM at periphery because of α’ colony. Therefore, the strength and elongation of the joint decrease gradually from center to periphery.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.matchar.2022.112536} (DOI). Jin, F.; Rao, H.; Wang, Q.; Wen, G.; Liu, P.; Liu, J.; Shen, J.; Li, J.; Xiong, J.; Ma, N.: Heat-pattern induced non-uniform radial microstructure and properties of Ti-6Al-4V joint prepared by rotary friction welding. In: Materials Characterization. Vol. 195 (2023) 112536. (DOI:  /10.1016/j.matchar.2022.112536)}}
@article{ovri_mechanistic_origin_2023, 
author={Ovri, H. and Markmann, J. and Barthel, J. and Kruth, M. and Dieringa, H. and Lilleodden, E.},
title={Mechanistic origin of the enhanced strength and ductility in Mg-rare earth alloys},
year={2023},
journal = {Acta Materialia},
volume = {244},
pages = {118550},
doi = {10.1016/j.actamat.2022.118550},
abstract = {Magnesium (Mg) alloys with low concentrations of rare earth additions are known to exhibit strengths and ductility that are significantly higher than those obtained in traditional Mg alloys. However, the mechanisms that underlie these improvements are still open to debate. We assessed these mechanism(s) by carrying out in-depth analysis of the deformation behavior in single crystals of pure Mg and a homogenized Mg-0.75 at.% Gd alloy oriented for twinning, pyramidal- and basal-slip. We observed a fivefold increase in basal CRSS, an eightfold increase in twinning CRSS and a fourfold decrease of the pyramidal/basal CRSS (P/B) ratio due to Gd addition. We also observed that while twinning and pyramidal slip activities were similar in the two material systems, basal slip was radically different. Specifically, basal slip was planar in the alloy but wavy in pure Mg. Our work reveals that these observations are a consequence of Gd-rich short-range ordered (SRO) clusters in the alloy. We show that interactions between dislocations and the SRO clusters would lead to significant increases in strength and slip activity, and consequently, ductility improvements in homogenized polycrystalline Mg-Gd alloys.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.actamat.2022.118550} (DOI). Ovri, H.; Markmann, J.; Barthel, J.; Kruth, M.; Dieringa, H.; Lilleodden, E.: Mechanistic origin of the enhanced strength and ductility in Mg-rare earth alloys. In: Acta Materialia. Vol. 244 (2023) 118550. (DOI:  /10.1016/j.actamat.2022.118550)}}
@article{huber_densification_of_2023, 
author={Huber, N. and Ryl, I. and Wu, Y. and Hablitzel, M. and Zandersons, B. and Richert, C. and Lilleodden, E.},
title={Densification of nanoporous metals during nanoindentation: The role of structural and mechanical properties},
year={2023},
journal = {Journal of Materials Research},
volume = {38},
pages = {853 - 866},
doi = {10.1557/s43578-022-00870-1},
abstract = {The analysis of the densification behavior of nanoporous metals in nanoindentation is challenging in simulations and experiments. A deeper understanding of the densification behavior provides valuable information about the different deformation mechanisms in nanoindentation and compression experiments. The developed two-scale model allows for predicting the densification field for variable microstructure and elastic–plastic behavior. It could be shown that the penetration depth of the densification field is mainly controlled by the ratio of the macroscopic work hardening rate to yield stress. The shape as well as the value at characteristic isolines of densification depend mainly on the macroscopic plastic response of the nanoporous material. This could be confirmed by nanoindentation experiments, where the densification under the indenter was measured for ligament sizes from 35 to 150 nm. Although the depth of the densification field was underpredicted by the simulations, the experiments confirmed the predicted trends.},
note = {Online available at: \url{https://dx.doi.org/10.1557/s43578-022-00870-1} (DOI). Huber, N.; Ryl, I.; Wu, Y.; Hablitzel, M.; Zandersons, B.; Richert, C.; Lilleodden, E.: Densification of nanoporous metals during nanoindentation: The role of structural and mechanical properties. In: Journal of Materials Research. Vol. 38 (2023) 853 - 866. (DOI:  /10.1557/s43578-022-00870-1)}}
@article{zou_laser_surface_2023, 
author={Zou, X. and Liu, L. and Chen, T. and Wu, L. and Chen, K. and Kong, L. and Wang, M.},
title={Laser surface treatment to enhance the adhesive bonding between steel and CFRP: Effect of laser spot overlapping and pulse fluence},
year={2023},
journal = {Optics and Laser Technology},
volume = {159},
pages = {109002},
doi = {10.1016/j.optlastec.2022.109002},
abstract = {Adhesive bonding is widely applied in joining between steel and carbon fiber reinforced plastics (CFRP), while the surface characteristics of steel have a significant effect on the joint strength. To improve the adhesive bonding between DP590 steel and CFRP, surface modifications of steel by laser surface treatment with different overlap rate of laser spot and pulse fluence were applied and investigated. The evolution of surface morphology, contact angle, surface energy, and surface chemical composition of DP590 steel after laser treatment with different parameters were also studied. The results showed that surface roughness, surface energy and polar component of surface energy after treatments were closely related to the interfacial bonding strength between steel and adhesives. Specifically, higher pulse fluence can increase the surface roughness of the steel, which reduced the contact angle and improve the surface energy, thus not only leading to a better mechanical interlocking effect, but also improving the surface wettability of the adhesive to the steel surface. When there was 50 % overlapping of the laser spots, the surface wettability was further improved. In addition, the strengths of steel-CFRP joints obtained with both epoxy adhesive E-120HP and polyurethane adhesive PU6700 were significantly enhanced by laser surface treatment. Especially for the joints bonded with E-120HP, which is a high-strength and poor-toughness adhesive, the shear strength can be increased by 299 %, from 4.10 ± 0.17 MPa to 16.35 ± 0.89 MPa after laser treatment. More importantly, the adhesive failure along steel-adhesive interface was entirely avoided. This study provides both technical and theoretical guidance of laser surface treatment for fabricating high-performance metal-polymer hybrid structures by adhesive bonding.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.optlastec.2022.109002} (DOI). Zou, X.; Liu, L.; Chen, T.; Wu, L.; Chen, K.; Kong, L.; Wang, M.: Laser surface treatment to enhance the adhesive bonding between steel and CFRP: Effect of laser spot overlapping and pulse fluence. In: Optics and Laser Technology. Vol. 159 (2023) 109002. (DOI:  /10.1016/j.optlastec.2022.109002)}}
@article{rath_anisotropy_and_2023, 
author={Rath, L. and Kallien, Z. and Roos, A. and dos Santos, J. and Klusemann, B.},
title={Anisotropy and mechanical properties of dissimilar Al additive manufactured structures generated by multi-layer friction surfacing},
year={2023},
journal = {The International Journal of Advanced Manufacturing Technology},
volume = {125},
number = {5-6},
pages = {2091 - 2102},
doi = {10.1007/s00170-022-10685-3},
abstract = {Friction surfacing (FS) is a solid-state layer deposition process for metallic materials at temperatures below their melting point. While the bonding of the deposited layers to the substrate is proven suitable for coating applications, so far the mechanical properties of additively manufactured stacks have not been systematically investigated. In particular, the effect of successive deposited FS layers, i.e., repetitive thermo-mechanical loading, on the interface properties as well as anisotropy and strength of the deposited stack is unknown. For this purpose, the mechanical properties of FS deposited multi-layer stacks from dissimilar aluminum alloys have been investigated, characterizing layer-to-layer as well as layer-to-substrate bonding interfaces via micro-flat tensile testing. Furthermore, directional dependencies in the stack and failure mechanisms are analyzed. The results show a homogeneous, fine-grained microstructure with average grain sizes between 4.2 and 4.6 μ m within the deposited material. The resulting tensile properties with no significant directional dependency present an ultimate tensile strength between 320 and 326 MPa exceeding the strength of the AA5083 H112 consumable base material. No difference was obtained in terms of layer-to-layer or layer-to-substrate interface strength. Furthermore, homogeneous hardness was observed within the deposited structure, which is in the range of AA5083 base material’s hardness of 91 HV. The results indicate that the FS process in conjunction with the material used is suitable for additively generated structures and highlight the potential of this solid-state layer deposition technology.},
note = {Online available at: \url{https://dx.doi.org/10.1007/s00170-022-10685-3} (DOI). Rath, L.; Kallien, Z.; Roos, A.; dos Santos, J.; Klusemann, B.: Anisotropy and mechanical properties of dissimilar Al additive manufactured structures generated by multi-layer friction surfacing. In: The International Journal of Advanced Manufacturing Technology. Vol. 125 (2023) 5-6, 2091 - 2102. (DOI:  /10.1007/s00170-022-10685-3)}}
@article{wang_on_the_2023, 
author={Wang, M. and Kashaev, N.},
title={On the optimal process window for powder-based laser-directed energy deposition of AA7050 under different robot programs and scanning strategies},
year={2023},
journal = {Journal of Manufacturing Processes},
volume = {90},
pages = {286 - 299},
doi = {10.1016/j.jmapro.2023.01.011},
abstract = {Powder-based laser-directed energy deposition (L-DED) has drawn lots of attention during the last years because of the multiple application areas, such as coating, repairing, and building 3D structures. One challenge in L-DED is the limited variety of applicable materials, especially in the case of aluminum alloys. To broaden the material spectrum, the processability and the optimal process window of high-strength Al-alloy AA7050 are investigated in the present study. Besides the process parameters, special emphasis was paid to the scanning strategy and the robot program controlling. The present results show a strong effect of scanning strategy and robot program on buildability, geometrical accuracy, melt pool visibility, porosity level, and crack initiation. Hot cracks can be reduced or eliminated by choosing an appropriate combination of scanning strategy and robot program. Meanwhile, the geometrical accuracy of specimens with any height was well maintained. Based on the systematic experimental study, appropriate L-DED process parameters were identified for the deposition of structures up to 24 layers with a lower porosity level (about 3.7 ± 0.8 %) and lower amount of hot cracks, which are comparable with that in the 12-layer structure.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jmapro.2023.01.011} (DOI). Wang, M.; Kashaev, N.: On the optimal process window for powder-based laser-directed energy deposition of AA7050 under different robot programs and scanning strategies. In: Journal of Manufacturing Processes. Vol. 90 (2023) 286 - 299. (DOI:  /10.1016/j.jmapro.2023.01.011)}}
@article{bossle_friction_stir_2023, 
author={Bossle, E.P. and Vicharapu, B. and Lemos, G.V.B. and Lessa, C.R.D.L. and Bergmann, L. and dos Santos, J.F. and Clarke, T.G.R. and De, A.},
title={Friction Stir Lap Welding of Inconel 625 and a High Strength Steel},
year={2023},
journal = {Metals},
volume = {13},
number = {1},
pages = {146},
doi = {10.3390/met13010146},
abstract = {The joining of dissimilar hard metals such as high-strength steel and nickel-based alloy is required for shipbuilding and offshore applications to enhance the strength, fracture toughness, and corrosion resistance of the exposed parts. However, the joining of these dissimilar alloys has remained a major challenge due to the limited solubility of Fe and Ni in each other, which commonly results in the formation of brittle intermetallic compounds. We present here a novel investigation on the joining of overlapped nickel-based alloy 625 and marine-grade GL E36 steel plates by friction stir lap welding (FSLW). The interface microstructure and its influence on joint strength are rigorously tested. The main bonding mechanism is found to be the mechanical mixing of Fe and Ni along the interface. The interface thermal cycles are computed by a three-dimensional numerical heat transfer model and their effects on the microstructure are examined. Multiple micro tensile specimens are extracted from the stir zone to examine the through-thickness variation in the stir zone properties. The welded joint is characterized further by evaluating the interface microhardness distribution, lap-shear strength, and surface residual stresses.},
note = {Online available at: \url{https://dx.doi.org/10.3390/met13010146} (DOI). Bossle, E.P.; Vicharapu, B.; Lemos, G.V.B.; Lessa, C.R.D.L.; Bergmann, L.; dos Santos, J.F.; Clarke, T.G.R.; De, A.: Friction Stir Lap Welding of Inconel 625 and a High Strength Steel. In: Metals. Vol. 13 (2023) 1, 146. (DOI:  /10.3390/met13010146)}}
@article{rodrigues_friction_riveting_2023, 
author={Rodrigues, C.F. and Blaga, L. and Klusemann, B.},
title={Friction Riveting of FR4 substrates for printed circuit boards: Influence of process parameters on process temperature development and joint properties},
year={2023},
journal = {Journal of Materials Research and Technology : JMRT},
volume = {24},
pages = {4639-4649},
doi = {10.1016/j.jmrt.2023.04.092},
abstract = {This work investigates the influence of Friction Riveting processing conditions on FR4-PCB substrate/AA2024 rivet joints in terms of process temperature evolution, joint formation, and joint physical-chemical and mechanical properties. The joints were manufactured using 4 mm diameter AA-2024-T3 rivets and FR4 laminates of 1.5 mm thickness with single or double copper-clad layers. The evolution of process temperature evolution was recorded on the FR4 substrate surface and correlated with the resulting joint formation. Most joints obtained with double copper clad layers developed process temperatures above 300 ºC, whereas joints produced with a single copper clad presented slightly lower temperatures, but still above 250 ºC. Rivet anchoring was achieved for both FR4 material combinations in the configuration of a single-base laminate, as well as two and even three overlapped laminates. Thermogravimetric analyses revealed that above 300 ºC intensive thermal degradation occurs on FR4 materials (with 30% mass change), followed by decomposition, resulting in non-uniform heat distribution throughout the thickness. The joint ultimate tensile force was higher for double copper-clad layers and the joints achieved within more than one laminate, showing higher anchoring efficiency.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jmrt.2023.04.092} (DOI). Rodrigues, C.F.; Blaga, L.; Klusemann, B.: Friction Riveting of FR4 substrates for printed circuit boards: Influence of process parameters on process temperature development and joint properties. In: Journal of Materials Research and Technology : JMRT. Vol. 24 (2023) 4639-4649. (DOI:  /10.1016/j.jmrt.2023.04.092)}}
@article{wang_effect_of_2023, 
author={Wang, J. and Fu, B. and Bergmann, L. and Liu, F. and Klusemann, B.},
title={Effect of Welding Speed on Friction Stir Welds of PM2000 Alloy},
year={2023},
journal = {Journal of Materials Engineering and Performance},
volume = {32},
number = {2},
pages = {577 - 586},
doi = {10.1007/s11665-022-07109-4},
abstract = {Friction stir welding (FSW) was investigated for producing joints of alloy PM2000 with welding speeds from 1 to 3 mm/s. The effect of welding speed on the microstructures and mechanical properties of the joints is analyzed in detail. Lower welding speeds result in fully penetrated PM2000 FSWed joints, while higher welding speeds lead to lack of penetration and small defects at the retreating side. The grain size in the stirring zone is not uniform, and abnormal grain growth in the onion rings structure was detected. The PM2000 FSWed joints showed good mechanical properties, i.e., tensile strength of 97% of the base material with even 6.7% higher elongation was obtained. As typical for FSWed ODS joints, the failure was located in the thermo-mechanical affected zone. In this regard, the stirring zone exhibited an impact toughness of up to 300% compared to the base metal owing to the grain refinement, illustrating the superior performance of joints of PM2000 produced by FSW.},
note = {Online available at: \url{https://dx.doi.org/10.1007/s11665-022-07109-4} (DOI). Wang, J.; Fu, B.; Bergmann, L.; Liu, F.; Klusemann, B.: Effect of Welding Speed on Friction Stir Welds of PM2000 Alloy. In: Journal of Materials Engineering and Performance. Vol. 32 (2023) 2, 577 - 586. (DOI:  /10.1007/s11665-022-07109-4)}}
@article{examilioti_on_anisotropic_2023, 
author={Examilioti, T.N. and Li, W. and Kashaev, N. and Ventzke, V. and Klusemann, B. and Alexopoulos, N.D.},
title={On anisotropic tensile mechanical behavior of Al-Cu-Li AA2198 alloy under different ageing conditions},
year={2023},
journal = {Journal of Materials Research and Technology : JMRT},
volume = {24},
pages = {895 - 908},
doi = {10.1016/j.jmrt.2023.02.206},
abstract = {The anisotropic mechanical behavior of Al–Cu–Li (AA2198) alloy under different artificial ageing conditions as well as for different thicknesses of the material was examined in the present investigation. Material characterization was performed for three different sheet directions, namely, longitudinal (0°), diagonal (45°) and transverse (90°) to the rolling direction. The results showed that the grain structure did not have significant changes by applying different artificial ageing times. In T3 heat treatment condition, only δ′ (Al3Li) phase was observed, while with increasing the ageing time, the major precipitates were T1 (Al2CuLi) phases. The latter was found to increase in size with artificial aging time. Almost similar yield strength values were observed for all investigated thicknesses, while the higher thickness specimens showed higher elongation at fracture values. Anisotropy was slightly higher at T3 condition, while the lowest anisotropy degree was noticed at the peak-aged condition. The specimens extracted in the diagonal direction showed high variation in mechanical properties, when compared with the respective results at the other two investigated directions, independently from the thickness of the specimens as well as from heat treatment condition. The smaller thickness specimens presented lower elongation at fracture values and for all investigated sheet directions, since they undergo plane stress conditions. Analysis of work hardening behavior showed that Bauschinger effect, which was not observed in T3 condition, became increasingly more prominent with artificial ageing time in all directions investigated.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jmrt.2023.02.206} (DOI). Examilioti, T.N.; Li, W.; Kashaev, N.; Ventzke, V.; Klusemann, B.; Alexopoulos, N.D. : On anisotropic tensile mechanical behavior of Al-Cu-Li AA2198 alloy under different ageing conditions. In: Journal of Materials Research and Technology : JMRT. Vol. 24 (2023) 895 - 908. (DOI:  /10.1016/j.jmrt.2023.02.206)}}
@article{kallien_combined_experimentalnumerical_2022, 
author={Kallien, Z. and Klusemann, B.},
title={Combined experimental-numerical analysis of the temperature evolution and distribution during friction surfacing},
year={2022},
journal = {Surface and Coatings Technology},
volume = {437},
pages = {128350},
doi = {10.1016/j.surfcoat.2022.128350},
abstract = {Friction surfacing (FS) is a solid state coating technology for similar and dissimilar metallic materials. The coating of the substrate with a consumable material is enabled due to frictional heat and plastic deformation and is performed below the materials' melting temperature. In this work, the spatio-temporal temperature field during FS is investigated within the substrate via a combined experimental-numerical approach. The study presents a robust and efficient thermal process model accounting for the contributions of friction and plasticity as heat input. The geometry of the applied heat source is dependent on the deposit geometry and the evolving flash. Extensive spatial temperature measurements for a dissimilar aluminum alloy combination are used in order to identify the required input parameters and to validate the model. The process temperature profiles for varied process parameters, such as axial force, rotational speed and travel speed as well as substrate thickness and backing plate material are systematically investigated, where experimental and numerical results are in good agreement. Deviations are in particular associated with possible experimental scatter and unknowns regarding the exact position of the measurement as well as modeling assumptions in terms of the heat source geometry. Overall, the detailed comparisons illustrate that the developed numerical model is able to obtain the temperature evolution and distribution during FS deposition with acceptable accuracy for a wide range of process conditions.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.surfcoat.2022.128350} (DOI). Kallien, Z.; Klusemann, B.: Combined experimental-numerical analysis of the temperature evolution and distribution during friction surfacing. In: Surface and Coatings Technology. Vol. 437 (2022) 128350. (DOI:  /10.1016/j.surfcoat.2022.128350)}}
@article{soujon_fundamental_study_2022, 
author={Soujon, M. and Kallien, Z. and Roos, A. and Zeller-Plumhoff, B. and Klusemann, B.},
title={Fundamental study of multi-track friction surfacing deposits for dissimilar aluminum alloys with application to additive manufacturing},
year={2022},
journal = {Materials & Design},
volume = {219},
pages = {110786},
doi = {10.1016/j.matdes.2022.110786},
abstract = {Friction surfacing is an emerging solid-state coating technology based on frictional heat induced plastic deformation at the tip of a consumable metallic stud that allows to deposit layers with a fine-grained recrystallized microstructure at temperatures below the melting point. The generation of sound, defect-free metallurgical joints between multiple adjacent overlapping friction surfacing deposits, also referred to as multi-track friction surfacing, from dissimilar aluminum alloys is the focus of this experimental work. An extensive volumetric defect analysis is carried out for various overlap configurations, including post-processing strategies in order to assess the inter-track bonding integrity using microscopic characterization techniques and micro-computed tomography. The effect of layer arrangement and overlap distance on the volumetric defect formation in both inter-track and layer-to-substrate interface is quantified and discussed. Post-processing via hybrid friction diffusion bonding process demonstrates a significant reduction in defect volume ratio, proving higher material efficiency. The gained knowledge was used to successfully build a multi-track multi-layer friction surfacing stack, demonstrating the suitability of this process for large-scale additive manufacturing components. The subsequent mechanical analysis reveals excellent homogeneous isotropic tensile properties of the additive structure in the range of the base material tensile strength.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.matdes.2022.110786} (DOI). Soujon, M.; Kallien, Z.; Roos, A.; Zeller-Plumhoff, B.; Klusemann, B.: Fundamental study of multi-track friction surfacing deposits for dissimilar aluminum alloys with application to additive manufacturing. In: Materials & Design. Vol. 219 (2022) 110786. (DOI:  /10.1016/j.matdes.2022.110786)}}
@article{mossaiby_multiadaptive_coupling_2022, 
author={Mossaiby, F. and Sheikhbahaei, P. and Shojaei, A.},
title={Multi-adaptive coupling of finite element meshes with peridynamic grids: robust implementation and potential applications},
year={2022},
journal = {Engineering with Computers},
doi = {10.1007/s00366-022-01656-z},
abstract = {Coupling of methods based on the classical continuum mechanics (CCM), with peridynamic (PD) models is a recent hot topic in the realm of computational mechanics. In the coupled models, to optimize the usage of computational resources, usually the application of PD (the more demanding procedure) is restricted to critical areas of the domain affected by discontinuities such as propagating cracks. The remaining parts of the domain are described by a more efficient CCM-based model such as the finite element method (FEM). Here, we develop a coupled FEM/PD model for dynamic fracture modeling. The proposed method simultaneously features the following: (1) it can adaptively change the coupling configuration throughout the simulation such that only critical zones, on the verge of crack nucleation/propagation, are tackled by the PD procedure, and (2) it appropriately supports different grid spacing of PD and FEM parts. We refer to a model possessing both the features as multi-adaptive. This is crucial for a highly efficient coupling scheme. The performance of the proposed method is analyzed in terms of accuracy and computational efficiency through different numerical examples. The results show that the proposed method is superior to using a refined PD model, since it provides the same level of accuracy at a much lower computational cost. As a novel application, we present the promising results of a crack propagation problem in an unbounded domain, solved using classical artificial boundary conditions on an outer FEM layer.},
note = {Online available at: \url{https://dx.doi.org/10.1007/s00366-022-01656-z} (DOI). Mossaiby, F.; Sheikhbahaei, P.; Shojaei, A.: Multi-adaptive coupling of finite element meshes with peridynamic grids: robust implementation and potential applications. In: Engineering with Computers. (2022) (DOI:  /10.1007/s00366-022-01656-z)}}
@article{examilioti_experimental_and_2022, 
author={Examilioti, T. and Papanikos, P. and Kashaev, N. and Klusemann, B. and Alexopoulos, N.},
title={Experimental and numerical investigation of laser beam-welded Al–Cu–Li joints using micro-mechanical characteristics},
year={2022},
journal = {Journal of Materials Research and Technology : JMRT},
volume = {19},
pages = {2431 - 2446},
doi = {10.1016/j.jmrt.2022.05.197},
abstract = {The local tensile mechanical properties of laser beam-welded joints of AA2198 alloy with Al-Si filler wire were experimentally investigated. For this purpose, micro-flat tensile specimens were extracted from the fusion zone and the heat-affected zone. The chemical composition of the filler wire affects the local mechanical properties in the fusion zone, showing an approximately 26 % decrease in yield strength from the radiation exposure side to the weld root side. The effect of post-weld heat treatment on the tensile mechanical behavior was additionally investigated for different heat treatment artificial ageing conditions. The maximum yield strength increase was noticed for 48 h of artificial ageing for the weld root side of the fusion zone. Several approximations were proposed to correlate the hardness measurements with the local tensile mechanical properties of the welded joint that allow for a fast assessment of the tensile mechanical behaviour of the welded joint. To evaluate the effect of (i) artificial ageing and (ii) geometrical imperfections of the weld on the mechanical behavior of the welded joint, finite element analyses were performed, using the local mechanical properties as input to the model. It is shown that the local mechanical properties of the fusion zone play a pivotal role on the strain localization and fracture of the welded joint.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jmrt.2022.05.197} (DOI). Examilioti, T.; Papanikos, P.; Kashaev, N.; Klusemann, B.; Alexopoulos, N.: Experimental and numerical investigation of laser beam-welded Al–Cu–Li joints using micro-mechanical characteristics. In: Journal of Materials Research and Technology : JMRT. Vol. 19 (2022) 2431 - 2446. (DOI:  /10.1016/j.jmrt.2022.05.197)}}
@article{prokhorov_fatigue_peculiarity_2022, 
author={Prokhorov, A. and Vshivkov, A. and Plekhov, O. and Kashaev, N.},
title={Fatigue peculiarity of metals treated by laser shock impact},
year={2022},
journal = {Procedia Structural Integrity},
volume = {37},
pages = {540 - 546},
doi = {10.1016/j.prostr.2022.01.120},
abstract = {The work is devoted to experimental investigation of laser shock peening (LSP) effect on the thermo-mechanical properties of metals. ARMCO-iron and Titanium Grade 2 are chosen for the study. Samples were subjected to laser shock peening. After that, investigation of residual stress on heat generation during fatigue loading was performed. To study the damage-induced heating the fatigue tests were coupled with infrared thermography measurements. The results of the study have shown that LSP procedure qualitatively changes temperature evolution in both materials under cyclic loading. The heating (energy dissipation) of specimens after LSP was several times higher than in initial state.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.prostr.2022.01.120} (DOI). Prokhorov, A.; Vshivkov, A.; Plekhov, O.; Kashaev, N.: Fatigue peculiarity of metals treated by laser shock impact. In: Procedia Structural Integrity . Vol. 37 (2022) 540 - 546. (DOI:  /10.1016/j.prostr.2022.01.120)}}
@article{silvaolaya_promoting_effect_2022, 
author={Silva Olaya, A.R. and Kühling, F. and Mahr, C. and Zandersons, B. and Rosenauer, A. and Weissmüller, J. and Wittstock, G.},
title={Promoting Effect of the Residual Silver on the Electrocatalytic Oxidation of Methanol and Its Intermediates on Nanoporous Gold},
year={2022},
journal = {ACS Catalysis},
volume = {12},
number = {8},
pages = {4415 - 4429},
doi = {10.1021/acscatal.1c05160},
abstract = {Nanoporous gold (NPG) obtained by dealloying Ag75Au25 with an overall residual Ag content of less than 1% was investigated as an electrocatalyst for the oxidation of methanol, formaldehyde, and formate in aqueous 0.1 M NaOH solution. The NPG was used to fill cavity microelectrodes, which allowed the recording of well-resolved voltammetry from the porous material. NPG differs from polycrystalline Au (Au(poly)) by its microstructure and its residual Ag content and also behaves distinctly different than Au(poly). The residual Ag content is higher at the surface of the ligaments than in the bulk. By cycling the NPG electrodes in 0.1 M H2SO4, the surface concentration of Ag could be decreased. It could then be set to a defined value by underpotential deposition (UPD) of Ag. The surface structure, and specifically its evolution upon the removal of Ag from the surface, was analyzed by the characteristic voltammetric features of Pb UPD. The effect of Ag on the electrocatalytic methanol oxidation reaction (MOR) is different in different potential regions. Ag coverage shifts the onset of the methanol oxidation current to less positive potentials. In the range of the peak current density, only a defined low Ag concentration enhanced the MOR current density compared to the Ag-free NPG. The {1 0 0} and {1 1 1} facets contributed the largest current, as concluded from selective poisoning experiments. At a potential of 1.63 V vs RHE, Ag2O at the surface is oxidized to AgO. Those layers can oxidize methanol and formate to CO2. The oxidation of formaldehyde proceeds at a much higher reaction rate than the MOR and formate oxidation; the reaction leads to CO and CO2 depending on the applied potential. Given the high oxidation rate of formaldehyde, it would be immediately further oxidized should it be formed as an intermediate of MOR. This is an important difference to the methanol oxidation at Pt. The water oxidation that occurs at the same potential range in the methanol-free solution was suppressed during CO2 formation.},
note = {Online available at: \url{https://dx.doi.org/10.1021/acscatal.1c05160} (DOI). Silva Olaya, A.R.; Kühling, F.; Mahr, C.; Zandersons, B.; Rosenauer, A.; Weissmüller, J.; Wittstock, G.: Promoting Effect of the Residual Silver on the Electrocatalytic Oxidation of Methanol and Its Intermediates on Nanoporous Gold. In: ACS Catalysis. Vol. 12 (2022) 8, 4415 - 4429. (DOI:  /10.1021/acscatal.1c05160)}}
@article{wang_on_the_2022, 
author={Wang, Q. and Huber, N. and Liu, X. and Kashaev, N.},
title={On the analysis of plasticity induced crack closure in welded specimens: A mechanism controlled by the stress intensity factor resulting from residual stresses},
year={2022},
journal = {International Journal of Fatigue},
volume = {162},
pages = {106940},
doi = {10.1016/j.ijfatigue.2022.106940},
abstract = {The aim of this paper is to clarify how and to what extent varied welding residual stresses (WRSes) affect the plane stress plasticity induced crack closure (PICC) simulation. A well-characterized, representative WRS field with tensile and compressive reversals was imported and the predicted PICC results were evaluated against the relevant WRS-free ones. It turned out that instead of WRS typically reported in the literature, there is actually a Kres (stress intensity factor resulting from residual stresses) controlled crack closure mechanism when investigating the PICC behavior in the presence of a WRS field, i.e., WRS influences PICC in the form of Kres. Four major categories where the crack tip was located in different Kres zones were defined using MT (middle tension) and SENT (single edge notch tension) specimens to investigate the mechanism in detail. In summary, the Kres value determined the general steady-state PICC level in the WRS field, i.e., a diminished steady-state opening stress level was predicted in the WRS field with a positive Kres regardless of whether the crack is located in a tensile or a compressive WRS zone, and an elevated value was estimated when the Kres was negative. Besides, the initial transient period was scrutinized that occurred in some WRS scenarios and the concept of primary and secondary plastic wake evolution was proposed to explain its formation. It was found that the transient behavior could be eradicated by tailoring the secondary plastic wake employing appropriate constitutive models and mesh refinement levels. The results attained in the present work provide some guidelines for the WRS-PICC modeling and simulation in the fracture mechanics community.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.ijfatigue.2022.106940} (DOI). Wang, Q.; Huber, N.; Liu, X.; Kashaev, N.: On the analysis of plasticity induced crack closure in welded specimens: A mechanism controlled by the stress intensity factor resulting from residual stresses. In: International Journal of Fatigue. Vol. 162 (2022) 106940. (DOI:  /10.1016/j.ijfatigue.2022.106940)}}
@article{lemos_mitigating_the_2022, 
author={Lemos, G.V.B. and Farina, A.B. and Piaggio, H. and Bergmann, L. and Ferreira, J.Z. and dos Santos, J.F. and Vander Voort, G. and Reguly, A.},
title={Mitigating the susceptibility to intergranular corrosion of alloy 625 by friction-stir welding},
year={2022},
journal = {Scientific Reports},
volume = {12},
number = {1},
pages = {3482},
doi = {10.1038/s41598-022-07473-0},
abstract = {In this work, friction-stir welding (FSW) was employed to alloy 625 grade I (soft annealed) sheets. Therefore, solid-state based welding was undertaken with a tool rotational speed of 200 rpm and a welding speed of 1 mm/s. Microstructural features were analyzed by light optical and scanning electron microscopy (LOM and SEM). Moreover, microhardness measurements were performed. The susceptibility to intergranular corrosion was verified by the double-loop electrochemical potentiokinetic reactivation (DL-EPR) test. Complementary, intergranular corrosion was also evaluated by the ASTM G28 Method A. FSW promoted grain refinement, increased microhardness, and reduction in the degree of sensitization. Finally, the mean corrosion rate observed in the ASTM G28 Method A test was 0.4406 mm/year, which suggests a good weld quality.},
note = {Online available at: \url{https://dx.doi.org/10.1038/s41598-022-07473-0} (DOI). Lemos, G.V.B.; Farina, A.B.; Piaggio, H.; Bergmann, L.; Ferreira, J.Z.; dos Santos, J.F.; Vander Voort, G.; Reguly, A.: Mitigating the susceptibility to intergranular corrosion of alloy 625 by friction-stir welding. In: Scientific Reports. Vol. 12 (2022) 1, 3482. (DOI:  /10.1038/s41598-022-07473-0)}}
@article{huang_tailoring_powder_2022, 
author={Huang, C. and List, A. and Shen, J. and Fu, B. and Yin, S. and Chen, T. and Klusemann, B. and Gärtner, F. and Klassen, T.},
title={Tailoring powder strengths for enhanced quality of cold sprayed Al6061 deposits},
year={2022},
journal = {Materials & Design},
volume = {215},
pages = {110494},
doi = {10.1016/j.matdesdx..2022.110494},
abstract = {As verified by literature, heat-treatments of as-atomized Al-alloy powders before cold spraying, result in microstructural homogenization and deposition efficiency increment. So far, a straightforward correlation between powder strength and consequences for the performance in cold spraying and deposit properties is still missing. This work thus provides reliable analyses of powder strengths in as-atomized and annealed states to the calculation of critical velocities and deposit quality parameter η, as well as the associated influences of powder strength on single-particle adhesion and deposit microstructures and properties. By annealing of as-atomized powder, its strength is reduced by about 60%, which allows decreasing the critical velocity for a successful deposition. Experimental results demonstrate that powder strength-based calculation of quality parameter η allows for a more realistic description of microstructural characteristics and deposits properties. The single-particle impact morphologies as well as the detachment features of adhering splats by cavitation tests visualize the respective deposition characteristics and bonding behaviors. The lower critical velocities by annealing contribute to better single splat adhesion, lower porosity, higher electrical conductivity, as well as improved tensile strength of deposits. The direct correlation of powder pre-annealing and strength in combination with cold spraying parameter variation allows defining effective strategies for improving deposit properties.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.matdesdx..2022.110494} (DOI). Huang, C.; List, A.; Shen, J.; Fu, B.; Yin, S.; Chen, T.; Klusemann, B.; Gärtner, F.; Klassen, T.: Tailoring powder strengths for enhanced quality of cold sprayed Al6061 deposits. In: Materials & Design. Vol. 215 (2022) 110494. (DOI:  /10.1016/j.matdesdx..2022.110494)}}
@article{panov_effect_of_2022, 
author={Panov, D. and Naumov, S. and Stepanov, N. and Sokolovsky, V. and Volokitina, E. and Kashaev, N. and Ventzke, V. and Dinse, R. and Riekehr, S. and Povolyaeva, E. and Nochovnaya, N. and Alekseev, E. and Zherebtsov, S. and Salishchev, G.},
title={Effect of pre-heating and post-weld heat treatment on structure and mechanical properties of laser beam-welded Ti2AlNb-based joints},
year={2022},
journal = {Intermetallics},
volume = {143},
pages = {107466},
doi = {10.1016/j.intermet.2022.107466},
abstract = {The effect of pre-heating and post-weld heat treatment on microstructure and mechanical properties of laser-welded joints in a Ti–23Al–23Nb-1.4V-0.8Zr-0.4Mo-0.4Si (at.%) alloy was studied. Laser beam-welding was carried out at room temperature as well as after pre-heating up to 800°С. The post-weld heat treatment comprised either air quenching from 920°С followed by aging at 800°С or only aging at 800°С. The microstructure of the fusion zone consisted of columnar β-grains after welding at room temperature and 400 °C or both the columnar and large equiaxed crystals at 600 and 800 °C. An increase in the pre-heating temperature caused the columnar β-crystals growth as well as an increase in the fusion zone and heat-affected zone widths. Meanwhile, a decrease in the Al and Ti content, as well as an increase in both the porosity and gaseous elements content (O and N) after welding at 600–800 °C were found. The microhardness of each joint obtained after welding with pre-heating temperatures up to 600 °C was lower than that of the base material. All the welded joints showed the yield strength and ultimate tensile strength levels between 1070 and 1110 MPa, which correspond to approximately 80% of the base metal level. Reasonable total elongation of the joint was achieved after welding at 400 °C (4.3%). The post-weld heat treatment involving air quenching from 920 °C with subsequent aging at 800 °C for 6 h demonstrated the best results. The heat treatment resulted in the precipitation of the O- and α2-phases and an increase in total elongation to 6.5%.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.intermet.2022.107466} (DOI). Panov, D.; Naumov, S.; Stepanov, N.; Sokolovsky, V.; Volokitina, E.; Kashaev, N.; Ventzke, V.; Dinse, R.; Riekehr, S.; Povolyaeva, E.; Nochovnaya, N.; Alekseev, E.; Zherebtsov, S.; Salishchev, G.: Effect of pre-heating and post-weld heat treatment on structure and mechanical properties of laser beam-welded Ti2AlNb-based joints. In: Intermetallics. Vol. 143 (2022) 107466. (DOI:  /10.1016/j.intermet.2022.107466)}}
@article{halak_changes_in_2022, 
author={Halak, R. and Rath, L. and Suhuddin, U. and dos Santos, J. and Klusemann, B.},
title={Changes in processing characteristics and microstructural evolution during friction extrusion of aluminum},
year={2022},
journal = {International Journal of Material Forming},
volume = {15},
number = {3},
pages = {24},
doi = {10.1007/s12289-022-01670-y},
abstract = {This study focuses on characterizing the microstructural evolution of the aluminum alloy 7075 in the friction extrusion process under different extrusion forces and die angles. Depending on these conditions, two fundamentally different extrusion types are found, showing significant differences in the process characteristics and microstructural evolution. One of the two extrusion types is associated with high extrusion force and low die angle, leading to fully recrystallized wires with average grain size around 1.2 μm. The microstructural analysis indicates that the microstructure present in the wires is generated in the charge material by the combination of tool geometry, load induced material flow and friction conditions in the initial stages of the friction extrusion process. The identified processing conditions and influencing factors introduce an alternative route for friction extrusion at low extrusion ratios, capable of producing completely refined wires.},
note = {Online available at: \url{https://dx.doi.org/10.1007/s12289-022-01670-y} (DOI). Halak, R.; Rath, L.; Suhuddin, U.; dos Santos, J.; Klusemann, B.: Changes in processing characteristics and microstructural evolution during friction extrusion of aluminum. In: International Journal of Material Forming. Vol. 15 (2022) 3, 24. (DOI:  /10.1007/s12289-022-01670-y)}}
@article{odermatt_coaxial_laser_2022, 
author={Odermatt, A. and Dorn, F. and Ventzke, V. and Kashaev, N.},
title={Coaxial laser directed energy deposition with wire of thin-walled duplex stainless steel parts: Process discontinuities and their impact on the mechanical properties},
year={2022},
journal = {CIRP Journal of Manufacturing Science and Technology},
volume = {37},
pages = {443 - 453},
doi = {10.1016/j.cirpj.2022.02.019},
abstract = {The topic of this paper is the process stability and its influence on the tensile material properties of duplex stainless steel manufactured via coaxial laser directed energy deposition with wire. The influence of slight changes in the prescribed offset per layer and laser power on the process stability, occurrence of discontinuities, and mechanical properties of duplex stainless steel 2209 parts was investigated. If the prescribed offset or laser power was too high, overheating of the melt-pool was observed. Otherwise, plunging of the wire through the melt-pool occurred. Stable processing was achieved by the adaptation of prescribed offset and laser power according to limited exponential growth laws. The overheating of the melt-pool leads to unsalvageable instabilities, whereas plunging of the wire through the melt-pool leads to self-stabilization by lowering the effective deposition rate and layer height. The discontinuities at sites, where wire plunged through the melt-pool are limited to the surface of the parts. The microstructure and tensile mechanical properties are unaffected by the presence of the surface discontinuities when they are removed by a machining step. The yield strength, ultimate tensile strength, and fracture strain exhibit a strong directionality, which can be explained by the anisotropy and inhomogeneity of the microstructure consisting of austenite-rich layers and ferrite-rich layer bands.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.cirpj.2022.02.019} (DOI). Odermatt, A.; Dorn, F.; Ventzke, V.; Kashaev, N.: Coaxial laser directed energy deposition with wire of thin-walled duplex stainless steel parts: Process discontinuities and their impact on the mechanical properties. In: CIRP Journal of Manufacturing Science and Technology. Vol. 37 (2022) 443 - 453. (DOI:  /10.1016/j.cirpj.2022.02.019)}}
@article{weissmller_giant_compliance_2022, 
author={Weissmüller, J. and Shi, S.},
title={Giant compliance and spontaneous buckling of beams containing mobile solute atoms},
year={2022},
journal = {Acta Materialia},
volume = {227},
pages = {117696},
doi = {10.1016/j.actamat.2022.117696},
abstract = {Recent experiments have shown that the elastic compliance of a porous metal can be substantially enhanced when mobile solute is alloyed into interstitial sites of the crystal lattice. The observations agree with predictions – due to Gorsky and to Larché and Cahn – for the elasticity of open systems in which the elastic responses is probed at constant chemical potential. The underlying mechanism involves an exchange of solute between tensile and compressive fibers in beam-like elements of the microstructure. Here, we analyze the elastic deformation of such elements in a continuum approach, accounting explicitly for the coupling between chemistry and mechanics. We consider a regular solution with linear elasticity in the limit of constant composition and with a linear composition-strain coupling. Materials parameters are matched to experiments on Pd-H, so as to realistically account for the balance between chemical and mechanical energies. At constant chemical potential, the elastic response can be strongly nonlinear. With decreasing temperature, the bending goes from a monotonic moment-curvature relation to one including a horizontal tangent and, hence, a state of giant bending compliance. Reducing the temperature further brings first a temperature interval with a simple bistability and finally one with degeneracy including – depending on the chemical potential or on the mean solute fraction – the possibility of finite curvature at zero moment. Quenching the uniform solution into a two-phase region of the alloy phase diagram can lead to spontaneous buckling at no load. Furthermore, degenerate moment-curvature relations allow for bending states in which the radius is not a constant along the beam axis. Intervals of lar ge strain at constant load are similar to superelasticity, but the underlying phase transformation is here not martensitic.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.actamat.2022.117696} (DOI). Weissmüller, J.; Shi, S.: Giant compliance and spontaneous buckling of beams containing mobile solute atoms. In: Acta Materialia. Vol. 227 (2022) 117696. (DOI:  /10.1016/j.actamat.2022.117696)}}
@article{pozdnyakov_coupled_modeling_2022, 
author={Pozdnyakov, V. and Keller, S. and Kashaev, N. and Klusemann, B. and Oberrath, J.},
title={Coupled Modeling Approach for Laser Shock Peening of AA2198-T3: From Plasma and Shock Wave Simulation to Residual Stress Prediction},
year={2022},
journal = {Metals},
volume = {12},
number = {1},
pages = {107},
doi = {10.3390/met12010107},
abstract = {Laser shock peening (LSP) is a surface modification technique to improve the mechanical properties of metals and alloys, where physical phenomena are difficult to investigate, due to short time scales and extreme physical values. In this regard, simulations can significantly contribute to understand the underlying physics. In this paper, a coupled simulation approach for LSP is presented. A global model of laser–matter–plasma interaction is applied to determine the plasma pressure, which is used as surface loading in finite element (FE) simulations in order to predict residual stress (RS) profiles in the target material. The coupled model is applied to the LSP of AA2198-T3 with water confinement, 3×3mm2 square focus and 20 ns laser pulse duration. This investigation considers the variation in laser pulse energy (3 J and 5 J) and different protective coatings (none, aluminum and steel foil). A sensitivity analysis is conducted to evaluate the impact of parameter inaccuracies of the global model on the resulting RS. Adjustment of the global model to different laser pulse energies and coating materials allows us to compute the temporal pressure distributions to predict RS with FE simulations, which are in good agreement with the measurements.},
note = {Online available at: \url{https://dx.doi.org/10.3390/met12010107} (DOI). Pozdnyakov, V.; Keller, S.; Kashaev, N.; Klusemann, B.; Oberrath, J.: Coupled Modeling Approach for Laser Shock Peening of AA2198-T3: From Plasma and Shock Wave Simulation to Residual Stress Prediction. In: Metals. Vol. 12 (2022) 1, 107. (DOI:  /10.3390/met12010107)}}
@article{mironov_on_the_2022, 
author={Mironov, S. and Ozerov, M. and Kalinenko, A. and Stepanov, N. and Plekhov, O. and Sikhamov, R. and Ventzke, V. and Kashaev, N. and Salishchev, G. and Semiatin, L. and Zherebtsov, S.},
title={On the relationship between microstructure and residual stress in laser-shock-peened Ti-6Al-4V},
year={2022},
journal = {Journal of Alloys and Compounds},
volume = {900},
pages = {163383},
doi = {10.1016/j.jallcom.2021.163383},
abstract = {The relationship between residual stress and microstructure evolution during laser shock peening (LSP) of Ti-6Al-4V was investigated. To this end, the program material was processed using a 5-J Q-switched Nd:YAG laser with a wavelength of 1064 nm and a pulse duration of 20 ns. The residual stresses developed during LSP were determined by means of the incremental-hole-drilling method, and the corresponding microstructures were established using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). From these observations, it was deduced that deformation and the resulting microstructure evolution during LSP were controlled by an inhibition of dislocation cross-slip, which, in turn, was attributed to the extremely short duration of the process. Hence, it was surmised that the unique residual-stress state generated during LSP is associated with two intrinsic characteristics of this technique, i.e., the very high imposed energy and the extremely short time scale. The large and non-uniform mechanical energy input gives rise to the residual stresses while the limited time span prevents stress relief via dislocation cross slip and climb.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jallcom.2021.163383} (DOI). Mironov, S.; Ozerov, M.; Kalinenko, A.; Stepanov, N.; Plekhov, O.; Sikhamov, R.; Ventzke, V.; Kashaev, N.; Salishchev, G.; Semiatin, L.; Zherebtsov, S.: On the relationship between microstructure and residual stress in laser-shock-peened Ti-6Al-4V. In: Journal of Alloys and Compounds. Vol. 900 (2022) 163383. (DOI:  /10.1016/j.jallcom.2021.163383)}}
@article{wang_a_multiscaled_2022, 
author={Wang, J. and Fu, B. and Shen, J. and Bergmann, L. and Lu, X. and dos Santos, J. and Klusemann, B.},
title={A multi-scaled process study of dissimilar friction stir welding of Eurofer RAFM steel to PM2000 ODS alloy},
year={2022},
journal = {Journal of Materials Processing Technology},
volume = {307},
pages = {117679},
doi = {10.1016/j.jmatprotec.2022.117679},
abstract = {Both the reduced activation ferritic/martensitic (RAFM) steel and oxide dispersion strengthened (ODS) alloys have shown high potential applications in the nuclear industry. In this study, Eurofer RAFM steel and PM2000 ODS alloy in butt joint configuration was welded by friction stir welding (FSW), and a multi-scaled process study including procedure analysis, macro-/micro-structure, mechanical properties as well as deformation behavior was conducted. To obtain defect-free welds with equal strength and toughness matching, an intermediate rotation speed of 300 rpm was applied since it results in sufficient material intermixing both within the stirred zone (SZ) and along the SZ boundary. The SZ is composed of quenching martensite from the Eurofer steel and the recrystallized ferrite from PM2000, which shows significantly increased microhardness and excellent resistance to local deformation. As a result, strain localization occurs within the Eurofer steel during tensile testing. Additionally, a unique phenomenon, abnormal grain growth (AGG), was identified within the SZ of the as-welded joint. The underlying mechanism of AGG is related to the reduction of grain boundary pinning due to the dissolution of nanoparticles. The equiaxed ferrite nucleus with a similar orientation, surrounded by low-angle grain boundaries, gradually merge with each other through grain annexation, resulting in the finally coarsened grains. The reported study offers fundamental knowledge of FSW of RAFM steel to ODS alloy dissimilar combinations, promoting the usage of RAFM/ODS hybrid structures in future applications.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jmatprotec.2022.117679} (DOI). Wang, J.; Fu, B.; Shen, J.; Bergmann, L.; Lu, X.; dos Santos, J.; Klusemann, B.: A multi-scaled process study of dissimilar friction stir welding of Eurofer RAFM steel to PM2000 ODS alloy. In: Journal of Materials Processing Technology. Vol. 307 (2022) 117679. (DOI:  /10.1016/j.jmatprotec.2022.117679)}}
@article{wang_effect_of_2022, 
author={Wang, H. and Keller, S. and Chang, Y. and Kashaev, N. and Yan, K. and Gurevich, E.L. and Ostendorf, A.},
title={Effect of laser shock peening without protective coating on the surface mechanical properties of NiTi alloy},
year={2022},
journal = {Journal of Alloys and Compounds},
volume = {896},
pages = {163011},
doi = {10.1016/j.jallcom.2021.163011},
abstract = {We study the effect of laser shock peening (LSP) without protective coating on the surface mechanical property of NiTi alloy. The Vickers microhardness and wear resistance are measured to determine the mechanical property of NiTi samples treated with different LSP parameters (3 J with 10 ns and 5 J with 20 ns). From the electron backscatter diffraction (EBSD) analysis, it can be found that the laser shock peening does not induce obvious grain refinement in the surface region of NiTi alloy. Both compressive and tensile residual stress in the top layer are determined using the hole drilling method. The results show that the LSP treatment without a protective coating increases the roughness and enhances the surface mechanical properties of NiTi alloy.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jallcom.2021.163011} (DOI). Wang, H.; Keller, S.; Chang, Y.; Kashaev, N.; Yan, K.; Gurevich, E.L.; Ostendorf, A.: Effect of laser shock peening without protective coating on the surface mechanical properties of NiTi alloy. In: Journal of Alloys and Compounds. Vol. 896 (2022) 163011. (DOI:  /10.1016/j.jallcom.2021.163011)}}
@article{yasakau_the_effect_2022, 
author={Yasakau, K. and Maltseva, A. and Lamaka, S. and Mei, D. and Ovri, H. and Volovitch, P. and Ferreira, M. and Zheludkevich, M.},
title={The effect of carboxylate compounds on Volta potential and corrosion inhibition of Mg containing different levels of iron},
year={2022},
journal = {Corrosion Science},
volume = {194},
pages = {109937},
doi = {10.1016/j.corsci.2021.109937},
abstract = {Corrosion protection and surface properties of Magnesium (Mg) containing 51 ppm Fe (HP-Mg) and 341 ppm Fe (CP-Mg) were assessed by EIS, AFM/SKPFM, and photoluminescence spectroscopy in NaCl solutions with/without fumarate (Fum), 2,5-pyridinedicarboxylate (PDCA) and salicylate (Sal) carboxylates. The PDCA was effective in corrosion inhibition of HP-Mg and CP-Mg, while the Sal was efficient in inhibition of CP-Mg only. Volta potential (VPD) changes on Mg were evaluated considering the contribution of molecular dipoles and chemical dipoles due to interaction of carboxylate groups present in carboxylates with Mg. VPD of CP-Mg increased due to adsorption of Fe(III)-salicylate complexes and salicylate molecules.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.corsci.2021.109937} (DOI). Yasakau, K.; Maltseva, A.; Lamaka, S.; Mei, D.; Ovri, H.; Volovitch, P.; Ferreira, M.; Zheludkevich, M.: The effect of carboxylate compounds on Volta potential and corrosion inhibition of Mg containing different levels of iron. In: Corrosion Science. Vol. 194 (2022) 109937. (DOI:  /10.1016/j.corsci.2021.109937)}}
@article{charalampidou_the_effect_2022, 
author={Charalampidou, C. and Braga, D. and Bergmann, L. and Kourkoulis, S. and da Silva, L. and Infante, V. and dos Santos, J. and Moreira, P. and Alexopoulos, N.},
title={The effect of prior adhesive bonding on the corrosion behavior of AA2024 FSWed single lap joints},
year={2022},
journal = {Mechanics of Materials},
volume = {164},
pages = {104122},
doi = {10.1016/j.mechmat.2021.104122},
abstract = {Friction stir welding (FSW), when in butt-joint configuration, was found to produce high-mechanically performing joints. However, when in overlap configuration, stress concentration is noticed at the weld edges that significantly reduces the mechanical performance of the joints. Additionally, the welding regions tend to enhance localized corrosion attack due to microstructural changes. In the present work, a new hybrid joint - that is a combination of friction stir welding with a prior step of adhesive bonding of the overlap surface - was investigated. Friction stir welded, adhesive bonded and hybrid single lap joints were exposed to exfoliation corrosion solution - for different exposure times - and mechanically tested to investigate the effect of adhesive bonding on the mechanical behavior of pre-corroded joints. The hybrid joint (adhesive bonding + friction stir welding) showed excellent tensile mechanical performance in terms of deformation, exhibiting approximately 100 % increase when compared against the respective values of adhesive bonded and/or friction stir welded joints. This was attributed to the elimination of the ‘hook defect’ in the friction stir welded area as well as to the out-of-plane displacement restriction of the bonded area. The corrosion-induced degradation mechanisms of the hybrid joint were also investigated and compared against the friction stir welded and the adhesive bonded joints for various exposure times. The hybrid joints outperform the friction stir welded and adhesive bonded joints for all the investigated corrosion exposure times; after very long corrosion exposure times (e.g. 48 h), the hybrid joints maintained their maximum tensile strength by almost 90 %, while the adhesive bonded and the friction stir welded joints retained 85 % and 59 %, respectively. Almost double fracture deformation was noticed for the hybrid joints for all the investigated corrosion exposure times. This superiority was attributed to the dual protection of the intermediate adhesive film; initially the sealing effect protects the lap joint at the primary corrosion stages until debonding takes place and additionally protects the friction stir welded area in-between the lapped sheets from localized corrosion on the interface between the thermo-mechanically affected and heat affected zones.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.mechmat.2021.104122} (DOI). Charalampidou, C.; Braga, D.; Bergmann, L.; Kourkoulis, S.; da Silva, L.; Infante, V.; dos Santos, J.; Moreira, P.; Alexopoulos, N.: The effect of prior adhesive bonding on the corrosion behavior of AA2024 FSWed single lap joints. In: Mechanics of Materials. Vol. 164 (2022) 104122. (DOI:  /10.1016/j.mechmat.2021.104122)}}
@article{li_evolution_of_2022, 
author={Li, Y. and Dinh-Ngo, B. and Markmann, J. and Weissmüller, J.},
title={Evolution of length scales and of chemical heterogeneity during primary and secondary dealloying},
year={2022},
journal = {Acta Materialia},
volume = {222},
pages = {117424},
doi = {10.1016/j.actamat.2021.117424},
abstract = {We study the evolution of silver-rich regions, or ‘clusters’, during the making of nanoporous gold by dealloying. The clusters, which are remnants of the master alloy that have evaded corrosion, impact the functional behavior of the material. Furthermore, they carry information on the structure size in the initial stages of dealloying. Using kinetic Monte Carlo simulations, we emulate electrochemical dealloying at various electrode potentials. Our simulations illustrate the two-stage characteristic of the process, where primary dealloying generates the initial network of nanoscale ligaments, while the subsequent secondary dealloying is characterized by coarsening and further dissolution. Silver-rich clusters, embedded in essentially pure gold, form during primary dealloying throughout the range of dealloying potentials of the study. At this point, their size scales with that of the ligaments. Both sizes decrease with increasing dealloying potential, and the trends of size versus potential agree with a Gibbs-Thompson type relation. Yet, when coarsening increases the ligament size during secondary dealloying, the size of the silver clusters remains constant. Directly accessing the initial ligament size of nanoporous gold in experiment is challenging, yet our study links this size to that of the silver-rich clusters. The clusters survive even in the later stages of dealloying and their size can be measured. This provides an experimental signature of the initial size.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.actamat.2021.117424} (DOI). Li, Y.; Dinh-Ngo, B.; Markmann, J.; Weissmüller, J.: Evolution of length scales and of chemical heterogeneity during primary and secondary dealloying. In: Acta Materialia. Vol. 222 (2022) 117424. (DOI:  /10.1016/j.actamat.2021.117424)}}
@article{dreistadt_an_effective_2022, 
author={Dreistadt, D. and Le, T. and Capurso, G. and Bellosta von Colbe, J. and Santhosh, A. and Pistidda, C. and Scharnagl, N. and Ovri, H. and Milanese, C. and Jerabek, P. and Klassen, T. and Jepsen, J.},
title={An effective activation method for industrially produced TiFeMn powder for hydrogen storage},
year={2022},
journal = {Journal of Alloys and Compounds},
volume = {919},
pages = {165847},
doi = {10.1016/j.jallcom.2022.165847},
abstract = {This work proposes an effective thermal activation method with low technical effort for industrially produced titanium-iron-manganese powders (TiFeMn) for hydrogen storage. In this context, the influence of temperature and particle size of TiFeMn on the activation process is systematically studied. The results obtained from this investigation suggest that the activation of the TiFeMn material at temperatures as low as 50 °C is already possible, with a combination of “Dynamic” and “Static” routines, and that an increase to 90 °C strongly reduces the incubation time for activation, i.e. the incubation time of the sample with the two routines at 90 °C is about 0.84 h, while ∼ 277 h is required for the sample treated at 50 °C in both “Dynamic” and “Static” sequences. Selecting TiFeMn particles of larger size also leads to significant improvements in the activation performance of the investigated material. The proposed activation routine makes it possible to overcome the oxide layer existing on the compound surface, which acts as a diffusion barrier for the hydrogen atoms. This activation method induces further cracks and defects in the powder granules, generating new surfaces for hydrogen absorption with greater frequency, and thus leading to faster sorption kinetics in the subsequent absorption-desorption cycles.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jallcom.2022.165847} (DOI). Dreistadt, D.; Le, T.; Capurso, G.; Bellosta von Colbe, J.; Santhosh, A.; Pistidda, C.; Scharnagl, N.; Ovri, H.; Milanese, C.; Jerabek, P.; Klassen, T.; Jepsen, J.: An effective activation method for industrially produced TiFeMn powder for hydrogen storage. In: Journal of Alloys and Compounds. Vol. 919 (2022) 165847. (DOI:  /10.1016/j.jallcom.2022.165847)}}
@article{sala_effect_of_2022, 
author={Sala, S. and Keller, S. and Chupakhin, S. and Pöltl, D. and Klusemann, B. and Kashaev, N.},
title={Effect of laser peen forming process parameters on bending and surface quality of Ti-6Al-4V sheets},
year={2022},
journal = {Journal of Materials Processing Technology},
volume = {305},
pages = {117578},
doi = {10.1016/j.jmatprotec.2022.117578},
abstract = {Laser peen forming (LPF) is a metal forming process that utilizes laser-induced mechanical shock waves to form desired shapes or modify bent structures. The present work focuses on the applicability of LPF to Ti-6Al-4V sheets, to identify an optimal LPF process parameter window and achieve desired bending without compromising the surface quality within the peened region. The effect of LPF process parameters, i.e. laser power density, overlap, type of sacrificial overlay, and the number of peening sequences was investigated for specimens with different thicknesses. The laser power density and number of peening sequences were the most influential parameters that affect the bending of the specimens. Using sacrificial overlay has a significant effect on the bending and surface quality of the specimens. Surface quality after LPF was assessed by measuring the roughness in the peened region. In experiments without a sacrificial overlay, a black titanium oxide residue on the peened region was observed and additionally, small micro-cracks were found in the near surface region. Further characterization of the peened region revealed that the average crack length increased with increase in laser power density. Two possible LPF process parameter combinations were identified to obtain bending in the peened region, where LPF with sacrificial overlay resulted in no surface damage. Furthermore, residual stresses were determined at various LPF process parameters by incremental hole-drilling method in the peened region.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jmatprotec.2022.117578} (DOI). Sala, S.; Keller, S.; Chupakhin, S.; Pöltl, D.; Klusemann, B.; Kashaev, N.: Effect of laser peen forming process parameters on bending and surface quality of Ti-6Al-4V sheets. In: Journal of Materials Processing Technology. Vol. 305 (2022) 117578. (DOI:  /10.1016/j.jmatprotec.2022.117578)}}
@article{bergmann_effect_of_2022, 
author={Bergmann, L. and Batistão, B. and de Alcantara, N. and Gargarella, P. and Klusemann, B.},
title={Effect of rotational speed and double-sided welding in friction stir–welded dissimilar joints of aluminum alloy and steel},
year={2022},
journal = {Welding in the World},
volume = {66},
number = {9},
pages = {1747 - 1756},
doi = {10.1007/s40194-022-01333-1},
abstract = {The effect of tool rotational speed and double-sided welding in friction stir welding of aluminum alloy AA5083 and GL A36 steel was investigated. Defect-free joints were obtained in single- and double-sided welding using a rotational speed of 300 rpm. The increase in rotational speed or the application of double-sided welding increased the amount of dispersed steel particles in the aluminum stir zone, which stimulated void formation in the joint. In spite of the grain refinement in the stir zone, hardness is similar for all weld zones of the aluminum alloy, increasing significantly just in the steel near the weld interface due to severe work hardening. Besides this, the studied rotational speeds and double-sided welding did not exert any significant influence on the tensile strength of the joints, despite that a symmetric joint configuration with the welding through the full material thickness is guaranteed in the double-sided welding. The formation of intermetallic compound (IMC) layers is observed due to interdiffusion in the aluminum/steel interface. Investigations via scanning electron microscopy and energy-dispersive X-ray spectroscopy reveal that the IMC layer with 300–400 nm thickness is composed of Fe2Al5 or FeAl3 throughout the entire weld interface.},
note = {Online available at: \url{https://dx.doi.org/10.1007/s40194-022-01333-1} (DOI). Bergmann, L.; Batistão, B.; de Alcantara, N.; Gargarella, P.; Klusemann, B.: Effect of rotational speed and double-sided welding in friction stir–welded dissimilar joints of aluminum alloy and steel. In: Welding in the World. Vol. 66 (2022) 9, 1747 - 1756. (DOI:  /10.1007/s40194-022-01333-1)}}
@article{ferrari_effects_of_2022, 
author={Ferrari, V.R. and Coury, F.G. and Suhuddin, U.F.H. and Alcântara, N.G. and dos Santos, J.F. and Ohashi, R. and Fujimoto, M. and Koga, G.Y.},
title={Effects of semi-solid structure on interface formation of dissimilar aluminum to galvanized steel welds produced by load-controlled Refill Friction Stir Spot Welding},
year={2022},
journal = {Journal of Manufacturing Processes},
volume = {84},
pages = {298 - 315},
doi = {10.1016/j.jmapro.2022.10.001},
abstract = {Refill Friction Stir Spot Welding (Refill FSSW) allows welding dissimilar materials providing excellent bonding between both parts. On this work, a multi-scale analysis of load-controlled Refill FSSW was performed to analyze dissimilar AA6016-T4 and Zn-coated DX56D steel joints. These were produced using optimized process parameters and analyzed in both as-welded and bake-hardened conditions. During the process, fusion and subsequent dispersion of Zn favored the formation of a semi-solid structure characterized by an intense microsegregation. Therefore, incipient melting of Zn-rich phase followed by eutectic reaction was observed. The presence of liquid phases along the grain boundaries led to a complex relationship between mechanical properties, microstructure and processing variables. Joints with enhanced mechanical properties were produced by limiting the growth of intermetallic compounds (IMC) at the interface, which coupled with stir zone (SZ) strengthening due to Zn dispersion, led to less pronounceable secondary bending effects. The bake hardening process was also found to have a substantial influence on diffusion-dependent mechanisms and, consequently, on the final performance of the welded joint. The results highlighted a great potential of load-controlled Refill FSSW for producing high-strength dissimilar joints in short cycles, which is desirable for applications in the automotive industry.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jmapro.2022.10.001} (DOI). Ferrari, V.R.; Coury, F.G.; Suhuddin, U.F.H.; Alcântara, N.G.; dos Santos, J.F.; Ohashi, R.; Fujimoto, M.; Koga, G.Y.: Effects of semi-solid structure on interface formation of dissimilar aluminum to galvanized steel welds produced by load-controlled Refill Friction Stir Spot Welding. In: Journal of Manufacturing Processes. Vol. 84 (2022) 298 - 315. (DOI:  /10.1016/j.jmapro.2022.10.001)}}
@article{liang_surface_recrystallization_2022, 
author={Liang, Z. and Lilleodden, E. and Ovri, H. and Pyczak, F.},
title={Surface Recrystallization in a Co-Based Superalloy During High Temperature Exposure},
year={2022},
journal = {Metallurgical and Materials Transactions A},
volume = {53},
number = {12},
pages = {4156 - 4160},
doi = {10.1007/s11661-022-06852-6},
abstract = {The effect of grinding on static recrystallization and oxidation of a novel Co-based superalloy has been studied. The evolution of surface recrystallization after heat treating at 850 °C in air was revealed by comparing ground specimens with electropolished ones. The loss of Al and Ti from the bulk material leads to the formation of a γ′-free region and further promotes recrystallization at the surface.},
note = {Online available at: \url{https://dx.doi.org/10.1007/s11661-022-06852-6} (DOI). Liang, Z.; Lilleodden, E.; Ovri, H.; Pyczak, F.: Surface Recrystallization in a Co-Based Superalloy During High Temperature Exposure. In: Metallurgical and Materials Transactions A. Vol. 53 (2022) 12, 4156 - 4160. (DOI:  /10.1007/s11661-022-06852-6)}}
@article{huber_a_modeling_2022, 
author={Huber, N. and Beirau, T.},
title={A modeling approach to predict the mechanical response of materials to irradiation damage from external sources: Nanoindentation of Pb-implanted ZrSiO4},
year={2022},
journal = {Materialia},
volume = {24},
pages = {101506},
doi = {10.1016/j.mtla.2022.101506},
abstract = {Materials exposed to external irradiation undergo damage and detoriation of mechanical properties that decays with the distance from the surface. Finite element simulations are used to predict the hardness and Young´s modulus as function of depth. The model incorporates the homogenized mechanical properties and the volumetric swelling, determined from micromechanical simulations, as function of the locally induced damage. Predicted Young's modulus data showed a good agreement with nanoindentation results and confirmed the established mapping of damage into depth dependent amorphous phase fraction in form of sigmoidal functions. The comparison of predicted hardness profiles with experimental data suggests a relaxation mechanism that removes the residual stress in the damaged surface layer during the ion implantation process. Furthermore, the results support the hypothesis that mechanical properties determined from intrinsic damage can be used to model also external radiation damage. The presented model is applicable to other types of materials and irradiation sources.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.mtla.2022.101506} (DOI). Huber, N.; Beirau, T.: A modeling approach to predict the mechanical response of materials to irradiation damage from external sources: Nanoindentation of Pb-implanted ZrSiO4. In: Materialia. Vol. 24 (2022) 101506. (DOI:  /10.1016/j.mtla.2022.101506)}}
@article{andr_microscale_damage_2022, 
author={André, N.M. and Alessio, R.P. and dos Santos, J.F. and Amancio-Filho, S.T.},
title={Microscale Damage Evolution and Failure Behavior of Metal–Composite Friction Spot Joints: Modelling and Experimental Analyses},
year={2022},
journal = {Metals},
volume = {12},
number = {12},
pages = {2080},
doi = {10.3390/met12122080},
abstract = {This study aimed to understand the damage evolution at the interface of AA2024-T3/CF-PPS friction spot joints. For this purpose, the finite element method was applied and the bonding zones of the joints were discretized based on a traction–separation law. It was observed that the damage had initiated at the AZ (adhesion zone) and then propagated as a symmetric linear front from the edges towards the center of the joined area. Nevertheless, as the damage advanced inside the PDZ (plastically deformed zone), its propagation became an asymmetrical linear front that evolved preferably from the free edge of the composite part due to the higher peeling stresses in this region (asymmetrical secondary bending of the structure). Based on the findings of this study, modifications are proposed to the failure theory previously stated for friction spot joints.},
note = {Online available at: \url{https://dx.doi.org/10.3390/met12122080} (DOI). André, N.M.; Alessio, R.P.; dos Santos, J.F.; Amancio-Filho, S.T.: Microscale Damage Evolution and Failure Behavior of Metal–Composite Friction Spot Joints: Modelling and Experimental Analyses. In: Metals. Vol. 12 (2022) 12, 2080. (DOI:  /10.3390/met12122080)}}
@article{brinker_how_nanoporous_2022, 
author={Brinker, M. and Thelen, M. and May, M. and Rings, D. and Krekeler, T. and Lakner, P. and Keller, T. and Bertram, F. and Huber, N. and Huber, P.},
title={How nanoporous silicon-polypyrrole hybrids flex their muscles in aqueous electrolytes: In operando high-resolution x-ray diffraction and electron tomography-based micromechanical computer simulations},
year={2022},
journal = {Physical Review Materials},
volume = {6},
number = {11},
pages = {116002},
doi = {10.1103/PhysRevMaterials.6.116002},
abstract = {Macroscopic strain experiments have revealed that silicon crystals traversed by parallel, channel-like nanopores functionalized with the artificial muscle polymer polypyrrole (PPy) exhibit large and reversible electrochemomechanical actuation in aqueous electrolytes. On a macroscopic scale these actuation properties are well understood. However, on the microscopical level this system still bears open questions, as to how the electrochemical expansion and contraction of PPy acts on to np-Si pore walls and how the collective motorics of the pore array emerges from the single-nanopore behavior. Here we present synchrotron-based, in operando x-ray diffraction on the evolving electrostrains in epilayers of this material grown on bulk silicon. An analysis of these experiments with micromechanical finite-element simulations, that are based on a full three-dimensional reconstruction of the nanoporous medium by transmission electron microscopy (TEM) tomography, shows that the in-plane mechanical response is dominantly isotropic despite the anisotropic elasticity of the single-crystalline host matrix. However, the structural anisotropy originating from the parallel alignment of the nanopores led to significant differences between the in- and out-of-plane electromechanical response. This response is not describable by a simple two-dimensional arrangement of parallel cylindrical channels. Rather, the simulations highlight that the dendritic shape of the silicon pore walls, including pore connections between the main channels, causes complex, highly inhomogeneous stress-strain fields in the crystalline host. Time-dependent x-ray scattering experiments on the dynamics of the actuator properties hint towards the importance of diffusion limitations, plastic deformation, and creep in the nanoconfined polymer upon (counter)ion adsorption and desorption, the very pore-scale processes causing the macroscopic electroactuation. From a more general perspective, our study demonstrates that the combination of TEM tomography-based micromechanical modeling with high-resolution x-ray scattering experiments provides a powerful approach for in operando analysis of nanoporous composites from the single nanopore up to the porous-medium scale.},
note = {Online available at: \url{https://dx.doi.org/10.1103/PhysRevMaterials.6.116002} (DOI). Brinker, M.; Thelen, M.; May, M.; Rings, D.; Krekeler, T.; Lakner, P.; Keller, T.; Bertram, F.; Huber, N.; Huber, P.: How nanoporous silicon-polypyrrole hybrids flex their muscles in aqueous electrolytes: In operando high-resolution x-ray diffraction and electron tomography-based micromechanical computer simulations. In: Physical Review Materials. Vol. 6 (2022) 11, 116002. (DOI:  /10.1103/PhysRevMaterials.6.116002)}}
@article{li_electrochemical_behavior_2022, 
author={Li, J. and Li, L.-Y. and Jia, P. and Okulov, I.V.},
title={Electrochemical Behavior of Nanoporous Gold/Polypyrrole Supercapacitor under Deformation},
year={2022},
journal = {Nanomaterials},
volume = {12},
number = {13},
pages = {2149},
doi = {10.3390/nano12132149},
abstract = {Due to the high demand of wearable electronics, flexible supercapacitors have been extensively developed in recent years. Yet, the effect of deformation in the interior electrode material suffered in practical applications on the performance received less attention. Here, we study the electrochemical behavior of macroscopic nanoporous gold/polypyrrole (NPG/PPy) in situ under compression deformation. Dealloying-driven NPG, a network constructed by bi-continuous nano-scaled ligaments and pores, can serve as a compression-tolerant substrate for PPy supercapacitor material. The electrochemical capacitance of NPG/PPy subjected to compression deformation is revealed to decrease at the scan rates and discharge current densities applied in this work. At the same time, the charge transfer resistance of NPG/PPy is found to increase. This electrochemical behavior is due to the locally reduced mass transport of electrolyte caused by the formation of new connections between the neighboring ligaments under the application of compression loads. The fundamental understanding of the effect of deformation on the performance of energy storage materials revealed in this study paves the way for their practical application in wearable devices.},
note = {Online available at: \url{https://dx.doi.org/10.3390/nano12132149} (DOI). Li, J.; Li, L.-Y.; Jia, P.; Okulov, I.V.: Electrochemical Behavior of Nanoporous Gold/Polypyrrole Supercapacitor under Deformation. In: Nanomaterials. Vol. 12 (2022) 13, 2149. (DOI:  /10.3390/nano12132149)}}
@article{ehrich_precipitation_evolution_2022, 
author={Ehrich, J. and Staron, P. and Karkar, A. and Roos, A. and Hanke, S.},
title={Precipitation Evolution in the Heat-Affected Zone and Coating Material of AA2024 Processed by Friction Surfacing},
year={2022},
journal = {Advanced Engineering Materials},
volume = {24},
number = {11},
pages = {2201019},
doi = {10.1002/adem.202201019},
abstract = {Herein, self-mating coating depositions are generated from Al–Cu–Mg alloy AA2024 by using the solid-state joining method, friction surfacing (FS). The precipitation evolution in the heat-affected zone (HAZ) of the substrate material and in the deposited coatings is analyzed using hardness mapping, temperature measurements, differential scanning calorimetry (DSC), transmission electron microscopy (TEM) as well as synchrotron small-angle X-Ray scattering (SAXS) used for mapping mean particle radius and particle volume fraction over the whole sample. Quantitative measurements of the thermal cycle using thermocouples positioned inside the substrate sheets reveal a distinguishing temperature distribution and a maximum temperature up to 420 °C close to the center of the bonding zone (BZ). The hardness distribution is frequently encountered in solid-state joining processes. It can be understood taking into account the complex modifications of the precipitate size distribution, including small Guinier–Preston–Bagaryatsky GPB (Al2CuMg)/Guinier–Preston GP(I) (Al2Cu)-zones and larger S′ (Al2CuMg)/θ′ (Al2Cu)-phases. Uniform precipitation of small and larger particles leads to an increase in hardness. It has become apparent that the highest hardness values within the HAZ are obtained when the volume fractions of small and larger particles are increased and equally distributed.},
note = {Online available at: \url{https://dx.doi.org/10.1002/adem.202201019} (DOI). Ehrich, J.; Staron, P.; Karkar, A.; Roos, A.; Hanke, S.: Precipitation Evolution in the Heat-Affected Zone and Coating Material of AA2024 Processed by Friction Surfacing. In: Advanced Engineering Materials. Vol. 24 (2022) 11, 2201019. (DOI:  /10.1002/adem.202201019)}}
@article{su_comparing_the_2022, 
author={Su, Y. and Li, W. and Shen, J. and Bergmann, L. and dos Santos, J.F. and Klusemann, B. and Vairis, A.},
title={Comparing the fatigue performance of Ti-4Al-0.005B titanium alloy T-joints, welded via different friction stir welding sequences},
year={2022},
journal = {Materials Science and Engineering: A},
volume = {859},
pages = {144227},
doi = {10.1016/j.msea.2022.144227},
abstract = {Ti–4Al-0.005B titanium alloy T-joints were produced with two different friction stir welding (FSW) sequences, and its effect on the low-cycle fatigue performance was investigated. Results show that hysteresis loop became a straight line with no significant fatigue damage occurring at low strain amplitudes (0.2% and 0.4%). As the strain amplitude increased to 0.6%, the area enclosed by the hysteresis loop increased for both T-joints and the base material (BM) due to fatigue damage accumulation. As the stress amplitude decreased gradually with increasing number of cycles, the fatigue life followed this decreasing trend. The fatigue life of single-weld T-joints is close to that of the double-weld T-joints, with a cyclic strain hardening index of the BM being in-between of the two T-joints. However, cyclic strength coefficient of BM is the lowest, and that of the double-weld T-joint is larger than that of the single-weld T-joint. The single-weld T-joint breaks at the heat affected zone (HAZ) on the advancing side, where the double-weld T-joint breaks at the HAZ of the second weld.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.msea.2022.144227} (DOI). Su, Y.; Li, W.; Shen, J.; Bergmann, L.; dos Santos, J.F.; Klusemann, B.; Vairis, A.: Comparing the fatigue performance of Ti-4Al-0.005B titanium alloy T-joints, welded via different friction stir welding sequences. In: Materials Science and Engineering: A. Vol. 859 (2022) 144227. (DOI:  /10.1016/j.msea.2022.144227)}}
@article{gachegova_influence_of_2022, 
author={Gachegova, E.A. and Sikhamov, R. and Ventzke, V. and Kashaev, N. and Plekhov, O.A.},
title={Influence of laser shock peening on low- and high-cycle fatigue of an OT4-0 titanium alloy},
year={2022},
journal = {Journal of Applied Mechanics and Technical Physics},
volume = {63},
number = {2},
pages = {335 - 342},
doi = {10.1134/S0021894422020171},
abstract = {Effect of laser shock peening on the fatigue life of an OT4-0 titanium alloy is studied. Laser peening is carried out using a Q-switched Nd:YAG laser operating at a pulse repetition rate of 10 Hz. It is suggested by the analysis of the effect of various laser treatment parameters on the magnitude and distribution of residual stresses over the sample thickness that an optimal type of laser shock treatment makes it possible to create a compressive residual stress region whose depth reaches up to 1 mm and whose maximum value is 600 MPa. The results of the study of the fracture surface structure show that the fatigue fracture mechanism changes, while the service life of samples significantly increases during both low- and high-cycle fatigue after laser shock peening.},
note = {Online available at: \url{https://dx.doi.org/10.1134/S0021894422020171} (DOI). Gachegova, E.A.; Sikhamov, R.; Ventzke, V.; Kashaev, N.; Plekhov, O.A.: Influence of laser shock peening on low- and high-cycle fatigue of an OT4-0 titanium alloy. In: Journal of Applied Mechanics and Technical Physics . Vol. 63 (2022) 2, 335 - 342. (DOI:  /10.1134/S0021894422020171)}}
@article{dahmene_dataset_from_2022, 
author={Dahmene, F. and Yaacoubi, S. and El Mountassir, M. and Porot, G. and Masmoudi, M. and Nennig, P. and Suhuddin, U. and dos Santos, J.},
title={Dataset from healthy and defective spot welds in refill friction stir spot welding using acoustic emission},
year={2022},
journal = {Data in Brief},
volume = {45},
pages = {108750},
doi = {10.1016/j.dib.2022.108750},
abstract = {The dataset presented in this paper deals with real-time measurements carried out during the welding of 78 spot welds including heathy and defective states. These measurements are composed of acoustic emission signals and welding parameters. Acoustic emission signals were captured by three different piezoelectric sensors, which are connected to a Vallen AMSY5 system through preamplifiers. Welding parameters where digitized using the M-SCOPE software. Both measurements can be used for the establishment of an automatic criterion able to detect defective spot welds in Refill Friction Stir Spot Welding.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.dib.2022.108750} (DOI). Dahmene, F.; Yaacoubi, S.; El Mountassir, M.; Porot, G.; Masmoudi, M.; Nennig, P.; Suhuddin, U.; dos Santos, J.: Dataset from healthy and defective spot welds in refill friction stir spot welding using acoustic emission. In: Data in Brief. Vol. 45 (2022) 108750. (DOI:  /10.1016/j.dib.2022.108750)}}
@article{cornec_numerical_analysis_2022, 
author={Cornec, A. and Lilleodden, E.},
title={Numerical analysis of micropillar compression behaviour and stress-strain curve estimation verified on glass fused silica},
year={2022},
journal = {Materials Today : Communications},
volume = {33},
pages = {104971},
doi = {10.1016/j.mtcomm.2022.104971},
abstract = {Microcompression testing became an incredibly popular approach to investigating the mechanical response of micro-scale volumes. Among many objectives, the determination of stress-strain relations from experimental force-displacement data is complicated, as compression micropillars are better considered as components a rather than samples, and an experimental force-displacement curve cannot be simply transferred to an accurate stress-strain curve. In this work the microcompression behaviour of fused silica – an amorphous, isotropic material – was investigated to quantitative the extent to which this novel approach can be used to achieve accurate stress-strain relations. Finite element simulations, assuming isotropic hyperelastic behaviour applied for an amorphous material, was essential in assessing the method, while also making comparison to experiments. Symmetric micropillars as well with imperfections were considered, combined with different friction coefficients to provide effects from e.g. slope of contact plane, inclined micropillar height, taper angle, or foot transition. For symmetric micropillars buckling phenomenon additionally occurred due to the predominant elastic deformation. Failure due to fracture was excluded in this approach. Based on the numerical simulations a sufficiently reliable, accurate, and verified approach was achieved providing the determination of stress-strain curves from experimental data and was also experimentally confirmed by a micropillar experiments. It is expected that the approach is also valid for other isotropic amorphous materials.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.mtcomm.2022.104971} (DOI). Cornec, A.; Lilleodden, E.: Numerical analysis of micropillar compression behaviour and stress-strain curve estimation verified on glass fused silica. In: Materials Today : Communications. Vol. 33 (2022) 104971. (DOI:  /10.1016/j.mtcomm.2022.104971)}}
@article{liu_phase_decomposition_2022, 
author={Liu, M. and Weissmüller, J.},
title={Phase decomposition in nanoporous Au-Pt},
year={2022},
journal = {Acta Materialia},
volume = {241},
pages = {118419},
doi = {10.1016/j.actamat.2022.118419},
abstract = {This study explores microstructure and phase decomposition in nanoporous Au-Pt made by dealloying. The starting alloy, , forms a uniform solid solution. Removing the Ag by dealloying at room temperature forms nanoporous equimolar Au-Pt with a ligament size as small as 4 nm. That alloy’s composition is in the Au-Pt phase diagram’s regime of spinodal instability. Surprisingly, in view of the instability and of the substantial atomic rearrangements accompanying dealloying, X-ray diffraction and transmission electron microscopy reveal a homogeneous single-phase state in the bulk of the nanoporous material. This can be traced back to enrichment of Pt at the surface, which depletes the bulk in Pt. The Pt-depleted bulk is in the metastable region of the alloy phase diagram, between the binodal and the spinodal. Annealing prompts curvature-driven coarsening by diffusion, diminishing the number of sites for Pt surface segregation. The ensuing enrichment of the bulk in Pt is accompanied by the formation first of crystallographically coherent, Pt-rich regions and later of semi-coherent regions of the Pt-rich phase. The morphology of the coherent regions is compatible with spinodal decomposition. Yet, the microstructure evolution pathway is nonstandard, since decomposition here concurs with rapid coarsening of the porous microstructure. Among the prospect of the nanoporous alloy are its high kinetic stability and the opportunity to tune the surface composition through the annealing temperature.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.actamat.2022.118419} (DOI). Liu, M.; Weissmüller, J.: Phase decomposition in nanoporous Au-Pt. In: Acta Materialia. Vol. 241 (2022) 118419. (DOI:  /10.1016/j.actamat.2022.118419)}}
@article{sandmann_influence_of_2022, 
author={Sandmann, P. and Keller, S. and Kashaev, N. and Ghouse, S. and Hooper, P. and Klusemann, B. and Davies, C.},
title={Influence of laser shock peening on the residual stresses in additively manufactured 316L by Laser Powder Bed Fusion: A combined experimental–numerical study},
year={2022},
journal = {Additive Manufacturing},
volume = {60},
pages = {103204},
doi = {10.1016/j.addma.2022.103204},
abstract = {Detrimental subsurface tensile residual stresses occur in laser powder bed fusion (LPBF) due to significant temperature gradients during the process. Besides heat treatments, laser shock peening (LSP) is a promising technology for tailoring residual stress profiles of additively manufactured components. A multi step process simulation is applied aiming at predicting the residual stress state after applying LSP to a cuboid shaped specimen manufactured by LPBF in two different building directions as well as comparing it with a post-build heat treatment. The validity of the numerical simulation is evaluated based on comparisons of residual stresses determined by incremental hole drilling technique within different stages of the multi step process: in the as-build condition, after subsequent heat treatment as well as after applying LSP to the as-build and heat treated specimens, showing overall a good experimental-numerical agreement throughout each of the process stages. Applying a heat treatment to the as-build LPBF sample at 700 °C for 6 h showed not to be effective in eliminating the surface tensile stress entirely, reducing the tensile residual stresses by 40%. However, the application of LSP on LPBF components showed promising results: LSP was able even to convert the detrimental near surface tensile residual stresses in the LPBF component into compressive residual stresses next to the surface, which is known to be beneficial for the fatigue performance.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.addma.2022.103204} (DOI). Sandmann, P.; Keller, S.; Kashaev, N.; Ghouse, S.; Hooper, P.; Klusemann, B.; Davies, C.: Influence of laser shock peening on the residual stresses in additively manufactured 316L by Laser Powder Bed Fusion: A combined experimental–numerical study. In: Additive Manufacturing. Vol. 60 (2022) 103204. (DOI:  /10.1016/j.addma.2022.103204)}}
@article{wang_wirebased_laser_2022, 
author={Wang, M. and Ventzke, V. and Kashaev, N.},
title={Wire-based laser directed energy deposition of AA7075: effect of process parameters on microstructure and mechanical properties},
year={2022},
journal = {Journal of Materials Research and Technology},
volume = {21},
pages = {388 - 403},
doi = {10.1016/j.jmrt.2022.09.051},
abstract = {The process development for wire-based laser directed energy deposition of AA7075 is studied. Thin-wall structures are produced to investigate the process-microstructure-mechanical performance relationship. By optimizing the process parameters and building strategies, the minimal porosity level of 0.8% and 0.3% can be achieved in the continuous and discontinuous building strategies, respectively. The porosity level exhibits a primary dependence on the specific energy and a secondary dependence on the ratio between wire feed rate and laser scan speed. Thin-wall structures show an average hardness of 115 HV0.1. In two optimized building strategies, the ultimate tensile strength of 400 MPa is achieved without the cost of ductility (fracture strain of 9.2%). Large columnar grains with preferential orientation and the distribution of secondary phases relative to the loading direction during tensile tests contribute to superior mechanical properties.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jmrt.2022.09.051} (DOI). Wang, M.; Ventzke, V.; Kashaev, N.: Wire-based laser directed energy deposition of AA7075: effect of process parameters on microstructure and mechanical properties. In: Journal of Materials Research and Technology. Vol. 21 (2022) 388 - 403. (DOI:  /10.1016/j.jmrt.2022.09.051)}}
@article{raza_modeling_of_2022, 
author={Raza, S. and Mittnacht, T. and Diyoke, G. and Schneider, D. and Nestler, B. and Klusemann, B.},
title={Modeling of temperature- and strain-driven intermetallic compound evolution in an Al–Mg system via a multiphase-field approach with application to refill friction stir spot welding},
year={2022},
journal = {Journal of the Mechanics and Physics of Solids},
volume = {169},
pages = {105059},
doi = {10.1016/j.jmps.2022.105059},
abstract = {The prospect of joining dissimilar materials via solid-state processes presents an opportunity to obtain multi-material structures having a synergy of desirable properties of the joined materials. However, the issue of the formation of intermetallic compounds at the weld interface of dissimilar materials arises with that, depending upon the temperature and pressure conditions as per phase diagram. As the thickness of the intermetallic compounds may determine the mechanical properties of the joint, understanding the driving mechanisms and evolution of these intermetallic compounds in solid-state joining processes, such as refill friction stir spot welding (refill FSSW), is crucial. In this contribution, we account for the effect of different driving forces in a multiphase-field approach and investigate the evolution of the intermetallic compounds driven by chemical and mechanical forces. A finite-element simulation of the refill FSSW is pursued to obtain the peak temperature and strain at different locations of the weld interface. The microstructure simulations obtained via the multiphase-field model give insight into the morphology and kinetics evolution of the intermetallic compounds for both, the absence of strain (purely chemically-driven model) as well as presence of strain (chemo-mechanically-driven model). The consideration of strain proves to result in thicker intermetallic compound layer. Furthermore, the impact of interface energy and initial grain configuration is found to be significant on the overall intermetallic compounds evolution.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jmps.2022.105059} (DOI). Raza, S.; Mittnacht, T.; Diyoke, G.; Schneider, D.; Nestler, B.; Klusemann, B.: Modeling of temperature- and strain-driven intermetallic compound evolution in an Al–Mg system via a multiphase-field approach with application to refill friction stir spot welding. In: Journal of the Mechanics and Physics of Solids. Vol. 169 (2022) 105059. (DOI:  /10.1016/j.jmps.2022.105059)}}
@article{wang_investigation_of_2022, 
author={Wang, M. and Kashaev, N.},
title={Investigation of process window for AA7075 considering effects of different wire feed directions in lateral Laser Metal Deposition},
year={2022},
journal = {Procedia CIRP},
volume = {111},
pages = {218 - 223},
doi = {10.1016/j.procir.2022.08.053},
abstract = {This work addresses the influences of the feed direction of AA7075 high-strength aluminum alloy in wire-based lateral laser metal deposition (LMD). The additive manufacturing process is investigated for the deposition of thin-walled structures. The interaction between wire and laser beam as well as the evolution of the melt pool are in-situ monitored by a high-speed camera. The consequences of different feed directions are analyzed in terms of processability, surface morphology, geometry, and porosity. Besides, the appropriate process parameters for AA7075 in lateral wire LMD are also studied. A maximal relative density level of about 99.7 % can be reached. No macro-cracks on the specimen surface or inside the specimen are observed. Optical microscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy are employed to characterize the microstructure and measure the chemical composition of specimen produced with the optimal process parameters. The plateau-like distribution of the hardness evolution and the uniform layer thickness in the middle of the thin-walled structure indicate that a stable LMD-process can be achieved.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.procir.2022.08.053} (DOI). Wang, M.; Kashaev, N.: Investigation of process window for AA7075 considering effects of different wire feed directions in lateral Laser Metal Deposition. In: Procedia CIRP. Vol. 111 (2022) 218 - 223. (DOI:  /10.1016/j.procir.2022.08.053)}}
@article{escobar_heterogenous_activation_2022, 
author={Escobar, J. and Gwalni, B. and Olszta, M. and Silverstein, J. and Ajantiwalay, T. and Overman, N. and Fu, W. and Li, Y. and Bergmann, L. and Maawad, E. and Klusemann, B. and dos Santos, J. and Devaraj, A.},
title={Heterogenous activation of dynamic recrystallization and twinning during friction stir processing of a Cu-4Nb alloy},
year={2022},
journal = {Journal of Alloys and Compounds},
volume = {928},
pages = {167007},
doi = {10.1016/j.jallcom.2022.167007},
abstract = {An interplay between high degree of shear deformation and deformation-induced heating occurs during friction stir processing (FSP) of metals. In medium-to-low stacking fault energy Cu alloys, this can lead to a complex spatially heterogenous activation of dynamic recrystallization (DRX) and twinning mechanisms. Within the Cu-Nb system, the presence of Nb is further expected to influence the DRX mechanism of the Cu matrix. However, the microstructural changes induced by the co-deformation of Nb during FSP are still not well understood. Therefore, this study uses a combination of multimodal microstructural characterization, solution thermodynamics-based predictions, and computational crystal plasticity simulation to reveal the various microstructural evolution mechanisms that can occur during FSP of a Cu-4at%Nb binary model alloy. The formation of softer DRX zones, and harder shear localization regions are revealed using electron backscatter diffraction, transmission electron microscopy, atom probe tomography, and crystal plasticity modeling.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jallcom.2022.167007} (DOI). Escobar, J.; Gwalni, B.; Olszta, M.; Silverstein, J.; Ajantiwalay, T.; Overman, N.; Fu, W.; Li, Y.; Bergmann, L.; Maawad, E.; Klusemann, B.; dos Santos, J.; Devaraj, A.: Heterogenous activation of dynamic recrystallization and twinning during friction stir processing of a Cu-4Nb alloy. In: Journal of Alloys and Compounds. Vol. 928 (2022) 167007. (DOI:  /10.1016/j.jallcom.2022.167007)}}
@article{azevedo_fatigue_behaviour_2022, 
author={Azevedo, L. and Kashaev, N. and Horstmann, C. and Ventzke, V. and Furtado, C. and Moreira, P. and Tavares, P.},
title={Fatigue behaviour of laser shock peened AISI D2 tool steel},
year={2022},
journal = {International Journal of Fatigue},
volume = {165},
pages = {107226},
doi = {10.1016/j.ijfatigue.2022.107226},
abstract = {Laser shock peening (LSP) is an advanced surface enhancement technique capable of imparting beneficial compressive residual stresses, thereby improving metal parts’ fatigue resistance and crack propagation resistance. This study presents the fatigue behaviour of AISI D2 tool steel samples subjected to LSP with a power density of 15 GW/cm2 and a double laser scanning sequence. The effect of LSP on quasi-static tensile properties was also addressed. The fatigue crack propagation was suppressed in LSP-treated samples when tested at = 10 MPa. The fatigue strength of treated samples was 32.9% higher compared to untreated samples. The LSP-treated samples have shown a larger fatigue fracture surface area than the as-received (AR) sample. In addition, the tendency to form secondary cracks in the fatigue fracture paths decreased due to LSP treatment. LSP treatment can effectively improve the fatigue resistance and crack propagation behaviour of AISI D2 steel. These improvements are due to significant compressive residual stresses in a superficial layer of the material. The present study provides a reference for improving the mechanical properties of AISI D2 steel by laser shock peening.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.ijfatigue.2022.107226} (DOI). Azevedo, L.; Kashaev, N.; Horstmann, C.; Ventzke, V.; Furtado, C.; Moreira, P.; Tavares, P.: Fatigue behaviour of laser shock peened AISI D2 tool steel. In: International Journal of Fatigue. Vol. 165 (2022) 107226. (DOI:  /10.1016/j.ijfatigue.2022.107226)}}
@article{henkelmann_selfdetachment_and_2022, 
author={Henkelmann, G. and Waldow, D. and Liu, M. and Lührs, L. and Li, Y. and Weissmüller, J.},
title={Self-Detachment and Subsurface Densification of Dealloyed Nanoporous Thin Films},
year={2022},
journal = {Nano Letters},
volume = {22},
number = {16},
pages = {6787 - 6793},
doi = {10.1021/acs.nanolett.2c02666},
abstract = {Experiment shows thin films of dealloyed nanoporous gold (NPG) spontaneously detaching from massive gold base layers. NPG can also densify near its external surface. This is naturally reproduced by kinetic Monte Carlo (KMC) simulation of dealloying and coarsening and so appears generic for nanoscale network materials evolving by surface diffusion. Near the porous layer’s external surface and near its interface with the base layer, gradients in the depth-profile of a laterally averaged mean surface curvature provide driving forces for diffusion and cause divergences of the net fluxes of matter, leading to accretion/densification or to erosion/disconnection. As a toy model, the morphology evolution of substrate-supported nanopillars by surface diffusion illustrates and confirms our considerations. Contrary to cylindrical nanowires, the ligaments in nanoporous materials exhibit pre-existing gradients in the mean curvature. The Plateau-Rayleigh long-wavelength stability criterion is then not applicable and the disconnection accelerated.},
note = {Online available at: \url{https://dx.doi.org/10.1021/acs.nanolett.2c02666} (DOI). Henkelmann, G.; Waldow, D.; Liu, M.; Lührs, L.; Li, Y.; Weissmüller, J.: Self-Detachment and Subsurface Densification of Dealloyed Nanoporous Thin Films. In: Nano Letters. Vol. 22 (2022) 16, 6787 - 6793. (DOI:  /10.1021/acs.nanolett.2c02666)}}
@article{cruzdasilva_numerical_investigation_2022, 
author={Cruz da Silva, Y. and Caminha Andrade, T. and Vieira de Oliveira Júnior, F. and dos Santos, J. and Marcondes, F. and Miranda, H. and Silva, C.},
title={Numerical investigation of dissimilar friction stir welding of AISI 304L and 410S stainless steels},
year={2022},
journal = {The International Journal of Advanced Manufacturing Technology},
volume = {121},
number = {3-4},
pages = {2721 - 2733},
doi = {10.1007/s00170-022-09283-0},
abstract = {Friction stir welding (FSW) has been successfully used to join dissimilar materials with advantages such as incipient chemical mixing and positive recrystallization of the microstructure. However, to understand how welding parameters affect the thermal cycle and the material flow around the tool is essential to produce joints without defects. In this work, a numerical simulation of dissimilar joints of AISI 304L austenitic stainless steel with AISI 410S ferritic stainless steel using the FSW technique was performed. The equations of the model were discretized by the finite volume method (FVM), and the mixture between the materials was modeled by the volume of fluid method (VOF) using the ANSYS-fluent simulator. The results predicted the temperatures during the welding for different conditions and viscosity changes successfully. Furthermore, they predicted a better combination of welding parameters in relation to flash formation. The VOF method predicted the mixture of the materials. Furthermore, the results indicated the location of each material and thus avoided unnecessary experimental tests.},
note = {Online available at: \url{https://dx.doi.org/10.1007/s00170-022-09283-0} (DOI). Cruz da Silva, Y.; Caminha Andrade, T.; Vieira de Oliveira Júnior, F.; dos Santos, J.; Marcondes, F.; Miranda, H.; Silva, C.: Numerical investigation of dissimilar friction stir welding of AISI 304L and 410S stainless steels. In: The International Journal of Advanced Manufacturing Technology. Vol. 121 (2022) 3-4, 2721 - 2733. (DOI:  /10.1007/s00170-022-09283-0)}}
@article{li_enhanced_electrochemical_2022, 
author={Li, J. and Markmann, J. and Mameka, N.},
title={Enhanced electrochemical actuation of nanoporous gold-polypyrrole hybrid under load},
year={2022},
journal = {Applied Physics Letters},
volume = {121},
number = {2},
pages = {021901},
doi = {10.1063/5.0093921},
abstract = {This work examines the actuation strain response of a nanoporous gold-polypyrrole electrochemical actuator under compression. The strain is monitored by in situ dilatometry and dynamic mechanical analysis when the material is wetted by an aqueous electrolyte and subjected to cyclic potential variation under various compressive loads ranging from −0.27 to −22.30 MPa. Contrary to previous studies that report reduced actuation amplitudes under load in the individual constituents of the material—nanoporous gold and polypyrrole, we find the strain amplitudes of the hybrid increase with increasing load and even while being deformed by plastic deformation. In this contribution, we discuss the phenomenon by taking into account the variations of the effective Young's modulus of the material that occur simultaneously with the actuation.},
note = {Online available at: \url{https://dx.doi.org/10.1063/5.0093921} (DOI). Li, J.; Markmann, J.; Mameka, N.: Enhanced electrochemical actuation of nanoporous gold-polypyrrole hybrid under load. In: Applied Physics Letters. Vol. 121 (2022) 2, 021901. (DOI:  /10.1063/5.0093921)}}
@article{decastro_tool_wear_2022, 
author={de Castro, C. and Shen, J. and Plaine, A. and Suhuddin, U. and de Alcantara, N. and dos Santos, J. and Klusemann, B.},
title={Tool wear mechanisms and effects on refill friction stir spot welding of AA2198-T8 sheets},
year={2022},
journal = {Journal of Materials Research and Technology : JMRT},
volume = {20},
pages = {857 - 866},
doi = {10.1016/j.jmrt.2022.07.092},
abstract = {Refill Friction Stir Spot Welding (refill FSSW) is a method for joining similar and dissimilar lightweight metallic materials or thermoplastic polymers. The technique produces welds that feature suitable mechanical properties with advantages such as the possibility of industrial scalability and automation. Still, some challenges need to be overcome in order to increase the adoption of this technique in industry. Tool wear is a key issue for friction-based processes, since it impacts the process costs and quality of the welds. In this study, a total of 2350 welds of AA2198-T8 sheets were performed and the effect of wear on probe and shoulder was investigated. While the probe did not suffer any considerable wear after this number of welds, the shoulder underwent wear in different areas, with distinct wear mechanisms. Adhesive wear and plastic deformation were determined as the primary damage mechanisms affecting different areas of the shoulder. Mechanical testing of selected welds has shown a trend towards reduction in the lap shear strength (LSS) as a function of tool wear. Macrostructural analysis of welds' geometrical features shows that profile changes at the shoulder due to wear led to a trend of reduction in stirred zone area and, consequently, joints’ LSS. Modifications in the worn shoulder profile were suggested as possible causes for changes in hook height, which was identified as a further determining factor to the observed reduction in LSS. Still, all tested welds surpassed the minimum lap shear strength standard requirements for aeronautical applications.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jmrt.2022.07.092} (DOI). de Castro, C.; Shen, J.; Plaine, A.; Suhuddin, U.; de Alcantara, N.; dos Santos, J.; Klusemann, B.: Tool wear mechanisms and effects on refill friction stir spot welding of AA2198-T8 sheets. In: Journal of Materials Research and Technology : JMRT. Vol. 20 (2022) 857 - 866. (DOI:  /10.1016/j.jmrt.2022.07.092)}}
@article{ozerov_laser_beam_2021, 
author={Ozerov, M. and Povolyaeva, E. and Stepanov, N. and Ventzke, V. and Dinse, R. and Kashaev, N. and Zherebtsov, S.},
title={Laser Beam Welding of a Ti-15Mo/TiB Metal–Matrix Composite},
year={2021},
journal = {Metals},
volume = {11},
number = {3},
pages = {506},
doi = {10.3390/met11030506},
abstract = {A Ti-15Mo/TiB metal–matrix composite was produced by spark plasma sintering at 1400 °C. The fractions of the elements in the initial powder mixture were 80.75 wt.% Ti, 14.25 wt.% Mo, and 5 wt.% TiB2. The initial structure of the synthesized composite was composed of bcc β titanium matrix and needle-like TiB reinforcements with an average thickness of 500 ± 300 nm. Microstructure and mechanical properties of the composite were studied after laser beam welding (LBW) was carried out at room temperature or various pre-heating temperatures: 200, 400, or 600 °C. The quality of laser beam welded joints was not found to be dependent noticeably on the pre-heating temperature; all welds consisted of pores the size of which reached 200–300 µm. In contrast to acicular individual particles in the base material, TiB whiskers in the weld zone were found to have a form of bunches. The maximum microhardness in the weld zone (~700 HV) was obtained after welding at room temperature or at 200 °C; this value was ~200 HV higher than that in the base material.},
note = {Online available at: \url{https://dx.doi.org/10.3390/met11030506} (DOI). Ozerov, M.; Povolyaeva, E.; Stepanov, N.; Ventzke, V.; Dinse, R.; Kashaev, N.; Zherebtsov, S.: Laser Beam Welding of a Ti-15Mo/TiB Metal–Matrix Composite. In: Metals. Vol. 11 (2021) 3, 506. (DOI:  /10.3390/met11030506)}}
@article{vicharapu_probing_underlying_2021, 
author={Vicharapu, B. and Lemos, G. and Bergmann, L. and dos Santos, J. and De, A. and Clarke, T.},
title={Probing underlying mechanisms for pcBN tool decay during friction stir welding of nickel-based alloys},
year={2021},
journal = {Tecnologia em Metalurgia, Materiais e Mineracao},
volume = {18},
pages = {e2455},
doi = {http://dx.doi.org/10.4322/2176-1523.20202455},
abstract = {Friction stir welding (FSW) of nickel-based alloys can provide joints with improved corrosion resistance and mechanical properties that are deteriorated significantly during fusion welding of these alloys. However, rapid wear and poor longevity of tools are major concerns for FSW of nickel-based alloys. Polycrystalline cubic Boron Nitride (pcBN) has emerged as an alternative tool material due to its enhanced strength and stiffness but its use for FSW of nickel-based alloys is rarely explored. An investigation is therefore undertaken to examine FSW of Inconel 625, which is a commonly used nickel-based alloy, by experimental investigation and computational process modelling. The potential failure mechanisms of pcBN tools during FSW of Inconel 625 are examined. The results showed that the thermal softening of the tungstenrhenium binder phase and dissolution of tungsten into Inconel 625 are potential mechanisms to early wear and failure of the pcBN tools for FSW of Inconel 625.},
note = {Online available at: \url{http://dx.doi.org/10.4322/2176-1523.20202455} (DOI). Vicharapu, B.; Lemos, G.; Bergmann, L.; dos Santos, J.; De, A.; Clarke, T.: Probing underlying mechanisms for pcBN tool decay during friction stir welding of nickel-based alloys. In: Tecnologia em Metalurgia, Materiais e Mineracao. Vol. 18 (2021)  e2455. (DOI:  10.4322/2176-1523.20202455)}}
@article{spoerkerdely_exploring_structural_2021, 
author={Spoerk-Erdely, P. and Staron, P. and Liu, J. and Kashaev, N. and Stark, A. and Hauschildt, K. and Maawad, E. and Mayer, S. and Clemens, H.},
title={Exploring Structural Changes, Manufacturing, Joining, and Repair of Intermetallic γ-TiAl-Based Alloys: Recent Progress Enabled by In Situ Synchrotron X-Ray Techniques},
year={2021},
journal = {Advanced Engineering Materials},
volume = {23},
number = {11},
pages = {2000947},
doi = {10.1002/adem.202000947},
abstract = {Intermetallic γ‐TiAl‐based alloys are a promising class of materials for lightweight high‐temperature applications. Following intensive research and development activities, they have recently entered service in the automotive and aircraft engine industries. In the course of the past decades, the development of these complex multiphase alloys has benefited considerably from the application of (in situ) X‐ray scattering and diffraction techniques. Herein, a practical introduction and overview of recent progress in this field of research are provided. In particular, four case studies taken from various stages in the alloy development (i.e., fundamental research—manufacturing, joining, and repair—and application) illustrate current prospects at modern synchrotron radiation sources, including detailed information on available setups for in situ high‐energy X‐ray diffraction and small‐angle X‐ray scattering experiments and a discussion of potential limitations in the use of these techniques.},
note = {Online available at: \url{https://dx.doi.org/10.1002/adem.202000947} (DOI). Spoerk-Erdely, P.; Staron, P.; Liu, J.; Kashaev, N.; Stark, A.; Hauschildt, K.; Maawad, E.; Mayer, S.; Clemens, H.: Exploring Structural Changes, Manufacturing, Joining, and Repair of Intermetallic γ-TiAl-Based Alloys: Recent Progress Enabled by In Situ Synchrotron X-Ray Techniques. In: Advanced Engineering Materials. Vol. 23 (2021) 11, 2000947. (DOI:  /10.1002/adem.202000947)}}
@article{schwab_tailoring_of_2021, 
author={Schwab, K. and Keller, S. and Kashaev, N. and Klusemann, B.},
title={Tailoring of residual stresses by specific use of defined prestress during laser shock peening},
year={2021},
journal = {Journal of Materials Processing Technology},
volume = {295},
pages = {117154},
doi = {10.1016/j.jmatprotec.2021.117154},
abstract = {The aim of the present study is to tailor laser shock peening-induced residual stresses by applying defined prestress. For this purpose, elastic prestress is introduced during laser shock peening application and subsequently released. The influence of prestress on the resulting residual stresses is investigated experimentally by a four-point bending device that allows to prestress the specimen during laser shock peening. Furthermore, a semi-analytical model of laser shock peening, extended by a contribution accounting for the prestress, is used to determine the prestress—residual stress relationship. A linear relation between prestress and compressive residual stress is found when the resulting compressive residual stresses are in the range of 20% to 100% of the yield strength. Generally, tensile prestress leads to a higher magnitude and penetration depth of resulting compressive residual stress after laser shock peening. As a proof of concept, prestress was used to alter a non-equibiaxial residual stress profile into an equibiaxial one, demonstrating the applicability of prestress as effective tool for residual stress design.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jmatprotec.2021.117154} (DOI). Schwab, K.; Keller, S.; Kashaev, N.; Klusemann, B.: Tailoring of residual stresses by specific use of defined prestress during laser shock peening. In: Journal of Materials Processing Technology. Vol. 295 (2021) 117154. (DOI:  /10.1016/j.jmatprotec.2021.117154)}}
@article{seiler_phasefield_modelling_2021, 
author={Seiler, M. and Keller, S. and Kashaev, N. and Klusemann, B. and Kästner, M.},
title={Phase-field modelling for fatigue crack growth under laser shock peening-induced residual stresses},
year={2021},
journal = {Archive of Applied Mechanics},
volume = {91},
number = {8},
pages = {3709 - 3723},
doi = {10.1007/s00419-021-01897-2},
abstract = {For the fatigue life of thin-walled components, not only fatigue crack initiation, but also crack growth is decisive. The phase-field method for fracture is a powerful tool to simulate arbitrary crack phenomena. Recently, it has been applied to fatigue fracture. Those models pose an alternative to classical fracture-mechanical approaches for fatigue life estimation. In the first part of this paper, the parameters of a phase-field fatigue model are calibrated and its predictions are compared to results of fatigue crack growth experiments of aluminium sheet material. In the second part, compressive residual stresses are introduced into the components with the help of laser shock peening. It is shown that those residual stresses influence the crack growth rate by retarding and accelerating the crack. In order to study these fatigue mechanisms numerically, a simple strategy to incorporate residual stresses in the phase-field fatigue model is presented and tested with experiments. The study shows that the approach can reproduce the effects of the residual stresses on the crack growth rate.},
note = {Online available at: \url{https://dx.doi.org/10.1007/s00419-021-01897-2} (DOI). Seiler, M.; Keller, S.; Kashaev, N.; Klusemann, B.; Kästner, M.: Phase-field modelling for fatigue crack growth under laser shock peening-induced residual stresses. In: Archive of Applied Mechanics. Vol. 91 (2021) 8, 3709 - 3723. (DOI:  /10.1007/s00419-021-01897-2)}}
@article{abbaszadeh_compression_behaviour_2021, 
author={Abbaszadeh, M. and Ventzke, V. and Neto, L. and Riekehr, S. and Martina, F. and Kashaev, N. and Hönnige, J. and Williams, S. and Klusemann, B.},
title={Compression Behaviour of Wire + Arc Additive Manufactured Structures},
year={2021},
journal = {Metals},
volume = {11},
number = {6},
pages = {877},
doi = {10.3390/met11060877},
abstract = {Increasing demand for producing large-scale metal components via additive manufacturing requires relatively high building rate processes, such as wire + arc additive manufacturing (WAAM). For the industrial implementation of this technology, a throughout understanding of material behaviour is needed. In the present work, structures of Ti-6Al-4V, AA2319 and S355JR steel fabricated by means of WAAM were investigated and compared with respect to their mechanical and microstructural properties, in particular under compression loading. The microstructure of WAAM specimens is assessed by scanning electron microscopy, electron back-scatter diffraction, and optical microscopy. In Ti-6Al-4V, the results show that the presence of the basal and prismatic crystal planes in normal direction lead to an anisotropic behaviour under compression. Although AA2319 shows initially an isotropic plastic behaviour, the directional porosity distribution leads to an anisotropic behaviour at final stages of the compression tests before failure. In S355JR steel, isotropic mechanical behaviour is observed due to the presence of a relatively homogeneous microstructure. Microhardness is related to grain morphology variations, where higher hardness near the inter-layer grain boundaries for Ti-6Al-4V and AA2319 as well as within the refined regions in S355JR steel is observed. In summary, this study analyzes and compares the behaviour of three different materials fabricated by WAAM under compression loading, an important loading condition in mechanical post-processing techniques of WAAM structures, such as rolling. In this regard, the data can also be utilized for future modelling activities in this direction.},
note = {Online available at: \url{https://dx.doi.org/10.3390/met11060877} (DOI). Abbaszadeh, M.; Ventzke, V.; Neto, L.; Riekehr, S.; Martina, F.; Kashaev, N.; Hönnige, J.; Williams, S.; Klusemann, B.: Compression Behaviour of Wire + Arc Additive Manufactured Structures. In: Metals. Vol. 11 (2021) 6, 877. (DOI:  /10.3390/met11060877)}}
@article{huber_a_strategy_2021, 
author={Huber, N.},
title={A Strategy for Dimensionality Reduction and Data Analysis Applied to Microstructure–Property Relationships of Nanoporous Metals},
year={2021},
journal = {Materials},
volume = {14},
number = {8},
pages = {1822},
doi = {10.3390/ma14081822},
abstract = {Nanoporous metals, with their complex microstructure, represent an ideal candidate for the development of methods that combine physics, data, and machine learning. The preparation of nanporous metals via dealloying allows for tuning of the microstructure and macroscopic mechanical properties within a large design space, dependent on the chosen dealloying conditions. Specifically, it is possible to define the solid fraction, ligament size, and connectivity density within a large range. These microstructural parameters have a large impact on the macroscopic mechanical behavior. This makes this class of materials an ideal science case for the development of strategies for dimensionality reduction, supporting the analysis and visualization of the underlying structure–property relationships. Efficient finite element beam modeling techniques were used to generate ~200 data sets for macroscopic compression and nanoindentation of open pore nanofoams. A strategy consisting of dimensional analysis, principal component analysis, and machine learning allowed for data mining of the microstructure–property relationships. It turned out that the scaling law of the work hardening rate has the same exponent as the Young’s modulus. Simple linear relationships are derived for the normalized work hardening rate and hardness. The hardness to yield stress ratio is not limited to 1, as commonly assumed for foams, but spreads over a large range of values from 0.5 to 3.},
note = {Online available at: \url{https://dx.doi.org/10.3390/ma14081822} (DOI). Huber, N.: A Strategy for Dimensionality Reduction and Data Analysis Applied to Microstructure–Property Relationships of Nanoporous Metals. In: Materials. Vol. 14 (2021) 8, 1822. (DOI:  /10.3390/ma14081822)}}
@article{bock_hybrid_modelling_2021, 
author={Bock, F. and Keller, S. and Huber, N. and Klusemann, B.},
title={Hybrid Modelling by Machine Learning Corrections of Analytical Model Predictions towards High-Fidelity Simulation Solutions},
year={2021},
journal = {Materials},
volume = {14},
number = {8},
pages = {1883},
doi = {10.3390/ma14081883},
abstract = {Within the fields of materials mechanics, the consideration of physical laws in machine learning predictions besides the use of data can enable low prediction errors and robustness as opposed to predictions only based on data. On the one hand, exclusive utilization of fundamental physical relationships might show significant deviations in their predictions compared to reality, due to simplifications and assumptions. On the other hand, using only data and neglecting well-established physical laws can create the need for unreasonably large data sets that are required to exhibit low bias and are usually expensive to collect. However, fundamental but simplified physics in combination with a corrective model that compensates for possible deviations, e.g., to experimental data, can lead to physics-based predictions with low prediction errors, also despite scarce data. In this article, it is demonstrated that a hybrid model approach consisting of a physics-based model that is corrected via an artificial neural network represents an efficient prediction tool as opposed to a purely data-driven model. In particular, a semi-analytical model serves as an efficient low-fidelity model with noticeable prediction errors outside its calibration domain. An artificial neural network is used to correct the semi-analytical solution towards a desired reference solution provided by high-fidelity finite element simulations, while the efficiency of the semi-analytical model is maintained and the applicability range enhanced. We utilize residual stresses that are induced by laser shock peening as a use-case example. In addition, it is shown that non-unique relationships between model inputs and outputs lead to high prediction errors and the identification of salient input features via dimensionality analysis is highly beneficial to achieve low prediction errors. In a generalization task, predictions are also outside the process parameter space of the training region while remaining in the trained range of corrections. The corrective model predictions show substantially smaller errors than purely data-driven model predictions, which illustrates one of the benefits of the hybrid modelling approach. Ultimately, when the amount of samples in the data set is reduced, the generalization of the physics-related corrective model outperforms the purely data-driven model, which also demonstrates efficient applicability of the proposed hybrid modelling approach to problems where data is scarce.},
note = {Online available at: \url{https://dx.doi.org/10.3390/ma14081883} (DOI). Bock, F.; Keller, S.; Huber, N.; Klusemann, B.: Hybrid Modelling by Machine Learning Corrections of Analytical Model Predictions towards High-Fidelity Simulation Solutions. In: Materials. Vol. 14 (2021) 8, 1883. (DOI:  /10.3390/ma14081883)}}
@article{zhang_recent_trends_2021, 
author={Zhang, X. and Lilleodden, E. and Wang, J.},
title={Recent trends on studies of nanostructured metals },
year={2021},
journal = {MRS Bulletin},
volume = {46},
number = {3},
pages = {217 - 224},
doi = {10.1557/s43577-021-00069-5},
abstract = {Nanostructured metals have been intensively investigated as these materials have abundant interfaces (grain boundaries and phase boundaries) that can drastically impact the mechanical and physical properties of materials. Significant research has been performed to understand the deformation mechanisms of nanostructured metals, and many of the major findings have been adopted by industry for the manufacturing of advanced materials for various applications. In this article, we highlight several recent breakthroughs and briefly introduce the focus of the articles in this issue that provide a more in-depth understanding of the forefronts of the field. Finally, we point out some of the research directions that may warrant further investigations.},
note = {Online available at: \url{https://dx.doi.org/10.1557/s43577-021-00069-5} (DOI). Zhang, X.; Lilleodden, E.; Wang, J.: Recent trends on studies of nanostructured metals . In: MRS Bulletin. Vol. 46 (2021) 3, 217 - 224. (DOI:  /10.1557/s43577-021-00069-5)}}
@article{bock_experimental_and_2021, 
author={Bock, F. and Herrnring, J. and Froend, M. and Enz, J. and Kashaev, N. and Klusemann, B.},
title={Experimental and numerical thermo-mechanical analysis of wire-based laser metal deposition of Al-Mg alloys},
year={2021},
journal = {Journal of Manufacturing Processes},
volume = {64},
pages = {982 - 995},
doi = {10.1016/j.jmapro.2021.02.016},
abstract = {A finite element model is employed to perform a sequentially coupled thermo-mechanical analysis for enabling rapid process simulations of temperature fields, residual stresses and distortions for the production of additively manufactured parts via laser metal deposition. Experimental identification of characteristic process features such as temperature distribution, melt pool dimensions and bead geometries were used for the initial built-up and calibration of the model. The addition of material during process simulation is realised through reactivating inactive elements during the transient heat transfer analysis and through reactivating a combination of inactive and quiet elements during the mechanical analysis. The travelling heat source is geometrically bounded to precisely control the volume of its energy distribution. The results of the transient heat transfer analysis are sequentially coupled to a mechanical analysis for obtaining information on the resulting residual stresses and deformation. Based on the good agreement between numerical and experimental results of the thermal analysis, conclusions on the corresponding residual stress distributions and deformation are made. It is shown that the model represents an efficient tool for process prediction regarding thermal history, residual stresses and final-part deformations. Finally, the model is utilised to identify parameters and conditions of the process that lead to reduced residual stresses and deformations of the investigated additive part.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jmapro.2021.02.016} (DOI). Bock, F.; Herrnring, J.; Froend, M.; Enz, J.; Kashaev, N.; Klusemann, B.: Experimental and numerical thermo-mechanical analysis of wire-based laser metal deposition of Al-Mg alloys. In: Journal of Manufacturing Processes. Vol. 64 (2021) 982 - 995. (DOI:  /10.1016/j.jmapro.2021.02.016)}}
@article{alhamdany_tube_drawing_2021, 
author={Al-Hamdany, N. and Salih, M. and Palkowski, H. and Carradò, A. and Gan, W. and Schell, N. and Brokmeier, H.},
title={Tube Drawing with Tilted Die: Texture, Dislocation Density and Mechanical Properties},
year={2021},
journal = {Metals},
volume = {11},
number = {4},
pages = {638},
doi = {10.3390/met11040638},
abstract = {Anisotropic behavior is a key characteristic for understanding eccentricity in tubes. In this paper, the effect of using a tilted die during tube drawing on eccentricity, texture, dislocation density, and mechanical properties is shown. Copper tubes were drawn with a ±5° tilted die for two passes. The increase or decrease in eccentricity can be controlled by controlling the angle of the tilted die. Two types of textures have been developed during tube drawing, namely plane strain and uniaxial types. Plain strain type texture is mainly characterized by the β fiber with a dominant copper component {112}<111>. The uniaxial deformation type is dominated by the <111> fiber, as commonly found by wire drawing. Texture sharpness increases with increasing drawing strain, and the texture varies significantly between the maximum and minimum wall thickness. This texture variation between maximum and minimum wall thickness has no significant influence on mechanical properties, which are more or less similar, but the increase in strength after each drawing pass is apparent. The dislocation density is low for the as-received tubes due to recovery and recrystallization. This is consistent with the as-received texture dominated by the cube component {001}<100>. During tube drawing, dislocation density increases as a function of the deformation strain. The variation of dislocation density between the maximum and minimum wall thickness in the tube deformed with −5° tilted die is higher than the variation in the tube deformed with +5° tilted die.},
note = {Online available at: \url{https://dx.doi.org/10.3390/met11040638} (DOI). Al-Hamdany, N.; Salih, M.; Palkowski, H.; Carradò, A.; Gan, W.; Schell, N.; Brokmeier, H.: Tube Drawing with Tilted Die: Texture, Dislocation Density and Mechanical Properties. In: Metals. Vol. 11 (2021) 4, 638. (DOI:  /10.3390/met11040638)}}
@article{shi_scaling_behavior_2021, 
author={Shi, S. and Li, Y. and Ngo-Dinh, B. and Markmann, J. and Weissmüller, J.},
title={Scaling behavior of stiffness and strength of hierarchical network nanomaterials},
year={2021},
journal = {Science},
volume = {371},
number = {6533},
pages = {1026 - 1033},
doi = {10.1126/science.abd9391},
abstract = {Structural hierarchy can enhance the mechanical behavior of materials and systems. This is exemplified by the fracture toughness of nacre or enamel in nature and by human-made architected microscale network structures. Nanoscale structuring promises further strengthening, yet macroscopic bodies built this way contain an immense number of struts, calling for scalable preparation schemes. In this work, we demonstrated macroscopic hierarchical network nanomaterials made by the self-organization processes of dealloying. Their hierarchical architecture affords enhanced strength and stiffness at a given solid fraction, and it enables reduced solid fractions by dealloying. Scaling laws for the mechanics and atomistic simulation support the observations. Because they expose the systematic benefits of hierarchical structuring in nanoscale network structures, our materials may serve as prototypes for future lightweight structural materials.},
note = {Online available at: \url{https://dx.doi.org/10.1126/science.abd9391} (DOI). Shi, S.; Li, Y.; Ngo-Dinh, B.; Markmann, J.; Weissmüller, J.: Scaling behavior of stiffness and strength of hierarchical network nanomaterials. In: Science. Vol. 371 (2021) 6533, 1026 - 1033. (DOI:  /10.1126/science.abd9391)}}
@article{wen_assessing_the_2021, 
author={Wen, Q. and Li, W. and Patel, V. and Bergmann, L. and Klusemann, B. and dos Santos, J.},
title={Assessing the Bonding Interface Characteristics and Mechanical Properties of Bobbin Tool Friction Stir Welded Dissimilar Aluminum Alloy Joints},
year={2021},
journal = {Acta Metallurgica Sinica (English Letters)},
volume = {34},
pages = {125 - 134},
doi = {10.1007/s40195-020-01101-4},
abstract = {This study focuses on the bonding interface characteristics and mechanical properties of the bobbin tool friction stir welded dissimilar AA6056 and AA2219 aluminum alloy joints using different welding speeds. Voids arise solely in the stir zone at the AA2219 side. A distinct boundary with limited material mixing develops at the middle section of the bonding interface, while excellent material mixing with an irregularly jagged pattern forms at the top and bottom sections of the bonding interface. Increasing the welding speed, the material mixing is rarely changed at the middle section in comparison with the bottom section. Furthermore, a small difference between Guinier–Preston dissolution and Q phase precipitation leads to rare change of hardness in the heat affected zone (HAZ) at the AA6056 side. The increased hardness of the HAZ at the AA2219 side is attributed to avoidance of the dissolution of θ″ phase precipitates. A maximum tensile strength of 181 MPa is obtained at 300 mm min−1. Fractures occur at the AA6056 side near the top and bottom surfaces and at the bonding interface in the middle section of the joints. The regions close to the top and bottom surfaces of the joints show a better ductility.},
note = {Online available at: \url{https://dx.doi.org/10.1007/s40195-020-01101-4} (DOI). Wen, Q.; Li, W.; Patel, V.; Bergmann, L.; Klusemann, B.; dos Santos, J.: Assessing the Bonding Interface Characteristics and Mechanical Properties of Bobbin Tool Friction Stir Welded Dissimilar Aluminum Alloy Joints. In: Acta Metallurgica Sinica (English Letters). Vol. 34 (2021) 125 - 134. (DOI:  /10.1007/s40195-020-01101-4)}}
@article{zerbst_damage_tolerant_2021, 
author={Zerbst, U. and Bruno, G. and Buffiere, Y. and Wegener, T. and Wu, T. and Zhang, X. and Kashaev, N. and Meneghetti, G. and Hrabe, N. and Madia, M. and Werner, T. and Hilgenberg, K. and Koukolíková, M. and Procházka, R. and Džugan, J. and Möller, B. and Beretta, S. and Evans, A. and Wagener, R. and Schnabel, K.},
title={Damage tolerant design of additively manufactured metallic components subjected to cyclic loading: State of the art and challenges},
year={2021},
journal = {Progress in Materials Science},
volume = {121},
pages = {100786},
doi = {10.1016/j.pmatsci.2021.100786},
abstract = {Undoubtedly, a better understanding and the further development of approaches for damage tolerant component design of AM parts are among the most significant challenges currently facing the use of these new technologies.

This article presents a thorough overview of the workshop discussions. It aims to provide a review of the parameters affecting the damage tolerance of parts produced by additive manufacturing (shortly, AM parts) with special emphasis on the process parameters intrinsic to the AM technologies, the resulting defects and the residual stresses. Based on these aspects, basic concepts are reviewed and critically discussed specifically for AM materials:

-

    Criteria for damage tolerant component design;
-

    Criteria for the determination of fatigue and fracture properties;
-

    Strategies for the determination of the fatigue life in dependence of different manufacturing conditions;
-

    Methods for the quantitative characterization of microstructure and defects;
-

    Methods for the determination of residual stresses;
-

    Effect of the defects and the residual stresses on the fatigue life and behaviour.

We see that many of the classic concepts need to be expanded in order to fit with the particular microstructure (grain size and shape, crystal texture) and defect distribution (spatial arrangement, size, shape, amount) present in AM (in particular laser powder bed fusion). For instance, 3D characterization of defects becomes essential, since the defect shapes in AM are diverse and impact the fatigue life in a different way than in the case of conventionally produced components. Such new concepts have immediate consequence on the way one should tackle the determination of the fatigue life of AM parts; for instance, since a classification of defects and a quantification of the tolerable shapes and sizes is still missing, a new strategy must be defined, whereby theoretical calculations (e.g. FEM) allow determining the maximum tolerable defect size, and non-destructive testing (NDT) techniques are required to detect whether such defects are indeed present in the component. Such examples show how component design, damage and failure criteria, and characterization (and/or NDT) become for AM parts fully interlinked. We conclude that the homogenization of these fields represents the current challenge for the engineer and the materials scientist.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.pmatsci.2021.100786} (DOI). Zerbst, U.; Bruno, G.; Buffiere, Y.; Wegener, T.; Wu, T.; Zhang, X.; Kashaev, N.; Meneghetti, G.; Hrabe, N.; Madia, M.; Werner, T.; Hilgenberg, K.; Koukolíková, M.; Procházka, R.; Džugan, J.; Möller, B.; Beretta, S.; Evans, A.; Wagener, R.; Schnabel, K.: Damage tolerant design of additively manufactured metallic components subjected to cyclic loading: State of the art and challenges. In: Progress in Materials Science. Vol. 121 (2021) 100786. (DOI:  /10.1016/j.pmatsci.2021.100786)}}
@article{huber_modelling_the_2021, 
author={Huber, N. and Beirau, T.},
title={Modelling the effect of intrinsic radiation damage on mechanical properties: The crystalline-to-amorphous transition in zircon},
year={2021},
journal = {Scripta Materialia},
volume = {197},
pages = {113789},
doi = {10.1016/j.scriptamat.2021.113789},
abstract = {Mechanical modelling using the level-cut Gaussian random field approach has been employed to simulate the effect of radiation induced amorphization on the Young´s modulus, Poisson´s ratio and hardness of zircon (ZrSiO4). A good agreement with previous nanoindentation experiments has been achieved. Two percolation transitions occur at ~16% and ~84% amorphous volume fraction, leading to deviations from linearity in the evolution of the Young´s modulus. Interface regions between crystalline and amorphous areas stabilise the hardness for a considerable amount of amorphous fraction. The modelling approach is promising for predicting the intrinsic radiation damage related evolution of the mechanical properties of various materials.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.scriptamat.2021.113789} (DOI). Huber, N.; Beirau, T.: Modelling the effect of intrinsic radiation damage on mechanical properties: The crystalline-to-amorphous transition in zircon. In: Scripta Materialia. Vol. 197 (2021) 113789. (DOI:  /10.1016/j.scriptamat.2021.113789)}}
@article{schnabel_crystal_plasticity_2021, 
author={Schnabel, J. and Scheider, I.},
title={Crystal Plasticity Modeling of Creep in Alloys with Lamellar Microstructures at the Example of Fully Lamellar TiAl},
year={2021},
journal = {Frontiers in Materials},
volume = {7},
pages = {581187},
doi = {10.3389/fmats.2020.581187},
abstract = {A crystal plasticity model of the creep behavior of alloys with lamellar microstructures is presented. The model is based on the additive decomposition of the plastic strain into a part that describes the instantaneous (i.e., high strain rate) plastic response due to loading above the yield point, and a part that captures the viscoplastic deformation at elevated temperatures. In order to reproduce the transition from the primary to the secondary creep stage in a physically meaningful way, the competition between work hardening and recovery is modeled in terms of the evolving dislocation density. The evolution model for the dislocation density is designed to account for the significantly different free path lengths of slip systems in lamellar microstructures depending on their orientation with respect to the lamella interface. The established model is applied to reproduce and critically discuss experimental findings on the creep behavior of polysynthetically twinned TiAl crystals. Although the presented crystal plasticity model is designed with the creep behavior of fully lamellar TiAl in mind, it is by no means limited to these specific alloys. The constitutive model and many of the discussed assumptions also apply to the creep behavior of other crystalline materials with lamellar microstructures.},
note = {Online available at: \url{https://dx.doi.org/10.3389/fmats.2020.581187} (DOI). Schnabel, J.; Scheider, I.: Crystal Plasticity Modeling of Creep in Alloys with Lamellar Microstructures at the Example of Fully Lamellar TiAl. In: Frontiers in Materials. Vol. 7 (2021) 581187. (DOI:  /10.3389/fmats.2020.581187)}}
@article{kashaev_effect_of_2021, 
author={Kashaev, N. and Groth, A. and Ventzke, V. and Horstmann, M. and Riekehr, S. and Staron, P. and Huber, N.},
title={Effect of laser heating on mechanical properties, residual stresses and retardation of fatigue crack growth in AA2024},
year={2021},
journal = {Fatigue and Fracture of Engineering Materials and Structures},
volume = {44},
number = {4},
pages = {887 - 900},
doi = {10.1111/ffe.13400},
abstract = {Local laser heating treatment using a defocussed laser beam was applied to the surface of 2‐mm‐thick AA2024‐T3 sheets. Two different treatment designs—namely, lines and circles—as well as the positioning and number of treatments were investigated regarding their potential to retard the propagation of through‐thickness fatigue cracks. The highest fatigue crack growth life extension of 285% was achieved by the application of four laser heating lines or two circles on each specimen side. The induced compressive residual stress field through the LH process is primarily responsible for an improvement in fatigue crack growth life. An emphasis was placed on investigating the effect of the treatment on the possible reduction of tensile and fatigue strength (S‐N life). If only one line was applied transverse to the loading direction or only one circle was used, the reduction of fatigue strength was comparable to the reduction of fatigue strength resulting from the stress concentration introduced due to the presence of a rivet hole.},
note = {Online available at: \url{https://dx.doi.org/10.1111/ffe.13400} (DOI). Kashaev, N.; Groth, A.; Ventzke, V.; Horstmann, M.; Riekehr, S.; Staron, P.; Huber, N.: Effect of laser heating on mechanical properties, residual stresses and retardation of fatigue crack growth in AA2024. In: Fatigue and Fracture of Engineering Materials and Structures. Vol. 44 (2021) 4, 887 - 900. (DOI:  /10.1111/ffe.13400)}}
@article{linka_constitutive_artificial_2021, 
author={Linka, K. and Hillgärtner, M. and Abdolazizi, K. and Aydin, R. and Itskov, M. and Cyron, C.},
title={Constitutive artificial neural networks: A fast and general approach to predictive data-driven constitutive modeling by deep learning},
year={2021},
journal = {Journal of Computational Physics},
volume = {429},
pages = {110010},
doi = {10.1016/j.jcp.2020.110010},
abstract = {In this paper we introduce constitutive artificial neural networks (CANNs), a novel machine learning architecture for data-driven modeling of the mechanical constitutive behavior of materials. CANNs are able to incorporate by their very design information from three different sources, namely stress-strain data, theoretical knowledge from materials theory, and diverse additional information (e.g., about microstructure or materials processing). CANNs can easily and efficiently be implemented in standard computational software. They require only a low-to-moderate amount of training data and training time to learn without human guidance the constitutive behavior also of complex nonlinear and anisotropic materials. Moreover, in a simple academic example we demonstrate how the input of microstructural data can endow CANNs with the ability to describe not only the behavior of known materials but to predict also the properties of new materials where no stress-strain data are available yet. This ability may be particularly useful for the future in-silico design of new materials. The developed source code of the CANN architecture and accompanying example data sets are available at https://github.com/ConstitutiveANN/CANN.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jcp.2020.110010} (DOI). Linka, K.; Hillgärtner, M.; Abdolazizi, K.; Aydin, R.; Itskov, M.; Cyron, C.: Constitutive artificial neural networks: A fast and general approach to predictive data-driven constitutive modeling by deep learning. In: Journal of Computational Physics. Vol. 429 (2021) 110010. (DOI:  /10.1016/j.jcp.2020.110010)}}
@article{keller_application_of_2021, 
author={Keller, S. and Klusemann, B.},
title={Application of stress intensity factor superposition in residual stress fields considering crack closure},
year={2021},
journal = {Engineering Fracture Mechanics},
volume = {243},
pages = {107415},
doi = {10.1016/j.engfracmech.2020.107415},
abstract = {The correlation between stress intensity factor (SIF) range and fatigue crack growth is a powerful tool for fail–safe design approaches applied to lightweight structures. The key role is the precise calculation of the SIFs of fatigue load cycles. Advanced material processing can shape residual stresses and make the SIF calculation a challenging task. While the consideration of tensile residual stresses is successfully tackled by the SIF superposition, the treatment of compressive residual stresses needs still clarification. This work demonstrates the application of the SIF superposition principle in regions containing high compressive residual stresses leading to crack closure effects. Crack closure depends on the combined load of residual and applied stresses and is interpreted as a change of crack geometry in this work. Thus the relation between the source, i.e. the applied or residual stress, and its consequence, i.e. the corresponding SIFs, depends on the interaction of the sources, i.e. the combined load. Due to this interaction, residual stress–induced changes of the fatigue behaviour cannot be linked to the residual or applied SIF only. This work proposes two alternative definitions of applied and residual SIF, allowing a clear correlation between either the residual or the applied SIF to fatigue behaviour changes.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.engfracmech.2020.107415} (DOI). Keller, S.; Klusemann, B.: Application of stress intensity factor superposition in residual stress fields considering crack closure. In: Engineering Fracture Mechanics. Vol. 243 (2021) 107415. (DOI:  /10.1016/j.engfracmech.2020.107415)}}
@article{sun_experimentalnumerical_study_2021, 
author={Sun, R. and Keller, S. and Zhu, Y. and Guo, W. and Kashaev, N. and Klusemann, B.},
title={Experimental-numerical study of laser-shock-peening-induced retardation of fatigue crack propagation in Ti-17 titanium alloy},
year={2021},
journal = {International Journal of Fatigue},
volume = {145},
pages = {106081},
doi = {10.1016/j.ijfatigue.2020.106081},
abstract = {Residual stresses induced by laser shock peening in Ti-17 titanium specimens were experimentally and numerically investigated to identify the mechanisms and generation conditions of the retardation of fatigue crack propagation (FCP). The retardation was experimentally observed with fatigue life prolonged by 150%. A multi-step simulation strategy for fatigue life prediction is applied, which successfully predicts the experimentally observed FCP behavior. The fractographic observations and numerical simulation indicate that crack closure, as opposed to other microstructural influences, is the dominant effect on retardation. The studies of multi-FCP aspects show that significant retardation occurs in specimens at high values of residual stresses, small peening gap distances, and lower externally applied loads.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.ijfatigue.2020.106081} (DOI). Sun, R.; Keller, S.; Zhu, Y.; Guo, W.; Kashaev, N.; Klusemann, B.: Experimental-numerical study of laser-shock-peening-induced retardation of fatigue crack propagation in Ti-17 titanium alloy. In: International Journal of Fatigue. Vol. 145 (2021) 106081. (DOI:  /10.1016/j.ijfatigue.2020.106081)}}
@article{landell_investigation_of_2021, 
author={Landell, R. and de Lima Lessa, C. and Bergmann, L. and dos Santos, J. and Kwietniewski, C. and Klusemann, B.},
title={Investigation of friction stir welding process applied to ASTM 572 steel plate cladded with Inconel®625},
year={2021},
journal = {Welding in the World},
volume = {65},
pages = {393 - 403},
doi = {10.1007/s40194-020-01007-w},
abstract = {This study investigates friction stir welding (FSW) in the dissimilar joining process of cladded plates. Samples of 4-mm thick ASTM 572 steel plate cladded with 3-mm thick Inconel®625 represent the base material. In order to limit mixing between the dissimilar materials to keep the corrosion resistance, a two-pass welding procedure was applied. Optimal welding parameters for each pass were identified. The welded specimens were evaluated by light microscopy, SEM equipped with EDS, and mechanical tests such as hardness, bending, and tensile testing. Defect-free joints with excellent surface finish have been obtained with a well-defined interfacial region between both materials. The FSW process changed the microstructure of both metals used in this study to a new refined grain region into the weld with complex microstructure inside the ASTM 572 steel, as well as change from a dendritic to an equiaxial microstructure in the Inconel®625. The breaking and the distribution of the intermetallic and secondary phases of the nickel alloy were promoted by the FSW process, moreover the second welding pass on the Inconel® tempered the steel which had previously been welded in the first FSW weld pass. The mechanical properties within the welding zone increased due to this microstructural rearrangement coupled with the Hall-Petch effect.},
note = {Online available at: \url{https://dx.doi.org/10.1007/s40194-020-01007-w} (DOI). Landell, R.; de Lima Lessa, C.; Bergmann, L.; dos Santos, J.; Kwietniewski, C.; Klusemann, B.: Investigation of friction stir welding process applied to ASTM 572 steel plate cladded with Inconel®625. In: Welding in the World. Vol. 65 (2021) 393 - 403. (DOI:  /10.1007/s40194-020-01007-w)}}
@article{tang_unloading_behaviors_2021, 
author={Tang, W. and Lee, J. and Wang, H. and Steglich, D. and Li, D. and Peng, Y. and Wu, P.},
title={Unloading behaviors of the rare-earth magnesium alloy ZE10 sheet},
year={2021},
journal = {Journal of Magnesium and Alloys},
volume = {9},
number = {3},
pages = {927 - 936},
doi = {10.1016/j.jma.2020.02.023},
abstract = {Due to their low symmetry in crystal structure, low elastic modulus (∼45 GPa) and low yielding stress, magnesium (Mg) alloys exhibit strong inelastic behaviors during unloading. As more and more Mg alloys are developed, their unloading behaviors were less investigated, especially for rare-earth (RE) Mg alloys. In the current work, the unloading behaviors of the RE Mg alloy ZE10 sheet is carefully studied by both mechanical tests and crystal plasticity modeling. In terms of the stress–strain curves, the inelastic strain, the chord modulus, and the active deformation mechanisms, the substantial anisotropy and the loading path dependency of the unloading behaviors of ZE10 sheets are characterized. The inelastic strains are generally larger under compressive Loading–UnLoading (L–UL) than under tensile L–UL, along the transverse direction (TD) than along the rolling direction (RD) under tensile L–UL, and along RD than along TD under compressive L–UL. The basal slip, twinning and de-twinning are found to be responsible for the unloading behaviors of ZE10 sheets.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jma.2020.02.023} (DOI). Tang, W.; Lee, J.; Wang, H.; Steglich, D.; Li, D.; Peng, Y.; Wu, P.: Unloading behaviors of the rare-earth magnesium alloy ZE10 sheet. In: Journal of Magnesium and Alloys. Vol. 9 (2021) 3, 927 - 936. (DOI:  /10.1016/j.jma.2020.02.023)}}
@article{bouali_influence_of_2021, 
author={Bouali, A. and André, N. and Silva Campos, M. and Serdechnova, M. and Dos Santos, J. and Amancio-Filho, S. and Zheludkevich, M.},
title={Influence of LDH conversion coatings on the adhesion and corrosion protection of friction spot-joined AA2024-T3/CF-PPS},
year={2021},
journal = {Journal of Materials Processing Technology},
volume = {67},
pages = {197 - 210},
doi = {10.1016/j.jmst.2020.06.038},
abstract = {Layered double hydroxide (LDH) conversion coatings loaded with corrosion inhibitors were suggested for the surface treatment of the aluminum alloy 2024-T3, prior to friction spot joining with carbon-fiber reinforced polyphenylene sulfide (AA2024-T3/CF-PPS). Vanadate was used as a model corrosion inhibitor. Lap shear testing method revealed an increase of 15% of the joint’s adhesion performance when treated with LDH and before exposure to salt spray. The evaluation of the joints after exposure to salt spray demonstrated a significant difference in the corrosion behavior of the joints when the AA2024-T3 is treated with LDH loaded with nitrate and vanadate species. The LDH intercalated with nitrate revealed a clear improvement in the mechanical and corrosion resistance performance of the joints, even after 6 weeks of salt spray. However, the LDH intercalated with vanadate failed in providing protection against corrosion as well as preserving the mechanical properties of the joints. The effect of the galvanic corrosion was further investigated by zero resistance ammeter measurements as well as localized scanning vibrating electrode technique.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jmst.2020.06.038} (DOI). Bouali, A.; André, N.; Silva Campos, M.; Serdechnova, M.; Dos Santos, J.; Amancio-Filho, S.; Zheludkevich, M.: Influence of LDH conversion coatings on the adhesion and corrosion protection of friction spot-joined AA2024-T3/CF-PPS. In: Journal of Materials Processing Technology. Vol. 67 (2021) 197 - 210. (DOI:  /10.1016/j.jmst.2020.06.038)}}
@article{borba_hydrothermal_aging_2021, 
author={Borba, N. and dos Santos, J. and Amancio-Filho, S.},
title={Hydrothermal aging of friction riveted thermoplastic composite joints for aircraft applications},
year={2021},
journal = {Composite Structures},
volume = {255},
pages = {112871},
doi = {10.1016/j.compstruct.2020.112871},
abstract = {In this paper, the sensitivity of carbon fiber reinforced polyether-ether-ketone friction riveted joints to hydrothermal aging was assessed, addressing the degradation mechanisms and post-aged quasi-static mechanical behavior of the joints. The joints were exposed to 71 °C and 95 % relative humidity for 28 days. Despite the oxidation of the metallic nut and washer as well as cavitation and degradation of the composite, a 23 % increase of joint mechanical performance was observed after 28 days of exposure. It is believed that the temperature and water uptake drove matrix post-crystallization at the surface of the fibers, which led to local strengthening of the composite in the rivet surrounding and, consequently, improved the joint residual strength.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.compstruct.2020.112871} (DOI). Borba, N.; dos Santos, J.; Amancio-Filho, S.: Hydrothermal aging of friction riveted thermoplastic composite joints for aircraft applications. In: Composite Structures. Vol. 255 (2021) 112871. (DOI:  /10.1016/j.compstruct.2020.112871)}}
@article{meng_recent_progress_2021, 
author={Meng, X. and Huang, Y. and Cao, J. and Shen, J. and Dos Santos, J.},
title={Recent progress on control strategies for inherent issues in friction stir welding},
year={2021},
journal = {Progress in Materials Science},
volume = {115},
pages = {100706},
doi = {10.1016/j.pmatsci.2020.100706},
abstract = {Friction stir welding (FSW), a mature solid-state joining method, has become a revolutionary welding technique over the past two decades because of its energy efficiency, environmental friendliness and high-quality joints. FSW is highly efficient in the joining of Al alloys, Mg alloys, Ti alloys, polymers and other dissimilar materials. Recently, FSW has gained considerable scientific and technological attention in several fields, including aerospace, railway, renewable energy and automobile. To broaden the adoption of FSW in manufacturing fields, three inherent issues—back support, weld thinning and keyhole defects—must be addressed to ensure the structural integrity, safety and service life of the manufactured products. This review covers the recent progress on the control strategies for these inherent issues, which are basically divided into self-supported FSW, non-weld-thinning FSW and friction stir-based remanufacturing. Herein, the aim is to focus on the corresponding technical development, process parameters, metallurgical features and mechanical properties. Additionally, the challenges and future outlooks are emphasized systematically.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.pmatsci.2020.100706} (DOI). Meng, X.; Huang, Y.; Cao, J.; Shen, J.; Dos Santos, J.: Recent progress on control strategies for inherent issues in friction stir welding. In: Progress in Materials Science. Vol. 115 (2021) 100706. (DOI:  /10.1016/j.pmatsci.2020.100706)}}
@article{herrnring_modeling_precipitation_2021, 
author={Herrnring, J. and Sundman, B. and Staron, P. and Klusemann, B.},
title={Modeling precipitation kinetics for multi-phase and multi-component systems using particle size distributions via a moving grid technique},
year={2021},
journal = {Acta Materialia},
volume = {215},
pages = {117053},
doi = {10.1016/j.actamat.2021.117053},
abstract = {The collection and coupling of thermodynamic data following the Calphad framework is important for the computational alloy and process design. The microstructure and the precipitation kinetics have a significant influence on the microstructure and mechanical properties of multi-component alloys in solid state; therefore, it is essential to account for solid state phase transformations via thermo-chemical process simulations. In this work an efficient numerical scheme for a Kampmann-Wagner numerical (KWN) model, which takes into account multi-component nucleation and growth theories via the coupling to the open thermodynamic software-package OpenCalphad, is developed and implemented. By the usage of the Calphad approach, it becomes feasible to describe complex multi-component alloy systems. The developed KWN model can take into account effects resulting from the generation or annihilation of vacancies by an off-equilibrium diffusion constant. For the solution of the particle size distribution an efficient and flexible moving grid algorithm is elaborated, which provides a robust and adaptive solution scheme for the simulation of nucleation, growth, coarsening and reversion. The model is applied to simulate the precipitation kinetics of recently published in-situ anomalous small angle X-ray scattering experiments studying reversion of an AA7xxx alloy and the identified model can reproduce the essential characteristics of these reversion experiments over a wide temperature range.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.actamat.2021.117053} (DOI). Herrnring, J.; Sundman, B.; Staron, P.; Klusemann, B.: Modeling precipitation kinetics for multi-phase and multi-component systems using particle size distributions via a moving grid technique. In: Acta Materialia. Vol. 215 (2021) 117053. (DOI:  /10.1016/j.actamat.2021.117053)}}
@article{li_nanoporous_goldpolypyrrole_2021, 
author={Li, J. and Markmann, J. and Weissmüller, J. and Mameka, N.},
title={Nanoporous gold-polypyrrole hybrid electrochemical actuators with tunable elasticity},
year={2021},
journal = {Acta Materialia},
volume = {212},
pages = {116852},
doi = {10.1016/j.actamat.2021.116852},
abstract = {This study explores the effective elastic response of hybrid electrochemical actuators based on nanoporous gold – decorated with a thin film of an electrosynthesized polypyrrole – during charging in an aqueous electrolyte. We found a new and yet unrevealed phenomenon in the hybrids – a reversible change of the material’s elasticity with alternating stiffening and softening behavior. Remarkably, the stiffness variations are larger and of opposite sign as compared to a non-coated nanoporous gold. The amplitude of the elastic modulus variation increases with the thickness of the polypyrrole layer, pointing to a dominant role of processes in the polymer bulk upon its doping or undoping. We propose that the reversible stiffness of the hybrid material is governed by the competition between the increased intermolecular bonding as consequence of interactions between the charged chains and dopant anions in the polymer and its plasticization due to solvent intake.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.actamat.2021.116852} (DOI). Li, J.; Markmann, J.; Weissmüller, J.; Mameka, N.: Nanoporous gold-polypyrrole hybrid electrochemical actuators with tunable elasticity. In: Acta Materialia. Vol. 212 (2021) 116852. (DOI:  /10.1016/j.actamat.2021.116852)}}
@article{lambiase_frictionbased_processes_2021, 
author={Lambiase, F. and Balle, F. and Blaga, L. and Liu, F. and Amancio-Filho, S.},
title={Friction-based processes for hybrid multi-material joining},
year={2021},
journal = {Composite Structures},
volume = {266},
pages = {113828},
doi = {10.1016/j.compstruct.2021.113828},
abstract = {The adoption of multi-material lightweight structures has been recognized as one of the most effective and promising solutions to improve fuel efficiency and accelerate the electrification of future transportation systems. A wider application of multi-material lightweight structures has been limited by our capability to fabricate them reliably and cost-effectively at a commercial scale. In the last decade, many friction-based joining processes have been developed and demonstrated their advantages over mechanical fastening and adhesive bonding processes in fabricating future multi-material lightweight structures. This article provides a comprehensive review on the recent advances of five promising friction-based joining processes (friction assisted joining, friction lap welding, friction spot joining, friction riveting, and ultrasonic welding) on the aspects of facilities, joining process, joining mechanism, applicable materials, surface pretreatments, and the influence of process parameters on the performance of the produce joints. This article also provides a summary of the performance of the produced joints under static load, dynamic load, various thermal cycles, or harsh chemical environments. The main similarities and differences among the joining processes are discussed. The paper points out the main knowledge gaps that need to be filled and the research that needs to be conducted to further advance the joining process. This review article will place the friction-based joining process at a new starting point with accelerated developing speed towards higher technical maturity to make the processes available for certifiable industrial applications.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.compstruct.2021.113828} (DOI). Lambiase, F.; Balle, F.; Blaga, L.; Liu, F.; Amancio-Filho, S.: Friction-based processes for hybrid multi-material joining. In: Composite Structures. Vol. 266 (2021) 113828. (DOI:  /10.1016/j.compstruct.2021.113828)}}
@article{prokhorov_the_effect_2021, 
author={Prokhorov, A. and Vshivkov, A. and Plekhov, O. and Kashaev, N. and Fomin, F. and Ozerov, M. and Zherebtsov, S.},
title={The Effect of LSP on the Structure Evolution and Self-Heating of ARMCO Iron under Cyclic Loading},
year={2021},
journal = {Metals},
volume = {11},
number = {8},
pages = {1198},
doi = {10.3390/met11081198},
abstract = {This work is devoted to the experimental investigation of the effect of laser shock peening (LSP) on the thermo-mechanical properties of metals. ARMCO iron was chosen as the model material for the study. Samples were subjected to LSP, and were tested following the procedure of the self-heating (Risitano) technique. To investigate the damage that was induced by heating, the fatigue tests were coupled with infrared thermography measurements. The results of the study showed that the LSP procedure qualitatively changes the temperature evolution in ARMCO iron during cyclic loading. The heating (energy dissipation) of the LSP treated specimen was several times higher than that of the specimen in the initial state. To explain the structural mechanisms of energy dissipation, the microstructure of the specimens was examined using transmission (TEM) and scanning (SEM) electron microscopy, as well as electron backscattering diffraction (EBSD). The results of the structural investigation confirm the qualitative change of defect evolution caused by LSP treatment.},
note = {Online available at: \url{https://dx.doi.org/10.3390/met11081198} (DOI). Prokhorov, A.; Vshivkov, A.; Plekhov, O.; Kashaev, N.; Fomin, F.; Ozerov, M.; Zherebtsov, S.: The Effect of LSP on the Structure Evolution and Self-Heating of ARMCO Iron under Cyclic Loading. In: Metals. Vol. 11 (2021) 8, 1198. (DOI:  /10.3390/met11081198)}}
@article{escobar_multimodal_analysis_2021, 
author={Escobar, J. and Gwalani, B. and Olszta, M. and Silverstein, J. and Overman, N. and Bergmann, L. and dos Santos, J.F. and Staron, P. and Maawad, E. and Klusemann, B. and Mathaudhu, S. and Devaraj, A.},
title={Multimodal analysis of spatially heterogeneous microstructural refinement and softening mechanisms in three-pass friction stir processed Al-4Si alloy},
year={2021},
journal = {Journal of Alloys and Compounds},
volume = {887},
pages = {161351},
doi = {10.1016/j.jallcom.2021.161351},
abstract = {Solid phase processing methods such as friction stir processing (FSP) offer pathways to refine the microstructure of metallic alloys through the combined action of deformation and deformation-induced heating. However, this thermomechanical coupling during FSP also leads to the occurrence of multiple competing microstructural evolution mechanisms which in turn can lead to locally varying mechanical properties, often distributed heterogeneously in the microstructure. This inherent microstructural and mechanical property heterogeneity in alloys subjected to FSP makes it rather challenging to reveal the microstructure-mechanical property relationships systematically. Therefore in this work, we systematically analyze the relationship between microstructural evolution and local microhardness in a model binary Al-4 at.% Si alloy subjected to three-pass friction stir processing. Spatially resolved high-energy synchrotron X-ray diffraction, electron backscattered diffraction, and scanning transmission electron microscopy were used to understand the heterogeneous microstructural evolution due to the FSP. Our results provide insight into how particle-stimulated grain nucleation, recovery, and recrystallization occur heterogeneously in the Al-Si alloy as a function of the distance from the stir zone, directly influencing the degree of softening. The systematic understanding developed by this work can guide future studies on the influence of FSP process parameters on the microstructural evolution mechanisms and its influence on local mechanical properties},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jallcom.2021.161351} (DOI). Escobar, J.; Gwalani, B.; Olszta, M.; Silverstein, J.; Overman, N.; Bergmann, L.; dos Santos, J.F.; Staron, P.; Maawad, E.; Klusemann, B.; Mathaudhu, S.; Devaraj, A.: Multimodal analysis of spatially heterogeneous microstructural refinement and softening mechanisms in three-pass friction stir processed Al-4Si alloy. In: Journal of Alloys and Compounds. Vol. 887 (2021) 161351. (DOI:  /10.1016/j.jallcom.2021.161351)}}
@article{kashaev_on_the_2021, 
author={Kashaev, N. and Keller, S. and Staron, P. and Maawad, E. and Huber, N.},
title={On the prediction of fatigue crack growth based on weight functions in residual stress fields induced by laser shock peening and laser heating},
year={2021},
journal = {Fatigue and Fracture of Engineering Materials and Structures},
volume = {44},
number = {12},
pages = {3463 - 3481},
doi = {10.1111/ffe.13579},
abstract = {This study deals with fatigue crack growth prediction for thin sheet AA2024 specimens with residual stresses introduced through laser shock peening and laser heating treatments. Different weight functions are used to calculate the stress intensity factor due to the presence of residual stresses. A superposition principle is used by calculating the total stress intensity factor considering the applied loads and residual stresses. The fatigue crack growth is predicted using the Paris' law based on the effective stress intensity factor range, in that the effect of residual stresses is considered by changing the total stress intensity factor ratio. It is concluded, that weight functions are a powerful tool to predict fatigue crack growth in AA2024 containing residual stress fields, as long as the gradient in the loading direction, as induced by laser shock peening and laser heating, is moderate.},
note = {Online available at: \url{https://dx.doi.org/10.1111/ffe.13579} (DOI). Kashaev, N.; Keller, S.; Staron, P.; Maawad, E.; Huber, N.: On the prediction of fatigue crack growth based on weight functions in residual stress fields induced by laser shock peening and laser heating. In: Fatigue and Fracture of Engineering Materials and Structures. Vol. 44 (2021) 12, 3463 - 3481. (DOI:  /10.1111/ffe.13579)}}
@article{liu_in_situ_2021, 
author={Liu, J. and Wu, T. and Wang, M. and Wang, L. and Zhou, Q. and Wang, K. and Staron, P. and Schell, N. and Huber, N. and Kashaev, N.},
title={In situ observation of competitive growth of α grains during β → α transformation in laser beam manufactured TiAl alloys},
year={2021},
journal = {Materials Characterization},
volume = {179},
pages = {111371},
doi = {10.1016/j.matchar.2021.111371},
abstract = {Low ductility has long been the bottleneck for high temperature application of TiAl alloys. It is reported that grain refinement through boride could improve its mechanical property. However, this refinement is suppressed at high cooling rate. This article delineates for the first time an in situ observation by synchrotron X-ray diffraction. It illustrates the mechanism of competitive nucleation and grain growth of Burgers and non-Burgers α grains during β → α transformation in a Ti–45Al–5Nb–0.2C–0.2B alloy (TNB-V5). Comparing with those in base material, the volume fraction and size of borides are significantly reduced in the welding zone. The non-Burgers α grains nucleate earlier than Burgers α. However, Burgers α grains grow much faster than non-Burgers α during β → α transformation in the welding zone, due to a high thermodynamic driving force of Burgers α grains. No orientation relationships between α and borides or between β and borides are observed in the fast cooling.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.matchar.2021.111371} (DOI). Liu, J.; Wu, T.; Wang, M.; Wang, L.; Zhou, Q.; Wang, K.; Staron, P.; Schell, N.; Huber, N.; Kashaev, N.: In situ observation of competitive growth of α grains during β → α transformation in laser beam manufactured TiAl alloys. In: Materials Characterization. Vol. 179 (2021) 111371. (DOI:  /10.1016/j.matchar.2021.111371)}}
@article{richert_image_segmentation_2021, 
author={Richert, C. and Wu, Y. and Hablitzel, M. and Lilleodden, E. and Huber, N.},
title={Image segmentation and analysis for densification mapping of nanoporous gold after nanoindentation},
year={2021},
journal = {MRS Advances},
volume = {6},
number = {20},
pages = {519 - 523},
doi = {10.1557/s43580-021-00099-w},
abstract = {Segmentation of scanning electron microscopy (SEM) images of focused ion beam (FIB) cross-sections through indented regions in nanoporous gold (np-Au) is carried out. A key challenge for image analysis of open porous materials is the appropriate binarization of the pore and gold ligament regions while excluding material lying below the cross-sectional plane. Here, a manual approach to thresholding is compared to global and local approaches. The global thresholding resulted in excessive deviations from the nominal solid fraction, due to a strong gray-scale gradient caused by the tilt angle during imaging and material shadowing. In contrast, the local thresholding approach delivered local solid fractions that were free of global gradients, and delivered a quality comparable to the manual segmentation. The extracted densification profiles vertically below the indenter as well as parallel to the surface showed an exponential-type decay from the indenter tip towards the nominal value of 1 far from the indenter.},
note = {Online available at: \url{https://dx.doi.org/10.1557/s43580-021-00099-w} (DOI). Richert, C.; Wu, Y.; Hablitzel, M.; Lilleodden, E.; Huber, N.: Image segmentation and analysis for densification mapping of nanoporous gold after nanoindentation. In: MRS Advances
. Vol. 6 (2021) 20, 519 - 523. (DOI:  /10.1557/s43580-021-00099-w)}}
@article{zandersons_on_factors_2021, 
author={Zandersons, B. and Lührs, L. and Li, Y. and Weissmüller, J.},
title={On factors defining the mechanical behavior of nanoporous gold},
year={2021},
journal = {Acta Materialia},
volume = {215},
pages = {116979},
doi = {10.1016/j.actamat.2021.116979},
abstract = {Nanoporous gold (NPG) made by dealloying takes the form of a network of nanoscale struts or “ligaments”. It is well established that the material’s mechanical behavior is strongly affected by its ligament size, and by its solid volume fraction, . We explore the mechanical behavior of NPG, with an emphasis on establishing a consistent data set with comparable but covering a significant range of initial . Specimens are prepared from Ag-Au master alloys with their Au atom fraction, in the range 0.20–0.35. Since dealloying replaces Ag with voids, may be expected to agree with . Yet, spontaneous plastic deformation events during dealloying can result in macroscopic shrinkage, decoupling from . This raises the question, how do and separately affect the mechanical behavior? We confirm two recent suggestions, namely i) a modified Roberts-Garboczi-type scaling law for Young’s modulus versus of the material in its as-prepared state and ii) the relevance of an apparent “load-bearing solid fraction” for Young’s modulus as well as strength. Yet, remarkably, we find that stiffness and strength of the as-prepared material show a much better correlation to as compared to . This can be understood as a consequence of the microstructural changes induced by shrinkage. Studying the microstructure evolution during annealing, we also confirm the suggestion that coarsening entails an enhanced loss in stiffness for samples with lesser solid fraction. This finding confirms concerns about the notion of self-similar coarsening as a general behavior of dealloying-made network materials.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.actamat.2021.116979} (DOI). Zandersons, B.; Lührs, L.; Li, Y.; Weissmüller, J.: On factors defining the mechanical behavior of nanoporous gold. In: Acta Materialia. Vol. 215 (2021) 116979. (DOI:  /10.1016/j.actamat.2021.116979)}}
@article{elder_grain_boundary_2021, 
author={Elder, K.L.M. and Beck Andrews, W. and Ziehmer, M. and Mameka, N. and Kirchlechner, C. and Davydok, A. and Micha, J.-S. and Chadwick, A.F. and Lilleodden, E.T. and Thornton, K. and Voorhees, P.W.},
title={Grain Boundary Formation Through Particle Detachment During Coarsening of Nanoporous Metals},
year={2021},
journal = {Proceedings of the National Academy of Sciences of the United States of America: PNAS},
volume = {118},
number = {30},
pages = {e2104132118},
doi = {10.1073/pnas.2104132118},
abstract = {Grain boundary formation during coarsening of nanoporous gold (NPG) is investigated wherein a nanocrystalline structure can form by particles detaching and reattaching to the structure. MicroLaue and electron backscatter diffraction measurements demonstrate that an in-grain orientation spread develops as NPG is coarsened. The volume fraction of the NPG sample is near the limit of bicontinuity, at which simulations predict that a bicontinuous structure begins to fragment into independent particles during coarsening. Phase-field simulations of coarsening using a computationally generated structure with a volume fraction near the limit of bicontinuity are used to model particle detachment rates. This model is tested by using the measured NPG structure as an initial condition in the phase-field simulations. We predict that up to ∼5% of the NPG structure detaches as a dealloyed Ag75Au25 sample is annealed at 300 °C for 420 min. The quantity of volume detached is found to be highly dependent on the volume fraction and volume fraction homogeneity of the nanostructure. As the void phase in the experiments cannot support independent particles, they must fall and reattach to the structure, a process that results in the formation of new grain boundaries. This particle reattachment process, along with other classic processes, leads to the formation of grain boundaries during coarsening in nanoporous metals. The formation of grain boundaries can impact a variety of applications, including mechanical strengthening; thus, the consideration and understanding of particle detachment phenomena are essential when studying nanoporous metals.},
note = {Online available at: \url{https://dx.doi.org/10.1073/pnas.2104132118} (DOI). Elder, K.L.M.; Beck Andrews, W.; Ziehmer, M.; Mameka, N.; Kirchlechner, C.; Davydok, A.; Micha, J.-S.; Chadwick, A.F.; Lilleodden, E.T.; Thornton, K.; Voorhees, P.W.: Grain Boundary Formation Through Particle Detachment During Coarsening of Nanoporous Metals. In: Proceedings of the National Academy of Sciences of the United States of America: PNAS. Vol. 118 (2021) 30, e2104132118. (DOI:  /10.1073/pnas.2104132118)}}
@article{fu_revealing_joining_2021, 
author={Fu, B. and Shen, J. and Suhuddin, U. and Pereira, A. and Maawad, E. and dos Santos, J. and Klusemann, B. and Rethmeier, M.},
title={Revealing joining mechanism in refill friction stir spot welding of AZ31 magnesium alloy to galvanized DP600 steel},
year={2021},
journal = {Materials & Design},
volume = {209},
pages = {109997},
doi = {10.1016/j.matdes.2021.109997},
abstract = {The application of magnesium (Mg) inevitably involves dissimilar welding with steel. A novel solid state spot welding method, refill friction stir spot welding (refill FSSW), was utilized to weld AZ31 Mg alloy to galvanized DP600 steel. Although Mg/Fe is an immiscible alloy system, defect-free welds with high strength were successfully obtained in a wide parameter window. The results of microstructure, interfacial reactions, and mechanical properties are reported to reveal the underlying joining mechanism. Due to the melting of Zn coating and subsequent Mg-Zn reactions, Mg-Zn eutectic and intermetallic compounds were detected within welds. Heterogeneous interfacial reactions occur along Mg/steel interface, and the relationship between interfacial structure and fracture behavior was investigated. The joining mechanism is associated with Zn coating and Fe-Al layer: 1) the presence of Zn coating is beneficial for achieving high-quality welding between Mg and steel, it protects the interface from oxidation and contributes to brazing of the weld; 2) the Al present in Mg alloy reacts with Fe, resulting in the growth of Fe-Al layer, which contributes to the diffusion bonding in the interface. The overall results clearly show that refill FSSW is a competitive welding method for joining Mg and galvanized steel.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.matdes.2021.109997} (DOI). Fu, B.; Shen, J.; Suhuddin, U.; Pereira, A.; Maawad, E.; dos Santos, J.; Klusemann, B.; Rethmeier, M.: Revealing joining mechanism in refill friction stir spot welding of AZ31 magnesium alloy to galvanized DP600 steel. In: Materials & Design. Vol. 209 (2021) 109997. (DOI:  /10.1016/j.matdes.2021.109997)}}
@article{su_comparing_the_2021, 
author={Su, Y. and Li, W. and Shen, J. and Fu, B. and dos Santos, J. and Klusemann, B. and Vairis, A.},
title={Comparing the local-global deformation mechanism in different friction stir welding sequences of Ti-4Al-0.005B titanium alloy T-joints},
year={2021},
journal = {Materials Science and Engineering: A},
volume = {823},
pages = {141698},
doi = {10.1016/j.msea.2021.141698},
abstract = {Titanium alloy T-joints were produced using two different friction stir welding (FSW) sequences, and the local-global deformation mechanisms until fracture were compared. Due to their differing FSW sequence characteristics, the optimal parameter ranges for the two T-joints are different. The stir zone (SZ) of the single-weld T-joint consists of lamellar α grains, while fine equiaxed α grains develop in the double-weld T-joint due to the selection of low heat input. Due to the different local microstructure zones in the joint, deformation inhomogeneity of the T-joint during tensile testing is observed. Independent of the welding sequence and for optimal process conditions, both T-joint configuration show nearly the same maximum tensile strength as the base material (BM), however at a relatively low fracture strain, below 20% of the BM. The local strain hardening rate in different zones of the T-joint was investigated. The strain hardening ability of SZ with fine grains is significantly higher than elsewhere, because the grain size contributes greatly to strain hardening behavior at low strain levels. The single-weld T-joint experienced a symmetric local strain distribution between advancing and retreating side. For the double-weld T-joint, there are significant differences between the first and the second weld area. The fracture morphologies of both T-joints are typical ductile, where the toughness of the single-weld joint is higher than that of the double-weld joint.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.msea.2021.141698} (DOI). Su, Y.; Li, W.; Shen, J.; Fu, B.; dos Santos, J.; Klusemann, B.; Vairis, A.: Comparing the local-global deformation mechanism in different friction stir welding sequences of Ti-4Al-0.005B titanium alloy T-joints. In: Materials Science and Engineering: A. Vol. 823 (2021) 141698. (DOI:  /10.1016/j.msea.2021.141698)}}
@article{gera_microstructure_mechanical_2021, 
author={Gera, D. and Fu, B. and Suhuddin, U. and Plaine, A. and Alcantara, N. and dos Santos, J. and Klusemann, B.},
title={Microstructure, mechanical and functional properties of refill friction stir spot welds on multilayered aluminum foils for battery application},
year={2021},
journal = {Journal of Materials Research and Technology : JMRT},
volume = {13},
pages = {2272 - 2286},
doi = {10.1016/j.jmrt.2021.06.017},
abstract = {The production of batteries often involves the joining of multilayered foils to a conductive tab. In the present study, a solid state spot welding method, the refill friction stir spot welding (refill FSSW), was employed for welding multilayered commercially pure aluminum (CP–Al) foils to 2024-T3 Al alloy sheets (tab). Defect-free welds with high lap shear strength (LSS) are obtained. In the stirred zone (SZ), 2024 Al alloy is only found within the shoulder refill region, which is greatly refined due to dynamic recrystallization. Unlike overlap joints in thicker sheets, a thermo-mechanically affected zone also forms above the SZ in the probe refill region. “Stop-action” experiments have been conducted to describe joint formation. The presence of the 2024 Al alloy tabs resulted in significant changes to material follow behavior and the formation of microstructural zones not previously observed in conventional refill FSSW overlap welds in thicker sheets. Most welds failed in SZ pull-out mode during LSS test. The cracks initiate at the interface between the upper sheet and the first layer of the multilayered foils and then propagate upward and circumferentially outside the SZ. Welds of multilayered Al foils produced by refill FSSW show low contact resistance. The decomposition of electrochemically active materials in batteries can be avoided by maintaining a minimum distance from the spot-weld. The produced welds with flat appearance, high mechanical properties, and potential to meet industry requirements imply that refill FSSW is a promising welding technique for battery production.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jmrt.2021.06.017} (DOI). Gera, D.; Fu, B.; Suhuddin, U.; Plaine, A.; Alcantara, N.; dos Santos, J.; Klusemann, B.: Microstructure, mechanical and functional properties of refill friction stir spot welds on multilayered aluminum foils for battery application. In: Journal of Materials Research and Technology : JMRT. Vol. 13 (2021) 2272 - 2286. (DOI:  /10.1016/j.jmrt.2021.06.017)}}
@article{fu_improved_mechanical_2021, 
author={Fu, B. and Shen, J. and Suhuddin, U. and Chen, T. and dos Santos, J. and Klusemann, B. and Rethmeier, M.},
title={Improved mechanical properties of cast Mg alloy welds via texture weakening by differential rotation refill friction stir spot welding},
year={2021},
journal = {Scripta Materialia},
volume = {203},
pages = {114113},
doi = {10.1016/j.scriptamat.2021.114113},
abstract = {Cast magnesium alloys welds produced by refill friction stir spot welding (refill FSSW) show low lap shear strength (LSS) and constantly fail in stirred zone (SZ) shear mode. The cause is most probably related to the heavily textured microstructure. Here, to re-engineer the resulting microstructure, we propose a novel process variant, the differential rotation refill FSSW (DR-refill FSSW). DR-refill FSSW stimulates discontinuous dynamic recrystallization and produces a bimodal microstructure with weakened texture. Therefore, the deformation incompatibility between SZ and thermal-mechanically affected zone is avoided. The welds have 50% higher LSS than that of standard refill FSSW welds, and fail in a different failure mode, i.e., SZ pull-out mode. DR-refill FSSW provides a new and effective strategy for improving the performance of spot welds based on microstructural engineering.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.scriptamat.2021.114113} (DOI). Fu, B.; Shen, J.; Suhuddin, U.; Chen, T.; dos Santos, J.; Klusemann, B.; Rethmeier, M.: Improved mechanical properties of cast Mg alloy welds via texture weakening by differential rotation refill friction stir spot welding. In: Scripta Materialia. Vol. 203 (2021) 114113. (DOI:  /10.1016/j.scriptamat.2021.114113)}}
@article{feier_process_transferability_2021, 
author={Feier, A. and Becheru, A. and Brîndușoiu, M. and Blaga, L.},
title={Process Transferability of Friction Riveting of AA2024-T351/Polyetherimide (PEI) Joints Using Hand-Driven, Low-Cost Drilling Equipment},
year={2021},
journal = {Processes},
volume = {9},
number = {8},
pages = {1376},
doi = {10.3390/pr9081376},
abstract = {The present work deals with the transferability of Friction Riveting joining technology from laboratory equipment to adapted in-house, low-cost machinery. A G13 drilling machine was modified for the requirements of the selected joining technique, and joints were performed using polyethermide plates and AA2024 aluminum alloy rivets of 6 mm diameter. This diameter was not previously reported for Friction Riveting. The produced joints were mechanically tested under tensile loading (pullout tests) with ultimate tensile forces of 9500 ± 900 N. All tested specimens failed through full-rivet pullout, which is the weakest reported joint in Friction Riveting. In order to understand this behavior, FE models were created and analyzed. The models produced were in agreement with the experimental results, with failure initiated within the polymer under stress concentrations in the polymeric material above the deformed metallic anchor at an ultimate value of the stress of 878 MPa at the surface of the joint. Stresses decreased to less than half of the maximum value around the anchoring zone while the rivet was removed and towards the surface. The paper thus demonstrates the potential ease of applying and reproducing Friction Riveting with simple machinery, while contributing to an understanding of the mechanical behavior (initialization of failure) of joints.},
note = {Online available at: \url{https://dx.doi.org/10.3390/pr9081376} (DOI). Feier, A.; Becheru, A.; Brîndușoiu, M.; Blaga, L.: Process Transferability of Friction Riveting of AA2024-T351/Polyetherimide (PEI) Joints Using Hand-Driven, Low-Cost Drilling Equipment. In: Processes. Vol. 9 (2021) 8, 1376. (DOI:  /10.3390/pr9081376)}}
@article{examilioti_effect_of_2021, 
author={Examilioti, T. and Kashaev, N. and Ventzke, V. and Klusemann, B. and Alexopoulos, N.},
title={Effect of filler wire and post weld heat treatment on the mechanical properties of laser beam-welded AA2198},
year={2021},
journal = {Materials Characterization},
volume = {178},
pages = {111257},
doi = {10.1016/j.matchar.2021.111257},
abstract = {The mechanical behavior of autogenously and non-autogenously laser beam-welded joints of Al-Cu-Li alloy AA2198 and the effect of post weld heat treatment are examined in this contribution. The deformation texture of the base material does not present any significant change in the macrotexture with applying different artificial ageing times. Autogenously and non-autogenously laser beam-welded joints present a decrease in yield stress and ultimate strength in the as-welded condition, approximately 45% and 36–38%, respectively, when compared with AA2198-Τ3 base material. The addition of the AA4047 filler wire increases the Si and Cu content in the grain interior and in the grain boundaries of the fusion zone of the welded joint. Micro-hardness measurements for autogenously laser-welded joints showed a decrease in hardness by 27% for the fusion zone and 42% for the heat-affected zone, when compared with the non-autogenously laser beam-welded joints. Α quality index was exploited to evaluate the tensile mechanical performance of the welded joints. It is observed that the non-autogenously welded joints always show a higher ‘quality’ than the respective autogenously welded joints and the highest quality index in terms of mechanical performance is achieved for the as-welded and the peak-aged conditions, respectively. Regardless of the post weld heat treatment condition, both autogenously and non-autogenously laser-welded specimens fractured in between the equiaxed and fusion zone during tensile loading.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.matchar.2021.111257} (DOI). Examilioti, T.; Kashaev, N.; Ventzke, V.; Klusemann, B.; Alexopoulos, N.: Effect of filler wire and post weld heat treatment on the mechanical properties of laser beam-welded AA2198. In: Materials Characterization. Vol. 178 (2021) 111257. (DOI:  /10.1016/j.matchar.2021.111257)}}
@article{odermatt_effect_of_2021, 
author={Odermatt, A. and Ventzke, V. and Dorn, F. and Dinsé, R. and Merhof, P. and Kashaev, N.},
title={Effect of laser beam welding on microstructure, tensile strength and fatigue behaviour of duplex stainless steel 2205},
year={2021},
journal = {Journal of Manufacturing Processes},
volume = {72},
pages = {148 - 158},
doi = {10.1016/j.jmapro.2021.10.020},
abstract = {This study focuses on the microstructure, tensile and fatigue properties of laser beam welded butt joints in 4 mm thick sheets of duplex stainless steel 2205. The microstructural characteristics of the joints were investigated via optical microscopy and electron backscattered diffraction. A 300 μm wide heat affect zone with increased ferrite content and a nearly fully ferritic 800 μm wide fusion zone were found. No porosity could be found with X-ray radiography. Microhardness measurements revealed increased strength in the fusion and heat affect zones of the weldments. Uniaxial tensile and stress controlled fatigue tests were performed in order to characterize the mechanical properties of specimens containing laser beam welded joints and the base material. The specimens containing weldments were stronger, but less ductile than the base material, due to the weld metal restricting deformation. The as-welded joints exhibited worse fatigue performance than the base material due to the notch at the excess weld metal. The fatigue properties of the specimens containing joints could be elevated to the base material level by a laser surface remelting treatment.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jmapro.2021.10.020} (DOI). Odermatt, A.; Ventzke, V.; Dorn, F.; Dinsé, R.; Merhof, P.; Kashaev, N.: Effect of laser beam welding on microstructure, tensile strength and fatigue behaviour of duplex stainless steel 2205. In: Journal of Manufacturing Processes. Vol. 72 (2021) 148 - 158. (DOI:  /10.1016/j.jmapro.2021.10.020)}}
@article{chiuzuli_effect_of_2021, 
author={Chiuzuli, F. and Batistão, B. and Bergmann, L. and Alcantara, N. and dos Santos, J. and Klusemann, B. and Gargarella, P.},
title={Effect of the Gap Width in AZ31 Magnesium Alloy Joints Obtained by Friction Stir Welding},
year={2021},
journal = {Journal of Materials Research and Technology : JMRT},
volume = {15},
pages = {5297 - 5306},
doi = {10.1016/j.jmrt.2021.10.115},
abstract = {Thin AZ31 magnesium alloy sheets, i.e., 2 mm thick, are welded by Friction Stir Welding (FSW) in butt joint configuration using gap width up to 1.15 mm. All welds present good surface finishing and no internal defects, except for the weld produced using the maximum gap width. A reduction of the weld thickness within the Stir Zone is seen with the increase in gap width, leading to a maximum thickness reduction of 8.5%. Microstructure and Vickers hardness investigations reveal no influence of the gap width on these properties. Up to a gap width of 0.51 mm, a slight decrease in the Ultimate Tensile Strength (UTS) is observed with increasing gap width. For larger gap widths, the UTS, as well as the fracture strain, are constant. To keep the metallurgical integrity, a maximum gap width of 1 mm seems acceptable for joints of thin AZ31 magnesium alloy sheets produced by FSW.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jmrt.2021.10.115} (DOI). Chiuzuli, F.; Batistão, B.; Bergmann, L.; Alcantara, N.; dos Santos, J.; Klusemann, B.; Gargarella, P.: Effect of the Gap Width in AZ31 Magnesium Alloy Joints Obtained by Friction Stir Welding. In: Journal of Materials Research and Technology : JMRT. Vol. 15 (2021) 5297 - 5306. (DOI:  /10.1016/j.jmrt.2021.10.115)}}
@article{janga_experimental_and_2021, 
author={Janga, V.S.R. and Awang, M. and Yamin, M.F. and Suhuddin, U.F.H. and Klusemann, B. and Dos Santos, J.F.},
title={Experimental and Numerical Analysis of Refill Friction Stir Spot Welding of Thin AA7075-T6 Sheets},
year={2021},
journal = {Materials},
volume = {14},
number = {23},
pages = {7485},
doi = {10.3390/ma14237485},
abstract = {The refill friction stir spot welding (refill FSSW) process is a solid-state joining process to produce welds without a keyhole in spot joint configuration. This study presents a thermo-mechanical model of refill FSSW, validated on experimental thermal cycles for thin aluminium sheets of AA7075-T6. The temperatures in the weld centre and outside the welding zone at selected points were recorded using K-type thermocouples for more accurate validation of the thermo-mechanical model. A thermo-mechanical three-dimensional refill FSSW model was built using DEFORM-3D. The temperature results from the refill FSSW numerical model are in good agreement with the experimental results. Three-dimensional material flow during plunging and refilling stages is analysed in detail and compared to experimental microstructure and hardness results. The simulation results obtained from the refill FSSW model correspond well with the experimental results. The developed 3D numerical model is able to predict the thermal cycles, material flow, strain, and strain rates which are key factors for the identification and characterization of zones as well for determining joint quality.},
note = {Online available at: \url{https://dx.doi.org/10.3390/ma14237485} (DOI). Janga, V.S.R.; Awang, M.; Yamin, M.F.; Suhuddin, U.F.H.; Klusemann, B.; Dos Santos, J.F.: Experimental and Numerical Analysis of Refill Friction Stir Spot Welding of Thin AA7075-T6 Sheets. In: Materials. Vol. 14 (2021) 23, 7485. (DOI:  /10.3390/ma14237485)}}
@article{ehrich_influence_of_2021, 
author={Ehrich, J. and Roos, A. and Klusemann, B. and Hanke, S.},
title={Influence of Mg content in Al alloys on processing characteristics and dynamically recrystallized microstructure of friction surfacing deposits},
year={2021},
journal = {Materials Science and Engineering: A},
volume = {819},
pages = {141407},
doi = {10.1016/j.msea.2021.141407},
abstract = {Friction Surfacing (FS) coatings are deposited by severe plastic deformation at elevated temperatures (≈0.8*Tliquidus), requiring different process parameters for alloys of even small composition variations. For Al alloys it is known that with increasing Mg content the thermal softening rate decreases, i.e. the material retains higher flow strength under thermomechanical processing. Further, the stacking fault energy (SFE) decreases with increasing Mg content, which influences gliding characteristics of dislocations, and also deformation and recrystallization behavior. To elucidate the influence of such known properties on FS process parameters and resulting coatings, three Al alloys differing only in Mg content (0.27, 2 and 3.5 wt.%) were processed by FS in this study.

Pronounced shear flow localization was observed for increasing Mg content, yielding thin and narrow coatings and requiring a reduction of process speeds. Further, the decrease in SFE with increasing Mg content resulted in lower recrystallized grain size and higher grain orientation differences, due to a lower tendency for dislocation annihilation by recovery.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.msea.2021.141407} (DOI). Ehrich, J.; Roos, A.; Klusemann, B.; Hanke, S.: Influence of Mg content in Al alloys on processing characteristics and dynamically recrystallized microstructure of friction surfacing deposits. In: Materials Science and Engineering: A. Vol. 819 (2021) 141407. (DOI:  /10.1016/j.msea.2021.141407)}}
@article{beirau_percolation_transitions_2021, 
author={Beirau, T. and Huber, N.},
title={Percolation transitions in pyrochlore: Radiation-damage and thermally induced structural reorganization},
year={2021},
journal = {Applied Physics Letters},
volume = {119},
number = {13},
pages = {131905},
doi = {10.1063/5.0068685},
abstract = {Finite element mechanical modeling is used to follow the evolution of the hardness (H), Young's modulus (E), and Poisson's ratio (ν) during the radiation-damage related crystalline-to-amorphous transition in pyrochlore (average main composition Ca2Nb2O6F). According to the model, two percolation transitions have been identified around 16% and 84% amorphous volume fraction, respectively. In this context, earlier results from thermally induced recrystallization experiments have found to indicate noticeable modifications on the short- and long-range order by passing the percolation thresholds. Both percolation points have found to act as specific kinetic barriers during stepwise annealing induced structural reorganization. As phases with pyrochlore structure have been considered as host structures for the long-term disposal of actinides, it is essential to gain better knowledge of their mechanical behavior under radiation-damage and subsequent temperature treatment. The obtained results validate the used models' robustness in predicting radiation-damage related mechanical modifications, at least for ceramics.},
note = {Online available at: \url{https://dx.doi.org/10.1063/5.0068685} (DOI). Beirau, T.; Huber, N.: Percolation transitions in pyrochlore: Radiation-damage and thermally induced structural reorganization. In: Applied Physics Letters. Vol. 119 (2021) 13, 131905. (DOI:  /10.1063/5.0068685)}}
@article{haensch_thermally_driven_2020, 
author={Haensch, M. and Graf, M. and Wang, W. and Nefedov, A. and Wöll, C. and Weissmüller, J. and Wittstock, G.},
title={Thermally Driven Ag–Au Compositional Changes at the Ligament Surface in Nanoporous Gold: Implications for Electrocatalytic Applications},
year={2020},
journal = {ACS Applied Nano Materials},
volume = {3},
number = {3},
pages = {2197 - 2206},
doi = {10.1021/acsanm.9b02279},
abstract = {Nanoporous gold (NPG) is a versatile, nanoporous bulk material with applications in catalysis, sensors, energy materials, and actuation. NPG obtained from dealloying Ag-rich Au–Ag alloys has interesting applications in electrocatalysis, for which methanol oxidation is an interesting test case. Such materials always contain a content of residual silver which may play a role in activating and binding of reaction intermediates. The residual Ag that is contained in NPG due to the dealloying of a Ag–Au alloy was recently found to be present in silver-rich islands, in contrast to being homogeneously distributed. Because of the importance of residual Ag on the surface science and catalytic properties of NPG, we investigated its distribution and chemical nature with the use of X-ray photoelectron spectroscopy. During the in situ annealing, changes of the near surface content of residual Ag were observed, and they were linked to coarsening of the gold ligaments. In addition, a depth-dependent analysis of synchrotron-based XPS results confirmed the surface segregation in the near surface layers of each ligament. The available data neither confirm nor exclude a further systematic enrichment or depletion of silver in the topmost atomic layer for NPG during electrochemical treatments in KOH solution or during thermal coarsening.},
note = {Online available at: \url{https://dx.doi.org/10.1021/acsanm.9b02279} (DOI). Haensch, M.; Graf, M.; Wang, W.; Nefedov, A.; Wöll, C.; Weissmüller, J.; Wittstock, G.: Thermally Driven Ag–Au Compositional Changes at the Ligament Surface in Nanoporous Gold: Implications for Electrocatalytic Applications. In: ACS Applied Nano Materials. Vol. 3 (2020) 3, 2197 - 2206. (DOI:  /10.1021/acsanm.9b02279)}}
@article{zhou_selective_laser_2020, 
author={Zhou, S. and Su, Y. and Wang, H. and Enz, J. and Ebel, T. and Yan, M. and },
title={Selective laser melting additive manufacturing of 7xxx series Al-Zn-Mg-Cu alloy: Cracking elimination by co-incorporation of Si and TiB2},
year={2020},
journal = {Additive Manufacturing},
volume = {36},
pages = {101458},
doi = {10.1016/j.addma.2020.101458},
abstract = {7xxx Al alloys such as Al-Zn-Mg-Cu are typical lightweight materials of excellent mechanical performance. Their near-net-shape manufacturing by selective laser melting (SLM) additive manufacturing, however, remains challenging due to hot-cracking prone nature of these alloys, when subjected to rapid solidification during the SLM process. In this study, we propose that co-incorporation of submicron Si and TiB2 to an Al-Zn-Mg-Cu alloy is capable to solve the long-standing problem by reducing solidification shrinkage and, simultaneously, enhancing its fracture toughness. Results show that solidification cracks indeed have been eliminated by the co-incorporation, along with much-refined microstructure. The resultant mechanical properties are high in ultimate tensile (556 ± 12 MPa) and yield strengths (455 ± 4.3 MPa). For disclosing the underlying mechanism, analytical means including high-resolution computer tomography, transmission electron microscopy and electron backscatter diffraction, as well as finite element simulation have been employed. It is aspired that the current approach can enable SLM to process critical engineering materials such as the hard-to-weld Al-Zn-Mg-Cu alloys.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.addma.2020.101458} (DOI). Zhou, S.; Su, Y.; Wang, H.; Enz, J.; Ebel, T.; Yan, M.; : Selective laser melting additive manufacturing of 7xxx series Al-Zn-Mg-Cu alloy: Cracking elimination by co-incorporation of Si and TiB2. In: Additive Manufacturing. Vol. 36 (2020) 101458. (DOI:  /10.1016/j.addma.2020.101458)}}
@article{examilioti_on_the_2020, 
author={Examilioti, T. and Kashaev, N. and Enz, J. and Klusemann, B. and Alexopoulos, N.},
title={On the influence of laser beam welding parameters for autogenous AA2198 welded joints},
year={2020},
journal = {The International Journal of  Advanced Manufacturing Technology},
volume = {110},
pages = {2079 - 2092},
doi = {10.1007/s00170-020-05893-8},
abstract = {The effects of different autogenous laser beam welding process parameters on the fusion zone (FZ) geometry, microstructure, and tensile mechanical properties were investigated for 5-mm-thick AA2198 alloy sheets. Porosity formation and hot cracking are observed for low laser powers and welding velocities, while the porosity level is essentially reduced with increasing laser power. The characteristic cross-sectional geometry of the welded joints changes with increasing laser power, taking shapes from narrow V shape to rectangular I shape, and the results are discussed based on the “closed” and “open” keyhole formation during laser beam welding. A methodology is exploited in terms of quantifying the geometrical dimensions of the cross-section of the FZ in order to promote the welded joints with a narrow width as well as with a rectangular shape. The optimal process parameters, leading to FZ close to the desirable rectangular I shape and with a low number of defects, are identified. Microstructural analyses reveal a pronounced transition zone in between the FZ and the heat-affected zone, which is subdivided into two narrow zones, the partially melted zone (PMZ) and the equiaxed zone. The narrow width of the FZ and PMZ, as well as the rectangular shape of the FZ, enables the autogenous welded joint to reach good tensile deformation properties.},
note = {Online available at: \url{https://dx.doi.org/10.1007/s00170-020-05893-8} (DOI). Examilioti, T.; Kashaev, N.; Enz, J.; Klusemann, B.; Alexopoulos, N.: On the influence of laser beam welding parameters for autogenous AA2198 welded joints. In: The International Journal of  Advanced Manufacturing Technology. Vol. 110 (2020) 2079 - 2092. (DOI:  /10.1007/s00170-020-05893-8)}}
@article{kallien_experimentally_established_2020, 
author={Kallien, Z. and Rath, L. and Roos, A. and Klusemann, B.},
title={Experimentally established correlation of friction surfacing process temperature and deposit geometry},
year={2020},
journal = {Surface and Coatings Technology},
volume = {397},
pages = {126040},
doi = {10.1016/j.surfcoat.2020.126040},
abstract = {Friction surfacing (FS), a solid-state joining process, is a coating technology for metallic materials. Friction and plastic deformation enable the deposition of a consumable material on a substrate below the melting temperature. Process temperatures are an important factor determining the quality and geometry of the deposit. A detailed experimental study of the process temperatures during FS of dissimilar aluminum alloys is performed. The process temperature profiles for varied process parameters, i.e. axial force, rotational speed and travel speed as well as process environment, are investigated. The results show that axial process force and rotational speed are the dominant process parameters affecting the temperatures during the FS process. Additionally, backing material and substrate thickness have significant impact on the process temperatures. The correlation of deposit geometry with process temperature shows thinner and slightly wider deposits for increasing process temperatures. This finding pronounces the importance of the temperature for the friction surfacing process with regard to geometry of the resulting deposit.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.surfcoat.2020.126040} (DOI). Kallien, Z.; Rath, L.; Roos, A.; Klusemann, B.: Experimentally established correlation of friction surfacing process temperature and deposit geometry. In: Surface and Coatings Technology. Vol. 397 (2020) 126040. (DOI:  /10.1016/j.surfcoat.2020.126040)}}
@article{zhang_simultaneously_enhancing_2020, 
author={Zhang, S. and Chen, G. and Qu, T. and Fang, G. and Bai, S. and Yan, Y. and Zhang, G. and Zhou, Z. and Shen, J. and Yao, D. and Zhang, Y. and Shi, Q.},
title={Simultaneously enhancing mechanical properties and electrical conductivity of aluminum by using graphene as the reinforcement},
year={2020},
journal = {Materials Letters},
volume = {265},
pages = {127440},
doi = {10.1016/j.matlet.2020.127440},
abstract = {In this study, we demonstrated simultaneously enhanced mechanical properties and electrical conductivity of pure aluminum (Al) by incorporating graphene as the reinforcement. The graphene/Al nanocomposite was fabricated by friction stir processing (FSP) combined with hot extrusion. It was found that graphene was homogeneously dispersed into Al matrix and directly bonded graphene/Al interfaces were formed, which were the structure basis for the simultaneously improved electrical and mechanical properties. This study provides new strategy for fabricating high-strength and highly conductive graphene/Al nanocomposites.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.matlet.2020.127440} (DOI). Zhang, S.; Chen, G.; Qu, T.; Fang, G.; Bai, S.; Yan, Y.; Zhang, G.; Zhou, Z.; Shen, J.; Yao, D.; Zhang, Y.; Shi, Q.: Simultaneously enhancing mechanical properties and electrical conductivity of aluminum by using graphene as the reinforcement. In: Materials Letters. Vol. 265 (2020) 127440. (DOI:  /10.1016/j.matlet.2020.127440)}}
@article{li_datasets_for_2020, 
author={Li, Y. and Dinh-Ngô, B. and Markmann, J. and Weissmüller, J.},
title={Datasets for the microstructure of nanoscale metal network structures and for its evolution during coarsening},
year={2020},
journal = {Data in Brief},
volume = {29},
pages = {105030},
doi = {10.1016/j.dib.2019.105030},
abstract = {The datasets in this work are files containing atom position coordinates of volume elements approximating nanoporous gold made by dealloying and annealing. The material is represented in an as-prepared state and in various stages of coarsening, as described in Phys. Rev. Mater, 3 (2019) 076001. Realistic initial structures of different solid fractions have been constructed by the leveled-wave algorithm, approximating mixtures at the end of early-stage spinodal decomposition. The microstructural evolution during coarsening by surface diffusion was approximated by on-lattice kinetic Monte-Carlo simulation. The data sets refer to solid fractions from 0.22 to 0.50, providing for different initial connectivity of the bicontinuous structures. Coarsening at two temperatures, 900 K and 1800 K, explores two different degrees of surface energy anisotropy – more faceted at 900 K and more rough at 1800 K. Each structure takes the form of a face-centred cubic lattice with approximately 32 million sites. A site can be occupied by either void or atom. 3D periodic boundary conditions are satisfied. Tables list each structure's properties, and specifically the specific surface area, two different measures for the ligament size, the net topological genus as well as the scaled genus. The atom coordinate files may serve as the basis for geometry analysis and for atomistic as well as finite element simulation studies of nanoporous as well as spinodally decomposed materials. The data sets are accessible via the TORE repository at http://hdl.handle.net/11420/3253.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.dib.2019.105030} (DOI). Li, Y.; Dinh-Ngô, B.; Markmann, J.; Weissmüller, J.: Datasets for the microstructure of nanoscale metal network structures and for its evolution during coarsening. In: Data in Brief. Vol. 29 (2020) 105030. (DOI:  /10.1016/j.dib.2019.105030)}}
@article{goushegir_durability_of_2020, 
author={Goushegir, S. and Scharnagl, N. and dos Santos, J. and Amancio-Filho, S.},
title={Durability of Metal-Composite Friction Spot Joints under Environmental Conditions },
year={2020},
journal = {Materials},
volume = {13},
number = {5},
pages = {1144},
doi = {10.3390/ma13051144},
abstract = {The current paper investigates the durability of the single-lap shear aluminum-composite friction spot joints and their behavior under harsh accelerated aging as well as natural weathering conditions. Four aluminum surface pre-treatments were selected to be performed on the joints based on previous investigations; these were sandblasting (SB), conversion coating (CC), phosphoric acid anodizing (PAA), and PAA with a subsequent application of primer (PAA-P). Most of the pre-treated specimens retained approximately 90% of their initial as-joined strength after accelerated aging experiments. In the case of the PAA pre-treatment, the joint showed a lower retained strength of about 60%. This was explained based on the penetration of humidity into the fine pores of the PAA pre-treated aluminum, reducing the adhesion between the aluminum and composite. Moreover, friction spot joints produced with three selected surface pre-treatments were held under outside natural weathering conditions for one year. PAA-P surface pre-treated specimens demonstrated the best performance with a retained strength of more than 80% after one year. It is believed that tight adhesion and chemical bonding reduced the penetration of humidity at the interface between the joining parts. View Full-Text},
note = {Online available at: \url{https://dx.doi.org/10.3390/ma13051144} (DOI). Goushegir, S.; Scharnagl, N.; dos Santos, J.; Amancio-Filho, S.: Durability of Metal-Composite Friction Spot Joints under Environmental Conditions . In: Materials. Vol. 13 (2020) 5, 1144. (DOI:  /10.3390/ma13051144)}}
@article{raza_multiphasefield_modeling_2020, 
author={Raza, S. and Klusemann, B.},
title={Multiphase-field modeling of temperature-driven intermetallic compound evolution in an Al–Mg system for application to solid-state joining processes},
year={2020},
journal = {Modelling and Simulation in Materials Science Engineering},
volume = {28},
number = {8},
pages = {085003},
doi = {10.1088/1361-651X/aba1df},
abstract = {Solid-state joining of dissimilar materials results typically in the formation of intermetallic compounds at the weld interface, which strongly determines the resulting mechanical properties. To tailor the joint strength, understanding of the formation of the intermetallic compound and their driving mechanisms is crucial. In this study, the evolution of temperature-driven Al3Mg2 and Al12Mg17 intermetallic compounds in an Al-Mg system for application to solid-state joining processes via a multiphase-field approach is numerically investigated. To this end, the CALPHAD approach to obtain the thermodynamic parameters of the relevant phases is used in conjunction with the multiphase-field model. The simulation results are qualitatively compared with experimental results in the literature in terms of thickness and morphology of intermetallic grains, exhibiting a reasonable agreement. The influence of grain boundary diffusion and interface energy on the morphology and kinetics of the intermetallic compound grains is investigated in detail with the established multiphase-field model.},
note = {Online available at: \url{https://dx.doi.org/10.1088/1361-651X/aba1df} (DOI). Raza, S.; Klusemann, B.: Multiphase-field modeling of temperature-driven intermetallic compound evolution in an Al–Mg system for application to solid-state joining processes. In: Modelling and Simulation in Materials Science Engineering. Vol. 28 (2020) 8, 085003. (DOI:  /10.1088/1361-651X/aba1df)}}
@article{patel_tailoring_grain_2020, 
author={Patel, V. and Li, W. and Liu, X. and Wen, Q. and Su, Y. and Shen, J. and Fu, B.},
title={Tailoring grain refinement through thickness in magnesium alloy via stationary shoulder friction stir processing and copper backing plate},
year={2020},
journal = {Materials Science and Engineering A},
volume = {784},
pages = {139322},
doi = {10.1016/j.msea.2020.139322},
abstract = {To develop ultrafine grains (UFG) in 6.35 mm thick magnesium alloy, stationary shoulder friction stir processing (SSFSP) with steel and copper backing plates was conducted. Steel backing plate produced uniform fine grains (FG) size of 4.98, 4.75, 4.12 μm in top, middle, bottom of the stir zone (SZ), respectively. In contrast, copper backing plate tailored microstructure from FG (4.1 μm) in the top to UFG (0.96 μm) in the bottom of SZ. SSFSP produced uniform and gradient microstructures, altering temperature gradient by placing steel and copper backing plates, respectively. It is worth to note that UFG microstructure achieved without usage of external cooling, owning to the copper backing plate. Most of the grains found under ~2 μm size in UFG microstructure. FG and UFG microstructures contributed to the enhancement in the ductility and strength, respectively. UFG resulted in significant improvement in hardness and tensile strength by ~80% and 24% of the base material, respectively. The intensity of strong basal texture throughout the thickness found independent of the backing plate type. Microstructure evolutions across the SZ thickness for both processing conditions are discussed using electron back scattered diffraction (EBSD).},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.msea.2020.139322} (DOI). Patel, V.; Li, W.; Liu, X.; Wen, Q.; Su, Y.; Shen, J.; Fu, B.: Tailoring grain refinement through thickness in magnesium alloy via stationary shoulder friction stir processing and copper backing plate. In: Materials Science and Engineering A. Vol. 784 (2020) 139322. (DOI:  /10.1016/j.msea.2020.139322)}}
@article{arndt_the_dealii_2020, 
author={Arndt, D. and Bangerth, W. and Blais, B. and Clevenger, T.C. and Fehling, M. and Grayver, A.V. and Heister, T. and Heltai, L. and Kronbichler, M. and Maier, M. and Munch, P. and Pelteret, J.-P. and Rastak, R. and Tomas, I. and Turcksin, B. and Wang, Z. and Wells, D.},
title={The deal.II library, Version 9.2},
year={2020},
journal = {Journal of Numerical Mathematics},
volume = {28},
number = {3},
pages = {131 - 146},
doi = {10.1515/jnma-2020-0043},
abstract = {This paper provides an overview of the new features of the finite element library deal.II, version 9.2.},
note = {Online available at: \url{https://dx.doi.org/10.1515/jnma-2020-0043} (DOI). Arndt, D.; Bangerth, W.; Blais, B.; Clevenger, T.C.; Fehling, M.; Grayver, A.V.; Heister, T.; Heltai, L.; Kronbichler, M.; Maier, M.; Munch, P.; Pelteret, J.-P.; Rastak, R.; Tomas, I.; Turcksin, B.; Wang, Z.; Wells, D.: The deal.II library, Version 9.2. In: Journal of Numerical Mathematics. Vol. 28 (2020) 3, 131 - 146. (DOI:  /10.1515/jnma-2020-0043)}}
@article{ageev_singleshot_femtosecond_2020, 
author={Ageev, E. and Andreeva, Y. and Ionin, A. and Kashaev, N. and Kudryashov, S. and Nikonorov, N. and Nuryev, R. and Petrov, A. and Rudenko, A. and Samokhvalov, A. and Saraeva, I. and Veiko, V.},
title={Single-shot femtosecond laser processing of Al-alloy surface: An interplay between Mbar shock waves, enhanced microhardness, residual stresses, and chemical modification},
year={2020},
journal = {Optics and Laser Technology},
volume = {126},
pages = {106131},
doi = {10.1016/j.optlastec.2020.106131},
abstract = {Ambient-air single-shot ablative femtosecond laser surface processing of an advanced Al-alloy AA5083 was characterized by non-contact broadband ultrasonics, scanning electron microscopy with energy-dispersive x-ray spectroscopy, x-ray diffraction, and Vickers microhardness tests. The characterization indicates that the generated Mbar-level shock waves induce not only a strong structural modification of the processed micron-thick surface layer with sub-GPa-level residual compressive and tensile stresses, raising its microhardness by almost 45%, but also significant depth-dependent chemical modification within the layer.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.optlastec.2020.106131} (DOI). Ageev, E.; Andreeva, Y.; Ionin, A.; Kashaev, N.; Kudryashov, S.; Nikonorov, N.; Nuryev, R.; Petrov, A.; Rudenko, A.; Samokhvalov, A.; Saraeva, I.; Veiko, V.: Single-shot femtosecond laser processing of Al-alloy surface: An interplay between Mbar shock waves, enhanced microhardness, residual stresses, and chemical modification. In: Optics and Laser Technology. Vol. 126 (2020) 106131. (DOI:  /10.1016/j.optlastec.2020.106131)}}
@article{maghsoudi_detwinningmediated_hardening_2020, 
author={Maghsoudi, M. and Ziehmer, M. and Lilleodden, E.},
title={Detwinning-mediated hardening in Mg: A microcompression study of a single twin boundary},
year={2020},
journal = {Materials Science and Engineering A},
volume = {772},
pages = {138747},
doi = {10.1016/j.msea.2019.138747},
abstract = {We present the first experimental measurement of the hardening arising from the detwinning of a single twin boundary in Mg. Microcompression tests were performed on two sets of microcolumns: (i) single crystals having a “parent” grain orientation of nearly (0 0 0 1) along the compression axis, and (ii) bicrystals involving the parent grain and a single twin boundary. A comparison of the stress-strain data shows significant differences in the deformation characteristics of the deformed microcolumns. The bicrystalline microcolumns undergo detwinning, as indicated by a stress plateau, which leads to a nominally single crystalline microcolumn of the orientation of the parent grain. Microcompression beyond the plateau shows that the detwinned microcolumns exhibit a considerably higher yield stress and strain hardening rate than the single crystalline “parent” microcolumns. Electron back-scattered diffraction analyses on the cross-sections of the deformed microcolumns reveal higher misorientations in the detwinned region indicative of a high content of unpaired dislocations (so-called GNDs), compared to the deformed parent microcolumns. This discrepancy in misorientation distribution between the samples is consistent with a detwinning-mediated hardening response, as observed, and points to the creation of dislocation debris as a consequence of the detwinning process.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.msea.2019.138747} (DOI). Maghsoudi, M.; Ziehmer, M.; Lilleodden, E.: Detwinning-mediated hardening in Mg: A microcompression study of a single twin boundary. In: Materials Science and Engineering A. Vol. 772 (2020) 138747. (DOI:  /10.1016/j.msea.2019.138747)}}
@article{bazazzadeh_an_adaptive_2020, 
author={Bazazzadeh, S. and Mossaiby, F. and Shojaei, A.},
title={An adaptive thermo-mechanical peridynamic model for fracture analysis in ceramics},
year={2020},
journal = {Engineering Fracture Mechanics},
volume = {223},
pages = {106708},
doi = {10.1016/j.engfracmech.2019.106708},
abstract = {A thermo-mechanical peridynamic model using adaptive grid refinement is developed to investigate crack propagation in ceramics. Compared to a standard peridynamic model, using uniform grid, this approach allows to increase the resolution of analysis only in the critical zones. The performance of this approach in solving 2D thermo-elastic problems is examined and then it is applied to study the fracture of a ceramic disk under central thermal shock. Finally, the proposed approach is adopted to investigate thermal shock in thin rectangular and circular slabs. The accuracy of the method is evaluated by comparing its numerical results with those obtained by applying the finite element method (FEM), a standard peridynamic approach or with experimental data available in the literature. A proper agreement is achieved at a smaller computational cost.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.engfracmech.2019.106708} (DOI). Bazazzadeh, S.; Mossaiby, F.; Shojaei, A.: An adaptive thermo-mechanical peridynamic model for fracture analysis in ceramics. In: Engineering Fracture Mechanics. Vol. 223 (2020) 106708. (DOI:  /10.1016/j.engfracmech.2019.106708)}}
@article{borba_mechanical_integrity_2020, 
author={Borba, N. and Kötter, B. and Fiedler, B. and dos Santos, J.F. and Amancio-Filho, S.T.},
title={Mechanical integrity of friction-riveted joints for aircraft applications},
year={2020},
journal = {Composite Structures},
volume = {232},
pages = {111542},
doi = {10.1016/j.compstruct.2019.111542},
abstract = {The predictability of damage evolution is a challenge for mechanical joints of composite structures due to the highly nonlinear material behavior. In this study, friction riveting was investigated as an alternative joining technology for composite laminates by analyzing experimentally the joint mechanical behavior under different loading scenarios. The failure and fracture micro-mechanisms of composite laminate single lap joints were studied under quasi-static and cyclic loading. The joints failed mainly by rivet detachment from the composite hole, followed by adhesive/cohesive failure of the squeezed material, and rivet pull-through failure. Despite lower quasi-static strength of friction-riveted joints (6.2 ± 0.3 kN) compared to reference bolted joints (8.7 ± 0.2 kN), their fatigue life was higher by 88%. The main improving contributions were: the squeezed material, working as an adhesive between the composite parts and an additional fracture micro-mechanism, and the absence of clearance at the rivet-composite interface, which promoted an improved load transfer between the joined parts.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.compstruct.2019.111542} (DOI). Borba, N.; Kötter, B.; Fiedler, B.; dos Santos, J.F.; Amancio-Filho, S.T.: Mechanical integrity of friction-riveted joints for aircraft applications. In: Composite Structures. Vol. 232 (2020) 111542. (DOI:  /10.1016/j.compstruct.2019.111542)}}
@article{philipp_the_accuracy_2020, 
author={Philipp, A. and Eichinger, J.F. and Aydin, R.C. and Georgiadis, A. and Cyron, C.J. and Retsch, M.},
title={The accuracy of laser flash analysis explored by finite element method and numerical fitting},
year={2020},
journal = {Heat and Mass Transfer},
volume = {56},
pages = {811 - 823},
doi = {10.1007/s00231-019-02742-7},
abstract = {Laser flash analysis (LFA) has become over the last decades a widely used standard technique to measure the thermal diffusivity of bulk materials under various conditions like different gases, atmospheric pressures, and temperatures. A curve fitting procedure forms the heart of LFA. This procedure bases on a mathematical model that should ideally account for inherent shortcomings of the experimental realization such as: duration of the heating pulse, heat losses to the environment and sample holder, non-opaque samples, and radiative heat transfer. The accuracy of the mathematical model and curve fitting algorithm underlying LFA defines an upper bound of the accuracy of LFA in general. Unfortunately, not much is known about the range of parameters and conditions for which this accuracy is acceptable. In this paper, we examine the limits of accuracy of LFA resulting from its underlying computational framework. To this end, we developed a particularly accurate and comprehensive computational framework and applied it to data from simulated experiments. We quantify the impact of different (simulated) experimental conditions on the accuracy of the results by comparing the fit results of our computational framework to the known simulation input parameters. This way we demonstrate that a state-of-the-art computational framework for LFA admits determining thermal conductivities of materials in a broad range from at least 0.16 W/mK to 238 W/mK with relative errors typically well below 4% even in the presence of common undesired experimental side effects.},
note = {Online available at: \url{https://dx.doi.org/10.1007/s00231-019-02742-7} (DOI). Philipp, A.; Eichinger, J.F.; Aydin, R.C.; Georgiadis, A.; Cyron, C.J.; Retsch, M.: The accuracy of laser flash analysis explored by finite element method and numerical fitting. In: Heat and Mass Transfer. Vol. 56 (2020) 811 - 823. (DOI:  /10.1007/s00231-019-02742-7)}}
@article{froend_microstructure_by_2020, 
author={Froend, M. and Ventzke, V. and Dorn, F. and Kashaev, N. and Klusemann, B. and Enz, J. and },
title={Microstructure by design: An approach of grain refinement and isotropy improvement in multi-layer wire-based laser metal deposition},
year={2020},
journal = {Materials Science and Engineering  A},
volume = {772},
pages = {138635},
doi = {10.1016/j.msea.2019.138635},
abstract = {The additive production of metallic components with high-throughput is usually associated with high process temperatures and slow cooling rates. This typically results in strongly oriented columnar grain growth along the building direction of the structure having exceedingly large grain sizes. As a result, such structures show typically low strength and anisotropic mechanical behaviour in as-deposited condition. Consequently, post-processing is commonly performed to homogenize and eventually increase the mechanical properties of the deposited structures. In this regard, precise control of the applied process energy allows a modification of the local temperature distribution and cooling conditions during the additive manufacturing process, which strongly influence the resulting solidification microstructure. The aim of the present study is the development of an approach that allows to influence the solidification conditions in wire-based laser metal deposition of an Al-Mg alloy through specific adjustments of the laser irradiation. It was found that significantly different solidification microstructures in as-deposited condition can be achieved by adjusting the laser beam irradiance within a range resulting in conduction mode welding conditions while keeping the heat input constant. The application of high laser beam irradiances, close to the transition to keyhole mode welding, results in structures with a homogeneous large-grained solidification microstructure exhibiting a degree of anisotropy of around 12% between building direction and the direction of deposition. In contrast, the use of low laser beam irradiance close to the lower limit of stable melting, results in structures with a significantly refined microstructure. Consequently, an increase of yield strength of up to around 20% and microhardness of up to 13%, as compared to structures processed with high laser beam irradiance, could be obtained. Moreover, the anisotropy of the as-deposited structure was reduced to a degree lower than 2%.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.msea.2019.138635} (DOI). Froend, M.; Ventzke, V.; Dorn, F.; Kashaev, N.; Klusemann, B.; Enz, J.; : Microstructure by design: An approach of grain refinement and isotropy improvement in multi-layer wire-based laser metal deposition. In: Materials Science and Engineering  A. Vol. 772 (2020) 138635. (DOI:  /10.1016/j.msea.2019.138635)}}
@article{borba_lowvelocity_impact_2020, 
author={Borba, N.Z. and Körbelin, J. and Fiedler, B. and dos Santos, J.F. and Amancio-Filho, S.T.},
title={Low-velocity impact response of friction riveted joints for aircraft application },
year={2020},
journal = {Materials and Design},
volume = {186},
pages = {108369},
doi = {10.1016/j.matdes.2019.108369},
abstract = {In this paper, the sensitivity of carbon fiber reinforced polyether-ether-ketone (CF-PEEK) friction riveted joints to impact damage was assessed as well as the damage propagation during fatigue and quasi-static mechanical testing. The joints were impacted with energies between 5 J and 30 J at room temperature and the impact damage was evaluated through microscopy and ultrasonic C-scan. Two damage types were identified: barely-visible impact damage with mainly shear-driven damage in the first plies of the composite and visible impact damage with delamination and premature failure of the rivet-composite interface owing to peel stresses upon the impact event. The joint strength and fatigue life were not compromised by the barely-visible impact damage, while a 40% decrease of quasi-static strength and lower fatigue resistance were achieved for visible impact damage. Despite altered fatigue behavior of impacted joints, damage accumulated towards fatigue was not critical to the joint mechanical integrity, confirmed by the residual strength of up to 96% after 1000000 cycles for 20 J impacts.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.matdes.2019.108369} (DOI). Borba, N.Z.; Körbelin, J.; Fiedler, B.; dos Santos, J.F.; Amancio-Filho, S.T. : Low-velocity impact response of friction riveted joints for aircraft application . In: Materials and Design. Vol. 186 (2020) 108369. (DOI:  /10.1016/j.matdes.2019.108369)}}
@article{herrnring_diffusiondriven_microstructure_2020, 
author={Herrnring, J. and Sundman, B. and Klusemann, B.},
title={Diffusion-driven microstructure evolution in OpenCalphad},
year={2020},
journal = {Computational Materials Science},
volume = {175},
pages = {109236},
doi = {10.1016/j.commatsci.2019.109236},
abstract = {The diffusion process in multicomponent alloys has a significant influence on the evolution of the microstructure. The Calphad approach is a powerful method for describing the equilibrium state as well as the kinetics of non-equilibrium systems via the Gibbs energy. In this work, the principles of multicomponent diffusion theory are considered intensively, and an equation for the fluxes in the case of substitutional-interstitial diffusion is given for implementation. Additionally, the calculation of mobility matrices and thermodynamic factors is addressed. As an application case, substitutional diffusion is implemented in OpenCalphad and is used for calculating the growth rate for spherical precipitates from a supersaturated aluminum matrix. The growth rate has been integrated into the Kampmann–Wagner numerical model, which describes nucleation, growth, and coarsening for spherical precipitates. A AlMgZnCu alloy is considered, which has great significance in the field of materials processing.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.commatsci.2019.109236} (DOI). Herrnring, J.; Sundman, B.; Klusemann, B.: Diffusion-driven microstructure evolution in OpenCalphad. In: Computational Materials Science. Vol. 175 (2020) 109236. (DOI:  /10.1016/j.commatsci.2019.109236)}}
@article{mossaiby_local_dirichlettype_2020, 
author={Mossaiby, F. and Shojaei, A. and Boroomand, B. and Zaccariotto, M. and Galvanetto, U.},
title={Local Dirichlet-type absorbing boundary conditions for transient elastic wave propagation problems},
year={2020},
journal = {Computer Methods in Applied Mechanics and Engineering},
volume = {362},
pages = {112856},
doi = {10.1016/j.cma.2020.112856},
abstract = {In this paper a new collocation technique for constructing time-dependent absorbing boundary conditions (ABCs) applicable to elastic wave motion is devised. The approach makes use of plane waves which satisfy the governing equations of motion to construct the absorbing boundary conditions. The plane waves are adjusted so that they can cope with the satisfaction of radiation boundary conditions. The proposed technique offers some advantages and exhibits the following features: it is easy to implement; its approximation scheme is local in space and time and thus it does not deal with any routine schemes such as Fourier and Laplace transform, making the method computationally less demanding; as the employed basis functions used to construct the absorbing boundary condition are residual-free, it requires neither any differential operator (to approximate the wave dispersion relation), nor any auxiliary variables; it constructs Dirichlet-type ABCs and hence no derivatives of the field variables are required for the imposition of radiation conditions. In this study, we apply the proposed technique to the solution procedure of a collocation approach based on the finite point method which proceeds in time by an explicit velocity-Verlet algorithm. It contributes to developing a consistent meshless framework for the solution of unbounded elastodynamic problems in time domain. We also apply the proposed method to a standard finite element solver. The performance of the method in solution of some 2D examples is examined. We shall show that the method exhibits appropriate results, conserves the energy almost exactly, and it performs stably in time even in the case of long-term computations.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.cma.2020.112856} (DOI). Mossaiby, F.; Shojaei, A.; Boroomand, B.; Zaccariotto, M.; Galvanetto, U.: Local Dirichlet-type absorbing boundary conditions for transient elastic wave propagation problems. In: Computer Methods in Applied Mechanics and Engineering. Vol. 362 (2020) 112856. (DOI:  /10.1016/j.cma.2020.112856)}}
@article{carrenomadinabeitia_sensitivity_studies_2020, 
author={Carreno-Madinabeitia, S. and Ibarra-Berastegi, G. and Sáenz, J. and Zorita, E. and Ulazia, A.},
title={Sensitivity Studies for a Hybrid Numerical–Statistical Short-Term Wind and Gust Forecast at Three Locations in the Basque Country (Spain)},
year={2020},
journal = {Atmosphere},
volume = {11},
number = {1},
pages = {45},
doi = {10.3390/atmos11010045},
abstract = {This study evaluates the performance of statistical models applied to the output of numerical models for short-term (1–24 h) hourly wind forecasts at three locations in the Basque Country. The target variables are horizontal wind components and the maximum wind gust at 3 h intervals. Statistical approaches such as persistence, analogues, linear regression, and random forest (RF) are used. The verification statistics used are coefficient of determination (R2) and root mean square error (RMSE). Statistical models use three inputs: (1) Local wind observations; (2) extended EOFs (empirical orthogonal functions) derived from past local observations and ERA-Interim variables in a previous 24-h period covering a domain around the area of study; and (3) wind forecasts provided by ERA-Interim. Results indicate that, for horizons less than 1–4 h, persistence is the best model. For longer predictions, RF provides the best forecasts. For horizontal components at 4–24 h horizons, RF slightly outperformed ERA-Interim wind forecasts. For gust, RF performs better than ERA-Interim for all the horizons. Persistence is the most influential factor for 2–5 h. Beyond this horizon, predictors from the ERA-Interim wind forecasts led the contribution. Hybrid numerical–statistical methods can be used to improve short-term wind forecasts.},
note = {Online available at: \url{https://dx.doi.org/10.3390/atmos11010045} (DOI). Carreno-Madinabeitia, S.; Ibarra-Berastegi, G.; Sáenz, J.; Zorita, E.; Ulazia, A.: Sensitivity Studies for a Hybrid Numerical–Statistical Short-Term Wind and Gust Forecast at Three Locations in the Basque Country (Spain). In: Atmosphere. Vol. 11 (2020) 1, 45. (DOI:  /10.3390/atmos11010045)}}
@article{vacchi_refill_friction_2020, 
author={Vacchi, G. and Silva, R. and Plaine, A. and Suhuddin, U. and Alcantara, N. and Sordi, V. and Rovere, C.},
title={Refill friction stir spot welded AA5754-H22/Ti-6Al-4V joints: Microstructural characterization and electrochemical corrosion behavior of aluminum surfaces},
year={2020},
journal = {Materials Today : Communications},
volume = {22},
pages = {100759},
doi = {10.1016/j.mtcomm.2019.100759},
abstract = {The present study assessed the influence of refill friction stir spot welding (RFSSW) process on the microstructure and electrochemical corrosion behavior of the AA5754-H22 alloy surface of an AA5754-H22/Ti-6Al-4 V overlapped joint. The results demonstrate that the RFSSW process promotes substantial microstrutural changes along the welded joint, which, in turn, reflect directly on the mechanical properties and corrosion behavior of distinct welding regions. The potentiodynamic polarization tests and electrochemical impedance spectroscopy measurements indicate that the stir zone region has better corrosion resistance than the other RFSS welded regions [heat affected zone and base metal] due to higher homogeneity and microstructure refinement. The achieved results are evidence that the RFSSW process is an interesting alternative for the welding of overlapping dissimilar joints.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.mtcomm.2019.100759} (DOI). Vacchi, G.; Silva, R.; Plaine, A.; Suhuddin, U.; Alcantara, N.; Sordi, V.; Rovere, C.: Refill friction stir spot welded AA5754-H22/Ti-6Al-4V joints: Microstructural characterization and electrochemical corrosion behavior of aluminum surfaces. In: Materials Today : Communications. Vol. 22 (2020) 100759. (DOI:  /10.1016/j.mtcomm.2019.100759)}}
@article{kashaev_on_the_2020, 
author={Kashaev, N. and Ushmaev, D. and Ventzke, V. and Klusemann, B. and Fomin, F.},
title={On the application of laser shock peening for retardation of surface fatigue cracks in laser beam‐welded AA6056},
year={2020},
journal = {Fatigue and Fracture of Engineering Materials and Structures},
volume = {43},
number = {7},
pages = {1500 - 1513},
doi = {10.1111/ffe.13226},
abstract = {The present study aims to investigate the extent to which the fatigue behaviour of laser beam‐welded AA6056‐T6 butt joints with an already existing crack can be improved through the application of laser shock peening. Ultrasonic testing was utilized for in situ (nondestructive) measurement of fatigue crack growth during the fatigue test. This procedure allowed the preparation of welded specimens with surface fatigue cracks with a depth of approximately 1.2 mm. The precracked specimens showed a 20% reduction in the fatigue limit compared with specimens without cracks in the as‐welded condition. Through the application of laser shock peening on the surfaces of the precracked specimens, it was possible to recover the fatigue life to the level of the specimens tested in the as‐welded condition. The results of this study show that laser shock peening is a very promising technique to recover the fatigue life of welded joints with surface cracks, which can be detected by nondestructive testing.},
note = {Online available at: \url{https://dx.doi.org/10.1111/ffe.13226} (DOI). Kashaev, N.; Ushmaev, D.; Ventzke, V.; Klusemann, B.; Fomin, F.: On the application of laser shock peening for retardation of surface fatigue cracks in laser beam‐welded AA6056. In: Fatigue and Fracture of Engineering Materials and Structures. Vol. 43 (2020) 7, 1500 - 1513. (DOI:  /10.1111/ffe.13226)}}
@article{sandmann_combined_experimentalnumerical_2020, 
author={Sandmann, P. and Nielsen, M. and Keller, S. and Maawad, E. and Staron, P. and Klusemann, B.},
title={Combined experimental–numerical study on residual stresses induced by a single impact as elementary process of mechanical peening},
year={2020},
journal = {Strain : the journal of the British Society for Strain Measurement},
volume = {56},
number = {4},
pages = {e12338},
doi = {10.1111/str.12338},
abstract = {Peening processes can be used as a fatigue enhancement treatment for metallic structures by locally introducing compressive residual stresses. A combined experimental–numerical study on a single‐impact process with a drop tower on the aluminium alloy AA5754, representing the elementary process of mechanical peening, has been performed to investigate different impact parameters on the residual stress profile. Residual stresses have been measured using high‐energy X‐Ray diffraction. A three‐dimensional finite element model is used to predict the residual stresses numerically. The elastic strain components from the numerical results are used to calculate residual stresses by assuming either a plane stress or a plane strain state for different specimen thickness to assess the validity of respective assumption. The validity of the numerical simulation is evaluated based on comparisons of the elastic strain profiles and the percentage loss in kinetic energy of the steel ball due to the impact for four different energies, showing overall a good agreement in the experimental–numerical comparisons.},
note = {Online available at: \url{https://dx.doi.org/10.1111/str.12338} (DOI). Sandmann, P.; Nielsen, M.; Keller, S.; Maawad, E.; Staron, P.; Klusemann, B.: Combined experimental–numerical study on residual stresses induced by a single impact as elementary process of mechanical peening. In: Strain : the journal of the British Society for Strain Measurement . Vol. 56 (2020) 4, e12338. (DOI:  /10.1111/str.12338)}}
@article{jeong_modellingassisted_description_2020, 
author={Jeong, Y. and Steglich, D.},
title={Modelling-assisted description of anisotropic edge failure in magnesium sheet alloy under mixed-mode loading},
year={2020},
journal = {International Journal of Mechanical Sciences},
volume = {181},
pages = {105680},
doi = {10.1016/j.ijmecsci.2020.105680},
abstract = {An uncoupled fracture criterion based on a simple damage indicator computed using a mean-field crystal plasticity framework is proposed and applied to predict failure of an AZ31 sheet originating from the edges. The damage indicator quantifies the contribution of strain components along the axes of orthotropy leading to material failure. The model is calibrated by uniaxial tension tests. The damage indicator is validated for various mixed-mode deformation histories realized by modified Arcan tests in various loading configurations. The loading history of respective fracture sites obtained from DIC analyses is directly employed to a visco-plastic self-consistent crystal plasticity model to obtain the stress responses. The results indicate that the damage indicator requires – beside the strain history – an input of stress triaxiality, by which an improved predictive accuracy can be achieved. This effect is quantified for various loading scenarios, in which cracks are initiated near or at the edge of the sample.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.ijmecsci.2020.105680} (DOI). Jeong, Y.; Steglich, D.: Modelling-assisted description of anisotropic edge failure in magnesium sheet alloy under mixed-mode loading. In: International Journal of Mechanical Sciences. Vol. 181 (2020) 105680. (DOI:  /10.1016/j.ijmecsci.2020.105680)}}
@article{scheider_numerical_residual_2020, 
author={Scheider, I. and Barbini, A. and dos Santos, J.},
title={Numerical residual strength prediction of stationary shoulder friction stir welding structures},
year={2020},
journal = {Engineering Fracture Mechanics},
volume = {230},
pages = {107010},
doi = {10.1016/j.engfracmech.2020.107010},
abstract = {The residual strength of a structure made of dissimilar Aluminium panels joined by a stationary shoulder friction stir welding (SSFSW) process is predicted by numerical simulation using finite elements including cohesive elements for crack propagation. The yield strength and strain hardening parameters within the stirred zone and adjacent thermo-mechanically affected and heat affected zones are derived from a tensile specimen cut out from the panel perpendicular to the weld seam. The identification is conducted by a hybrid numerical/experimental procedure with an inverse search by help of digital image correlation in order to obtain the strain field at the welded surface and to compare them to the numerical calculation. The crack propagation parameters are retrieved from specimens with crack in the stir zone and heat affected zone on either side. After this identification procedure, the fracture behaviour of a coupon specimen with a crack crossing the weld is predicted.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.engfracmech.2020.107010} (DOI). Scheider, I.; Barbini, A.; dos Santos, J.: Numerical residual strength prediction of stationary shoulder friction stir welding structures. In: Engineering Fracture Mechanics. Vol. 230 (2020) 107010. (DOI:  /10.1016/j.engfracmech.2020.107010)}}
@article{sikhamov_the_influence_2020, 
author={Sikhamov, R. and Fomin, F. and Klusemann, B. and Kashaev, N.},
title={The Influence of Laser Shock Peening on Fatigue Properties of AA2024-T3 Alloy with a Fastener Hole},
year={2020},
journal = {Metals},
volume = {10},
number = {4},
pages = {495},
doi = {10.3390/met10040495},
abstract = {The objective of the present study was to estimate the influence of laser shock peening on the fatigue properties of AA2024-T3 specimens with a fastener hole and to investigate the possibility to heal the initial cracks in such specimens. Fatigue cracks of different lengths were introduced in the specimens with a fastener hole before applying laser shock peening. Deep compressive residual stresses, characterized by the hole drilling method, were generated into the specimens by applying laser shock peening on both sides. Subsequently, the specimens were subjected to fatigue tests. The results show that laser shock peening has a positive effect regarding the fatigue life improvement in the specimens with a fastener hole. In addition, laser shock peening leads to a healing effect on fatigue cracks. The efficiency of this effect depends on the initial crack length. The effect of laser shock peening on the fatigue life periods was determined by using resonant frequency graphs.},
note = {Online available at: \url{https://dx.doi.org/10.3390/met10040495} (DOI). Sikhamov, R.; Fomin, F.; Klusemann, B.; Kashaev, N.: The Influence of Laser Shock Peening on Fatigue Properties of AA2024-T3 Alloy with a Fastener Hole. In: Metals. Vol. 10 (2020) 4, 495. (DOI:  /10.3390/met10040495)}}
@article{li_ultrathin_and_2020, 
author={Li, M. and Scheider, I. and Bor, B. and Domènech, B. and Schneider, G.A. and Giuntini, D.},
title={Ultra-thin and ultra-strong organic interphase in nanocomposites with supercrystalline particle arrangement: Mechanical behavior identification via multiscale numerical modeling},
year={2020},
journal = {Composites Science and Technology},
volume = {198},
pages = {108283},
doi = {10.1016/j.compscitech.2020.108283},
abstract = {A key challenge in the development of inorganic-organic nanocomposites is the mechanical behavior identification of the organic phase. For supercrystalline materials, in which the organic phase ranges down to sub-nm areas, the identification of the organic materials' mechanical properties is however experimentally inaccessible. The supercrystalline nanocomposites investigated here are 3D superlattices of self-assembled iron oxide nanoparticles, surface-functionalized with crosslinked oleic acid ligands. They exhibit the highest reported values of Young's modulus, nanohardness and strength for inorganic-organic nanocomposites. A multiscale numerical modeling approach is developed to identify these properties using supercrystalline representative volume elements, in which the nanoparticles are arranged in a face-centered cubic superlattice and the organic phase is modeled as a thin layer interfacing each particle. A Drucker-Prager-type elastoplastic constitutive law with perfectly plastic yielding is identified as being able to describe the supercrystals' response in nanoindentation accurately. As the nanoparticles behave in a purely elastic manner with very high stiffness, the underlying constitutive law of the organic phase is also identified to be Drucker-Prager-type elastoplastic, with a Young's modulus of 13GPa and a uniaxial tensile yield stress of 900MPa, remarkably high values for an organic material, and matching well with experimental and DFT-based estimations. Furthermore, a sensitivity study indicates that small configurational changes within the supercrystalline lattice do not significantly alter the overall stiffness behavior. Multiscale numerical modeling is thus proven to be able to identify the nanomechanical properties of supercrystals, and can ultimately be used to tailor these materials' mechanical behavior starting from superlattice considerations.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.compscitech.2020.108283} (DOI). Li, M.; Scheider, I.; Bor, B.; Domènech, B.; Schneider, G.A.; Giuntini, D.: Ultra-thin and ultra-strong organic interphase in nanocomposites with supercrystalline particle arrangement: Mechanical behavior identification via multiscale numerical modeling. In: Composites Science and Technology. Vol. 198 (2020) 108283. (DOI:  /10.1016/j.compscitech.2020.108283)}}
@article{eichinger_computercontrolled_biaxial_2020, 
author={Eichinger, J. and Paukner, D. and Szafron, J. and Aydin, R. and Humphrey, J. and Cyron, C.},
title={Computer-Controlled Biaxial Bioreactor for Investigating Cell-Mediated Homeostasis in Tissue Equivalents},
year={2020},
journal = {Journal of biomechanical engineering},
volume = {142},
number = {7},
pages = {071011},
doi = {10.1115/1.4046201},
abstract = {Soft biological tissues consist of cells and extracellular matrix (ECM), a network of diverse proteins, glycoproteins, and glycosaminoglycans that surround the cells. The cells actively sense the surrounding ECM and regulate its mechanical state. Cell-seeded collagen or fibrin gels, so-called tissue equivalents, are simple but powerful model systems to study this phenomenon. Nevertheless, few quantitative studies document the stresses that cells establish and maintain in such gels; moreover, most prior data were collected via uniaxial experiments whereas soft tissues are mainly subject to multiaxial loading in vivo. To begin to close this gap between existing experimental data and in vivo conditions, we describe here a computer-controlled bioreactor that enables accurate measurements of the evolution of mechanical tension and deformation of tissue equivalents under well-controlled biaxial loads. This device allows diverse studies, including how cells establish a homeostatic state of biaxial stress and if they maintain it in response to mechanical perturbations. It similarly allows, for example, studies of the impact of cell and matrix density, exogenous growth factors and cytokines, and different types of loading conditions (uniaxial, strip-biaxial, and biaxial) on these processes. As illustrative results, we show that NIH/3T3 fibroblasts establish a homeostatic mechanical state that depends on cell density and collagen concentration. Following perturbations from this homeostatic state, the cells were able to recover biaxial loading similar to homeostatic. Depending on the precise loads, however, they were not always able to fully maintain that state.},
note = {Online available at: \url{https://dx.doi.org/10.1115/1.4046201} (DOI). Eichinger, J.; Paukner, D.; Szafron, J.; Aydin, R.; Humphrey, J.; Cyron, C.: Computer-Controlled Biaxial Bioreactor for Investigating Cell-Mediated Homeostasis in Tissue Equivalents. In: Journal of biomechanical engineering. Vol. 142 (2020) 7, 071011. (DOI:  /10.1115/1.4046201)}}
@article{ferreira_investigation_of_2020, 
author={Ferreira, A. and Campanelli, L. and Suhuddin, U. and Alcantara, N. and dos Santos, J.},
title={Investigation of internal defects and premature fracture of dissimilar refill friction stir spot welds of AA5754 and AA6061},
year={2020},
journal = {The International Journal of  Advanced Manufacturing Technology},
volume = {106},
pages = {3523 - 3531},
doi = {10.1007/s00170-019-04819-3},
abstract = {The occurrence of internal defects in welded samples of AA5754-AA6061 produced by refill friction stir spot welding was investigated. A design of experiments using Box-Behnken method followed by a statistical examination using analysis of variance (ANOVA) and response surface modeling were utilized as analysis tools, which proved to be a reliable optimization methodology. This optimization successfully produced sound joints with high lap-shear strength. The statistical analysis showed a large influence of linear plunge depth, quadratic rotational speed, and two-way interaction of feeding rate and rotational speed on lap-shear strength of the welds. A quadratic hypersurface model for predicting weld performance was successfully generated. The subsequent investigation was performed by changing welding parameters, one factor at a time (OFAT), which confirmed the high dependence of lap-shear strength on rotational speed by producing an undesirable outlier. Metallographical analysis on the outlier sample pointed out the occurrence of voids and refilling defects, associated in large scale to low friction heat input. The outlier sample also produced a wing-shaped structure that possibly obstructed the flow of softened material toward void closure. The existence of those defects shows evidence of premature crack in the outlier sample. A subtle adjustment in rotational speed to1000 rpm proved to be sufficient to eliminate the defects and produce stronger welds. Although the problem of refilling defects could be solved, the mechanical properties in the weld were worsened compared to that of base material.},
note = {Online available at: \url{https://dx.doi.org/10.1007/s00170-019-04819-3} (DOI). Ferreira, A.; Campanelli, L.; Suhuddin, U.; Alcantara, N.; dos Santos, J.: Investigation of internal defects and premature fracture of dissimilar refill friction stir spot welds of AA5754 and AA6061. In: The International Journal of  Advanced Manufacturing Technology. Vol. 106 (2020) 3523 - 3531. (DOI:  /10.1007/s00170-019-04819-3)}}
@article{okulov_surface_functionalization_2020, 
author={Okulov, I. and Joo, S. and Okulov, A. and Volegov, A. and Luthringer, B. and Willumeit-Römer, R. and Zhang, L. and Mädler, L. and Eckert, J. and Kato, H.},
title={Surface Functionalization of Biomedical Ti-6Al-7Nb Alloy by Liquid Metal Dealloying },
year={2020},
journal = {Nanomaterials},
volume = {10},
number = {8},
pages = {1479},
doi = {10.3390/nano10081479},
abstract = {Surface functionalization is an effective approach to change the surface properties of a material to achieve a specific goal such as improving the biocompatibility of the material. Here, the surface of the commercial biomedical Ti-6Al-7Nb alloy was functionalized through synthesizing of a porous surface layer by liquid metal dealloying (LMD). During LMD, the Ti-6Al-7Nb alloy is immersed in liquid magnesium (Mg) and both materials react with each other. Particularly, aluminum (Al) is selectively dissolved from the Ti-6Al-7Nb alloy into liquid Mg while titanium (Ti) and niobium (Nb) diffuse along the metal/liquid interface to form a porous structure. We demonstrate that the porous surface layer in the Ti-6Al-7Nb alloy can be successfully tailored by LMD. Furthermore, the concentration of harmful Al in this porous layer is reduced by about 48% (from 5.62 ± 0.11 wt.% to 2.95 ± 0.05 wt.%) after 30 min of dealloying at 1150 K. The properties of the porous layer (e.g., layer thickness) can be tuned by varying the dealloying conditions. In-vitro tests suggest improved bone formation on the functionalized porous surface of the Ti-6Al-7Nb alloy.},
note = {Online available at: \url{https://dx.doi.org/10.3390/nano10081479} (DOI). Okulov, I.; Joo, S.; Okulov, A.; Volegov, A.; Luthringer, B.; Willumeit-Römer, R.; Zhang, L.; Mädler, L.; Eckert, J.; Kato, H.: Surface Functionalization of Biomedical Ti-6Al-7Nb Alloy by Liquid Metal Dealloying . In: Nanomaterials. Vol. 10 (2020) 8, 1479. (DOI:  /10.3390/nano10081479)}}
@article{silva_on_the_2020, 
author={Silva, D. and Campanelli, L. and Bergmann, L. and dos santos, J. and Hammer, P. and Della Rovere, C. and Aquino, J.},
title={On the stability of the passive Ti-6Al-4V film of friction stir welds with stainless steel: Effect of not native metal species},
year={2020},
journal = {Electrochimica Acta},
volume = {358},
pages = {136900},
doi = {10.1016/j.electacta.2020.136900},
abstract = {Mechanical and microstructural characteristics of Ti-6Al-4V/stainless steel (SS) dissimilar friction stir welds have been well described in the literature; however, little is known about the electrochemical properties of such welds in terms of the passive film stability of TiO2 grown in oxidizing media. To clarify this issue, potentiodynamic polarization, cyclic voltammetry, and electrochemical impedance measurements were carried out in the Ti-6Al-4V alloy to analyze the effects of Fe and Cr contamination from the underlying SS on the passive film stability of TiO2 in concentrated (6.0 and 11.5 mol L–1) HNO3 solutions. Lower transpassive potentials were observed for samples in the stirred zone (SZ) than those of the base metal (BM) due to Fe and Cr contamination. Anodic charges obtained during cyclic voltammetry using 6.0 mol L–1 HNO3 showed that the grown passive film was completely dissolved and regrown after consecutive scans, except for the BM sample. According to the results of X-ray photoelectron spectroscopy (XPS) analyses an Al depleted layer was obtained for the latter condition, which confirms the stability of TiO2 film. The increasing values of charge transfer resistance obtained through electrochemical impedance measurements at distinct potentials in the passive region also supported the stability of the TiO2 film grown in 6.0 mol L–1 HNO3 solution. The formation of a medium frequency inductive loop and low frequency constant phase element are related to the dissolution of the oxide film and adsorption of NO3 species into the formed passive film, respectively, as evidenced by XPS analyses.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.electacta.2020.136900} (DOI). Silva, D.; Campanelli, L.; Bergmann, L.; dos santos, J.; Hammer, P.; Della Rovere, C.; Aquino, J.: On the stability of the passive Ti-6Al-4V film of friction stir welds with stainless steel: Effect of not native metal species. In: Electrochimica Acta. Vol. 358 (2020) 136900. (DOI:  /10.1016/j.electacta.2020.136900)}}
@article{ziehmer_the_isothermal_2020, 
author={Ziehmer, M. and Lilleodden, E.},
title={The isothermal evolution of nanoporous gold from the ring perspective - an application of graph theory},
year={2020},
journal = {Acta Materialia},
volume = {199},
pages = {669 - 679},
doi = {10.1016/j.actamat.2020.08.026},
abstract = {The ring structures of five isothermally annealed nanoporous gold (npg) samples were analyzed explicitly by applying results and algorithms from graph theory to skeletonized 3D reconstructions from focused ion beam (FIB) tomography data. Simplified skeletons of the reconstructions were utilized, in which the real ligaments are reduced to straight edges between the branching points of the npg microstructure. So-called minimum weight cycle bases of each skeleton graph’s cycle vector space were calculated, assigning different weight functions to these straight edges: equal weights, Euclidean lengths, and the real ligament lengths from backmapping the Euclidean skeleton edges to the skeletonized real ligament sections. These cycle bases contain the maximum number of linearly independent rings that cannot be generated by smaller rings via the ring sum specified in the cycle vector space. Such a decomposition of the npg network structures into the fundamental ring building blocks served to provide a new perspective of the isothermal evolution of npg, since the coarsening of the npg network structure could be examined from analyzing the local ring topologies and the classification of the ring topological classes. Our results suggest an increasing relative dominance of ligament pinch-off events over ring collapse events, manifesting in a broadening of the distribution of topological classes, and leading to a small but steady increase of the average number of ring edges. Furthermore, self-similar evolution of the investigated sample series cannot be stated. The implications on the topological evolution of npg as a function of the solid volume fraction are discussed.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.actamat.2020.08.026} (DOI). Ziehmer, M.; Lilleodden, E.: The isothermal evolution of nanoporous gold from the ring perspective - an application of graph theory. In: Acta Materialia. Vol. 199 (2020)  669 - 679. (DOI:  /10.1016/j.actamat.2020.08.026)}}
@article{feistauer_an_investigation_2020, 
author={Feistauer, E. and dos Santos, J. and Amanci-Filho, S.},
title={An investigation of the ultrasonic joining process parameters effect on the mechanical properties of metal-composite hybrid joints},
year={2020},
journal = {Welding in the World},
volume = {64},
pages = {1481 - 1495},
doi = {10.1007/s40194-020-00927-x},
abstract = {The ultrasonic joining process was recently introduced as an alternative concept to join through-the-thickness reinforced metal-composite hybrid structures. In this work, the investigation of joining process parameters effect on the joint mechanical performance of Ti-6Al-4V-glass-fiber-reinforced polyetherimide overlap joints was carried out by Box-Behnken design of experiments. The individual and combined effects of joining energy, sonotrode oscillation amplitude, and joining pressure on the ultimate lap shear force were elucidated by response surfaces method and analysis of variance. As a result of this study, a set of optimized joining parameters were obtained to produce joints with high ultimate lap shear force. The obtained reliable reduced model (R2 = 82%) displays a major influence of joining energy (25.3%) and sonotrode oscillation amplitude (21.2%) on the joint mechanical performance. Two-way interaction response surfaces were used to support strategies to optimize the maximum ultimate lap shear force. By comparing the optimized joint condition produced in this work with previously published results an improvement of 79% in ultimate lap shear force was attained, thereby, proving the potential of the proposed process optimization procedure.},
note = {Online available at: \url{https://dx.doi.org/10.1007/s40194-020-00927-x} (DOI). Feistauer, E.; dos Santos, J.; Amanci-Filho, S.: An investigation of the ultrasonic joining process parameters effect on the mechanical properties of metal-composite hybrid joints. In: Welding in the World. Vol. 64 (2020) 1481 - 1495. (DOI:  /10.1007/s40194-020-00927-x)}}
@article{sonkusare_a_critical_2020, 
author={Sonkusare, R. and Biswas, K. and Al-Hamdany, N. and Brokmeier, H.G. and Kalsar, R. and Schell, N. and Gurao, N.P.},
title={A critical evaluation of microstructure-texture-mechanical behavior heterogeneity in high pressure torsion processed CoCuFeMnNi high entropy alloy},
year={2020},
journal = {Materials Science and Engineering: A},
volume = {782},
pages = {139187},
doi = {10.1016/j.msea.2020.139187},
abstract = {The present study aims to understand the evolution of textural and microstructural heterogeneity and its effect on evolution of mechanical properties of an equiatomic FCC CoCuFeMnNi high entropy alloy (HEA) disc subjected to high pressure torsion (HPT). HPT was performed on disc specimen with a hydrostatic pressure of 5 GPa for 0.1, 0.5, 1 and 5 turns at room temperature where the hardness saturated at 1941 MPa at the periphery of the sample after five turns. Synchrotron diffraction texture analysis of five-turn HPT sample reveals characteristic shear texture with the dominance of A and A* components near central region of the disc and it shifts to C {001}<110> component near the periphery of the disc. X-ray diffraction analysis shows decrease in crystalline size with simultaneous increase in dislocation density for five-turn HPT sample with increasing strain from centre to the periphery of the disc. Microstructural analysis using electron back scatter diffraction and transmission electron microscopy indicates extensive grain fragmentation (≈55 nm) at the periphery of five-turn sample. The evolution of hardness from centre to the periphery of the disc cannot be explained only on the basis of evolution of grain size and dislocation density. The increase in contribution from solid solution strengthening due to partial dissolution of copper rich nano-clusters is expected to be the underlying cause for increase in the hardness. Thus, evolution of gradient microstructure, texture, and chemistry opens up new vistas for designing functionally graded materials for engineering applications.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.msea.2020.139187} (DOI). Sonkusare, R.; Biswas, K.; Al-Hamdany, N.; Brokmeier, H.G.; Kalsar, R.; Schell, N.; Gurao, N.P.: A critical evaluation of microstructure-texture-mechanical behavior heterogeneity in high pressure torsion processed CoCuFeMnNi high entropy alloy. In: Materials Science and Engineering: A. Vol. 782 (2020) 139187. (DOI:  /10.1016/j.msea.2020.139187)}}
@article{abibe_processrelated_changes_2020, 
author={Abibe, A. and Sônego, M. and Canto, L. and dos Santos, J. and Amancio-Filho, S.},
title={Process-Related Changes in Polyetherimide Joined by Friction-Based Injection Clinching Joining (F-ICJ)},
year={2020},
journal = {Materials},
volume = {13},
number = {5},
pages = {1027},
doi = {10.3390/ma13051027},
abstract = {This work presents a comprehensive study on the effects of the Friction-based Injection Clinching Joining (F-ICJ) process on the microstructure and local properties of the stake head. The manuscript evaluates the consequences on the quasi-static mechanical performance of hybrid joints of amorphous polyetherimide (PEI) with aluminium AA6082. Through an overlay of microhardness map on a cross-polarized transmitted-light optical microscopy (CP-TLOM) image, two lower-strength microstructural zones in the PEI stake head were observed: a plastically-deformed zone (PDZ) and a thermo-mechanically-affected zone (PTMAZ). When compared to the base material, PDZ and PTMAZ have a reduction of 12%–16% and 8%–12%, respectively, in local mechanical properties. The reduced local strength was associated with distinct volumes of loosely packed PEI chains with unsteady chain conformation and thus larger free volume in the affected regions. The mechanical strength reduction is reversible through physical aging by thermal annealing the joints, which additionally shows that process-induced thermomechanical degradation of PEI by chain scission, as evidenced by size exclusion chromatography (SEC) analysis, does not appear to affect local mechanical strength. An evaluation of typical loading regimes of staked joints in lap shear (average ultimate force of 1419 ± 43 N) and cross tensile (average ultimate force of 430 ± 44 N) testing indicates that the process-induced changes of PEI do not compromise the global mechanical performance of such a structure. These findings provide a better understanding of the relationships between processing, microstructure, and properties for further F-ICJ process optimization.},
note = {Online available at: \url{https://dx.doi.org/10.3390/ma13051027} (DOI). Abibe, A.; Sônego, M.; Canto, L.; dos Santos, J.; Amancio-Filho, S.: Process-Related Changes in Polyetherimide Joined by Friction-Based Injection Clinching Joining (F-ICJ). In: Materials. Vol. 13 (2020) 5, 1027. (DOI:  /10.3390/ma13051027)}}
@article{dasilva_numerical_investigation_2020, 
author={da Silva, Y. and Oliveira Júnior, F. and dos Santos, J. and Marcondes, F. and Silva, C.},
title={Numerical investigation of the influence of FSW parameters on the heat and mass transfer of austenitic stainless steels},
year={2020},
journal = {Welding in the World},
volume = {64},
number = {4},
pages = {2019 - 2032},
doi = {http://dx.doi.org/10.1007/s40194-020-00980-6},
abstract = {The friction stir weld (FSW) method was developed in 1991 by The Welding Institute (TWI) and is very useful for manufacturing components with low fusion weldability. The success of this relatively new technique is due, in part, to an appropriate combination of some parameters. In order to understand the influence of the parameters such as rotation speed, axial force, and welding velocity, simulations were carried out using the AISI 304L stainless steel. In this work, the process was considered to be a 3D non-Newtonian fluid and the heat input was calculated from the friction between the tool and the plate and from the plastic deformation. The thermal results were compared with the experimental results from the thermocouple measurements. Furthermore, the material flow was related to the formation of defects observed in the experimental welds. The results of the simulation were able to determine the temperature distribution and heat flow, as well as to predict defects in the welding. The simulated viscosity values enabled the prediction of the parameters most likely to cause the formation of flashes. In addition, the injection of inert particles into the model made it possible to predict the formation of wormholes.},
note = {Online available at: \url{http://dx.doi.org/10.1007/s40194-020-00980-6} (DOI). da Silva, Y.; Oliveira Júnior, F.; dos Santos, J.; Marcondes, F.; Silva, C.: Numerical investigation of the influence of FSW parameters on the heat and mass transfer of austenitic stainless steels. In: Welding in the World. Vol. 64 (2020) 4, 2019 - 2032. (DOI:  10.1007/s40194-020-00980-6)}}
@article{hesselsilva_refill_friction_2020, 
author={Hessel Silva, B. and Zepon, G. and Bolfarini, C. and dos Santos, J.},
title={Refill friction stir spot welding of AA6082-T6 alloy: Hook defect formation and its influence on the mechanical properties and fracture behavior},
year={2020},
journal = {Materials Science and Engineering: A},
volume = {773},
pages = {138724},
doi = {10.1016/j.msea.2019.138724},
abstract = {Process parameters optimization was carried out to evaluate the individual effect of rotational speed, feeding rate and plunge depth on the weld strength of an AA6082-T6 aluminum alloy produced by Refill Friction Stir Spot Welding. Statistical analysis allowed to maximize the weld peel and shear strength and a strong correlation between plunge depth and weld resistance was found. It was shown that plunge depth has a strong effect on the formation and shape of the hook defect. Moreover, the fracture behavior of the welds is strongly dependent on the hook defect configuration. By applying the so-called one-factor at a time (OFAT) method combined with macro and microstructure characterization it was possible to identify three possible hook defect configurations. A comprehensive description of the different hook configuration formation is presented by analyzing the microstructure of samples from interrupted welding tests. The configuration of the hook defect depends on the position and direction of the material flow around the sleeve and the drop region. Macro and microstructure analysis of interrupted mechanical test specimens allowed the characterization of the crack initiation site and crack propagation path according to qualitative observations of hook configuration, bonding ligament and the interface region between the heat affected zone and the thermal mechanically affected zone. It was found that the fracture mode is also strongly related to the configuration of the hook defect. The optimized welding condition was reached using intermediate values of plunge depth, which produces a hook pointing down configuration.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.msea.2019.138724} (DOI). Hessel Silva, B.; Zepon, G.; Bolfarini, C.; dos Santos, J.: Refill friction stir spot welding of AA6082-T6 alloy: Hook defect formation and its influence on the mechanical properties and fracture behavior. In: Materials Science and Engineering: A. Vol. 773 (2020) 138724. (DOI:  /10.1016/j.msea.2019.138724)}}
@article{santini_microstructure_features_2020, 
author={Santini, F. and Plaine, A. and Afonso, C. and Bergmann, L. and Alcantara, N. and dos Santos, J. and Miyazaki, M.},
title={Microstructure Features and Mechanical Properties of Double-Sided Friction Stir Welded Joints of AA2050-T84 Thick Plates},
year={2020},
journal = {Materials Research},
volume = {23},
number = {6},
pages = {e20200309},
doi = {10.1590/1980-5373-MR-2020-0309},
abstract = {As part of an ongoing process to fully assess the potential for friction stir welding (FSW) to be used in the aerospace industry, an attempt was made to produce double sided FSW joints at traverse speeds equal or higher than 5 mm/s of AA2050-T84 12.7 mm thick plates for high-volume production applications. With an emphasis on weld quality, the local and global mechanical properties were evaluated and correlated with microstructure of the welding area. Sound welds with no volumetric defects were obtained for tool traverse speeds up to 12 mm/s, resulting in yield and ultimate tensile strengths corresponding to 65% and 77% of base material, respectively. The metallurgical and mechanical characterization demonstrate that density of Cu-rich precipitates has a first order effect on micro-hardness variation. In the stir zone the dissolution temperature of this precipitate is achieved and its volume fraction is greatly reduced. The remaining precipitates seems to be partially dissolved and undergone a significant thickening at the welding zones in which the process temperature has not reached the dissolution temperature. Weld fractures after tensile tests were observed to start in the region of hardness minima.},
note = {Online available at: \url{https://dx.doi.org/10.1590/1980-5373-MR-2020-0309} (DOI). Santini, F.; Plaine, A.; Afonso, C.; Bergmann, L.; Alcantara, N.; dos Santos, J.; Miyazaki, M.: Microstructure Features and Mechanical Properties of Double-Sided Friction Stir Welded Joints of AA2050-T84 Thick Plates. In: Materials Research. Vol. 23 (2020) 6, e20200309. (DOI:  /10.1590/1980-5373-MR-2020-0309)}}
@article{yamin_mechanical_performance_2020, 
author={Yamin, M. and Awang, M. and Suhuddin, U. and Sallih, N. and Klusemann, B. and Dos Santos, J.},
title={Mechanical performance optimization of similar thin AA 7075‐T6 sheets produced by refill friction stir spot welding : Optimierung der mechanischen Leistungfähigkeit für artgleich produzierte AA 7075-T6-Bleche durch Rühr-Reib-Punkt-Schweißen},
year={2020},
journal = {Materials Science and Engineering Technology - Materialwissenschaft und Werkstofftechnik},
volume = {51},
number = {6},
pages = {830 - 835},
doi = {10.1002/mawe.201900253},
abstract = {Refill friction stir spot welding was applied to weld similar thin AA 7075‐T6 aluminum alloy sheets in a spot‐like joint configuration without a keyhole. The welds were produced using a small tool consisting of sleeve and probe with diameters of 6 mm and 4 mm, respectively. Design of experiment was employed to optimize the welding parameters in terms of the cross tensile strength by using Box Behnken Design. Based on analysis of variance, it can be concluded that plunge depth strongly affects the mechanical performance of the weld. Optimal welding parameters in terms of rotational speed, plunge depth and speed are identified to reach a cross tensile strength of up to 660 N.},
note = {Online available at: \url{https://dx.doi.org/10.1002/mawe.201900253} (DOI). Yamin, M.; Awang, M.; Suhuddin, U.; Sallih, N.; Klusemann, B.; Dos Santos, J.: Mechanical performance optimization of similar thin AA 7075‐T6 sheets produced by refill friction stir spot welding : Optimierung der mechanischen Leistungfähigkeit für artgleich produzierte AA 7075-T6-Bleche durch Rühr-Reib-Punkt-Schweißen. In: Materials Science and Engineering Technology - Materialwissenschaft und Werkstofftechnik. Vol. 51 (2020) 6, 830 - 835. (DOI:  /10.1002/mawe.201900253)}}
@article{okulov_nanoporous_highentropy_2020, 
author={Okulov, A. and Joo, S. and Kim, H. and Kato, H. and Okulov, I.},
title={Nanoporous High-Entropy Alloy by Liquid Metal Dealloying},
year={2020},
journal = {Metals},
volume = {10},
number = {10},
pages = {1396},
doi = {10.3390/met10101396},
abstract = {High-entropy nanomaterials possessing high accessible surface areas have demonstrated outstanding catalytic performance, beating that found for noble metals. In this communication, we report about the synthesis of a new, nanoporous, high-entropy alloy (HEA) possessing open porosity. The nanoporous, high-entropy Ta19.1Mo20.5Nb22.9V30Ni7.5 alloy (at%) was fabricated from a precursor (TaMoNbV)25Ni75 alloy (at%) by liquid metal dealloying using liquid magnesium (Mg). Directly after dealloying, the bicontinuous nanocomposite consisting of a Mg-rich phase and a phase with a bulk-centered cubic (bcc) structure was formed. The Mg-rich phase was removed with a 3M aqueous solution of nitric acid to obtain the open, porous, high-entropy Ta19.1Mo20.5Nb22.9V30Ni7.5 alloy (at%). The ligament size of this nanoporous HEA is about 69 ± 9 nm, indicating the high surface area in this material.},
note = {Online available at: \url{https://dx.doi.org/10.3390/met10101396} (DOI). Okulov, A.; Joo, S.; Kim, H.; Kato, H.; Okulov, I.: Nanoporous High-Entropy Alloy by Liquid Metal Dealloying. In: Metals. Vol. 10 (2020) 10, 1396. (DOI:  /10.3390/met10101396)}}
@article{wang_the_formation_2020, 
author={Wang, J. and Castro, C. and Lu, X.},
title={The Formation Mechanisms and Improvement Measures for Penetrating Cracks in QAl9-4/Q345B Welded Joint},
year={2020},
journal = {Journal of Materials Engineering and Performance},
volume = {29},
pages = {2346 - 2354},
doi = {10.1007/s11665-020-04749-2},
abstract = {The dissimilar joining of QAl9-4 aluminum-bronze alloy to Q345B low carbon low alloy steel was performed by fusion welding using different techniques. The results indicated a certain amount of transverse cracks and voids in the QAl9-4/Q345B joints welded by the SMAW process, while defect-free joints were obtained using the GTAW process. The microstructure of samples produced by the SMAW process exhibited transverse cracks with typical partially oxidized intergranular cracking characteristics. Banded films rich in Cu at the grain boundaries were observed, which were demonstrated to be related to premature failure of the samples under tensile and impact load, indicating that the transverse cracks are hot cracks caused by the penetration of Cu element. Good strength and good toughness of QAl9-4/Q345B welded joints were obtained by the GTAW process.},
note = {Online available at: \url{https://dx.doi.org/10.1007/s11665-020-04749-2} (DOI). Wang, J.; Castro, C.; Lu, X.: The Formation Mechanisms and Improvement Measures for Penetrating Cracks in QAl9-4/Q345B Welded Joint. In: Journal of Materials Engineering and Performance. Vol. 29 (2020) 2346 - 2354. (DOI:  /10.1007/s11665-020-04749-2)}}
@article{wang_investigation_of_2020, 
author={Wang, J. and Castro, C. and Zou, Y. and Wang, D. and Lu, X.},
title={Investigation of prior austenite grain and delta ferrite in CLAM welded joints after different diffusion annealing processes},
year={2020},
journal = {Fusion Engineering and Design},
volume = {159},
pages = {111815},
doi = {10.1016/j.fusengdes.2020.111815},
abstract = {CLAM steel is one of the structural material used in test blanket modules as a barrier or blanket for fusion reactors. Different diffusion annealing processes were employed in order to investigate the effect of δ-ferrite elimination and prior austenite grain coarsening. The results show that both alloying elements diffusion and microstructures coarsening during the diffusion annealing treatment influence the contents and morphologies of δ-ferrite. The polygonal blocky δ-ferrite and the coarse grains were determined as the main factors deteriorating the impact toughness for the CLAM welded joint. A CLAM welded joint with good impact toughness and appropriate microstructure in terms of grain size and δ-ferrite content was obtained after diffusion annealing process at 1100 °C for 10 h.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.fusengdes.2020.111815} (DOI). Wang, J.; Castro, C.; Zou, Y.; Wang, D.; Lu, X.: Investigation of prior austenite grain and delta ferrite in CLAM welded joints after different diffusion annealing processes. In: Fusion Engineering and Design. Vol. 159 (2020) 111815. (DOI:  /10.1016/j.fusengdes.2020.111815)}}
@article{zellerplumhoff_nanotomographic_evaluation_2020, 
author={Zeller-Plumhoff, B. and Robisch, A. and Pelliccia, D. and Longo, E. and Slominska, H. and Hermann, A. and Krenkel, M. and Storm, M. and Estrin, Y. and Willumeit-Römer, R. and Salditt, T. and Orlov, D.},
title={Nanotomographic evaluation of precipitate structure evolution in a Mg–Zn–Zr alloy during plastic deformation},
year={2020},
journal = {Scientific Reports},
volume = {10},
pages = {16101},
doi = {10.1038/s41598-020-72964-x},
abstract = {Magnesium and its alloys attract increasingly wide attention in various fields, ranging from transport to medical solutions, due to their outstanding structural and degradation properties. These properties can be tailored through alloying and thermo-mechanical processing, which is often complex and multi-step, thus requiring in-depth analysis. In this work, we demonstrate the capability of synchrotron-based nanotomographic X-ray imaging methods, namely holotomography and transmission X-ray microscopy, for the quantitative 3D analysis of the evolution of intermetallic precipitate (particle) morphology and distribution in magnesium alloy Mg–5.78Zn–0.44Zr subjected to a complex multi-step processing. A rich history of variation of the intermetallic particle structure in the processed alloy provided a testbed for challenging the analytical capabilities of the imaging modalities studied. The main features of the evolving precipitate structure revealed earlier by traditional light and electron microscopy methods were confirmed by the 3D techniques of synchrotron-based X-ray imaging. We further demonstrated that synchrotron-based X-ray imaging enabled uncovering finer details of the variation of particle morphology and number density at various stages of processing—above and beyond the information provided by visible light and electron microscopy.},
note = {Online available at: \url{https://dx.doi.org/10.1038/s41598-020-72964-x} (DOI). Zeller-Plumhoff, B.; Robisch, A.; Pelliccia, D.; Longo, E.; Slominska, H.; Hermann, A.; Krenkel, M.; Storm, M.; Estrin, Y.; Willumeit-Römer, R.; Salditt, T.; Orlov, D.: Nanotomographic evaluation of precipitate structure evolution in a Mg–Zn–Zr alloy during plastic deformation. In: Scientific Reports. Vol. 10 (2020) 16101 . (DOI:  /10.1038/s41598-020-72964-x)}}
@article{pinacipriano_singlephase_friction_2020, 
author={Pina Cipriano, G. and Ahiya, A. and dos Santos, J. and Vilaça, P. and Amancio-Filho, S.},
title={Single-phase friction riveting: metallic rivet deformation, temperature evolution, and joint mechanical performance},
year={2020},
journal = {Welding in the World},
volume = {64},
pages = {47 - 58},
doi = {10.1007/s40194-019-00803-3},
abstract = {The present work explores the feasibility of single-phase friction riveting on unreinforced thermoplastics. In single phase, the load is kept constant throughout the process, avoiding the forging phase with higher axial force, used in the conventional process. This process variant can constitute an answer when payload restrictions exist. The results demonstrate the feasibility of single-phase friction riveting on unreinforced polyetherimide plates joined by AA2024 rivets with 5 mm of diameter. A Box-Behnken design of experiments and analysis of variance were used to set parameter matrix and understand the correlations between parameters and joint properties. A large variation of the mechanical energy input was observed (151–529 J). Over-deformation and material rupture were observed in higher energy conditions. Lower energy input yielded a bell-shaped rivet plastic deformation, corresponding to the best performance. The maximum process temperatures varied between 461 and 509 °C. This friction riveting process variant allowed a considerable high mechanical strength to be achieved, with ultimate tensile force of 7486 N, comparable with the two-phase friction riveting process, albeit applying lower axial forces, such as 2400 N. Within the investigated conditions, this study proves the feasibility of the single-phase process, achieving good global mechanical performance and energetically efficient conditions, without forging phase.},
note = {Online available at: \url{https://dx.doi.org/10.1007/s40194-019-00803-3} (DOI). Pina Cipriano, G.; Ahiya, A.; dos Santos, J.; Vilaça, P.; Amancio-Filho, S.: Single-phase friction riveting: metallic rivet deformation, temperature evolution, and joint mechanical performance. In: Welding in the World. Vol. 64 (2020) 47 - 58. (DOI:  /10.1007/s40194-019-00803-3)}}
@article{dorosrio_a_combined_2020, 
author={do Rosário, J. and Häntsch, Y. and Schneider, G. and Lilleodden, E.},
title={A combined compression and indentation study of mechanical metamaterials based on inverse opal coatings},
year={2020},
journal = {Acta Materialia},
volume = {195},
pages = {98 - 108},
doi = {10.1016/j.actamat.2020.04.025},
abstract = {A relatively new class of tailored photonic metamaterials based on the inverse opal (IO) structure shows multifunctionality with exceptional mechanical response due to its periodic porous arch-like structure. Exploiting the smaller is stronger paradigm through varying its pore size and the addition of atomic layer deposition (ALD) films, allow tailorable strength and elastic modulus. Quantification of such properties are achieved through flat punch nanoindentation testing. Results are validated by comparison to microcompression tests, a widely used technique to circumvent the complex stress state normally imposed by indentation, but in the case of high porosity is greatly simplified, approximating uniaxial stress; results from both mechanical loading approaches show strong similarities. All results showed a dependence of strength and elastic modulus on the ratio of the deformation size, i.e., micropillar or flat punch diameter, to the pore size, a trend which is well described by the influence of the boundary conditions of the test method rather than an intrinsic size effect. At larger ratios the values approach a constant value. Furthermore, the mechanical response can be tailored through the deposition of a thin film on the shell structure of the silica IO structures; 34 nm of TiO2 was shown to produce a 10-fold increase in strength and 5-fold increase in elastic modulus.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.actamat.2020.04.025} (DOI). do Rosário, J.; Häntsch, Y.; Schneider, G.; Lilleodden, E.: A combined compression and indentation study of mechanical metamaterials based on inverse opal coatings. In: Acta Materialia. Vol. 195 (2020) 98 - 108. (DOI:  /10.1016/j.actamat.2020.04.025)}}
@article{andr_impact_resistance_2020, 
author={André, N. and dos Santos, J. and Amancio-Filho, S.},
title={Impact resistance of metal-composite hybrid joints produced by frictional heat},
year={2020},
journal = {Composite Structures},
volume = {233},
pages = {111754},
doi = {10.1016/j.compstruct.2019.111754},
abstract = {The impact resistance of aluminum alloy 2024-T3 and carbon-fiber-reinforced polyphenylene sulfide joints was investigated using drop weight test. The joints were aluminum-side and composite-side impacted to provide a preliminary design guideline for hybrid joints. Four energy levels were investigated for each side: 2 J, 4 J, 6 J and 8 J. The joints presented rebounding behavior for all the energy levels. It implies that in all the cases, the impact energy was not totally absorbed by the joints, although the joints failed at 8 J of impact energy. The interface of the joint presented its threshold for absorption of impact energy around 6.5 J, which was reached when the joint was impacted with 8 J of potential energy, independently of the surface under impact. Thus, this study showed that a single friction spot joint could absorb up to 103 kJ.m−2 of joined area. The joints impacted from the aluminum side presented residual strengths of 84% (2 J), 30% (4 J), and 25% (6 J). For composite-side impacted joints, the residual strengths were 80% (2 J), 54% (4 J), and 45% (6 J). Generally, the aluminum-side impacted joints showed lower residual strength than the composite-side impacted joints. The impact energy introduced from the aluminum side was mostly absorbed in the plastic deformation of the aluminum part, bending the aluminum and promoting the detachment of the interface. Otherwise, the impact energy introduced from the composite side was mostly absorbed by the creation/extension of internal damage through the plies of the composite. Thus, it is expected that the impact energy was only partially transferred to the interface of the joint in the case of composite-side impact. Consequently, these joints presented higher residual strength after impact than the aluminum-side impacted joints.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.compstruct.2019.111754} (DOI). André, N.; dos Santos, J.; Amancio-Filho, S.: Impact resistance of metal-composite hybrid joints produced by frictional heat. In: Composite Structures. Vol. 233 (2020) 111754. (DOI:  /10.1016/j.compstruct.2019.111754)}}
@article{huber_comment_to_2020, 
author={Huber, N. and Richert, C.},
title={Comment to “Skeletonization-based beam finite element models for stochastic bicontinuous materials: Application to simulations of nanoporous gold” by C. Soyarslan et al. [J. Mater. Res. 33(20), 3371 (2018)]},
year={2020},
journal = {Journal of Materials Research},
volume = {35},
number = {20},
pages = {2831 - 2834},
doi = {10.1557/jmr.2020.257},
abstract = {Soyarslan et al. [J. Mater. Res. 33(20), 3371 (2018)] proposed a beam-finite element model for the computation of effective elastic properties of nanoporous materials, where the ligament diameter along the skeleton is determined with the biggest sphere algorithm. Although this algorithm is often used in the literature, it is known that it systematically overestimates the diameter in network structures. Thus, the need for further stiffening of the junction zones as proposed by the authors is in contradiction to the literature. Furthermore, the factor 40 appears to be one order of magnitude too high. We show that the 3D microstructures generated from random Gaussian fields contain features that are violating the assumption of circular cross-sections and, therefore, cannot be captured by the biggest sphere algorithm. Consequently, the authors required an unphysically high value of 40 to compensate this hidden effect.},
note = {Online available at: \url{https://dx.doi.org/10.1557/jmr.2020.257} (DOI). Huber, N.; Richert, C.: Comment to “Skeletonization-based beam finite element models for stochastic bicontinuous materials: Application to simulations of nanoporous gold” by C. Soyarslan et al. [J. Mater. Res. 33(20), 3371 (2018)]. In: Journal of Materials Research. Vol. 35 (2020) 20, 2831 - 2834. (DOI:  /10.1557/jmr.2020.257)}}
@article{richert_a_review_2020, 
author={Richert, C. and Huber, N.},
title={A Review of Experimentally Informed Micromechanical Modeling of Nanoporous Metals: From Structural Descriptors to Predictive Structure–Property Relationships },
year={2020},
journal = {Materials},
volume = {13},
number = {15},
pages = {3307},
doi = {10.3390/ma13153307},
abstract = {Nanoporous metals made by dealloying take the form of macroscopic (mm- or cm-sized) porous bodies with a solid fraction of around 30%. The material exhibits a network structure of “ligaments” with an average ligament diameter that can be adjusted between 5 and 500 nm. Current research explores the use of nanoporous metals as functional materials with respect to electrochemical conversion and storage, bioanalytical and biomedical applications, and actuation and sensing. The mechanical behavior of the network structure provides the scope for fundamental research, particularly because of the high complexity originating from the randomness of the structure and the challenges arising from the nanosized ligaments, which can be accessed through an experiment only indirectly via the testing of the macroscopic properties. The strength of nanoscale ligaments increases systematically with decreasing size, and owing to the high surface-to-volume ratio their elastic and plastic properties can be additionally tuned by applying an electric potential. Therefore, nanoporous metals offer themselves as suitable model systems for exploring the structure–property relationships of complex interconnected microstructures as well as the basic mechanisms of the chemo-electro-mechanical coupling at interfaces. The micromechanical modeling of nanoporous metals is a rapidly growing field that strongly benefits from developments in computational methods, high-performance computing, and visualization techniques; it also benefits at the same time through advances in characterization techniques, including nanotomography, 3D image processing, and algorithms for geometrical and topological analysis. The review article collects articles on the structural characterization and micromechanical modeling of nanoporous metals and discusses the acquired understanding in the context of advancements in the experimental discipline. The concluding remarks are given in the form of a summary and an outline of future perspectives.},
note = {Online available at: \url{https://dx.doi.org/10.3390/ma13153307} (DOI). Richert, C.; Huber, N.: A Review of Experimentally Informed Micromechanical Modeling of Nanoporous Metals: From Structural Descriptors to Predictive Structure–Property Relationships . In: Materials. Vol. 13 (2020) 15, 3307. (DOI:  /10.3390/ma13153307)}}
@article{shojaei_dirichlet_absorbing_2020, 
author={Shojaei, A. and Hermann, A. and Seleson, P. and Cyron, C.},
title={Dirichlet absorbing boundary conditions for classical and peridynamic diffusion-type models},
year={2020},
journal = {Computational Mechanics},
volume = {66},
pages = {773 - 793},
doi = {10.1007/s00466-020-01879-1},
abstract = {Diffusion-type problems in (nearly) unbounded domains play important roles in various fields of fluid dynamics, biology, and materials science. The aim of this paper is to construct accurate absorbing boundary conditions (ABCs) suitable for classical (local) as well as nonlocal peridynamic (PD) diffusion models. The main focus of the present study is on the PD diffusion formulation. The majority of the PD diffusion models proposed so far are applied to bounded domains only. In this study, we propose an effective way to handle unbounded domains both with PD and classical diffusion models. For the former, we employ a meshfree discretization, whereas for the latter the finite element method (FEM) is employed. The proposed ABCs are time-dependent and Dirichlet-type, making the approach easy to implement in the available models. The performance of the approach, in terms of accuracy and stability, is illustrated by numerical examples in 1D, 2D, and 3D.},
note = {Online available at: \url{https://dx.doi.org/10.1007/s00466-020-01879-1} (DOI). Shojaei, A.; Hermann, A.; Seleson, P.; Cyron, C.: Dirichlet absorbing boundary conditions for classical and peridynamic diffusion-type models. In: Computational Mechanics. Vol. 66 (2020) 773 - 793. (DOI:  /10.1007/s00466-020-01879-1)}}
@article{odermatt_prediction_of_2020, 
author={Odermatt, A. and Richert, C. and Huber, N.},
title={Prediction of elastic-plastic deformation of nanoporous metals by FEM beam modeling: A bottom-up approach from ligaments to real microstructures},
year={2020},
journal = {Materials Science and Engineering A},
volume = {791},
pages = {139700},
doi = {10.1016/j.msea.2020.139700},
abstract = {For the prediction of elastic-plastic deformation behavior of nanoporous materials, a computationally efficient method is needed that integrates the complex 3D network structure and the large variation of ligament shapes in a representative volume element. Finite element simulations based on beam elements are most efficient, but for a quantitative prediction, a correction is required that accounts for the effects of the mass around the junctions. To this end, a nodal correction is presented that covers a wide range of parabolic-spherical ligament shapes. Smooth functions are provided that define the extension of the nodal corrected elements along the ligament axis, their radius and their yield stress as functions of the individual ligament shape. It is shown that the increase in radius of the nodal beam elements can be replaced by scaled material parameters. Simulations of randomized FEM beam networks revealed that, in relation to the randomization of the ligament axis, the distribution of the ligament shape has a stronger impact on the macroscopic stress–strain response and should thus receive particular attention during the characterization of nanoporous microstructures. This also emphasizes the importance of the thickness analysis via image processing. Combining a nodal corrected FEM beam model with geometry data derived from image multiplication of the skeleton and Euclidean distance transform of a nanoporous gold FIB-SEM tomography dataset significantly improves the prediction of the stress–strain curve. The remaining deviation is expected to stem from the known underestimation of the real ligament diameter by the Euclidean distance transform as well as local variations in the circularity of the ligaments.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.msea.2020.139700} (DOI). Odermatt, A.; Richert, C.; Huber, N.: Prediction of elastic-plastic deformation of nanoporous metals by FEM beam modeling: A bottom-up approach from ligaments to real microstructures. In: Materials Science and Engineering A. Vol. 791 (2020) 139700. (DOI:  /10.1016/j.msea.2020.139700)}}
@article{alessio_prediction_of_2020, 
author={Alessio, R. and Andre, N. and Goushegir, S. and dos Santos, J. and Mazzaferro, J. and T. Amancio-Filho, S.},
title={Prediction of the mechanical and failure behavior of metal-composite hybrid joints using cohesive surfaces},
year={2020},
journal = {Materials Today Communications},
volume = {24},
pages = {101205},
doi = {10.1016/j.mtcomm.2020.101205},
abstract = {Friction Spot Joining (FSpJ) is an alternative technique developed to manufacture hybrid lightweight structures by joining metal to composites. This work has developed a finite element model to evaluate the failure behavior of aluminum alloy 2024-T3 and carbon-fiber-reinforced polyphenylene sulfide single spot joints produced by FSpJ. Cohesive surface behavior was applied to model the interface between aluminum and composite in the joint. The different bonding zones of the FSpJ joint were discretized in the model with a specific traction-separation law. The numerical and experimental force versus displacement curves have presented deviations of 8% for the ultimate lap shear force (ULSF) and 1.6% for displacement at failure. The evolution of the damage in the joint occurred preferably from the free edge of the composite due to the differential stiffness between aluminum and the composite. The influence of the edge distance on the mechanical behavior of the joints was also investigated using FEM. It has been observed that longer overlap lengths redistribute the stress in the bonding area more uniformly, thereby delaying the damage evolution in the bonding zones.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.mtcomm.2020.101205} (DOI). Alessio, R.; Andre, N.; Goushegir, S.; dos Santos, J.; Mazzaferro, J.; T. Amancio-Filho, S.: Prediction of the mechanical and failure behavior of metal-composite hybrid joints using cohesive surfaces. In: Materials Today Communications. Vol. 24 (2020) 101205. (DOI:  /10.1016/j.mtcomm.2020.101205)}}
@article{brinker_giant_electrochemical_2020, 
author={Brinker, M. and Dittrich, G. and Richert, C. and Lakner, P. and Krekeler, T. and Keller, T. and Huber, N. and Huber, P.},
title={Giant electrochemical actuation in a nanoporous silicon-polypyrrole hybrid material},
year={2020},
journal = {Science Advances},
volume = {6},
number = {40},
pages = {eaba1483},
doi = {10.1126/sciadv.aba1483},
abstract = {The absence of piezoelectricity in silicon makes direct electromechanical applications of this mainstream semiconductor impossible. Integrated electrical control of the silicon mechanics, however, would open up new perspectives for on-chip actuorics. Here, we combine wafer-scale nanoporosity in single-crystalline silicon with polymerization of an artificial muscle material inside pore space to synthesize a composite that shows macroscopic electrostrain in aqueous electrolyte. The voltage-strain coupling is three orders of magnitude larger than the best-performing ceramics in terms of piezoelectric actuation. We trace this huge electroactuation to the concerted action of 100 billions of nanopores per square centimeter cross section and to potential-dependent pressures of up to 150 atmospheres at the single-pore scale. The exceptionally small operation voltages (0.4 to 0.9 volts), along with the sustainable and biocompatible base materials, make this hybrid promising for bioactuator applications.},
note = {Online available at: \url{https://dx.doi.org/10.1126/sciadv.aba1483} (DOI). Brinker, M.; Dittrich, G.; Richert, C.; Lakner, P.; Krekeler, T.; Keller, T.; Huber, N.; Huber, P.: Giant electrochemical actuation in a nanoporous silicon-polypyrrole hybrid material. In: Science Advances. Vol. 6 (2020) 40, eaba1483. (DOI:  /10.1126/sciadv.aba1483)}}
@article{steglich_mixedmode_deformation_2020, 
author={Steglich, D.},
title={Mixed-Mode Deformation and Failure of a Magnesium Sheet Quantified using a Modified Arcan Fixture},
year={2020},
journal = {Experimental Mechanics},
volume = {60},
pages = {109 - 118},
doi = {10.1007/s11340-019-00542-y},
abstract = {The anisotropic plastic deformation and the failure behaviour of a rolled magnesium sheet is quantified by means of a modified Arcan loading device. Combined mode I/II loadings are applied at room temperature. Anti-buckling guides enforce parallel motion of the fixture. The evolution of local strain fields during loading is analysed by means of digital image correlation. Two target functions are constructed from each test: one including the kinetic, another describing the kinematical response. The failure strain as a function of the loading direction and sheet orientation is quantified. It is shown that the failure mechanism is independent of the loading angle. Guidelines for future constitutive model developments are provided in terms of the exploration of the samples motion, the uniformity of strain fields and their respective significance.},
note = {Online available at: \url{https://dx.doi.org/10.1007/s11340-019-00542-y} (DOI). Steglich, D.: Mixed-Mode Deformation and Failure of a Magnesium Sheet Quantified using a Modified Arcan Fixture. In: Experimental Mechanics. Vol. 60 (2020) 109 - 118. (DOI:  /10.1007/s11340-019-00542-y)}}
@article{batistao_characterization_of_2020, 
author={Batistao, B. and Bergmann, L. and Gargarela, P. and Alcantara, N. and dos Santos, J. and Klusemann, B.},
title={Characterization of dissimilar friction stir welded lap joints of AA5083 and GL D36 steel},
year={2020},
journal = {Journal of Materials Research and Technology},
volume = {9},
number = {6},
pages = {15132 - 15142},
doi = {10.1016/j.jmrt.2020.10.078},
abstract = {Dissimilar AA5083 to GL D36 steel welds produced by Friction Stir Welding in lap joint configuration, with the aluminum plate placed on the advancing side, are studied regarding their mechanical, microstructural and interfacial properties for varying process parameters, i.e. welding and tool rotational speed. An increase of welding speed or decrease of the rotational speed causes the formation of tunnel defects, a decrease of the steel hook height and reduction of grain size in the aluminum stir zone. The maximum hardness is observed at the weld interface, due to the presence of intermetallic compound layers, identified as the Fe-rich phases as FeAl and Fe3Al. As the rotational speed increases, an increase of the IMCs thickness in the weld interface is found, which contributes to the degradation of the lap shear strength, due to the brittleness and high hardness of these phases. Overall, the maximum lap shear strength is obtained for welds showing macro (steel hook) and micro interlocks, as well as the formation of thin IMC layers at the weld interface.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jmrt.2020.10.078} (DOI). Batistao, B.; Bergmann, L.; Gargarela, P.; Alcantara, N.; dos Santos, J.; Klusemann, B.: Characterization of dissimilar friction stir welded lap joints of AA5083 and GL D36 steel. In: Journal of Materials Research and Technology. Vol. 9 (2020) 6, 15132 - 15142. (DOI:  /10.1016/j.jmrt.2020.10.078)}}
@article{berger_open_porous_2020, 
author={Berger, S. and Okulov, I.},
title={Open Porous α + β Titanium Alloy by Liquid Metal Dealloying for Biomedical Applications},
year={2020},
journal = {Metals},
volume = {10},
number = {11},
pages = {1450},
doi = {10.3390/met10111450},
abstract = {Open porous dendrite-reinforced TiMo alloy was synthesized by liquid metal dealloying of the precursor Ti47.5Mo2.5Cu50 (at.%) alloy in liquid magnesium (Mg). The porous TiMo alloy consists of α-titanium and β-titanium phases and possesses a complex microstructure. The microstructure consists of micrometer scale β-titanium dendrites surrounded by submicrometer scale α-titanium ligaments. Due to the dendrite-reinforced microstructure, the porous TiMo alloy possesses relatively high yield strength value of up to 180 MPa combined with high deformability probed under compression loading. At the same time, the elastic modulus of the porous TiMo alloy (below 10 GPa) is in the range of that found for human bone. This mechanical behavior along with the open porous structure is attractive for biomedical applications and suggests opportunities for using the porous TiMo alloy in implant applications.},
note = {Online available at: \url{https://dx.doi.org/10.3390/met10111450} (DOI). Berger, S.; Okulov, I.: Open Porous α + β Titanium Alloy by Liquid Metal Dealloying for Biomedical Applications. In: Metals. Vol. 10 (2020) 11, 1450. (DOI:  /10.3390/met10111450)}}
@article{li_topology_evolution_2019, 
author={Li, Y. and Ngo, B.-N.D. and Markmann, J. and Weissmueller, J.},
title={Topology evolution during coarsening of nanoscale metal network structures},
year={2019},
journal = {Physical Review Materials},
volume = {3},
number = {7},
pages = {076001},
doi = {10.1103/PhysRevMaterials.3.076001},
abstract = {Many experiments exploit curvature-driven, surface-diffusion-mediated coarsening for tuning the characteristic structure size of metal network structures made by dealloying, such as nanoporous gold. Here we study this process by kinetic Monte Carlo simulation. The initial microstructures are leveled Gaussian random fields, approximating spinodally decomposed mixtures, of different solid fraction φ. Earlier work establishes these structures as valid representations of the nanoporous gold microstructure. We find that the coarsening law for the characteristic spacing between the ligaments of the network is universal, whereas the time evolution of the characteristic ligament diameter is not. The expected time exponent 1/4 is confirmed by our simulation. Contrary to what may be expected based on continuum models, the degree of surface faceting or roughness has no apparent effect on the coarsening kinetics. In the time interval of our study, the network connectivity—as measured by a scaled density of topological genus—remains sensibly invariant for networks with φ≥0.3, consistent with previous reports of a self-similar evolution of the microstructure during coarsening. Yet, networks with lesser φ lose their connectivity on coarsening and can even undergo a percolation-to-cluster transition. This process is slow for φ only little below 0.3 and it accelerates in networks with lesser φ. The dependency of the connectivity evolution on φ may explain controversial findings on the microstructure evolution of nanoporous gold in experimental studies.},
note = {Online available at: \url{https://dx.doi.org/10.1103/PhysRevMaterials.3.076001} (DOI). Li, Y.; Ngo, B.-N.D.; Markmann, J.;   Weissmueller, J.: Topology evolution during coarsening of nanoscale metal network structures. In: Physical Review Materials. Vol. 3 (2019) 7, 076001. (DOI:  /10.1103/PhysRevMaterials.3.076001)}}
@article{braeu_anisotropic_stiffness_2019, 
author={Braeu, F.A. and Aydin, R.C. and Cyron, C.J.},
title={Anisotropic stiffness and tensional homeostasis induce a natural anisotropy of volumetric growth and remodeling in soft biological tissues},
year={2019},
journal = {Biomechanics and Modeling in Mechanobiology},
volume = {18},
pages = {327 - 345},
doi = {10.1007/s10237-018-1084-x},
abstract = {Growth in soft biological tissues in general results in anisotropic changes of the tissue geometry. It remains a key challenge in biomechanics to understand, quantify, and predict this anisotropy. In this paper, we demonstrate that anisotropic tissue stiffness and the well-known mechanism of tensional homeostasis induce a natural anisotropy of the geometric changes resulting from volumetric growth in soft biological tissues. As a rule of thumb, this natural anisotropy makes differential tissue volume elements dilate mainly in the direction(s) of lowest stiffness. This simple principle is shown to explain the experimentally observed growth behavior in a host of different soft biological tissues without relying on any additional heuristic assumptions or quantities (such as ad hoc defined growth tensors).},
note = {Online available at: \url{https://dx.doi.org/10.1007/s10237-018-1084-x} (DOI). Braeu, F.A.; Aydin, R.C.; Cyron, C.J.: Anisotropic stiffness and tensional homeostasis induce a natural anisotropy of volumetric growth and remodeling in soft biological tissues. In: Biomechanics and Modeling in Mechanobiology. Vol. 18 (2019) 327 - 345. (DOI:  /10.1007/s10237-018-1084-x)}}
@article{queirozcaetano_intergranular_corrosion_2019, 
author={Queiroz Caetano, G.de and Carvalho Silva, C. and Motta, M.F. and Miranda, H.C. and Farias, J.P. and Bergmann, L.A. and dos Santos, J.F.},
title={Intergranular corrosion evaluation of friction stir welded AISI 410S ferritic stainless steel},
year={2019},
journal = {Journal of Materials Science and Technology},
volume = {8},
number = {2},
pages = {1878 - 1887},
doi = {10.1016/j.jmrt.2019.01.004},
abstract = {This study aimed to investigate the susceptibility of AISI 410S ferritic stainless steel to intergranular corrosion when friction stir welded (FSW) using the double-loop electrochemical potentiokinetic reactivation (DL-EPR) test. The highest values obtained for the ratio between the reactivation current (Ir) and the activation current (Ia) were found at the top of the advancing side for the two conditions tested. The steel for Condition 1, which was welded with a rotational speed of 800 rpm and high heat input, gave Ir/Ia peaks 60% greater than Condition 2, which was welded with a rotational speed of 450 rpm and a lower heat input. These peaks were attributed to the presence of precipitates with high chromium content of about 21%. In these FSW welds the sensitization of the AISI 410S steel was detected by the electrochemical test according to the intensity of the undesirable phases formed. The DL-EPR test was clearly able to quantify the different levels of sensitization in the FSW welds according to the energy used by the process parameters.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jmrt.2019.01.004} (DOI). Queiroz Caetano, G.de; Carvalho Silva, C.; Motta, M.F.; Miranda, H.C.; Farias, J.P.; Bergmann, L.A.; dos Santos, J.F.: Intergranular corrosion evaluation of friction stir welded AISI 410S ferritic stainless steel. In: Journal of Materials Science and Technology. Vol. 8 (2019) 2, 1878 - 1887. (DOI:  /10.1016/j.jmrt.2019.01.004)}}
@article{liu_surfacedriven_actuation_2019, 
author={Liu, L.-Z. and Mameka, N. and Markmann, J. and Jin, H.-J. and Weissmueller, J.},
title={Surface-driven actuation: Sign reversal under load and surface load-memory effect},
year={2019},
journal = {Physical Review Materials},
volume = {3},
number = {6},
pages = {066001},
doi = {10.1103/PhysRevMaterials.3.066001},
abstract = {Motivated by suggestions that hybrid nanomaterials from nanoporous metal and aqueous electrolyte can be used as actuators, we study the impact of an external load on the actuation behavior of nanoporous gold impregnated with aqueous electrolyte. At no load, we observe the well-documented trend for a more positive electrode potential prompting elongation of the nanoporous body. For purely capacitive electrode processes we confirm that the elastic response to external load is simply superimposed on the potential-induced elongation, so that the strain per electric charge is invariant with the load. The observations so far are consistent with the expectation for surface-stress driven actuation in a linear elastic materials system. Surprisingly, however, actuation in the regime of oxygen electrosorption responds strongly to loading: as the load is increased, the strain per charge gradually drops to zero and even inverts its direction. In other words, the actuator moves backward when asked to do work against a substantial external load. Furthermore, we demonstrate that the length change in response to lifting the oxygen adsorbate layer depends on the load that was present at the instant of oxysorption. This “load memory effect” has analogies to shape-memory behavior in massive alloys. Yet, contrary to shape-memory alloys, the microscopic origin is here a surface phase transition. We argue that the observation is a signature of the reorientation of local surface domains with anisotropic surface stress, and that the required atomic transport process acts only while mobile adatoms are supplied during the deposition or lifting of the oxygen adsorbate layer.},
note = {Online available at: \url{https://dx.doi.org/10.1103/PhysRevMaterials.3.066001} (DOI). Liu, L.-Z.; Mameka, N.; Markmann, J.; Jin, H.-J.; Weissmueller, J.: Surface-driven actuation: Sign reversal under load and surface load-memory effect. In: Physical Review Materials. Vol. 3 (2019) 6, 066001. (DOI:  /10.1103/PhysRevMaterials.3.066001)}}
@article{lemos_residual_stress_2019, 
author={Lemos, G.V.B. and Farina, A.B. and Menezes Nunes, R. and Pereira da Cunha, P.H.C. and Bergmann, L. and dos Santos, J.F. and Reguly, A.},
title={Residual stress characterization in friction stir welds of alloy 625},
year={2019},
journal = {Journal of Materials Research and Technology : JMRT},
volume = {8},
number = {3},
pages = {2528 - 2537},
doi = {10.1016/j.jmrt.2019.02.011},
abstract = {Alloy 625 (UNS N06625) welded sheets were evaluated in the present study. Friction stir welding (FSW) was performed in a range of tool rotational speed from 1200 to 200 rpm, welding speed from 1.0 to 1.5 mm/s and constant axial force. Residual stress states were investigated by X-ray diffraction (XRD). Besides, microstructural features were analyzed by optical microscopy (OM), and scanning electron microscopy (SEM). The FSW application was effective in the Ni-based alloy, promoting different levels of grain refinement, microstructural characteristics, and enhanced microhardness. Results also showed that distinct process parameters led to changes in the joints and distinguishable residual stress distributions. In general, as the tool rotational speed decreased, the grain refinement increased, more homogeneous microstructures and microhardness profiles, and lower residual stresses were achieved within the stirred zones.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jmrt.2019.02.011} (DOI). Lemos, G.V.B.; Farina, A.B.; Menezes Nunes, R.; Pereira da Cunha, P.H.C.; Bergmann, L.; dos Santos, J.F.; Reguly, A.: Residual stress characterization in friction stir welds of alloy 625. In: Journal of Materials Research and Technology : JMRT. Vol. 8 (2019) 3, 2528 - 2537. (DOI:  /10.1016/j.jmrt.2019.02.011)}}
@article{kallien_effect_of_2019, 
author={Kallien, Z. and Keller, S. and Ventzke, V. and Kashaev, N. and Klusemann, B.},
title={Effect of Laser Peening Process Parameters and Sequences on Residual Stress Profiles},
year={2019},
journal = {Metals},
volume = {9},
number = {6},
pages = {655},
doi = {10.3390/met9060655},
abstract = {Laser Peening (LP) is a surface modification technology that can induce high residual stresses in a metallic material. The relation between LP process parameters, in particular laser sequences, as well as pulse parameters and the resulting residual stress state was investigated in this study. The residual stress measurements, performed with the hole drilling technique, showed a non-equibiaxial stress profile in laser peened AA2024-T3 samples with a clad layer for certain parameter combinations. Shot overlap and applied energy density were found to be crucial parameters for the characteristic of the observed non-equibiaxial residual stress profile. Furthermore, the investigation showed the importance of the advancing direction, as the advancing direction influences the direction of the higher compressive residual stress component. The direction of higher residual stresses was parallel or orthogonal to the rolling direction of the material. The effect was correlated to the microstructural observation obtained via electron backscattered diffraction. Additionally, for peening with two sequences of different advancing directions, the study showed that the order of applied advancing directions was important for the non-equibiaxiality of the resulting residual stress profile.},
note = {Online available at: \url{https://dx.doi.org/10.3390/met9060655} (DOI). Kallien, Z.; Keller, S.; Ventzke, V.; Kashaev, N.; Klusemann, B.: Effect of Laser Peening Process Parameters and Sequences on Residual Stress Profiles. In: Metals. Vol. 9 (2019) 6, 655. (DOI:  /10.3390/met9060655)}}
@article{schnabel_work_hardening_2019, 
author={Schnabel, J.E. and Bargmann, S. and Paul, J.D.H. and Oehring, M. and Pyczak, F.},
title={Work hardening and recovery in fully lamellar TiAl: relative activity of deformation systems},
year={2019},
journal = {Philosophical Magazine},
volume = {99},
number = {2},
pages = {148 - 180},
doi = {10.1080/14786435.2018.1532121},
abstract = {The relative activity of deformation systems during work hardening and thermal recovery has been investigated in fully lamellar TiAl. This has been done by a combination of a series of deformation/static recovery experiments and numerical simulations based on a defect density-based crystal plasticity model. Firstly, active deformation systems in differently oriented polysynthetically twinned crystals/single lamellar colonies have been studied. Subsequently, numerical experiments on a polycolony microstructure have been used to investigate the inhomogeneous microplasticity (i.e. the typical microyield) in fully lamellar TiAl. From this, it has been possible to analyse how changes in the lamella thickness, domain size and colony size influence the onset of macroscopic yield. Based on static recovery experiments with differently oriented polysynthetically twinned crystals, numerical studies have revealed trends in the recovery of work hardening in both polysynthetically twinned crystals and polycolony microstructures.},
note = {Online available at: \url{https://dx.doi.org/10.1080/14786435.2018.1532121} (DOI). Schnabel, J.E.; Bargmann, S.; Paul, J.D.H.; Oehring, M.; Pyczak, F.: Work hardening and recovery in fully lamellar TiAl: relative activity of deformation systems. In: Philosophical Magazine. Vol. 99 (2019) 2, 148 - 180. (DOI:  /10.1080/14786435.2018.1532121)}}
@article{burkhardt_laser_welding_2019, 
author={Burkhardt, I. and Ventzke, V. and Riekehr, S. and Kashaev, N. and Enz, J.},
title={Laser welding and microstructural characterization of dissimilar γ-TiAl-Ti6242 joints},
year={2019},
journal = {Intermetallics},
volume = {104},
pages = {74 - 83},
doi = {10.1016/j.intermet.2018.09.012},
abstract = {Crack-free dissimilar TNM-Ti6242 joints were successfully obtained by laser welding with preheating temperatures of 400 °C, 600 °C and 800 °C, in spite of the differing thermophysical properties of the used alloys. The microstructure of the joints was investigated by optical microscopy, SEM, EDX, EBSD and the local mechanical properties were determined by microhardness measurements. The microstructure coarsens with increasing preheating temperature. Homogenous mixture of both alloys in the fusion zone was achieved, even so local microsegregations of Ti, Al and Nb occurred. The fusion zone mainly consists of α2 (Ti3Al). A transition zone, present as a β/βO seam, was revealed for preheating temperatures of 400 °C and 600 °C. For preheating to 800 °C the β/βO seam was penetrated with α2 lamellas. Since the alloying elements of the other alloy were detected in the heat-affected zone, diffusion processes occurred. The average microhardness in the fusion zone of the dissimilar TNM-Ti6242 joints is independent of the preheating temperature and is higher than the base material microhardness. Comparing the microhardness in the fusion zone of similar Ti6242 and TNM joints with dissimilar TNM-Ti6242 joints, the microhardness values of the dissimilar TNM-Ti6242 joints range between the values of the similar Ti6242 and TNM joints. However, the values in the fusion zone are closer to the microhardness values of the similar TNM joint, which is caused by the mainly α2 containing fusion zone of the dissimilar TNM-Ti6242 joints.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.intermet.2018.09.012} (DOI). Burkhardt, I.; Ventzke, V.; Riekehr, S.; Kashaev, N.; Enz, J.: Laser welding and microstructural characterization of dissimilar γ-TiAl-Ti6242 joints. In: Intermetallics. Vol. 104 (2019) 74 - 83. (DOI:  /10.1016/j.intermet.2018.09.012)}}
@article{bock_a_review_2019, 
author={Bock, F.E. and Aydin, R.C. and Cyron, C.J. and Huber, N. and Kalidindi, S.R. and Klusemann, B.},
title={A Review of the Application of Machine Learning and Data Mining Approaches in Continuum Materials Mechanics},
year={2019},
journal = {Frontiers in Materials},
volume = {6},
pages = {110},
doi = {10.3389/fmats.2019.00110},
abstract = {Machine learning tools represent key enablers for empowering material scientists and engineers to accelerate the development of novel materials, processes and techniques. One of the aims of using such approaches in the field of materials science is to achieve high-throughput identification and quantification of essential features along the process-structure-property-performance chain. In this contribution, machine learning and statistical learning approaches are reviewed in terms of their successful application to specific problems in the field of continuum materials mechanics. They are categorized with respect to their type of task designated to be either descriptive, predictive or prescriptive; thus to ultimately achieve identification, prediction or even optimization of essential characteristics. The respective choice of the most appropriate machine learning approach highly depends on the specific use-case, type of material, kind of data involved, spatial and temporal scales, formats, and desired knowledge gain as well as affordable computational costs. Different examples are reviewed involving case-by-case dependent application of different types of artificial neural networks and other data-driven approaches such as support vector machines, decision trees and random forests as well as Bayesian learning, and model order reduction procedures such as principal component analysis, among others. These techniques are applied to accelerate the identification of material parameters or salient features for materials characterization, to support rapid design and optimization of novel materials or manufacturing methods, to improve and correct complex measurement devices, or to better understand and predict fatigue behavior, among other examples. Besides experimentally obtained datasets, numerous studies draw required information from simulation-based data mining. Altogether, it is shown that experiment- and simulation-based data mining in combination with machine leaning tools provide exceptional opportunities to enable highly reliant identification of fundamental interrelations within materials for characterization and optimization in a scale-bridging manner. Potentials of further utilizing applied machine learning in materials science and empowering significant acceleration of knowledge output are pointed out.},
note = {Online available at: \url{https://dx.doi.org/10.3389/fmats.2019.00110} (DOI). Bock, F.E.; Aydin, R.C.; Cyron, C.J.; Huber, N.; Kalidindi, S.R.; Klusemann, B.: A Review of the Application of Machine Learning and Data Mining Approaches in Continuum Materials Mechanics. In: Frontiers in Materials. Vol. 6 (2019) 110. (DOI:  /10.3389/fmats.2019.00110)}}
@article{braga_fatigue_performance_2019, 
author={Braga, D.F.O. and Maciel, R. and Bergmann, L. and da Silva, L.F.M. and Infante, V. and dos Santos, J.F. and Moreira, P.M.G.P.},
title={Fatigue performance of hybrid overlap friction stir welding and adhesive bonding of an Al‐Mg‐Cu alloy},
year={2019},
journal = {Fatigue and Fracture of Engineering Materials and Structures},
volume = {42},
number = {6},
pages = {1262 - 1270},
doi = {10.1111/ffe.12933},
abstract = {The need for weight reduction and leaner manufacturing and assembly processes in aircraft construction has led to the pursuit of welding technologies. One such technology that has been considered for this application is friction stir welding (FSW). Since it is a solid‐state joining method, it creates high performing joints in a wide range of materials while avoiding overlap lengths and added weight from fasteners, crack stoppers, doublers, etc. However, the adoption of this technology to the assembly of large fuselage shell components is challenging, due to geometric tolerance management requirements. In this paper, a hybrid joining method is proposed for such application, involving FSW and adhesive bonding. Fatigue performance of single lap joints of AA2024‐T3 Al‐Mg‐Cu alloy was assessed and benchmarked against FSW overlap and adhesive bonded joints. Significant strength and ductility increase was achieved through the hybridization of the overlap FSW joints. Fatigue strength of the hybrid joints was also higher than FSW overlap joints, although not as high as adhesive bonded joints.},
note = {Online available at: \url{https://dx.doi.org/10.1111/ffe.12933} (DOI). Braga, D.F.O.; Maciel, R.; Bergmann, L.; da Silva, L.F.M.; Infante, V.; dos Santos, J.F.; Moreira, P.M.G.P.: Fatigue performance of hybrid overlap friction stir welding and adhesive bonding of an Al‐Mg‐Cu alloy. In: Fatigue and Fracture of Engineering Materials and Structures. Vol. 42 (2019) 6, 1262 - 1270. (DOI:  /10.1111/ffe.12933)}}
@article{entringer_the_effect_2019, 
author={Entringer, J. and Meisnar, M. and Reimann, M. and Blawert, C. and Zheludkevich, M. and dos Santos, J.F.},
title={The effect of grain boundary precipitates on stress corrosion cracking in a bobbin tool friction stir welded Al-Cu-Li alloy},
year={2019},
journal = {Materials Letters: X},
volume = {2},
pages = {100014},
doi = {10.1016/j.mlblux.2019.100014},
abstract = {Evidence of stress corrosion cracking has been observed in exposed semi-stationary bobbin tool friction stir welded aluminum-copper-lithium alloy 2060-T8. Microstructural analysis confirmed the heterogeneous microstructure transformation caused by the thermomechanical impact of the welding process. Grain boundary phase accumulation initiated anodic dissolution in NaCl solution under stress. In the center and the heat affected zone of the weld, the microstructure was found to form overaged and high copper containing equilibrium phases promoting intergranular stress corrosion.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.mlblux.2019.100014} (DOI). Entringer, J.; Meisnar, M.; Reimann, M.; Blawert, C.; Zheludkevich, M.; dos Santos, J.F.: The effect of grain boundary precipitates on stress corrosion cracking in a bobbin tool friction stir welded Al-Cu-Li alloy. In: Materials Letters: X. Vol. 2 (2019) 100014. (DOI:  /10.1016/j.mlblux.2019.100014)}}
@article{costapereiradacunha_effect_of_2019, 
author={Costa Pereira da Cunha, P.H. and Braga, Lemos, G,V. and Bergmann, L. and Reguly, A. and dos Santos, J.F. and Marinho, R.R. and Piza Paes, M.T.},
title={Effect of welding speed on friction stir welds of GL E36 shipbuilding steel},
year={2019},
journal = {Journal of Materials Research and Technology : JMRT},
volume = {8},
number = {1},
pages = {1041 - 1051},
doi = {10.1016/j.jmrt.2018.07.014},
abstract = {The aim of this study was to characterize mechanical and microstructural characteristics of friction-stir-welded GL E36 shipbuilding steel. The tool rotational speed was kept constant at 500 rpm and different welding speeds were used (1, 2 and 3 mm/s) to achieve different heat inputs. Thermal cycles were monitored by thermocouples placed near the weld face. The welded joints showed a very good esthetics and homogeneous surface quality that indicate a stability of the considered process parameters. The welded joints properties were analyzed by metallography and mechanical tests such as microhardness, tensile and bending. Macrostructural observations were done at the beginning, middle and ending of the welded length. In addition, radiographic inspection was carried out. The pcBN tool exhibited good wear behavior even after welding around 8.5 m where no apparent loss in dimensions and geometrical features of the probe and shoulder were found. The macrographs displayed different microstructural features and material flow pattern among the heat inputs achieved. A large microstructure gradient was observed, especially within the stirred zone. All the tensile samples broke at the base material showing that the joints achieved higher strength. Microhardness peaks of about 400 HV were also encountered in all the joints. Finally, for welding speeds of 2–3 mm/s the thermocouples presented the most uniform thermal profiles.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jmrt.2018.07.014} (DOI). Costa Pereira da Cunha, P.H.; Braga, Lemos, G,V.; Bergmann, L.; Reguly, A.; dos Santos, J.F.; Marinho, R.R.; Piza Paes, M.T.: Effect of welding speed on friction stir welds of GL E36 shipbuilding steel. In: Journal of Materials Research and Technology : JMRT. Vol. 8 (2019) 1, 1041 - 1051. (DOI:  /10.1016/j.jmrt.2018.07.014)}}
@article{abbaszadeh_numerical_investigation_2019, 
author={Abbaszadeh, M. and Hönnige, J.R. and Martina, F. and Neto, L. and Kashaev, N. and Colegrove, P. and Williams, S. and Klusemann, B.},
title={Numerical Investigation of the Effect of Rolling on the Localized Stress and Strain Induction for Wire + Arc Additive Manufactured Structures},
year={2019},
journal = {Journal of Materials Engineering and Performance},
volume = {28},
number = {8},
pages = {4931 - 4942},
doi = {10.1007/s11665-019-04249-y},
abstract = {Cold rolling can be used in-process or post-process to improve microstructure, mechanical properties and residual stress in directed-energy-deposition techniques, such as the high deposition rate wire + arc additive manufacturing (WAAM) process. Finite element simulations of the rolling process are employed to investigate the effect of rolling parameters, in particular rolling load and roller profile radius on the residual stress field as well as plastic strain distribution for the profiled roller. The results show the response to rolling of commonly used structural metals in WAAM, i.e., AA2319, S335JR steel and Ti-6Al-4V, taking into account the presence of residual stresses. The rolling load leads to changes in the location and the maximum value of the compressive residual stresses, as well as the depth of the compressive residual stresses. However, the roller profile radius only changes the maximum value of these compressive residual stresses. Changing the rolling load influences the equivalent plastic strain close to the top surface of the wall as well as in deeper areas, whereas the influence of the roller profile radius is negligible. The plastic strain distribution is virtually unaffected by the initial residual stresses prior to rolling. Finally, design curves were generated from the simulations for different materials, suggesting ideal rolling load and roller profile combinations for microstructural improvement requiring certain plastic strains at a specific depth of the additive structure.},
note = {Online available at: \url{https://dx.doi.org/10.1007/s11665-019-04249-y} (DOI). Abbaszadeh, M.; Hönnige, J.R.; Martina, F.; Neto, L.; Kashaev, N.; Colegrove, P.; Williams, S.; Klusemann, B.: Numerical Investigation of the Effect of Rolling on the Localized Stress and Strain Induction for Wire + Arc Additive Manufactured Structures. In: Journal of Materials Engineering and Performance. Vol. 28 (2019) 8, 4931 - 4942. (DOI:  /10.1007/s11665-019-04249-y)}}
@article{entringer_influence_of_2019, 
author={Entringer, J. and Reimann, M. and Norman, A. and dos Santos, J.F.},
title={Influence of Cu/Li ratio on the microstructure evolution of bobbin-tool friction stir welded Al–Cu–Li alloys},
year={2019},
journal = {Journal of Materials Research and Technology : JMRT},
volume = {8},
number = {2},
pages = {2031 - 2040},
doi = {10.1016/j.jmrt.2019.01.014},
abstract = {Two modern aluminum lithium alloys were welded by semi-stationary bobbin tool friction stir welding. The influence of the Cu/Li ratio on precipitation phenomena under process heat impact was investigated by comparing the response of low Cu/Li alloy 2196-T8 and high Cu/Li alloy 2060-T8. Identical process parameters with a weld pitch of one rotation per mm were used to conduct flawless weldments. The thermal history and microstructural features were studied and correlated to the resulting mechanical properties of the welds. Analysis of microstructure using differential scanning calorimetry and high energy X-ray diffraction technique showed significant differences in the precipitation sequence of the base metal and in the welded samples of the two alloys of interest. A low Cu/Li ratio led to a higher softening resulting in a reduction of 43% of base metal yield strength while the high Cu/Li ratio alloy AA 2060 could demonstrate more thermal stability (38% reduction). Severe dissolution of the T1 precipitate and presence of equilibrium phases were confirmed for the stirred zone of both alloys. The heat affected zone suffered dissolution and overaging reactions leading to a mechanically unfavorable microstructure. The low Cu/Li alloy 2196 developed a higher process temperatures and exhibited a more evolved precipitation sequence.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jmrt.2019.01.014} (DOI). Entringer, J.; Reimann, M.; Norman, A.; dos Santos, J.F.: Influence of Cu/Li ratio on the microstructure evolution of bobbin-tool friction stir welded Al–Cu–Li alloys. In: Journal of Materials Research and Technology : JMRT. Vol. 8 (2019) 2, 2031 - 2040. (DOI:  /10.1016/j.jmrt.2019.01.014)}}
@article{cipriano_fundamentals_of_2019, 
author={Cipriano, G.P. and Blaga, L.A. and dos Santos, J.F. and Vilaca, P. and Amancio-Filho, S.T.},
title={Fundamentals of Force-Controlled Friction Riveting: Part II - Joint Global Mechanical Performance and Energy Efficiency},
year={2019},
journal = {Materials},
volume = {11},
number = {12},
pages = {2489},
doi = {10.3390/ma11122489},
abstract = {The present work investigates the correlation between energy efficiency and global mechanical performance of hybrid aluminum alloy AA2024 (polyetherimide joints), produced by force-controlled friction riveting. The combinations of parameters followed a central composite design of experiments. Joint formation was correlated with mechanical performance via a volumetric ratio (0.28–0.66 a.u.), with a proposed improvement yielding higher accuracy. Global mechanical performance and ultimate tensile force varied considerably across the range of parameters (1096–9668 N). An energy efficiency threshold was established at 90 J, until which, energy input displayed good linear correlations with volumetric ratio and mechanical performance (R-sq of 0.87 and 0.86, respectively). Additional energy did not significantly contribute toward increasing mechanical performance. Friction parameters (i.e., force and time) displayed the most significant contributions to mechanical performance (32.0% and 21.4%, respectively), given their effects on heat development. For the investigated ranges, forging parameters did not have a significant contribution. A correlation between friction parameters was established to maximize mechanical response while minimizing energy usage. The knowledge from Parts I and II of this investigation allows the production of friction riveted connections in an energy efficient manner and control optimization approach, introduced for the first time in friction riveting.},
note = {Online available at: \url{https://dx.doi.org/10.3390/ma11122489} (DOI). Cipriano, G.P.; Blaga, L.A.; dos Santos, J.F.; Vilaca, P.; Amancio-Filho, S.T.: Fundamentals of Force-Controlled Friction Riveting: Part II - Joint Global Mechanical Performance and Energy Efficiency. In: Materials. Vol. 11 (2019) 12, 2489. (DOI:  /10.3390/ma11122489)}}
@article{aydin_general_multifidelity_2019, 
author={Aydin, R.C. and Braeu, F.A. and Cyron, C.J.},
title={General multi-fidelity framework for training artificial neural networks with computational models},
year={2019},
journal = {Frontiers in Materials},
volume = {6},
pages = {61},
doi = {10.3389/fmats.2019.00061},
abstract = {Training of artificial neural networks (ANNs) relies on the availability of training data. If ANNs have to be trained to predict or control the behavior of complex physical systems, often not enough real-word training data are available, for example, because experiments or measurements are too expensive, time-consuming or dangerous. In this case, generating training data by way of realistic computational simulations is a viable and often the only promising alternative. Doing so can, however, be associated with a significant and often even prohibitive computational cost, which forms a serious bottleneck for the application of machine learning to complex physical systems. To overcome this problem, we propose in this paper a both systematic and general approach. It uses cheap low-fidelity computational models to start the training of the ANN and gradually switches to higher-fidelity training data as the training of the ANN progresses. We demonstrate the benefits of this strategy using examples from structural and materials mechanics. We demonstrate that in these examples the multi-fidelity strategy introduced herein can reduce the total computational cost – compared to simple brute-force training of ANNs – by a half up to one order of magnitude. This multi-fidelity strategy can thus be hoped to become a powerful and versatile tool for the future combination of computational simulations and artificial intelligence, in particular in areas such as structural and materials mechanics.},
note = {Online available at: \url{https://dx.doi.org/10.3389/fmats.2019.00061} (DOI). Aydin, R.C.; Braeu, F.A.; Cyron, C.J.: General multi-fidelity framework for training artificial neural networks with computational models. In: Frontiers in Materials. Vol. 6 (2019) 61. (DOI:  /10.3389/fmats.2019.00061)}}
@article{raza_computational_modeling_2019, 
author={Raza, S.H. and Soyarslan, C. and Bargmann, S. and Klusemann, B.},
title={Computational modeling of amorphous polymers: A Lagrangian logarithmic strain space formulation of a glass–rubber constitutive model},
year={2019},
journal = {Computer Methods in Applied Mechanics and Engineering},
volume = {344},
pages = {887 - 909},
doi = {10.1016/j.cma.2018.10.007},
abstract = {We present a reformulation of the finite strain, rate dependent inelastic glass-rubber material model suggested by Buckley and Jones (1995) and extended by Adams et al. (2000) for modeling the deformation of amorphous polymers in the Lagrangian logarithmic strain space. This not only warrants a hyperelastic characterization in the bonding part which remedies problems associated with hypoelastic approaches devising objective stress rates selected on ad hoc basis, see, e.g., Dooling et al. (2001) and Li and Buckley (2009), but also allows a transparent and naturally objective implementation analogous to the geometrically linear theory. A numerical implementation into Abaqus is pursued where algorithms for stress update and tangent moduli computations are reported. It is shown that significant reduction in nonlinear equation system size is possible in the computation of both bonding and conformational part. The characterization tests include constant-width tension, equi-biaxial tension, and simple shear. To demonstrate the robustness of the developed framework, two hypothetical problems of extreme deformation under tensile and combined tensile and torsion loading are considered. Finally, simulation of an injection stretch-blow molding process is presented as an application problem.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.cma.2018.10.007} (DOI). Raza, S.H.; Soyarslan, C.; Bargmann, S.; Klusemann, B.: Computational modeling of amorphous polymers: A Lagrangian logarithmic strain space formulation of a glass–rubber constitutive model. In: Computer Methods in Applied Mechanics and Engineering. Vol. 344 (2019) 887 - 909. (DOI:  /10.1016/j.cma.2018.10.007)}}
@article{manenteandre_evaluation_of_2019, 
author={Manente Andre, N. and dos Santos, J.F. and Amancio-Filho, S.T.},
title={Evaluation of Joint Formation and Mechanical Performance of the AA7075-T6/CFRP Spot Joints Produced by Frictional Heat},
year={2019},
journal = {Materials},
volume = {12},
number = {6},
pages = {891},
doi = {10.3390/ma12060891},
abstract = {The development of lightweight hybrid metal–polymer structures has recently attracted interest from the transportation industry. Nevertheless, the possibility of joining metals and polymers or composites is still a great challenge. Friction Spot Joining (FSpJ) is a prize-winning friction-based joining technique for metal–polymer hybrid structures. The technology is environment-friendly and comprises very short joining cycles (2 to 8 s). In the current work, aluminum alloy 7075-T6 and carbon-fiber-reinforced polyphenylene sulfide (CF-PPS) friction spot joints were produced and evaluated for the first time in the literature. The spot joints were investigated in terms of microstructure, mechanical performance under quasi-static loading and failure mechanisms. Macro- and micro-mechanical interlocking were identified as the main bonding mechanism, along with adhesion forces as a result of the reconsolidated polymer layer. Moreover, the influence of the joining force on the mechanical performance of the joints was addressed. Ultimate lap shear forces up to 4068 ± 184 N were achieved in this study. A mixture of adhesive–cohesive failure mode was identified, while cohesive failure was dominant. Finally, a qualitative comparison with other state-of-the-art joining technologies for hybrid structures demonstrated that the friction spot joints eventually exhibit superior/similar strength than/to concurrent technologies and shorter joining times.},
note = {Online available at: \url{https://dx.doi.org/10.3390/ma12060891} (DOI). Manente Andre, N.; dos Santos, J.F.;  Amancio-Filho, S.T.: Evaluation of Joint Formation and Mechanical Performance of the AA7075-T6/CFRP Spot Joints Produced by Frictional Heat. In: Materials. Vol. 12 (2019) 6, 891. (DOI:  /10.3390/ma12060891)}}
@article{chupakhin_application_of_2019, 
author={Chupakhin, S. and Klusemann, B. and Huber, N. and Kashaev, N.},
title={Application of design of experiments for laser shock peening process optimization},
year={2019},
journal = {The International Journal of  Advanced Manufacturing Technology},
volume = {102},
number = {5 - 8},
pages = {1567 - 1581},
doi = {10.1007/s00170-018-3034-2},
abstract = {Laser shock peening—a very promising life enhancement technique—has demonstrated great success regarding the improvement of fatigue behavior via deep compressive residual stresses. However, the prediction and adaption of residual stress fields on basis of the laser peening parameters are still not comprehensively established. The aim of the current work is to investigate the effects of the laser pulse energy, the number of treatment overlaps as well as the laser spot size on the resulting residual stress distribution, characterized by following quantities: the residual stress close to the surface, the maximum compressive residual stress, and the integral compressive stress area over the specimen depth. For a systematic investigation of all main and interaction-based process parameter effects, and a subsequent parameter optimization, the general full factorial design is employed. The results show that laser shock peening with different process parameter combinations, inducing residual stresses with comparable integral stress area, can lead to a minimum fatigue life extension of approx. 100,000 cycles, representing a minimum fatigue life of 250% of the base material. The experimental scatter in the number of cycles to failure follows the Weibull distribution which qualitatively correlates with the standard deviation of the integral stress area.},
note = {Online available at: \url{https://dx.doi.org/10.1007/s00170-018-3034-2} (DOI). Chupakhin, S.; Klusemann, B.; Huber, N.; Kashaev, N.: Application of design of experiments for laser shock peening process optimization. In: The International Journal of  Advanced Manufacturing Technology. Vol. 102 (2019) 5 - 8, 1567 - 1581. (DOI:  /10.1007/s00170-018-3034-2)}}
@article{brandstaeter_mechanics_of_2019, 
author={Brandstaeter, S. and Fuchs, S.L. and Aydin, R.C. and Cyron, C.J.},
title={Mechanics of the stomach: A review of an emerging field of biomechanics},
year={2019},
journal = {GAMM-Mitteilungen},
volume = {42},
number = {3},
pages = {e201900001},
doi = {10.1002/gamm.201900001},
abstract = {Mathematical and computational modeling of the stomach is an emerging field of biomechanics where several complex phenomena, such as gastric electrophysiology, fluid mechanics of the digesta, and solid mechanics of the gastric wall, need to be addressed. Developing a comprehensive multiphysics model of the stomach that allows studying the interactions between these phenomena remains one of the greatest challenges in biomechanics. A coupled multiphysics model of the human stomach would enable detailed in‐silico studies of the digestion of food in the stomach in health and disease. Moreover, it has the potential to open up unprecedented opportunities in numerous fields such as computer‐aided medicine and food design. This review article summarizes our current understanding of the mechanics of the human stomach and delineates the challenges in mathematical and computational modeling which remain to be addressed in this emerging area.},
note = {Online available at: \url{https://dx.doi.org/10.1002/gamm.201900001} (DOI). Brandstaeter, S.; Fuchs, S.L.; Aydin, R.C.; Cyron, C.J.: Mechanics of the stomach: A review of an emerging field of biomechanics. In: GAMM-Mitteilungen. Vol. 42 (2019) 3, e201900001. (DOI:  /10.1002/gamm.201900001)}}
@article{falck_microstructure_and_2019, 
author={Falck, R. and dos Santos, J.F. and Amancio-Filho, S.T.},
title={Microstructure and Mechanical Performance of Additively Manufactured Aluminum 2024-T3/Acrylonitrile Butadiene Styrene Hybrid Joints Using an AddJoining Technique},
year={2019},
journal = {Materials},
volume = {12},
number = {6},
pages = {864},
doi = {10.3390/ma12060864},
abstract = {AddJoining is an emerging technique that combines the principles of the joining method and additive manufacturing. This technology is an alternative method to produce metal–polymer (composite) structures. Its viability was demonstrated for the material combination composed of aluminum 2024-T3 and acrylonitrile butadiene styrene to form hybrid joints. The influence of the isolated process parameters was performed using the one-factor-at-a-time approach, and analyses of variance were used for statistical analysis. The mechanical performance of single-lap joints varied from 910 ± 59 N to 1686 ± 39 N. The mechanical performance thus obtained with the optimized joining parameters was 1686 ± 39 N, which failed by the net-tension failure mode with a failure pattern along the 45° bonding line. The microstructure of the joints and the fracture morphology of the specimens were studied using optical microscopy and scanning electron microscopy. From the microstructure point of view, proper mechanical interlocking was achieved between the coated metal substrate and 3D-printed polymer. This investigation can be used as a base for further improvements on the mechanical performance of AddJoining hybrid-layered applications.},
note = {Online available at: \url{https://dx.doi.org/10.3390/ma12060864} (DOI). Falck, R.; dos Santos, J.F.; Amancio-Filho, S.T.: Microstructure and Mechanical Performance of Additively Manufactured Aluminum 2024-T3/Acrylonitrile Butadiene Styrene Hybrid Joints Using an AddJoining Technique. In: Materials. Vol. 12 (2019) 6, 864. (DOI:  /10.3390/ma12060864)}}
@article{cardillo_effect_of_2019, 
author={Cardillo, M.E.B. and Shen, J. and de Alcantara, N.G. and Afonso, C.R.M. and dos Santos, J.F.},
title={Effect of friction spot welding parameters on the joint formation and mechanical properties of Al to Cu},
year={2019},
journal = {Welding in the World},
volume = {63},
number = {1},
pages = {33 - 41},
doi = {10.1007/s40194-018-0632-4},
abstract = {Friction spot welding is an appealing technique for joining dissimilar materials, such as aluminum and copper that have significant differences in physical and mechanical properties. To optimize the welding process, a full-factorial design was employed. It is found that in addition to the plunge depth, the interaction between the rotational speed and the plunge depth significantly influences the lap-shear strength of the Al/Cu dissimilar joints. Further investigations on macro- and microstructures show that increasing the plunge depth could deform the Cu sheet into a concave shape to form a mechanical interlocking, and thus increase the joint lap-shear strength; increasing the tool rotational speed, however, may compromise this effect because of the formed tunnel defects on the interface due to high thermal exposure.},
note = {Online available at: \url{https://dx.doi.org/10.1007/s40194-018-0632-4} (DOI). Cardillo, M.E.B.; Shen, J.; de Alcantara, N.G.; Afonso, C.R.M.; dos Santos, J.F.: Effect of friction spot welding parameters on the joint formation and mechanical properties of Al to Cu. In: Welding in the World. Vol. 63 (2019) 1, 33 - 41. (DOI:  /10.1007/s40194-018-0632-4)}}
@article{kabir_grainwise_simulation_2019, 
author={Kabir, M.R. and Cornec, A.},
title={Grain-wise simulation of stochastic damage and failure verified on a TiAl polycrystal
},
year={2019},
journal = {Materials Science and Engineering  A},
volume = {748},
pages = {146 - 160},
doi = {10.1016/j.msea.2019.01.045},
abstract = {Microstructure of alloys contains typically stochastic distributed constituents (grains) with uneven properties. Recent progresses in computational modelling enable microstructure-sensitive and multi-scale simulations methods, where stochastic properties can be considered with an increasing resolution of local details. In this work a stochastic approach was proposed where several numerical aspects are treated in a finite element framework: (i) determination of grain-wise properties; (ii) the kind of stochastic distribution; (iii) introduction of necessary but appropriate idealizations regarding real microstructure; (iv) use of appropriate constitutive models for deformation, damage and fracture. The proposed stochastic approach was applied and verified on a TiAl polycrystal with significant stochastic nature. The strong anisotropic deformation behaviour, due to the oriented lamellar grains consisting of relevant TiAl phases (α2 and γ), was determined at first by a two-scale crystal plasticity model, and then, the results were transformed to a homogenized grain behaviour corresponding to each oriented lamellar grains. The simulations provide a significant deformation scatter which was used in the presented stochastic approach. Regarding the stochastic evolution of damage till failure, a cohesive model was applied at idealized grains along the fracture plane. Simulation results showed that failure of the first grain was closely related to the macroscopic failure of tensile tests, which provides estimation of grain-wise damage properties. Further, unsymmetrical weighted distribution shapes were introduced to consider inhomogeneous dispersed properties. The cohesive model with these stochastic properties allows a deep and qualified understanding of internal grain-wise damage evolution, first grain failure, and unstable crack extension across the fracture surface. In particular, deformation constraints among grains with different properties play major roles in the evolution of the local damage till component failure.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.msea.2019.01.045} (DOI). Kabir, M.R.; Cornec, A.: Grain-wise simulation of stochastic damage and failure verified on a TiAl polycrystal
. In: Materials Science and Engineering  A. Vol. 748 (2019) 146 - 160. (DOI:  /10.1016/j.msea.2019.01.045)}}
@article{ovri_grainscale_investigation_2019, 
author={Ovri, H. and Steglich, D. and Dieringa, H. and Lilleodden, E.T.},
title={Grain-scale investigation of the anisotropy of Portevin-Le Chatelier effect in Mg AZ91 alloy},
year={2019},
journal = {Materials Science and Engineering  A},
volume = {740-741},
pages = {226 - 234},
doi = {10.1016/j.msea.2018.10.099},
abstract = {An aspect of Portevin-Le Chatelier (PLC) type plastic instability that is yet to be understood is its orientation dependence. Such knowledge is crucial in view of its implications for texture weakening and, by extension, improvement in formability in Mg–based alloys. In this work, insight into the micromechanisms that govern PLC and its orientation dependence in single grains of Mg AZ91 is achieved using a combination of spherical nanoindentation, local orientation image analysis and crystal plasticity based finite element simulations, which was specifically used to identify the anisotropy in slip activity for the investigated orientations. Moreover, a statistical thermal activation model that is based on the distribution of load jumps between consecutive displacement bursts in the load vs. displacement response is presented. The paper demonstrates the ability of the model to predict the thermal activation parameters for PLC effect. On the basis of the results, we propose a mechanistically sound model for PLC effect that explains the underlying micromechanisms, the role of Al and Zn atoms, and the origin of the orientation dependence of the phenomenon. We also highlight the influence of the PLC effect on formability in Mg–based alloys.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.msea.2018.10.099} (DOI). Ovri, H.; Steglich, D.; Dieringa, H.; Lilleodden, E.T.: Grain-scale investigation of the anisotropy of Portevin-Le Chatelier effect in Mg AZ91 alloy. In: Materials Science and Engineering  A. Vol. 740-741 (2019) 226 - 234. (DOI:  /10.1016/j.msea.2018.10.099)}}
@article{larsson_nanoporous_gold_2019, 
author={Larsson, E. and Guersoy, D. and De Carlo, F. and Lilleodden, E.T. and Storm, M. and Wilde, F. and Hu, K. and Mueller, M. and Greving, I.},
title={Nanoporous gold: a hierarchical and multiscale 3D test pattern for characterizing X-ray nano-tomography systems},
year={2019},
journal = {Journal of Synchrotron Radiation},
volume = {26},
number = {1},
pages = {194 - 204},
doi = {10.1107/S1600577518015242},
abstract = {Full-field transmission X-ray microscopy (TXM) is a well established technique, available at various synchrotron beamlines around the world as well as by laboratory benchtop devices. One of the major TXM challenges, due to its nanometre-scale resolution, is the overall instrument stability during the acquisition of the series of tomographic projections. The ability to correct for vertical and horizontal distortions of each projection image during acquisition is necessary in order to achieve the effective 3D spatial resolution. The effectiveness of such an image alignment is also heavily influenced by the absorption properties and strong contrast of specific features in the scanned sample. Here it is shown that nanoporous gold (NPG) can be used as an ideal 3D test pattern for evaluating and optimizing the performance of a TXM instrument for hard X-rays at a synchrotron beamline. Unique features of NPG, such as hierarchical structures at multiple length scales and high absorbing capabilities, makes it an ideal choice for characterization, which involves a combination of a rapid-alignment algorithm applied on the acquired projections followed by the extraction of a set of both 2D- and 3D-descriptive image parameters. This protocol can be used for comparing the efficiency of TXM instruments at different synchrotron beamlines in the world or benchtop devices, based on a reference library of scanned NPG samples, containing information about the estimated horizontal and vertical alignment values, 2D qualitative parameters and quantitative 3D parameters. The possibility to tailor the ligament sizes of NPG to match the achievable resolution in combination with the high electron density of gold makes NPG an ideal 3D test pattern for evaluating the status and performance of a given synchrotron-based or benchtop-based TXM setup.},
note = {Online available at: \url{https://dx.doi.org/10.1107/S1600577518015242} (DOI). Larsson, E.; Guersoy, D.; De Carlo, F.; Lilleodden, E.T.; Storm, M.; Wilde, F.; Hu, K.; Mueller, M.; Greving, I.: Nanoporous gold: a hierarchical and multiscale 3D test pattern for characterizing X-ray nano-tomography systems. In: Journal of Synchrotron Radiation. Vol. 26 (2019) 1, 194 - 204. (DOI:  /10.1107/S1600577518015242)}}
@article{zocollerborba_the_influence_2019, 
author={Zocoller Borba, N. and dos Santos, J.F. and Amancio-Filho, S.T.},
title={The Influence of Clamping Pressure on Joint Formation and Mechanical Performance of Ti6Al4V/CF-PEEK Friction-Riveted Joints},
year={2019},
journal = {Materials},
volume = {12},
number = {5},
pages = {745},
doi = {10.3390/ma12050745},
abstract = {This work aims at investigating the influence of pre-set clamping pressure on the joint formation and mechanical strength of overlapping direct-friction-riveted joints. A pneumatic fixture device was developed for this work, with clamping pressure varying from 0.2 MPa to 0.6 MPa. A case study on overlapping joints using Ti6Al4V rivets and woven carbon fiber-reinforced polyether-ether-ketone (CF-PEEK) parts were produced. Digital image correlation and microscopy revealed the expected compressive behavior of the clamping system and the continuous pressure release upon the joining process owing to the rivet plastic deformation and the polymer squeezing flow. Two preferential paths of material flow were identified through the alternate replacement of the upper and lower composite parts by a poly-methyl-methacrylate (PMMA) plate—the composite upward and squeezing flow between the parts which induced their separation. The ultimate lap shear forces up to 6580 ± 383 N were achieved for the direct-friction-riveted CF-PEEK overlap joints. The formation of a gap to accommodate squeezed polymer between the composite parts during the process had no influence on the joint mechanical performance. The increase in the clamping pressure for joints produced with a low friction force did not affect the joint-anchoring efficiency and consequently the joint strength. On the other hand, the combined effect of a high-friction force and clamping pressure induced the inverted bell shape of the plastically deformed rivet tip, a lower anchoring efficiency, and the delamination of the composite, all of which decrease the mechanical strength by 31%. Therefore, the higher the friction force and clamping pressure, the more defects would be generated in the composite parts and the more changes in the shape of the plastically deformed rivet tip, leading to a lower level of quasi-static mechanical performance. All the joints failed by initial bearing of the composite and final rivet pull-out. The findings of this work can contribute to further improvement of the clamping design for industrial application.},
note = {Online available at: \url{https://dx.doi.org/10.3390/ma12050745} (DOI). Zocoller Borba, N.; dos Santos, J.F.; Amancio-Filho, S.T.: The Influence of Clamping Pressure on Joint Formation and Mechanical Performance of Ti6Al4V/CF-PEEK Friction-Riveted Joints. In: Materials. Vol. 12 (2019) 5, 745. (DOI:  /10.3390/ma12050745)}}
@article{okulov_anomalously_low_2019, 
author={Okulov, I.V. and Geslin, P.-A. and Soldatov, I.V. and Ovri, H. and Joo, S.-H. and Kato, H.},
title={Anomalously low modulus of the interpenetrating-phase composite of Fe and Mg obtained by liquid metal dealloying},
year={2019},
journal = {Scripta Materialia},
volume = {163},
pages = {133 - 136},
doi = {10.1016/j.scriptamat.2019.01.017},
abstract = {A bulk interpenetrating-phase composite consisting of immiscible Fe and Mg metals is fabricated by liquid metal dealloying. The composite exhibits an anomalously low value of the Young's modulus of 20 ± 3 GPa, when probed in compression. The Young's modulus values obtained from nanoindentation and ultrasonic measurements are, however, significantly higher than that in compression, but still remain lower than theoretical values obtained from the Hashin-Shtrikman bounds and a micromechanics model. Such a deviation is explained by the weak interfaces between Fe and Mg phases that promote phase boundary sliding upon mechanical loading, leading to a low effective modulus.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.scriptamat.2019.01.017} (DOI). Okulov, I.V.; Geslin, P.-A.; Soldatov, I.V.; Ovri, H.; Joo, S.-H.; Kato, H.: Anomalously low modulus of the interpenetrating-phase composite of Fe and Mg obtained by liquid metal dealloying. In: Scripta Materialia. Vol. 163 (2019) 133 - 136. (DOI:  /10.1016/j.scriptamat.2019.01.017)}}
@article{talebi_the_scaled_2019, 
author={Talebi, H. and Silani, M. and Klusemann, B.},
title={The scaled boundary finite element method for computational homogenization of heterogeneous media},
year={2019},
journal = {International Journal for Numerical Methods in Engineering},
volume = {118},
number = {1},
pages = {1 - 17},
doi = {10.1002/nme.6002},
abstract = {Materials exhibit macroscopic properties that are dependent on the underlying components at lower scales. Computational homogenization using the Finite Element Method (FEM) is often used to determine the effective mechanical properties based on the microstructure. However use of FEM might suffer from several difficulties such as mesh generation, application of periodic boundary conditions or computations in presence of material interfaces and further discontinuities. In this paper we present an alternative approach for computational homogenization of heterogeneous structures based on the Scaled Boundary Finite Element Method (SBFEM). Based on quadtrees, we are applying a simple meshing strategy to create polygonal elements for arbitrary complex microstructures by using a relatively small number of elements. We show on selected numerical examples that the proposed computational homogenization technique represents a suitable alternative to classical FEM approaches capable of avoiding some of the mentioned difficulties while accurately and effectively calculating the macroscopic mechanical properties. An example of a two‐scale semi‐concurrent coupling between FEM and SBFEM is presented, illustrating the complementarity of both approaches.},
note = {Online available at: \url{https://dx.doi.org/10.1002/nme.6002} (DOI). Talebi, H.; Silani, M.; Klusemann, B.: The scaled boundary finite element method for computational homogenization of heterogeneous media. In: International Journal for Numerical Methods in Engineering. Vol. 118 (2019) 1, 1 - 17. (DOI:  /10.1002/nme.6002)}}
@article{keller_experimentally_validated_2019, 
author={Keller, S. and Horstmann, M. and Kashaev, N. and Klusemann, B.},
title={Experimentally validated multi-step simulation strategy to predict the fatigue crack propagation rate in residual stress fields after laser shock peening},
year={2019},
journal = {International Journal of Fatigue},
volume = {124},
pages = {265 - 276},
doi = {0.1016/j.ijfatigue.2018.12.014},
abstract = {Laser shock peening (LSP) is a promising technology to retard the fatigue crack propagation (FCP) in metallic lightweight structures. A multi-step simulation strategy to predict FCP in LSP-induced residual stress fields is proposed and applied. The simulation strategy involves an LSP process simulation, a transfer approach to include the plastic strains in a C(T) specimen model to calculate the residual stresses and a FCP simulation to determine the stress intensity factors. The FCP rate is finally determined via FCP equations. The validity of the simulation strategy including the crack driving quantities prediction is experimentally demonstrated by a novel ‘simulation’ approach.},
note = {Online available at: \url{https://dx.doi.org/0.1016/j.ijfatigue.2018.12.014} (DOI). Keller, S.; Horstmann, M.; Kashaev, N.; Klusemann, B.: Experimentally validated multi-step simulation strategy to predict the fatigue crack propagation rate in residual stress fields after laser shock peening. In: International Journal of Fatigue. Vol. 124 (2019) 265 - 276. (DOI:  /0.1016/j.ijfatigue.2018.12.014)}}
@article{sonego_thermomechanical_degradation_2019, 
author={Sonego, M. and Abibe, A. and Canevarolo, S. and Bettini, S. and dos Santos, J. and Canto, L. and Amancio-Filho, S.},
title={Thermomechanical Degradation of Polyetherimide (PEI) by Friction-Based Joining and the Effects on Quasi-Static Mechanical Strength of Hybrid Joints},
year={2019},
journal = {International Polymer Processing},
volume = {34},
number = {1},
pages = {100 - 110},
doi = {10.3139/217.3679},
abstract = {This study investigated quantitatively the thermomechanical degradation of polyetherimide (PEI) due to Friction-based Injection Clinching Joining (F-ICJ) and the effects on the mechanical strength of hybrid joints with aluminum. PEI samples extracted from process-affected regions of the joints were characterized in terms of their molecular weight distribution (MWD) and glass transition temperature (Tg), while mechanical strength of the joints was evaluated by cross tensile testing. PEI samples produced by the most severe joining condition showed decrease of 37 % of number-average molecular weight (Mn) and 17 % of weight-average molecular weight (Mw), while polydispersity index (Mw/Mn) increased 33 % as compared with as-received polymer. The chain scission distribution function (CSDF) indicated non-random multiple scissions as the main degradation mechanism of PEI due to F-ICJ. From the dependence of Tg with Mn the parameters of the Fox-Flory equation for PEI were obtained. A fractional factorial design of experiments was adopted to analyze the influence of the process parameters on the polymer degradation, based on Tg values. High level of PEI degradation and microstructural defects caused by high energy inputs have combined negative effect on the ultimate cross tensile force and displacement of joints. In general, these results can contribute to the knowledge of thermomechanical degradation of PEI and help with the optimization of F-ICJ.},
note = {Online available at: \url{https://dx.doi.org/10.3139/217.3679} (DOI). Sonego, M.; Abibe, A.; Canevarolo, S.; Bettini, S.; dos Santos, J.; Canto, L.; Amancio-Filho, S.: Thermomechanical Degradation of Polyetherimide (PEI) by Friction-Based Joining and the Effects on Quasi-Static Mechanical Strength of Hybrid Joints. In: International Polymer Processing. Vol. 34 (2019) 1, 100 - 110. (DOI:  /10.3139/217.3679)}}
@article{ovri_on_the_2019, 
author={Ovri, H. and Lilleodden, E.T.},
title={On the Estimation of Thermal Activation Parameters for Portevin–Le Chatelier Effect from Nanoindentation Data},
year={2019},
journal = {JOM: Journal of the Minerals, Metals and Materials Society},
volume = {71},
number = {10},
pages = {3343 - 3349},
doi = {10.1007/s11837-019-03697-0},
abstract = {The development of methods to ascertain the activation enthalpy, ΔE a ΔEa, for Portevin–Le Chatelier (PLC) effect is of interest as it facilitates understanding of the underlying mechanisms and the identification of solute species that age dislocations during deformation. Currently, most models for estimating ΔE a ΔEa are based on the critical strain, ε c εc, for the onset of PLC during macroscopic uniaxial tests. However, an ε c εc is not always observed, and some of the models incorporate unverified dependences. In this work, we present a nanoindentation-based approach for estimating ΔE a ΔEa and the activation volume for the phenomenon. The approach is based on a more theoretically sound foundation and obviates the need for ε c εc. The derived parameters are in good agreement with reported values for the Al-Mg alloy studied herein. The results are discussed in terms of strain rate, indentation depth, and indenter geometry, and reveal the utility of the technique for investigations of PLC more generally.},
note = {Online available at: \url{https://dx.doi.org/10.1007/s11837-019-03697-0} (DOI). Ovri, H.; Lilleodden, E.T.: On the Estimation of Thermal Activation Parameters for Portevin–Le Chatelier Effect from Nanoindentation Data. In: JOM: Journal of the Minerals, Metals and Materials Society. Vol. 71 (2019) 10, 3343 - 3349. (DOI:  /10.1007/s11837-019-03697-0)}}
@article{moochani_friction_stir_2019, 
author={Moochani, A. and Omidvar, H. and Ghaffarian, S. and Goushegir, S.},
title={Friction stir welding of thermoplastics with a new heat-assisted tool design: mechanical properties and microstructure},
year={2019},
journal = {Welding in the World},
volume = {63},
pages = {181 - 190},
doi = {10.1007/s40194-018-00677-x},
abstract = {Traditional tools in friction stir welding (FSW) of thermoplastics fail to achieve high quality and strong welds. In this paper, a new heat-assisted stationary shoulder FSW tool design, which provides constant tool temperature during the process using a controllable hot air gun, is introduced. Effect of the process parameters, including tool temperature, rotational speed, and traverse speed, on the microstructure and mechanical properties of polypropylene sheets was investigated using Taguchi method and analysis of variance. Welded joints showed tensile strength up to 96% and elongation at break up to 99% of the base material. Samples with high mechanical performance showed a wider stir zone within thin flow layers, which arranged in a regular pattern, under polarized microscopy. Differential scanning calorimetry demonstrated that higher tool temperature results in lower degree of crystallinity. Scanning electron microscopy revealed that the sample with high mechanical properties has a craze-free fracture surface. However, the sample with the lowest mechanical properties produced a corrugated fracture surface full of crazes.},
note = {Online available at: \url{https://dx.doi.org/10.1007/s40194-018-00677-x} (DOI). Moochani, A.; Omidvar, H.; Ghaffarian, S.; Goushegir, S.: Friction stir welding of thermoplastics with a new heat-assisted tool design: mechanical properties and microstructure. In: Welding in the World. Vol. 63 (2019) 181 - 190. (DOI:  /10.1007/s40194-018-00677-x)}}
@article{feistauer_a_review_2019, 
author={Feistauer, E. and dos Santos, J. and Amancio-Filho, S.},
title={A review on direct assembly of through‐the‐thickness reinforced metal–polymer composite hybrid structures},
year={2019},
journal = {Polymer Engineering & Science},
volume = {59},
number = {4},
pages = {661 - 674},
doi = {10.1002/pen.25022},
abstract = {Constant efforts to reduce the structural weight of transportation systems as a solution to control emission levels are currently shaping the way modern cars and airplanes are designed and manufactured. Increased attention has been given to innovative metal–composites multi‐material concepts for the production of lightweight structures. However, the nature of these very dissimilar materials makes their joining a rather complicated task. Recently several technologies have been proposed to overcome process limitation and increase the load transfer between metal and composite in hybrid structures. One of the promising solutions is a new concept known as direct assembling with through‐the‐thickness reinforcements. In this concept, the composite material of a hybrid joint is directly assembled upon a surface‐structured metallic part. Features structured on the metallic part, by a manufacturing phase, act as a through‐the‐thickness reinforcement improving the out‐of‐plane strength and load transfer capabilities of such joints. The current status and state‐of‐art direct assembling technologies are reviewed in this article. Examples of reviewed metal structuring techniques include micromachining, stamping, Surfi‐Sculpt, additive manufacturing, cold metal transfer, and metal injection molding structuring. Direct assembling techniques addressed in this article are vacuum‐assisted resin infusion, resin transfer molding, prepreg/autoclave assembly, and ultrasonic joining. POLYM. ENG. SCI., 59:661–674, 2019. © 2018 The Authors. Polymer Engineering & Science published by Wiley Periodicals, Inc. on behalf of Society of Plastics Engineers.},
note = {Online available at: \url{https://dx.doi.org/10.1002/pen.25022} (DOI). Feistauer, E.; dos Santos, J.; Amancio-Filho, S.: A review on direct assembly of through‐the‐thickness reinforced metal–polymer composite hybrid structures. In: Polymer Engineering & Science. Vol. 59 (2019) 4, 661 - 674. (DOI:  /10.1002/pen.25022)}}
@article{wu_electrochemomechanical_coupling_2019, 
author={Wu, Y. and Markmann, J. and Lilleodden, E.},
title={Electro-chemo-mechanical coupling of nanoporous gold at the microscale },
year={2019},
journal = {Applied Physics Letters},
volume = {115},
number = {25},
pages = {251602},
doi = {10.1063/1.5128049},
abstract = {The observation of reversible strengthening and stiffening of nanoporous gold (NPG) under electrochemical potential has opened opportunities to exploit this material for multifunctional applications. Yet the complex structural geometry and length-scales involved make a definitive understanding of structural correlations to the behaviors difficult at best. Achievement of coupled electro-chemo-mechanical testing at the micrometer scale is a key step toward this goal. Here, we introduce an experimental approach to investigate the elastic and plastic behaviors of NPG under electrochemical potential at the microscale using a modified nanoindentation setup and multiple load function. The in situ experiments in electrolyte show a significant increase by 32% in strength of pillars in a positive potential regime where oxygen adsorption occurred. This response was found to be reversible, which agrees with macroscopic results, while the elastic modulus was shown to be insensitive to the applied potential—an observation inconsistent with recent bulk dynamic mechanical analysis results.},
note = {Online available at: \url{https://dx.doi.org/10.1063/1.5128049} (DOI). Wu, Y.; Markmann, J.; Lilleodden, E.: Electro-chemo-mechanical coupling of nanoporous gold at the microscale . In: Applied Physics Letters. Vol. 115 (2019) 25, 251602. (DOI:  /10.1063/1.5128049)}}
@article{maltanava_effect_of_2019, 
author={Maltanava, H. and Poznyak, S. and Ivanovskaya, M. and Scharnagl, N. and Starykevich, M. and Salak, A. and de Rosario Soares, M. and Mazanik, A.},
title={Effect of fluoride-mediated transformations on electrocatalytic performance of thermally treated TiO2 nanotubular layers},
year={2019},
journal = {Journal of Fluorine Chemistry},
volume = {221},
pages = {34 - 41},
doi = {10.1016/j.jfluchem.2019.02.006},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jfluchem.2019.02.006} (DOI). Maltanava, H.; Poznyak, S.; Ivanovskaya, M.; Scharnagl, N.; Starykevich, M.; Salak, A.; de Rosario Soares, M.; Mazanik, A.: Effect of fluoride-mediated transformations on electrocatalytic performance of thermally treated TiO2 nanotubular layers. In: Journal of Fluorine Chemistry . Vol. 221 (2019) 34 - 41. (DOI:  /10.1016/j.jfluchem.2019.02.006)}}
@article{mgbemere_preparation_and_2019, 
author={Mgbemere, H. and Ekpe, I. and Lawal1, G. and Ovri, H. and Chaudhary, A.},
title={Preparation and Characterization of Zeolite type 4A using Kaolin from Ajebo; Nigeria },
year={2019},
journal = {Pertanika journal of science & technology},
volume = {27},
number = {4},
pages = {2427 - 2438},
abstract = {This work investigates the hydrothermal synthesis and characterization of zeolite-4A from kaolin found in Ajebo, Nigeria calcined at 700 and 900oC respectively. The synthesized zeolite-4A was further characterised using X-ray Fluorescence (XRF), Fourier Transform Infrared spectrometer (FTIR), Scanning Electron Microscopy (SEM), X-Ray diffraction (XRD), Brunauer-Emmet-Teller (BET) surface area analysis as well as Differential Thermal Analysis/Thermo-gravimetric (TG). Water adsorption capacity tests were also carried out on  the  synthesized  zeolite-4A.  The  results  from  the  XRF  measurements  indicated  that  the  amount  of  Al2O3  and  SiO2  in  the  studied  kaolin  was  similar  to  the  standard  kaolin  composition  making  it  a  perfect  candidate  for  zeolite-4A  synthesis.  FTIR  showed  the  characteristic zeolite peaks while XRD confirmed the crystalline nature of the synthesized zeolite-4A. TG studies showed that the zeolite-4A samples were stable up to temperatures of 700oC. This stability as well as the surface area and pore size of 7 Å makes it potentially suitable for use in water treatment applications. The SEM showed cubic crystals which were typical of the morphology of zeolite-4A with water adsorption capacity of approximately 29%.  These  results  indicate  that  zeolite-4A  can  be  synthesized  from  kaolin  found  in  Ajebo  as  an  inexpensive  alternative  to  traditionally  sourced  materials  and  also  is  suitable for use as adsorption agent.},
note = {Mgbemere, H.; Ekpe, I.;  Lawal1, G.; Ovri, H.; Chaudhary, A.: Preparation and Characterization of Zeolite type 4A using Kaolin from Ajebo; Nigeria . In: Pertanika journal of science & technology. Vol. 27 (2019) 4, 2427 - 2438.}}
@article{lvarez_development_of_2019, 
author={Álvarez, P. and Escribano, R. and Zubiri, F. and Fomin, F. and Kashaev, N. and Bauer, S.},
title={Development of laser straightening (LS) strategies to remove distortion in welded aeronautical structures},
year={2019},
journal = {AIP Conference Proceedings},
volume = {2113},
pages = {070003},
doi = {10.1063/1.5112608},
abstract = {Manufacturing of stiffened aeronautical structures requires the joining of stringers to thin skin. Structures targeted in this work are composed by Ti-6Al-4V (Grade 5) stringers and commercially pure Ti (cp-Ti, Grade 2) skin. The stringers are laser beam welded (LBW) to the skin in T-joint configuration. Despite the highly concentrated and relatively low heat input of the laser source, the reduced thickness of the skin (0.8 mm) leads to significant angular distortion and so- called “Zeppelin effect”. Moreover, buckling distortion is observed in medium size panels (500 x 500 mm) including several stringers. Within this study, laser straightening (LS) process has been developed to mitigate as-welded distortion. The process is applied on the reverse of the skin and is based on the temperature gradient mechanism (TGM). The same welding source (disk laser) and optic head were employed for both LBW and LS. Consequently, the complete manufacturing of the structure can be done in just one working station. Different LS strategies were applied with the aim of removing welding induced distortion. They included both constant and variable laser power runs, single and multiple runs and different scanning sequences. After optimization of LS process, medium size panels with maximum distortion of less than 2.6 mm were obtained. Initial distortion was higher than 11 mm, meaning that approximately 80% of welding induced distortion was effectively removed.},
note = {Online available at: \url{https://dx.doi.org/10.1063/1.5112608} (DOI). Álvarez, P.; Escribano, R.; Zubiri, F.; Fomin, F.; Kashaev, N.; Bauer, S.: Development of laser straightening (LS) strategies to remove distortion in welded aeronautical structures. In: AIP Conference Proceedings. Vol. 2113 (2019) 070003. (DOI:  /10.1063/1.5112608)}}
@article{panina_laser_beam_2019, 
author={Panina, E. and Yurchenko, N. and Zherebtsov, S. and Stepanov, N. and Salishchev, G. and Ventzke, V. and Dinse, R. and Kashaev, N.},
title={Laser Beam Welding of a Low Density Refractory High Entropy Alloy},
year={2019},
journal = {Metals},
volume = {9},
number = {12},
pages = {1351},
doi = {10.3390/met9121351},
abstract = {The effect of laser beam welding on the structure and properties of a Ti1.89NbCrV0.56 refractory high entropy alloy was studied. In particular, the effect of different pre-heating temperatures was examined. Due to the low ductility of the material, laser beam welding at room temperature resulted in the formations of hot cracks. Sound butt joints without cracks were produced using pre-heating to T ≥ 600 °C. In the initial as-cast condition, the alloy consisted of coarse bcc grains with a small amount of lens-shaped C15 Laves phase particles. A columnar microstructure was formed in the welds; the thickness of the grains increased with the temperature of pre-heating before welding. The Laves phase particles were formed in the seams after welding at 600 °C or 800 °C, however, these particles were not observed after welding at room temperature or at 400 °C. Soaking at elevated temperatures did not change the microstructure of the base material considerably, however, “additional” small Laves particles formed at 600 °C or 800 °C. Tensile test of welded specimens performed at 750 °C resulted in the fracture of the base material because of the higher hardness of the welds. The latter can be associated with the bcc grains refinement in the seams.},
note = {Online available at: \url{https://dx.doi.org/10.3390/met9121351} (DOI). Panina, E.; Yurchenko, N.; Zherebtsov, S.; Stepanov, N.; Salishchev, G.; Ventzke, V.; Dinse, R.; Kashaev, N.: Laser Beam Welding of a Low Density Refractory High Entropy Alloy. In: Metals. Vol. 9 (2019) 12, 1351. (DOI:  /10.3390/met9121351)}}
@article{alba_application_of_2019, 
author={Alba, D. and Roos, A. and Wimmer, G. and Gonzalez, A. and Hanke, S. and Dos Santos, J.},
title={Application of response surface methodology for optimization of hybrid friction diffusion bonding of tube-to-tube-sheet connections in coil-wound heat exchangers},
year={2019},
journal = {Journal of Materials Research and Technology : JMRT},
volume = {8},
number = {2},
pages = {1701 - 1711},
doi = {10.1016/j.jmrt.2018.11.012},
abstract = {This study evaluates the application of a new solid state joining process referred to as hybrid friction diffusion bonding. Based on heat processing and pressure, accelerated diffusion joins the materials. In the present study, two aluminum alloys were welded and characterized using leak tightness tests, tensile pull out tests, and metallographic analysis. Response surface methodology was used to optimize the tensile strength of single-hole tube-sheet samples. A Box–Behnken design was selected to evaluate the relations between the important process parameters and the ultimate tensile strength response to obtain optimal welding parameters. The data were analyzed with analysis of variance and were fitted to a second-order polynomial equation. The three-dimensional response surfaces derived from the mathematical models were applied to determine several optimum input parameters conditions. Under these conditions, the experimental ultimate tensile strength value was 202 MPa, which represents 95% of the base material strength. The experimental results obtained under optimum operating conditions were in agreement with the predicted values. Axial force was found to be the most significant factor affecting the joint strength followed by rotational speed. This can be attributed to their influence on the amount of mechanical energy introduced during the process, which is the parameter that primarily determines the joint strength.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jmrt.2018.11.012} (DOI). Alba, D.; Roos, A.; Wimmer, G.; Gonzalez, A.; Hanke, S.; Dos Santos, J.: Application of response surface methodology for optimization of hybrid friction diffusion bonding of tube-to-tube-sheet connections in coil-wound heat exchangers. In: Journal of Materials Research and Technology : JMRT. Vol. 8 (2019) 2, 1701 - 1711. (DOI:  /10.1016/j.jmrt.2018.11.012)}}
@article{dovale_effects_of_2019, 
author={do Vale, N. and Fitseva, V. and Hanke, S. and Filho, S. and dos Santos, J.},
title={Effects of Friction Surfacing on the Characteristics of Consumable Rods of Ti-6Al-4V},
year={2019},
journal = {Materials Research : Revista Brasileira de Materiais},
volume = {22},
pages = {e20180888},
doi = {10.1590/1980-5373-MR-2018-0888},
abstract = {Friction surfacing (FS) is a coating technique applied mainly in corrosion protection and repair of components. The study addresses the effects of deposition and rotational speeds on the rods characteristics and process efficiency for the deposition of Ti-6Al-4V on self-mating substrates by FS. The consumption rate was 1.8 mm/s, deposition speeds of 8, 16 and 24 mm/s and rotational speeds of 2000, 3000 and 4000 rpm. It was shown that the flash forms primarily at the rod, ascending around the tip and leaving the coating without flash. The higher deposition speeds led to a decrease in rod thickness and diameter. For higher rotational speeds, an increase in diameter and decrease in thickness is observed for the flash on the rod. Experiments have shown that the rotational and deposition speeds have a decisive influence on the flash formation. Its microstructure changes due to the welding process and a change in hardness can be observed.},
note = {Online available at: \url{https://dx.doi.org/10.1590/1980-5373-MR-2018-0888} (DOI). do Vale, N.; Fitseva, V.; Hanke, S.; Filho, S.; dos Santos, J.: Effects of Friction Surfacing on the Characteristics of Consumable Rods of Ti-6Al-4V. In: Materials Research : Revista Brasileira de Materiais . Vol. 22 (2019) e20180888. (DOI:  /10.1590/1980-5373-MR-2018-0888)}}
@article{graf_surfacetovolume_ratio_2019, 
author={Graf, M. and Jalas, D. and Weissmüller, J. and Petrov, A.Y. and Eich, M.},
title={Surface-to-Volume Ratio Drives Photoelelectron Injection from Nanoscale Gold into Electrolyte},
year={2019},
journal = {ACS Catalysis},
volume = {9},
number = {4},
pages = {3366 - 3374},
doi = {10.1021/acscatal.9b00384},
abstract = {Hot charge carriers from plasmonic nanomaterials currently receive increased attention because of their promising potential in important applications such as solar water splitting. While a number of important contributions were made on plasmonic charge carrier generation and their transfer into the metal’s surrounding in the last decades, the local origin of those carriers is still unclear. With our study employing a nanoscaled bicontinuous network of nanoporous gold, we take a comprehensive look at both subtopics in one approach and give unprecedented insights into the physical mechanisms controlling the broadband optical absorption and the generation and injection of hot electrons into an adjacent electrolyte where they enhance electrocatalytic hydrogen evolution. This absorption behavior is very different from the well-known localized surface plasmon resonance effects observed in metallic nanoparticles. For small ligament sizes, the plasmon decay in our network is strongly enhanced via surface collisions of electrons. These surface collisions are responsible for the energy transfer to the carriers and thus the creation of hot electrons from a broad spectrum of photon energies. As we reduce the gold ligament sizes below 30 nm, we demonstrate an occurring transition from absorption that is purely exciting 5d-electrons from deep below the Fermi level to an absorption which significantly excites “free” 6sp-electrons to be emitted. We differentiate these processes via assessing the internal quantum efficiency of the gold network photoelectrode as a function of the feature size providing a size-dependent understanding of the hot electron generation and injection processes in nanoscale plasmonic systems. We demonstrate that the surface effect, compared with the volume effect, becomes dominant and leads to significantly improved efficiencies. The most important fact to recognize is that in the surface photoeffect presented here, absorption and electron transfer are both part of the same quantum mechanical event.},
note = {Online available at: \url{https://dx.doi.org/10.1021/acscatal.9b00384} (DOI). Graf, M.; Jalas, D.; Weissmüller, J.; Petrov, A.Y.; Eich, M.: Surface-to-Volume Ratio Drives Photoelelectron Injection from Nanoscale Gold into Electrolyte. In: ACS Catalysis. Vol. 9 (2019) 4, 3366 - 3374. (DOI:  /10.1021/acscatal.9b00384)}}
@article{gnegel_numerical_investigation_2019, 
author={Gnegel, S. and Li, J. and Mameka, N. and Huber, N. and Düster, A.},
title={Numerical Investigation of Polymer Coated Nanoporous Gold},
year={2019},
journal = {Materials},
volume = {12},
number = {13},
pages = {2178},
doi = {10.3390/ma12132178},
abstract = {Nanoporous metals represent a fascinating class of materials. They consist of a bi-continuous three-dimensional network of randomly intersecting pores and ligaments where the ligaments form the skeleton of the structure. The open-pore structure allows for applying a thin electrolytic coating on the ligaments. In this paper, we will investigate the stiffening effect of a polymer coating numerically. Since the coating adds an additional difficulty for the discretization of the microstructure by finite elements, we apply the finite cell method. This allows for deriving a mesh in a fully automatic fashion from the high resolution 3D voxel model stemming from the 3D focused ion beam-scanning electron microscope tomography data of nanoporous gold. By manipulating the voxel model in a straightforward way, we add a thin polymer layer of homogeneous thickness numerically and study its effect on the macroscopic elastic properties systematically. In order to lower the influence of the boundary conditions on the results, the window method, which is known from homogenization procedures, is applied. In the second part of the paper, we fill the gap between numerical simulations and experimental investigations and determine real material properties of an electrolytic applied polypyrrole coating by inverse computations. The simulations provide an estimate for the mechanical properties of the ligaments and the polymeric coating and are in accordance with experimental data.},
note = {Online available at: \url{https://dx.doi.org/10.3390/ma12132178} (DOI). Gnegel, S.; Li, J.; Mameka, N.; Huber, N.; Düster, A.: Numerical Investigation of Polymer Coated Nanoporous Gold. In: Materials. Vol. 12 (2019) 13, 2178. (DOI:  /10.3390/ma12132178)}}
@article{vale_comparison_of_2019, 
author={Vale, N. and Fitseva, V. and Urtiga Filho, S. and dos santos, J. and Hanke, S.},
title={Comparison of Friction Surfacing Process and Coating Characteristics of Ti-6Al-4V and Ti Grade 1},
year={2019},
journal = {JOM: The Journal of the Minerals, Metals and Materials Society},
volume = {71},
pages = {4339 - 4348},
doi = {10.1007/s11837-019-03677-4},
abstract = {Friction surfacing is a coating process for extending the service life of components by repairing surface damaged, reducing wear, and improving anticorrosion properties. Ti-6Al-4V and titanium grade 1 have been deposited onto Ti-6Al-4V substrate to investigate the differences in material and processing behavior and analyze the coatings’ geometry and hardness. The deposition speed and consumption rate were kept constant at 16 mm/s and 1.8 mm/s, respectively, while the rotational speed was varied to 2000 rpm, 3000 rpm, or 4000 rpm. The force increased with the rotational speed, being about 10 times higher for Ti-6Al-4V compared with titanium grade 1. The peak temperatures were higher for titanium grade 1, and the β-transus temperature was exceeded in all experiments. The hardness of the coatings was about 16% higher compared with that of the Ti-6Al-4V substrate, due to formation of martensitic structure. The hardness did not vary significantly across the width of the coatings.},
note = {Online available at: \url{https://dx.doi.org/10.1007/s11837-019-03677-4} (DOI). Vale, N.; Fitseva, V.; Urtiga Filho, S.; dos santos, J.; Hanke, S.: Comparison of Friction Surfacing Process and Coating Characteristics of Ti-6Al-4V and Ti Grade 1. In: JOM: The Journal of the Minerals, Metals and Materials Society. Vol. 71 (2019) 4339 - 4348. (DOI:  /10.1007/s11837-019-03677-4)}}
@article{hablitzel_on_measuring_2019, 
author={Hablitzel, M. and Lilleodden, E.},
title={On measuring the independent mechanical response of the polymer phase from nanoporous gold polymer composites},
year={2019},
journal = {Scripta Materialia},
volume = {170},
pages = {67 - 70},
doi = {10.1016/j.scriptamat.2019.04.026},
abstract = {This work aims to understand the mechanical properties and potential size effect in the polymeric phase of nanoporous gold composites. We take inspiration from the extraction metallurgy of gold to leach out the Au phase from the composites, fabricating a novel nanostructured polymeric material, which was subsequently investigated by micromechanical techniques. In the case of nanoporous epoxy, no dependency on the microstructural length-scale was observed in either the elastic or plastic response, and the modulus could be well predicted by an isostrain law applied to the properties measured on the bulk polymer.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.scriptamat.2019.04.026} (DOI). Hablitzel, M.; Lilleodden, E.: On measuring the independent mechanical response of the polymer phase from nanoporous gold polymer composites. In: Scripta Materialia. Vol. 170 (2019) 67 - 70. (DOI:  /10.1016/j.scriptamat.2019.04.026)}}
@article{ma_ultrastrong_nanocomposites_2019, 
author={Ma, S. and Scheider, I. and Bargmann, S.},
title={Ultrastrong nanocomposites with interphases: Nonlocal deformation and damage behavior},
year={2019},
journal = {European Journal of Mechanics: A, Solids},
volume = {75},
pages = {93 - 108},
doi = {10.1016/j.euromechsol.2019.01.011},
abstract = {The focus of this work is on matrix-inclusion nanocomposites and their mechanical behavior, particularly taking into account inelasticity and damage. We propose a nonlocal damage model based on a micropolar continuum theory which captures the heterogeneous interphases in the nanostructure. The model is valid for a large range of matrix-inclusion nanocomposites. The effects of the interaction between nanoparticles, the thickness of the interphase and the size of nanoparticles on the overall mechanical properties of the nanocomposite are analyzed to optimize the microstructure of the nanocomposites. 3D micromechanical simulations are conducted for the particular example of a tailored, ultrastrong nanocomposite. It has extraordinary mechanical properties, and to date, is the strongest synthetic inorganic-organic nanocomposite. The simulation results are compared to experimental data from microcantilever beams for different process temperatures.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.euromechsol.2019.01.011} (DOI). Ma, S.; Scheider, I.; Bargmann, S.: Ultrastrong nanocomposites with interphases: Nonlocal deformation and damage behavior. In: European Journal of Mechanics: A, Solids. Vol. 75 (2019) 93 - 108. (DOI:  /10.1016/j.euromechsol.2019.01.011)}}
@article{su_determination_of_2019, 
author={Su, H. and Wu, C.},
title={Determination of the traverse force in friction stir welding with different tool pin profiles},
year={2019},
journal = {Science and Technology of Welding and Joining},
volume = {24},
number = {3},
pages = {209 - 217},
doi = {10.1080/13621718.2018.1512738},
abstract = {A methodology is developed for the estimation of the traverse force in friction stir welding (FSW) for various pin profiles by combining the results of numerical modelling and experimental monitoring. The effect of pin profiles on the traverse force is evaluated by introducing a modified ratio of the plastic deformation zone, which is obtained by numerical modelling. The formula is validated with the experimental data in the literature and indicates that the traverse force decreases exponentially with increasing ratio of the plastic deformation zone. The proposed methodology provides a concise approach for the estimation of the traverse force for various pin profiles in FSW and can be adopted for the design and assessment of the FSW tool.},
note = {Online available at: \url{https://dx.doi.org/10.1080/13621718.2018.1512738} (DOI). Su, H.; Wu, C.: Determination of the traverse force in friction stir welding with different tool pin profiles. In: Science and Technology of Welding and Joining. Vol. 24 (2019) 3, 209 - 217. (DOI:  /10.1080/13621718.2018.1512738)}}
@article{richert_computation_of_2019, 
author={Richert, C. and Odermatt, A. and Huber, N.},
title={Computation of Thickness and Mechanical Properties of Interconnected Structures: Accuracy, Deviations, and Approaches for Correction},
year={2019},
journal = {Frontiers in Materials},
volume = {6},
pages = {327},
doi = {10.3389/fmats.2019.00327},
abstract = {Identifying local thickness information of fibrous or highly porous structures is challenging.
The analysis of tomography data calls for computationally fast, robust, and accurate
algorithms. This work systematically investigates systematic errors in the thickness
computation and the impact of observed deviations on the predicted mechanical
properties using a set of 16 model structures with varying ligament shape and solid
fraction. Strongly concave, cylindrical, and convex shaped ligaments organized in a
diamond structure are analyzed. The predicted macroscopic mechanical properties
represent a highly sensitive measure for systematic errors in the computed geometry.
Therefore, the quality of proposed correctionmethods is assessed via FEMbeammodels
that can be automatically generated from the measured data and allow an efficient
prediction of the mechanical properties. The results show that low voxel resolutions can
lead to an overprediction of up to 30% in the Young’s modulus. A model scanned with
a resolution of 200 voxels per unit cell edge (8M voxels) reaches an accuracy of a few
percent. Analyzing models of this resolution with the Euclidean distance transformation
showed an underprediction of up to 20% for highly concave shapes whereas cylindrical
and slightly convex shapes are determined at high accuracy. For the Thickness algorithm,
the Young’s modulus and yield strength are overpredicted by up to 100% for highly
concave ligament shapes. A proposed Smallest Ellipse approach corrects the Thickness
data and reduces this error to 20%. It can be used as input for a further robust
correction of the Thickness data using an artificial neural network. This approach is highly
accuratewith remnant errors in the predictedmechanical properties of only a few percent.
Furthermore, the data from the FEM beam models are compared to results from FEM
solidmodels providing deeper insights toward further developments on nodal corrections
for FEM beam models. As expected, the FEM beam models show an increasing
overprediction of the compliance with increasing solid fraction. As an unexpected result,
the mechanical strength can however be underpredicted or overpredicted, depending
on the ligament shape. Therefore, a nodal correction is needed that solves contradicting
tasks in terms of stiffness and strength.},
note = {Online available at: \url{https://dx.doi.org/10.3389/fmats.2019.00327} (DOI). Richert, C.; Odermatt, A.; Huber, N.: Computation of Thickness and Mechanical Properties of Interconnected Structures: Accuracy, Deviations, and Approaches for Correction. In: Frontiers in Materials. Vol. 6 (2019) 327. (DOI:  /10.3389/fmats.2019.00327)}}
@article{keller_crack_closure_2019, 
author={Keller, S. and Horstmann, M. and Kashaev, N. and Klusemann, K.},
title={Crack closure mechanisms in residual stress fields generated by laser shock peening: A combined experimental-numerical approach},
year={2019},
journal = {Engineering Fracture Mechanics},
volume = {221},
pages = {106630},
doi = {10.1016/j.engfracmech.2019.106630},
abstract = {Laser shock peening (LSP) is successfully applied to retard fatigue cracks in metallic lightweight structures by introducing specific, in particular compressive, residual stress fields. In this work, experiments and a multi-step simulation strategy are used to explain the fatigue crack retarding and accelerating mechanisms within these LSP-induced residual stress fields. Crack face contact is identified as main mechanism to retard the fatigue crack as the stress distribution changes and the stress intensity factor range decreases. Crack face contact is experimentally detected by load vs. crack opening displacement (COD) curves and scanning electron microscopy (SEM) of the crack faces, as well as during numerical simulations. The convincing agreement between experiment and simulation, especially regarding the specific crack face contact areas, allowed the proper evaluation of the stress intensity factors depending on the crack length. It is found that crack closure is indeed one of the main reasons for the efficient application of LSP for fatigue crack retardation. Furthermore, the occurrence of crack closure does not indicate a zero value stress intensity factor in complex residual stress fields, as the areas of crack face contact depend strongly on the LSP-induced compressive residual stresses.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.engfracmech.2019.106630} (DOI). Keller, S.; Horstmann, M.; Kashaev, N.; Klusemann, K.: Crack closure mechanisms in residual stress fields generated by laser shock peening: A combined experimental-numerical approach. In: Engineering Fracture Mechanics. Vol. 221 (2019) 106630. (DOI:  /10.1016/j.engfracmech.2019.106630)}}
@article{froend_thermal_analysis_2019, 
author={Froend, M. and Ventzke, V. and Kashaev, N. and Klusemann, B. and Enz, J.},
title={Thermal analysis of wire-based direct energy deposition of Al-Mg using different laser irradiances},
year={2019},
journal = {Additive Manufacturing},
volume = {29},
pages = {100800},
doi = {10.1016/j.addma.2019.100800},
abstract = {The wire-based direct energy deposition of metallic lightweight materials such as titanium or aluminium alloys has recently received increasing attention in industry and academia. However, high-throughput deposition is mostly associated with process-limiting phenomena such as the development of high temperatures resulting in poor surface quality as well as coarse and unidirectional solidification microstructures. In this regard, laser systems, which are already widely used in industrial processes, allow for a great variety in the controllability of energy inputs, thereby enabling the control of process temperatures and resulting microstructures. The subject of the current study is the detailed elucidation and evaluation of important features such as the development of temperature gradients, resulting cooling rates and thermal cycles for different laser beam irradiances. Significant heat accumulation and process instabilities as well as inhomogeneous thermal profiles along the length and height of the parts were observed at a high laser beam irradiance. In contrast, lower laser beam irradiance resulted in a more stable process with increased cooling rates, which favourably influenced the refinement of the solidification microstructure.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.addma.2019.100800} (DOI). Froend, M.; Ventzke, V.; Kashaev, N.; Klusemann, B.; Enz, J.: Thermal analysis of wire-based direct energy deposition of Al-Mg using different laser irradiances. In: Additive Manufacturing. Vol. 29 (2019) 100800. (DOI:  /10.1016/j.addma.2019.100800)}}
@article{husser_modeling_twinninginduced_2019, 
author={Husser, E. and Bargmann, S.},
title={Modeling twinning-induced lattice reorientation and slip-in-twin deformation },
year={2019},
journal = {Journal of the Mechanics and Physics of Solids},
volume = {122},
pages = {315 - 339},
doi = {10.1016/j.jmps.2018.09.020},
abstract = {The deformation behavior of hexagonal close packed (hcp) materials involves dislocation slip as well as deformation twinning, including a competition between those two. This is due to the limited number of easy to activate slip modes. We present a model that captures dislocation slip, dislocation interaction, size-dependent hardening and deformation twinning. It also accounts for the sudden change of the crystal lattice orientation at the very final stage of the twinning shear process which allows to describe dislocation glide deformation within a twinned region. Along with this, the model further considers the change in the elastic properties associated with the new lattice orientation. Finite element results are presented for the specific example of magnesium (Mg) and for different characteristic loading conditions in order to mimic local stress distributions as they occur in different regions within a single crystal or grain, e.g., close to a boundary and far off. In addition, the impact of twinning on the mechanical response of Mg single crystal during microcompression is investigated. We show that the suggested model is well capable of predicting the complex microstructural deformation behavior in Mg and compare our numerical results to experimental data.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jmps.2018.09.020} (DOI). Husser, E.; Bargmann, S.: Modeling twinning-induced lattice reorientation and slip-in-twin deformation . In: Journal of the Mechanics and Physics of Solids. Vol. 122 (2019) 315 - 339. (DOI:  /10.1016/j.jmps.2018.09.020)}}
@article{kashaev_fatigue_behaviour_2019, 
author={Kashaev, N. and Ventzke, V. and Petrov, N. and Horstmann, M. and Zherebtsov, S. and Shaysultanov, D. and Sanin, V. and Stepanov, N.},
title={Fatigue behaviour of a laser beam welded CoCrFeNiMn-type high entropy alloy},
year={2019},
journal = {Materials Science and Engineering A},
volume = {766},
pages = {138358},
doi = {10.1016/j.msea.2019.138358},
abstract = {Laser beam welding was used to produce butt joints from the CoCrFeNiMn-type high entropy alloy. The alloy in the initial condition had an fcc single-phase coarse-grained structure. Laser welding resulted in the M7C3-type carbides precipitation in the fcc matrix. The carbide particles precipitation resulted in a considerable increase in microhardness from 150 HV 0.5 for the as-sintered condition to 205 HV 0.5 in the fusion zone. Laser beam welding had a negligible effect on both static mechanical properties and fatigue behaviour of the alloy. The endurance limit of either type of specimens (i.e. with and without welding seam) was 200 MPa. Fracture of all specimens with the laser beam welded seams occurred in the base material area during both tensile and fatigue testing. Weak effect of welding on static/fatigue behaviour of the alloy can be attributed to the higher hardness of the fusion zone, resulting in strain localization in the base material area. An increase in load resulted in activation of secondary slip systems and formation of deformation twins in fatigue specimens.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.msea.2019.138358} (DOI). Kashaev, N.; Ventzke, V.; Petrov, N.; Horstmann, M.; Zherebtsov, S.; Shaysultanov, D.; Sanin, V.; Stepanov, N.: Fatigue behaviour of a laser beam welded CoCrFeNiMn-type high entropy alloy. In: Materials Science and Engineering A. Vol. 766 (2019) 138358. (DOI:  /10.1016/j.msea.2019.138358)}}
@article{ambrosi_growth_and_2019, 
author={Ambrosi, D. and Ben Amar, M. and Cyron, C,J. and De Simone, A. and Goriely, A. and Humphrey, J.D. and Kuhl, E.},
title={Growth and remodelling of living tissues: perspectives, challenges and opportunities},
year={2019},
journal = {Journal of the Royal Society Interface},
volume = {16},
number = {157},
pages = {20190233},
doi = {10.1098/rsif.2019.0233},
abstract = {One of the most remarkable differences between classical engineering materials and living matter is the ability of the latter to grow and remodel in response to diverse stimuli. The mechanical behaviour of living matter is governed not only by an elastic or viscoelastic response to loading on short time scales up to several minutes, but also by often crucial growth and remodelling responses on time scales from hours to months. Phenomena of growth and remodelling play important roles, for example during morphogenesis in early life as well as in homeostasis and pathogenesis in adult tissues, which often adapt to changes in their chemo-mechanical environment as a result of ageing, diseases, injury or surgical intervention. Mechano-regulated growth and remodelling are observed in various soft tissues, ranging from tendons and arteries to the eye and brain, but also in bone, lower organisms and plants. Understanding and predicting growth and remodelling of living systems is one of the most important challenges in biomechanics and mechanobiology. This article reviews the current state of growth and remodelling as it applies primarily to soft tissues, and provides a perspective on critical challenges and future directions.},
note = {Online available at: \url{https://dx.doi.org/10.1098/rsif.2019.0233} (DOI). Ambrosi, D.; Ben Amar, M.; Cyron, C,J.; De Simone, A.; Goriely, A.; Humphrey, J.D.; Kuhl, E.: Growth and remodelling of living tissues: perspectives, challenges and opportunities. In: Journal of the Royal Society Interface. Vol. 16 (2019) 157, 20190233. (DOI:  /10.1098/rsif.2019.0233)}}
@article{andre_corrosion_behavior_2019, 
author={Andre, N.M. and Bouali, A. and Maawad, E. and Staron, P. and dos Santos, J.F. and Zheludkevich, M.L. and Amancio-Filho, S.T.},
title={Corrosion behavior of metal–composite hybrid joints: Influence of precipitation state and bonding zones},
year={2019},
journal = {Corrosion Science},
volume = {158},
pages = {108075},
doi = {10.1016/j.corsci.2019.07.002},
abstract = {The corrosion behavior of AA2024-T3/carbon-fiber-reinforced polyphenylene sulfide joints was investigated. The joints were exposed to salt spray from one to six weeks. The residual strength of these joints was assessed using lap shear test. The corroded surfaces and interfaces were analyzed using small angle X-ray scattering, scanning electron microscopy, and energy dispersive spectroscopy. Regarding the top surface of the joints, the aluminum part corroded preferably in the heat-affected zone (HAZ). It was demonstrated that the HAZ is more susceptible to corrosion than the stir zone (SZ) due to the anodic sites formed by coarse intermetallic particles and S’(S) phase precipitation. Besides, the macro-galvanic coupling between the zones may also potentialize the corrosion in HAZ as the base material and SZ displayed a lower volume fraction of S’(S) than HAZ. In addition, the corrosion at the interface of the joints was evaluated. Four different stages in the development of corrosion at the interface were identified. At Stage I, the joints showed fast strength degradation (0% to -24% of ultimate lap shear force (ULSF) due to water absorption and NaCl migration into the composite. At Stage II, the strength degradation of the joints was stalled (-24% to -28% of ULSF) due to the protection provided to the bonding area by the reconsolidated layer of polymer at the borders of the joint. The polymeric layer acted as a protective coating on the aluminum surface. At Stage III, the corrosion overcame the polymeric layer by reaching the bonding area of the joint. As a result, the strength of the joints rapidly degraded from -28% to -44% of ULSF. Finally, at Stage IV, one expects generalized corrosion in the bonding area, leading to the final strength degradation of the joint.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.corsci.2019.07.002} (DOI). Andre, N.M.; Bouali, A.; Maawad, E.; Staron, P.; dos Santos, J.F.; Zheludkevich, M.L.; Amancio-Filho, S.T.: Corrosion behavior of metal–composite hybrid joints: Influence of precipitation state and bonding zones. In: Corrosion Science. Vol. 158 (2019) 108075. (DOI:  /10.1016/j.corsci.2019.07.002)}}
@article{pozdnyakov_twostep_simulation_2019, 
author={Pozdnyakov, V. and Keller, S. and Kashaev, N. and Klusemann, B. and Oberrath, J.},
title={Two-step simulation approach for laser shock peening},
year={2019},
journal = {PAMM: Proceedings in Applied Mathematics and Mechanics},
volume = {19},
number = {1},
pages = {e201900497},
doi = {10.1002/pamm.201900497},
abstract = {Laser shock peening (LSP) is a surface modification technique to introduce compressive residual stresses (RS) with a high magnitude in the near surface region of the material. Due to non‐linear interactions (e.g. laser absorption by plasma, shock wave propagation, etc.) and a high number of parameters, it is difficult to study and optimize the process based on experiments alone. Therefore, a two‐step simulation approach is proposed in this paper, where two models are combined, because one model of the complete process is difficult to derive, due to the different characteristics of the plasma formation and the shock wave propagation in the material. On one hand, a global model including plasma and shock wave descriptions is applied for the LSP of an aluminium sample with water confinement. The numerical solution of this model, applied for a 3×3 mm2 focus size, 5 J and 20 ns (full width at half maximum (FWHM)) laser pulse, allows to determine the temporal plasma pressure evolution on the material surface. On the other hand, a finite element simulation is used to calculate the RS distribution within the target material, where the plasma pressure is applied as a surface loading for the aluminium alloy AA2198‐T3. The simulated residual stresses are fitted to measurements via parameter variation of the global model. The identified values and the two‐step simulation approach can be used in future work to predict stress states of materials after LSP for various process parameters variations.},
note = {Online available at: \url{https://dx.doi.org/10.1002/pamm.201900497} (DOI). Pozdnyakov, V.; Keller, S.; Kashaev, N.; Klusemann, B.; Oberrath, J.: Two-step simulation approach for laser shock peening. In: PAMM: Proceedings in Applied Mathematics and Mechanics. Vol. 19 (2019) 1, e201900497. (DOI:  /10.1002/pamm.201900497)}}
@article{lage_a_study_2019, 
author={Lage, S. and Campanelli, L. and Guerra, A. and Shen, J. and dos Santos, J. and da Silva, P. and Bolfarini, C.},
title={A study of the parameters influencing mechanical properties and the fatigue performance of refill friction stir spot welded AlMgSc alloy},
year={2019},
journal = {The International Journal of Advanced Manufacturing Technology},
volume = {100},
pages = {101 - 110},
doi = {10.1007/s00170-018-2696-0},
abstract = {Friction spot welds of 1.6-mm-thick AlMgSc alloy were investigated in this work. A design of experiment method was used to evaluate the effect of process parameters on the shear static strength. The optimized condition of parameters was employed in the assessment of the fatigue behavior. The typical hook feature was minimized by restricting the tool penetration into only the upper sheet. As a consequence, shear strength was sensitive to the extension of the welded region rather than the hook morphology. The fatigue performance was affected by the multiple crack initiation sites that resulted from a complex stress state during the axial loading. Striations were observed in practically the entire crack propagation region, suggesting that unstable fatigue crack growth did not take place in this specific weld configuration.},
note = {Online available at: \url{https://dx.doi.org/10.1007/s00170-018-2696-0} (DOI). Lage, S.; Campanelli, L.; Guerra, A.; Shen, J.; dos Santos, J.; da Silva, P.; Bolfarini, C.: A study of the parameters influencing mechanical properties and the fatigue performance of refill friction stir spot welded AlMgSc alloy. In: The International Journal of Advanced Manufacturing Technology. Vol. 100 (2019) 101 - 110. (DOI:  /10.1007/s00170-018-2696-0)}}
@article{feistauer_effect_of_2018, 
author={Feistauer, E.E. and Bergmann, L.A. and dos Santos, J.F.},
title={Effect of reverse material flow on the microstructure and performance of friction stir welded T-joints of an Al-Mg alloy},
year={2018},
journal = {Materials Science and Engineering  A},
volume = {731},
pages = {454 - 464},
doi = {10.1016/j.msea.2018.06.056},
abstract = {Friction stir welding (FSW) has been developed and commercially applied with success to connect large and complex structures. However, process optimization is still required to improve the mechanical performance of the T assemblies. Therefore, a second welding pass was applied in this work and was performed backwards, while maintaining the same tool rotation direction. Thus, due to the creation of a reverse material flow, a second advance side over the previously retreating side of the joint was formed, which significantly reduced the defects typically found in FSWed T-joints. The joints were manufactured with dissimilar Al–Mg alloys (AA5083), which is of particular interest to the shipbuilding sector. The microstructural analysis revealed that the second pass significantly reduced the kissing bonding defect on the joints retreating side. As a result, the mechanical properties were improved under quasi-static loading, reaching performance levels comparable to those of the base material. A digital image correlation system (DIC) linked to a tensile test system was used to investigate the local strain fields of the T-joints under two different loading conditions. The fatigue strength was also evaluated and the FSWed T-joints reached the fatigue keen with a nominal load range of 88.4 MPa under skin loading.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.msea.2018.06.056} (DOI). Feistauer, E.E.; Bergmann, L.A.; dos Santos, J.F.: Effect of reverse material flow on the microstructure and performance of friction stir welded T-joints of an Al-Mg alloy. In: Materials Science and Engineering  A. Vol. 731 (2018) 454 - 464. (DOI:  /10.1016/j.msea.2018.06.056)}}
@article{soyarslan_3d_stochastic_2018, 
author={Soyarslan, C. and Bargmann, S. and Pradas, M. and Weissmueller, J.},
title={3D stochastic bicontinuous microstructures: Generation, topology and elasticity},
year={2018},
journal = {Acta Materialia},
volume = {149},
pages = {326 - 340},
doi = {10.1016/j.actamat.2018.01.005},
abstract = {Motivated by recent experimental investigations of the mechanical behavior of nanoporous metal we explore an efficient and robust method for generating 3D representative volume elements (RVEs) with strikingly similar behavior. Our approach adopts Cahn's method of generating a Gaussian random field by taking a superposition of standing sinusoidal waves of fixed wavelength but random in direction and phase. In its theory part, our study describes closed-form expressions for how the solid volume fraction affects the binarization level, mean structure size, specific surface area, averages of mean and Gaussian curvature, and the scaled topological genus. Based on numerical studies we report on criteria for achieving representative realizations of the structure by proper choice of the number of waves and element size. We also show that periodic structures are readily created. We analyze the mechanical properties considering linear and infinitesimal elasticity and evaluate the residual anisotropy (which can be made small) and the effective values of the Young's modulus and Poisson's ratio. The numerical results are in excellent agreement with experimental findings for the variation of stiffness with solid fraction of nanoporous gold made by dealloying. We propose scaling relations that achieve naturally a perfect agreement with the numerical and experimental data. The scaling relation for the stiffness accounts for a percolation-to-cluster transition in the random field microstructure at a finite solid fraction. We propose that this transition is the origin of the previously reported anomalous compliance of nanoporous gold.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.actamat.2018.01.005} (DOI). Soyarslan, C.; Bargmann, S.; Pradas, M.; Weissmueller, J.: 3D stochastic bicontinuous microstructures: Generation, topology and elasticity. In: Acta Materialia. Vol. 149 (2018) 326 - 340. (DOI:  /10.1016/j.actamat.2018.01.005)}}
@article{michl_electrocapillary_coupling_2018, 
author={Michl, A. and Weissmueller, J. and Mueller, S.},
title={Electrocapillary Coupling at Metal Surfaces from First Principles: On the Impact of Excess Charge on Surface Stress and Relaxation},
year={2018},
journal = {Langmuir},
volume = {34},
number = {16},
pages = {4920 - 4928},
doi = {10.1021/acs.langmuir.7b04261},
abstract = {We study the response of the surface stress to excess charge via ab initio simulation of metal surfaces in an external electric field. We focus on “simple” sp-bonded metals to gain insight into the mechanisms underlying electrocapillary coupling. Both the direct effect on the surface stress via charging of the bonds and the indirect effect resulting from the charge-induced relaxation are analyzed and discussed in relation to the trends of the coupling coefficients, which—owing to a Maxwell relation—are determined in terms of the response of the work function to strain. Al(111), Mg(0001), and Na(110) are investigated as prototypical sp-bonded metal surfaces with positive, vanishing, and negative coupling parameters, respectively. Mg(0001) and Al(111) exhibit an inward relaxation of the first atomic layer upon negative charging, whereas an outward relaxation occurs for Na(110). The indirect contribution of the relaxation to the coupling coefficient has the same sign as the total response and makes up about 30% of its magnitude for Al(111) and Na(110). Our study highlights that even the response behavior of the so-called simple metals is by no means readily captured within simple models.},
note = {Online available at: \url{https://dx.doi.org/10.1021/acs.langmuir.7b04261} (DOI). Michl, A.; Weissmueller, J.; Mueller, S.: Electrocapillary Coupling at Metal Surfaces from First Principles: On the Impact of Excess Charge on Surface Stress and Relaxation. In: Langmuir. Vol. 34 (2018) 16, 4920 - 4928. (DOI:  /10.1021/acs.langmuir.7b04261)}}
@article{froend_process_development_2018, 
author={Froend, M. and Riekehr, S. and Kashaev, N. and Klusemann, B. and Enz, J.},
title={Process development for wire-based laser metal deposition of 5087 aluminium alloy by using fibre laser},
year={2018},
journal = {Journal of Manufacturing Processes},
volume = {34 A},
pages = {721 - 732},
doi = {http://dx.doi.org/10.1016/j.jmapro.2018.06.033},
abstract = {In recent decades, laser metal deposition, as a part of additive manufacturing, developed into a promising methodology in industrial fields. In recent years, there has been an increased interest in the processability of lightweight high-strength structural materials, such as aluminium alloys. However, in terms of wire-based laser metal deposition, there is still a lack of knowledge with regard to the processability of aluminium alloys. In this research, the process development for wire-based laser metal deposition of a 5087 aluminium alloy (AlMg4.5 MnZr) has been conducted. It is observed that pre-heating is beneficial in terms of porosity and distortion reduction. Within optimized parameter ranges, it is possible to control the geometric shape, dilution, and aspect ratios of the deposited layers in a systematic way. Accordingly, defect-free layers with tailored geometrical features can be processed and adapted to specific process requirements.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.jmapro.2018.06.033} (DOI). Froend, M.; Riekehr, S.; Kashaev, N.; Klusemann, B.; Enz, J.: Process development for wire-based laser metal deposition of 5087 aluminium alloy by using fibre laser. In: Journal of Manufacturing Processes. Vol. 34 A (2018) 721 - 732. (DOI:  10.1016/j.jmapro.2018.06.033)}}
@article{hanke_a_method_2018, 
author={Hanke, S. and Staron, P. and Fischer, T. and Fitseva, V. and dos Santos, J.F.},
title={A method for the in-situ study of solid-state joining techniques using synchrotron radiation - observation of phase transformations in Ti-6Al-4V after friction surfacing},
year={2018},
journal = {Surface and Coatings Technology},
volume = {335},
pages = {355 - 367},
doi = {10.1016/j.surfcoat.2017.12.049},
abstract = {The solid-state deposition process Friction Surfacing (FS) was applied to Ti-6Al-4V alloy on portable welding equipment at a high-energy synchrotron beamline. The heat input and coating thickness were altered by varying the deposition speed. X-ray diffraction was carried out in-situ during the deposition process and the cooling of the coated samples. Phase transformations were evaluated and correlated with thermal cycles determined by thermocouples and an infrared camera. SEM investigation of the coating microstructure was conducted to examine the morphology of the α phase. During FS the coating material is severely deformed and dynamically recrystallized in the β phase state at temperatures > 1300 °C. Small changes in the β grain size were observed within the first 2 s after deposition only. Depending on the cooling rate it transforms into different types of α phase during cooling. Phase transformation rates were found to correlate well with the differences in α morphology. The two faster translational speeds showed transformation rates > 45 vol%/s and a partially martensitic microstructure.
When a thick coating is deposited at low translational speed, α → β transformation continues for several seconds after deposition, followed by a slow cooling rate resulting in martensite free coatings containing αm from massive transformation. The potential gain and the deficiencies of this complex in-situ study of a technical process, instead of simplified model experiments, for the understanding of fundamental mechanisms involved in FS are discussed.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.surfcoat.2017.12.049} (DOI). Hanke, S.; Staron, P.; Fischer, T.; Fitseva, V.; dos Santos, J.F.: A method for the in-situ study of solid-state joining techniques using synchrotron radiation - observation of phase transformations in Ti-6Al-4V after friction surfacing. In: Surface and Coatings Technology. Vol. 335 (2018) 355 - 367. (DOI:  /10.1016/j.surfcoat.2017.12.049)}}
@article{wang_oxygen_adsorption_2018, 
author={Wang, L.C. and Zhong, Y. and Widmann, D. and Weissmueller, J. and Behm, R.J.},
title={Oxygen Adsorption and Low-Temperature CO Oxidation on a Nanoporous Au Catalyst: Reaction Mechanism and Foreign Metal Effects
},
year={2018},
journal = {Topics in Catalysis},
volume = {61},
number = {5-6},
pages = {446 - 461},
doi = {10.1007/s11244-017-0881-2},
abstract = {To further our understanding of the role of trace impurities of the second metal in the catalytic performance of unsupported, nanoporous Au (NPG) catalysts, in particular for the activation of O2, we have prepared a NPG catalyst by electrochemical leaching of Cu from a AuCu alloy and investigated its behavior in the CO oxidation reaction. The structural and chemical properties of the as-prepared catalyst as well as that after reaction for 1000 min were characterized by scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The nature of the surface oxygen species and the oxygen storage capacity were investigated and quantified by multi-pulse experiments in a temporal analysis of products (TAP) reactor. The catalytic behavior in the low-temperature CO oxidation reaction was evaluated both in a TAP reactor under dynamic vacuum conditions and in a conventional micro-reactor under atmospheric pressure. We discuss implications of these results and of similar data obtained previously on a Ag-containing NPG catalyst on the reaction mechanism and on the role of the second metal in the reaction and its impact on the reaction characteristics.},
note = {Online available at: \url{https://dx.doi.org/10.1007/s11244-017-0881-2} (DOI). Wang, L.C.; Zhong, Y.; Widmann, D.; Weissmueller, J.; Behm, R.J.: Oxygen Adsorption and Low-Temperature CO Oxidation on a Nanoporous Au Catalyst: Reaction Mechanism and Foreign Metal Effects
. In: Topics in Catalysis. Vol. 61 (2018) 5-6, 446 - 461. (DOI:  /10.1007/s11244-017-0881-2)}}
@article{reimann_microstructure_evolution_2018, 
author={Reimann, M. and Goebel, J. and dos Santos, J.F.},
title={Microstructure Evolution and Mechanical Properties of Keyhole Repair Welds in AA 2219-T851 using Refill Friction Stir Spot Welding},
year={2018},
journal = {Journal of Materials Engineering and Performance},
volume = {27},
number = {10},
pages = {5220 - 5226},
doi = {10.1007/s11665-018-3519-z},
abstract = {The search for a suitable friction-based keyhole repair technique that fulfills the requirements for high-quality repair welds has become an important research topic, especially for aerospace applications. In order to provide and analyze an universal keyhole repair method for lightweight metals, refill friction stir spot welding is applied to through-hole repairs in 3- and 6-mm-thick sheets of precipitate hardening AA 2219-T851. Keyholes with a diameter of 7.5 mm were repair welded achieving a defect-free microstructure. The correlation between the microstructural evolution imposed by the repair process and the resulting mechanical properties is shown. A comprehensive analysis of the precipitate evolution in peak-aged AA 2219 during RFSSW is presented. Thermal cycle measurements revealed high heating rates and peak temperatures of up to 520 °C in the weld center. The thermal cycle caused mainly dissolution and minor equilibrium phase formation in the stirred zone. In the HAZ, overaging of the strengthening precipitates dominates with minor dissolution and equilibrium phase formation only in the direct proximity of the SZ. Microstructural analysis revealed typical weld zone formation with inhomogeneous grain size distribution in the SZ. The resulting mechanical properties are dominated by an inhomogeneous hardness distribution with lowest hardness in the TMAZ at 5 mm from the center of the weld. During tensile loading main yielding and the final fracture occur in the area of lowest strength. Tensile testing showed yield strength of 40 to 46% and UTS of 28 to 25% below BM values in 3- and 6-mm-thick sheets, respectively. The sheet thickness and post-weld natural aging were found to influence the mechanical properties of the weld significantly.},
note = {Online available at: \url{https://dx.doi.org/10.1007/s11665-018-3519-z} (DOI). Reimann, M.; Goebel, J.; dos Santos, J.F.: Microstructure Evolution and Mechanical Properties of Keyhole Repair Welds in AA 2219-T851 using Refill Friction Stir Spot Welding. In: Journal of Materials Engineering and Performance. Vol. 27 (2018) 10, 5220 - 5226. (DOI:  /10.1007/s11665-018-3519-z)}}
@article{kashaev_laser_beam_2018, 
author={Kashaev, N. and Ventzke, V. and Stepanov, N. and Shaysultanov, D. and Sanin, V. and Zherebtsov, S.},
title={Laser beam welding of a CoCrFeNiMn-type high entropy alloy produced by self-propagating high-temperature synthesis},
year={2018},
journal = {Intermetallics},
volume = {96},
pages = {63 - 71},
doi = {10.1016/j.intermet.2018.02.014},
abstract = {Fiber laser beam welding of a CoCrFeNiMn-type high entropy alloy (HEA) produced by self-propagating high-temperature synthesis (SHS) was reported in this work. The SHS-fabricated alloy was characterized by both ∼2 times reduced Mn content in comparison with that of the other principal components and the presence of impurities including Al, C, S, and Si. The as-fabricated alloy was composed of columnar fcc grains with coarse precipitates of MnS and fine Cr-rich M23C6 carbides. Successful defect-free butt joint of the alloy was obtained using a laser power of 2 kW and a welding speed of 5 m/min. Welding resulted in changes in texture and structure of the fcc matrix. In addition, precipitation of nanoscale B2 phase particles in the weld zone was observed. A pronounced increase in microhardness from (153 ± 3) HV 0.5 (base material) to (208 ± 6) HV 0.5 (fusion zone) was observed. The B2 phase precipitation after welding was found to be in a reasonable agreement with the ThermoCalc predictions. Quantitative analysis demonstrated that the increase in hardness can be associated with the B2 phase precipitation. Possibilities of the development of HEAs with intrinsic hardening ability after laser processing are discussed.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.intermet.2018.02.014} (DOI). Kashaev, N.; Ventzke, V.; Stepanov, N.; Shaysultanov, D.; Sanin, V.; Zherebtsov, S.: Laser beam welding of a CoCrFeNiMn-type high entropy alloy produced by self-propagating high-temperature synthesis. In: Intermetallics. Vol. 96 (2018) 63 - 71. (DOI:  /10.1016/j.intermet.2018.02.014)}}
@article{goebel_influence_of_2018, 
author={Goebel, J. and Reimann, M. and dos Santos, J.F.},
title={Influence of Cu/Li Ratio on the Welding Forces and Mechanical Properties of Two Bobbin Tool Friction Stir Welded Al-Cu-Li Alloys},
year={2018},
journal = {Journal of Materials Engineering and Performance},
volume = {27},
number = {10},
pages = {5212 - 5219},
doi = {10.1007/s11665-018-3551-z},
abstract = {Increasing space activities produce a high number of space objects and lead to increasing collision risks which urges leading industries to look for future removal strategies. Material substitution in order to raise demisability during atmospheric reentry is a possible solution. Modern aluminum lithium alloys are under consideration to replace high-temperature melting materials like titanium. Further, friction stir welding was proposed as suitable joining technology in order to avoid high heat inputs during manufacturing. In this work, two modern Al-Li-Cu alloys, AA 2060 and AA 2196, in peak-aged temper were welded using the stationary shoulder variant of bobbin tool friction stir welding. Identical process parameters led to defect-free welds in both alloys. The macrostructural and microstructural features are shown and analyzed. The welds were mechanically tested to an efficiency of 78 and 70% of the base metal ultimate tensile strength for AA 2060 T8 and AA 2196 T8, respectively. The process forces as well as the thermal cycle experienced by the workpiece material were used to explain the mechanical performance. The difference in composition regarding the Cu/Li ratio of the alloys was taken into account when the mechanical properties were correlated with the thermally affected microstructure of the weldments.},
note = {Online available at: \url{https://dx.doi.org/10.1007/s11665-018-3551-z} (DOI). Goebel, J.; Reimann, M.; dos Santos, J.F.: Influence of Cu/Li Ratio on the Welding Forces and Mechanical Properties of Two Bobbin Tool Friction Stir Welded Al-Cu-Li Alloys. In: Journal of Materials Engineering and Performance. Vol. 27 (2018) 10, 5212 - 5219. (DOI:  /10.1007/s11665-018-3551-z)}}
@article{okulov_nanoporous_magnesium_2018, 
author={Okulov, I.V. and Lamaka, S.V. and Wada, T. and Yubuta, K. and Zheludkevich, M.L. and Weissmueller, J. and Markmann, J. and Kato, H.},
title={Nanoporous magnesium},
year={2018},
journal = {Nano Research},
volume = {11},
number = {12},
pages = {6428 - 6435},
doi = {10.1007/s12274-018-2167-9},
abstract = {In this study, we present freestanding nanoporous magnesium as a novel lightweight material with high potential for structural and functional applications. Thus far, the high reactivity of Mg with oxygen and aqueous media prevented the fabrication of nanoporous Mg. First, in order to synthesize nanoporous Mg, we fabricated a bicontinuous nanocomposite consisting of interpenetrating Mg and non-Mg phases by liquid metal dealloying. The non-Mg phases in the nanocomposite protect Mg against corrosion. Second, we etched the non-Mg phases from the nanocomposite, leaving nanoporous Mg, using HF solution. This process is advantageous because the nanoporous Mg was passivated by a MgF2 layer during the etching. Our approach is very flexible, and we demonstrate that versatile microstructures of the nanoporous Mg—e.g., nanoscale bicontinuous network, hierarchical, or plate-like structures—can be designed for the given needs. More importantly, these nanoporous Mg samples can readily be exposed to air without being harmed by corrosion.},
note = {Online available at: \url{https://dx.doi.org/10.1007/s12274-018-2167-9} (DOI). Okulov, I.V.; Lamaka, S.V.; Wada, T.; Yubuta, K.; Zheludkevich, M.L.; Weissmueller, J.; Markmann, J.; Kato, H.: Nanoporous magnesium. In: Nano Research
. Vol. 11 (2018) 12, 6428 - 6435. (DOI:  /10.1007/s12274-018-2167-9)}}
@article{dossantos_understanding_precipitate_2018, 
author={dos Santos, J.F. and Staron, P. and Fischer, T. and Robson, J.D. and Kostka, A. and Colegrove, P. and Wang, H. and Hilgert, J. and Bergmann, L. and Huetsch, L.L. and Huber, N. and Schreyer, A.},
title={Understanding precipitate evolution during friction stir welding of Al-Zn-Mg-Cu alloy through in-situ measurement coupled with simulation},
year={2018},
journal = {Acta Materialia},
volume = {148},
pages = {163 - 172},
doi = {10.1016/j.actamat.2018.01.020},
abstract = {Friction Stir Welding (FSW) imparts both heat and deformation to the metal being joined, producing profound microstructural changes that determine the weld properties. In the case of welding of aerospace aluminium alloys, the most important change is the modification of the size, nature, and fraction of strengthening precipitates. To understand these changes requires the ability to measure the microstructural evolution during the welding process. This paper describes a new tool, the FlexiStir system, a portable friction stir unit designed for use in a high-energy synchrotron beamline that enables in-situ studies of microstructural evolution during FSW. FlexiStir has been used to measure precipitate evolution during FSW of aluminium alloy 7449-TAF and provide time-resolved measurement of precipitate size and volume fraction via small angle X-ray scattering (SAXS). These measurements have been interpreted with the aid of a previously developed microstructural model. The model predictions and SAXS measurements are in good qualitative agreement and demonstrate the complex precipitate transformation, dissolution, and reprecipitation events that occur during welding.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.actamat.2018.01.020} (DOI). dos Santos, J.F.; Staron, P.; Fischer, T.; Robson, J.D.; Kostka, A.; Colegrove, P.; Wang, H.; Hilgert, J.; Bergmann, L.; Huetsch, L.L.; Huber, N.; Schreyer, A.: Understanding precipitate evolution during friction stir welding of Al-Zn-Mg-Cu alloy through in-situ measurement coupled with simulation. In: Acta Materialia. Vol. 148 (2018) 163 - 172. (DOI:  /10.1016/j.actamat.2018.01.020)}}
@article{weissmueller_dealloyed_nanoporous_2018, 
author={Weissmueller, J. and Sieradzki, K.},
title={Dealloyed nanoporous materials with interface-controlled behavior},
year={2018},
journal = {MRS Bulletin},
volume = {43},
number = {1},
pages = {14 - 19},
doi = {10.1557/mrs.2017.299},
abstract = {Dealloying, the selective dissolution of less noble elements from an alloy, enables the preparation of monolithic macroscale bodies, which at the nanostructure level exhibit a network of “ligaments” with a well-defined characteristic size that can be tuned to between a few nanometers and several microns. These porous solids can be made with macroscale dimensions, and, prior to dealloying, can be shaped to form engineered components. Their surface-to-volume ratio is extremely large and their bicontinuous structure provides transport pathways to tune the surface state under control of an electric or chemical potential. These materials present new opportunities for exploring the impact of surfaces on material behaviors and for exploiting surface effects in novel materials design strategies. New experimental approaches unraveling surface effects involving small-scale plasticity and elasticity have been demonstrated. Approaches to new functional materials include electrochemical potential switching of strength, stiffness, fracture resistance, fluid sorption, actuation, and quasi-piezoelectric strain sensing.},
note = {Online available at: \url{https://dx.doi.org/10.1557/mrs.2017.299} (DOI). Weissmueller, J.; Sieradzki, K.: Dealloyed nanoporous materials with interface-controlled behavior. In: MRS Bulletin. Vol. 43 (2018) 1, 14 - 19. (DOI:  /10.1557/mrs.2017.299)}}
@article{jin_mechanical_response_2018, 
author={Jin, H.-J. and Weissmueller, J. and Farkas, D.},
title={Mechanical response of nanoporous metals: A story of size, surface stress, and severed struts},
year={2018},
journal = {MRS Bulletin},
volume = {43},
number = {1},
pages = {35 - 42},
doi = {10.1557/mrs.2017.302},
abstract = {Nanoporous metals made by dealloying are macroscopic network architectures that can contain ∼1015 nanoscale struts or ligaments per sample. Their mechanical performance is critical to their applications as functional or lightweight high-strength materials. Testing nanoporous metals at the macroscopic scale offers opportunities for unraveling the properties of nanoscale solids in general. The central questions in this area include whether the macroscopic strength and elastic modulus of nanoporous metals can be correlated with the properties of nanoscale ligaments by the classical Gibson–Ashby equations, whether the dealloying-made network structure differs from the conventional foam metals, how network connectivity influences mechanical response, and how ligament size and surface properties affect the elastic and plastic response of nanoscale solids and that of nanoporous metals, particularly the tension–compression asymmetry in strength. This article reviews the fundamental observations of the mechanical response of nanoporous metals with a focus on gold and the emerging understanding of the aforementioned issues.},
note = {Online available at: \url{https://dx.doi.org/10.1557/mrs.2017.302} (DOI). Jin, H.-J.; Weissmueller, J.; Farkas, D.: Mechanical response of nanoporous metals: A story of size, surface stress, and severed struts. In: MRS Bulletin. Vol. 43 (2018) 1, 35 - 42. (DOI:  /10.1557/mrs.2017.302)}}
@article{bargmann_generation_of_2018, 
author={Bargmann, S. and Klusemann, B. and Markmann, J. and Schnabel, J.E. and Schneider, K. and Soyarslan, C. and Wilmers, J.},
title={Generation of 3D representative volume elements for heterogeneous materials: A review},
year={2018},
journal = {Progress in Materials Science},
volume = {96},
pages = {322 - 384},
doi = {10.1016/j.pmatsci.2018.02.003},
abstract = {This work reviews state of the art representative volume element (RVE) generation techniques for heterogeneous materials. To this end, we present a systematic classification considering a wide range of heterogeneous materials of engineering interest. Here, we divide heterogeneous solids into porous and non-porous media, with 0 < void volume fraction < 1 and void volume fraction = 0, respectively. Further subdivisions are realized based on various morphological features. The corresponding generation methods are classified into three categories: (i) experimental methods targeting reconstruction through experimental characterization of the microstructure, (ii) physics based methods targeting simulation of the physical process(es) responsible for the microstructure formation and evolution, and (iii) geometrical methods concentrating solely on mimicking the morphology (ignoring the physical basis of the microstructure formation process). These comprise of various mathematical tools such as digital image correlation, tessellation, random field generation, and differential equation solvers. For completeness, relevant up-to-date software tools, used at various stages of RVE generation – either commercial or open-source – are summarized. Considered methods are reviewed based on their efficiency and predictive performance with respect to geometrical and topological properties of the microstructures.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.pmatsci.2018.02.003} (DOI). Bargmann, S.; Klusemann, B.; Markmann, J.; Schnabel, J.E.; Schneider, K.; Soyarslan, C.; Wilmers, J.: Generation of 3D representative volume elements for heterogeneous materials: A review. In: Progress in Materials Science. Vol. 96 (2018) 322 - 384. (DOI:  /10.1016/j.pmatsci.2018.02.003)}}
@article{wang_improving_weld_2018, 
author={Wang, F.F. and Li, W.Y. and Shen, J. and Wen, Q. and dos Santos, J.F.},
title={Improving weld formability by a novel dual-rotation bobbin tool friction stir welding},
year={2018},
journal = {Journal of Materials Science and Technology},
volume = {34},
number = {1},
pages = {135 - 139},
doi = {10.1016/j.jmst.2017.11.001},
abstract = {A novel dual-rotation bobbin tool friction stir welding (DBT-FSW) was developed, in which the upper shoulder (US) and lower shoulder (LS) have different rotational speeds. This process was tried to weld 3.2 mm thick aluminum-lithium alloy sheets. The metallographic analysis and torque measurement were carried out to characterize the weld formability. Experimental results show that compared to conventional bobbin tool friction stir welding, the DBT-FSW has an excellent process stability, and can produce the defect-free joints in a wider range of welding parameters. These can be attributed to the significant improvement of material flow caused by the formation of a staggered layer structure and the unbalanced force between the US and LS during the DBT-FSW process.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jmst.2017.11.001} (DOI). Wang, F.F.; Li, W.Y.; Shen, J.; Wen, Q.; dos Santos, J.F.: Improving weld formability by a novel dual-rotation bobbin tool friction stir welding. In: Journal of Materials Science and Technology. Vol. 34 (2018) 1, 135 - 139. (DOI:  /10.1016/j.jmst.2017.11.001)}}
@article{enz_hot_cracking_2018, 
author={Enz, J. and Carrarin, C. and Riekehr, S. and Ventzke, V. and Kashaev, N.},
title={Hot cracking behaviour of an autogenously laser welded Al-Cu-Li alloy},
year={2018},
journal = {The International Journal of  Advanced Manufacturing Technology},
volume = {95},
number = {1-4},
pages = {299 - 310},
doi = {10.1007/s00170-017-1197-x},
abstract = {AA2198 is a relatively new light-weight and high-performance Al-Cu-Li alloy considered for aviation and space applications. However, Al-Cu-Li alloys generally exhibit severe weldability problems for all fusion-welding techniques, such as laser-beam welding. In particular, porosity formation and hot cracking are observed for the laser-beam welding of these alloys. A common remedy for hot cracking is the use of an appropriate filler wire with a high Si content. In the present study, three different approaches for improving the hot cracking susceptibility of AA2198 laser beam welded without any filler material are presented. For this purpose, pre-heating of the weld samples to elevated temperatures, pre-loading of the weld samples perpendicular to the welding direction, or an optimization of the laser-beam welding parameters were conducted. The autogenously welded samples were assessed with regard to the resulting total crack length and their mechanical properties. It was demonstrated that all of the presented approaches led to a reduction of hot cracking. However, the largest effect was observed for the use of low levels of laser power and welding velocity. The mechanical properties of the optimised autogenously welded samples are only marginally inferior as for the samples laser welded with the Al-Si filler wire AA4047.},
note = {Online available at: \url{https://dx.doi.org/10.1007/s00170-017-1197-x} (DOI). Enz, J.; Carrarin, C.; Riekehr, S.; Ventzke, V.; Kashaev, N.: Hot cracking behaviour of an autogenously laser welded Al-Cu-Li alloy. In: The International Journal of  Advanced Manufacturing Technology. Vol. 95 (2018) 1-4, 299 - 310. (DOI:  /10.1007/s00170-017-1197-x)}}
@article{keller_experimental_and_2018, 
author={Keller, S. and Chupakhin, S. and Staron, P. and Maawad, E. and Kashaev, N. and Klusemann, B.},
title={Experimental and numerical investigation of residual stresses in laser shock peened AA2198},
year={2018},
journal = {Journal of Materials Processing Technology},
volume = {255},
pages = {294 - 307},
doi = {10.1016/j.jmatprotec.2017.11.023},
abstract = {Laser shock peening (LSP) is a surface treatment which improves the fatigue performance of metallic structures by introducing compressive residual stresses. The aim of this paper is the investigation of LSP of the aluminium alloy AA2198. This investigation includes the variation of the laser power density (2.78 GW/cm2 to 25 GW/cm2) and the squared laser focus (1 mm × 1 mm and 3 mm × 3 mm). Additionally, two different temper stages (T3 and T8) and thicknesses (3.2 mm and 4.8 mm) of AA2198 are considered. The study of the LSP process is split into two parts; at first, LSP experiments are performed to clarify the influence of the temper stage, the focus size, the laser power density and the thickness of the specimen on the residual stress field. Secondly, a process model based on the finite element method is employed which requires in particular the adjustment of a suitable laser induced pressure pulse. Due to the different yield strength and strain hardening behaviour of the different temper conditions, AA2198-T8 shows a lower penetration depth of compressive residual stresses compared to AA2198-T3. A smaller focus size leads to higher compressive residual stresses near the surface but a lower penetration depth. To investigate possible shock wave reflections, different base layers in the LSP process are investigated considering a free, a clamped and a glued back-side of the specimen. No differences in terms of resulting residual stresses were observed. The experimental study provides some preliminary assumptions which are used to simplify the simulation set-up. Residual stresses are measured by the incremental hole drilling method using electronic speckle pattern interferometry (ESPI) as well as synchrotron X-ray diffraction. The calculated residual stresses in the simulation are averaged layer-wise over a sample area for comparison with the measured residual stresses. The model is used to simulate the LSP process for the considered temper stages and focus sizes to predict the resulting residual stresses. Simulated and measured residual stress profiles show for the different cases very good agreement.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jmatprotec.2017.11.023} (DOI). Keller, S.; Chupakhin, S.; Staron, P.; Maawad, E.; Kashaev, N.; Klusemann, B.: Experimental and numerical investigation of residual stresses in laser shock peened AA2198. In: Journal of Materials Processing Technology. Vol. 255 (2018) 294 - 307. (DOI:  /10.1016/j.jmatprotec.2017.11.023)}}
@article{lee_fracture_prediction_2018, 
author={Lee, J.-Y. and Steglich, D. and Lee, M.-G.},
title={Fracture prediction based on a two-surface plasticity law for the anisotropic magnesium alloys AZ31 and ZE1},
year={2018},
journal = {International Journal of Plasticity},
volume = {105},
pages = {1 - 23},
doi = {10.1016/j.ijplas.2017.10.002},
abstract = {The objective of the present study was to characterize the fracture limits of two magnesium sheet alloys, AZ31 and ZE10, using classical and Mohr-Coulomb-type ductile fracture criteria and to evaluate these criteria for different loading conditions in the framework of finite element (FE) simulations. A recently proposed two-yield surface plasticity model, which separates the strain contributions of dislocation glide and mechanical twinning on the (10–12) plane, was adopted to describe the strength differential effect and anisotropic hardening behaviors of the magnesium alloys. The deformation and fracture behaviors of the materials were measured in uniaxial tension, U-notched tension, and shear, thus encompassing a wide range of stress states. The fracture criteria parameters were optimized using an experiment–simulation hybrid approach. The suggested deformation and fracture models were applied to the analysis of thin square tubes under two loading conditions, namely, axial tube compression and three-point bending. The simulation results were compared with those of the respective structure tests. The two-yield-surface model was found to be able to successfully reproduce the punch load–displacement responses in both cases, revealing its superior performance relative to the von Mises model. In the case of failure prediction, both the classical and Mohr-Coulomb-type fracture criteria resulted in similar predictions for tube compression. However, the failure prediction for three-point bending was found to be highly dependent on the fracture criteria, among which the MMC criterion provided the most realistic prediction. The prediction results were further analyzed by investigating the stress history and damage evolution in the critical regions of the specimens during tube compression and three-point bending.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.ijplas.2017.10.002} (DOI). Lee, J.-Y.; Steglich, D.; Lee, M.-G.: Fracture prediction based on a two-surface plasticity law for the anisotropic magnesium alloys AZ31 and ZE1. In: International Journal of Plasticity. Vol. 105 (2018) 1 - 23. (DOI:  /10.1016/j.ijplas.2017.10.002)}}
@article{manenteandre_composite_surface_2018, 
author={Manente Andre, N. and Goushegir, S.M. and Scharnagl, N. and dos Santos, J.F. and Canto, L.B. and Amancio-Filho, S.T.},
title={Composite surface pre-treatments: improvement on adhesion mechanisms and mechanical performance of metal-composite friction spot joints with additional film interlayer},
year={2018},
journal = {The Journal of Adhesion},
volume = {94},
number = {9},
pages = {723 - 742},
doi = {10.1080/00218464.2017.1378101},
abstract = {Friction spot joints of aluminum alloy 2024-T3 and carbon-fiber-reinforced polyphenylene sulfide (CF-PPS) were produced with PPS film interlayer. Mechanical grinding, sandblasting and sandblasting combined with plasma activation were performed on the composite part to enhance the interface adhesion. The surface features – roughness, wettability and chemical activation – were correlated with the ultimate lap shear force of the joints. The composite surface with the highest surface roughness (sandblasting: 5.3 ± 0.6 µm) led to joints approximately 95% stronger (3068 ± 192 N) than the joints with the lowest surface roughness (mechanical grinding: 0.6 ± 0.1 µm, 1573 ± 84 N). The increase in surface roughness enlarged the effective contact surface area, leading to a better micro-mechanical interlocking between PPS film and composite. Although functional groups were identified in the plasma-treated specimens using X-ray photoelectron spectroscopy, no contribution to the mechanical strength of the joints were observed. The fracture surface analysis supported the conclusion that sandblasting was the most effective treatment, maximizing the mechanical performance of the joints. Impressions containing pieces of carbon fibers were identified on the interlayer surface. It indicates effective micro-mechanical interlocking at the interface of interlayer-composite achieved with the sandblasted specimens.},
note = {Online available at: \url{https://dx.doi.org/10.1080/00218464.2017.1378101} (DOI). Manente Andre, N.; Goushegir, S.M.; Scharnagl, N.; dos Santos, J.F.; Canto, L.B.; Amancio-Filho, S.T.: Composite surface pre-treatments: improvement on adhesion mechanisms and mechanical performance of metal-composite friction spot joints with additional film interlayer. In: The Journal of Adhesion
. Vol. 94 (2018) 9, 723 - 742. (DOI:  /10.1080/00218464.2017.1378101)}}
@article{borba_directfriction_riveting_2018, 
author={Borba, N.Z. and Blaga, L. and dos Santos, J.F. and Amancio-Filho, S.T.},
title={Direct-Friction Riveting of polymer composite laminates for aircraft applications},
year={2018},
journal = {Materials Letters},
volume = {215},
pages = {31 - 34},
doi = {10.1016/j.matlet.2017.12.033},
abstract = {Friction Riveting is an alternative joining technology to the conventional mechanical fastening suitable for woven-reinforced polymer composites. In this paper, the feasibility of Direct-Friction Riveting is demonstrated for Ti6Al4V rivet and carbon-fiber reinforced polyether-ether-ketone laminate single lap joints. Due to high shear rates, elevated process temperatures (500-900°C) and fast cooling rates (38 ± 2°C/s) experienced by the rivet tip, α’-martensitic structures were identified in the rivet anchoring zone along with fiber and polymer entrapment at the rivet-composite interface. An average ultimate lap shear force of 7.4 ± 0.6 kN similar to conventional lock-bolted single lap joints was achieved. These results indicate that Direct-Friction Riveting is a competitive method with potential for improvement and further application in aircraft structures.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.matlet.2017.12.033} (DOI). Borba, N.Z.; Blaga, L.; dos Santos, J.F.; Amancio-Filho, S.T.: Direct-Friction Riveting of polymer composite laminates for aircraft applications. In: Materials Letters. Vol. 215 (2018) 31 - 34. (DOI:  /10.1016/j.matlet.2017.12.033)}}
@article{martinazzi_estudo_da_2018, 
author={Martinazzi, D. and Lemos, G.V.B. and Cardoso, H.R.P. and dos Santos, R.E. and Ferreira, J.Z. and Bergmann, L. and dos Santos, J.F. and Reguly, A.},
title={Estudo da Sensitizacao em Juntas Soldadas de Inconel® 625 Produzidas Atraves da Soldagem por Friccao e Mistura Mecanica - Sensitization Study in Friction Stir Welds of Inconel®625},
year={2018},
journal = {Periodico Tche Quimica},
volume = {15},
number = {29},
pages = {53 - 60},
abstract = {Resumo: Os novos desafios da indútria do óleo e gás requerem a utilização de materiais com maior de estabilidade química e propriedades mecânicas superiores. A liga 625, popularmente conhecida como Inconel® 625, é comumente utilizada como revestimento de pipelines e outros componentes. Portanto, o estudo de métodos de união que produzem juntas soldadas com excelente qualidade é essencial. Neste estudo, chapas soldadas de Inconel 625 foram produzidas através da Soldagem por Fricção e Mistura Mecânica (Friction Stir Welding) e estas foram submetidas a um tratamento térmico para avaliação da susceptibilidade à corrosão intergranular com a técnica de Reativação Potenciocinética de Ciclo Duplo (Double Loop Electrochemical Potentiokinetic Reactivation Test, DL-EPR). A influência do tratamento térmico na sensitização das juntas soldadas também foi avaliada através de microscopia ótica e microdureza. Os resultados indicam a formação de carbonetos devido ao aumento de dureza após o tratamento térmico e, assim, diferentes graus de sensitização. 


Abstract:The new challenges of the oil and gas industry require noble materials with chemical stability and
greater mechanical properties. Alloy 625, popularly known as Inconel® 625, is used as a cladding material for pipelines and other components. Therefore, the study of joining methods that produce excellent welded joints is essential. Thus, in this study, welded sheets of Inconel 625 were produced by Friction Stir Welding(FSW) and afterwards they were subjected to a heat treatment to evaluate the susceptibility to sensitization by the Double Loop Electrochemical Potentiokinetic Reactivation (DL-EPR)technique. In addition, microhardnessprofiles were performed before and after the isothermal treatment. The microhardness results indicated that the increased hardness is due to the carbides formation after heat treatment. On the other hand, electrochemical tests showed that FSW process can significantly affect the degree of sensitization.},
note = {Martinazzi, D.; Lemos, G.V.B.; Cardoso, H.R.P.; dos Santos, R.E.; Ferreira, J.Z.; Bergmann, L.; dos Santos, J.F.; Reguly, A.: Estudo da Sensitizacao em Juntas Soldadas de Inconel® 625 Produzidas Atraves da Soldagem por Friccao e Mistura Mecanica - Sensitization Study in Friction Stir Welds of Inconel®625. In: Periodico Tche Quimica. Vol. 15 (2018) 29, 53 - 60.}}
@article{lu_improving_the_2018, 
author={Lu, J. and Huber, N. and Kashaev, N.},
title={Improving the fatigue performance of airframe structures via the hybridized application of geometrical modifications and laser heating},
year={2018},
journal = {Fatigue and Fracture of Engineering Materials and Structures},
volume = {41},
number = {5},
pages = {1183 - 1195},
doi = {10.1111/ffe.12762},
abstract = {This study aimed to investigate an optimization method that can maximize fatigue crack retardation based on the concepts of crenellation and residual stress engineering. By applying both concepts, fatigue crack retardation was achieved by the systematic modulation of the panel thickness and by the superposition of a beneficial residual stress field induced by laser heating. To identify an optimized implementation of both concepts, an advanced finite element method-genetic algorithm coupled approach was proposed, where each possible configuration in terms of the crenellation geometry and the positioning of the laser heating lines was encoded in a binary string. The inclusion of the residual stress field induced by the laser heating in the finite element method model was achieved by the inherent strain approach. It was found that the optimized configurations showed from 38% up to 77% fatigue life extensions, which were much larger than the linear superimposition of the fatigue life improvements by each individual technique.},
note = {Online available at: \url{https://dx.doi.org/10.1111/ffe.12762} (DOI). Lu, J.; Huber, N.; Kashaev, N.: Improving the fatigue performance of airframe structures via the hybridized application of geometrical modifications and laser heating. In: Fatigue and Fracture of Engineering Materials and Structures. Vol. 41 (2018) 5, 1183 - 1195. (DOI:  /10.1111/ffe.12762)}}
@article{shen_texture_development_2018, 
author={Shen, J. and Lage, S.B.M. and Suhuddin, U.F.H. and Bolfarini, C. and dos Santos, J.F.},
title={Texture Development and Material Flow Behavior During Refill Friction Stir Spot Welding of AlMgSc},
year={2018},
journal = {Metallurgical and Materials Transactions  A},
volume = {49},
number = {1},
pages = {241 - 254},
doi = {10.1007/s11661-017-4381-6},
abstract = {The microstructural evolution during refill friction stir spot welding of an AlMgSc alloy was studied. The primary texture that developed in all regions, with the exception of the weld center, was determined to be 〈110〉 fibers and interpreted as a simple shear texture with the 〈110〉 direction aligned with the shear direction. The material flow is mainly driven by two components: the simple shear acting on the horizontal plane causing an inward-directed spiral flow and the extrusion acting on the vertical plane causing an upward-directed or downward-directed flow. Under such a complex material flow, the weld center, which is subjected to minimal local strain, is the least recrystallized. In addition to the geometric effects of strain and grain subdivision, thermally activated high-angle grain boundary migration, particularly continuous dynamic recrystallization, drives the formation of refined grains in the stirred zone.},
note = {Online available at: \url{https://dx.doi.org/10.1007/s11661-017-4381-6} (DOI). Shen, J.; Lage, S.B.M.; Suhuddin, U.F.H.; Bolfarini, C.; dos Santos, J.F.: Texture Development and Material Flow Behavior During Refill Friction Stir Spot Welding of AlMgSc. In: Metallurgical and Materials Transactions  A. Vol. 49 (2018) 1, 241 - 254. (DOI:  /10.1007/s11661-017-4381-6)}}
@article{okulov_open_porous_2018, 
author={Okulov, I.V. and Okulov, A.V. and Soldatov, I.V. and Luthringer, B. and Willumeit-Roemer, R. and Wada, T. and Kato, H. and Weissmueller, J. and Markmann, J.},
title={Open porous dealloying-based biomaterials as a novel biomaterial platform},
year={2018},
journal = {Materials Science and Engineering  C},
volume = {88},
pages = {95 - 103},
doi = {10.1016/j.msec.2018.03.008},
abstract = {The close match of stiffness between implant material and bone is critically important to avoid stress-shielding effect and ensure a fast healing of injured tissues. Here, we introduce liquid metal dealloying method for synthesis of robust open porous biomaterials possessing low Young's modulus. The remarkable advantage of the liquid metal dealloying method is a large flexibility in selecting chemical composition of a desired porous biomaterial together with unique tunable microstructure. To demonstrate the versatility of the method, a number of open porous TixZr100-x alloys with different chemical compositions and microstructural characteristics was developed by dealloying precursor (TixZr100-x)yCu100-y alloys in liquid magnesium. The effects of the processing conditions and the precursors' chemical composition on the microstructure of the porous TixZr100-x as well as their mechanical behavior were discussed in detail. In particular, the porous TixZr100-x distinguish themselves due to a low and tunable stiffness ranging from 3.2 to 15.1 GPa and a rather high strength reaching up to 480 MPa. This unique combination of mechanical properties of the new open porous TixZr100-x alloys becomes even more interesting in view of preliminary biological tests highlighting their excellent cytocompatibility. Overall, the liquid metal dealloying provides an opportunity for designing a new biomaterials platform with flexible tunable functionality.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.msec.2018.03.008} (DOI). Okulov, I.V.; Okulov, A.V.; Soldatov, I.V.; Luthringer, B.; Willumeit-Roemer, R.; Wada, T.; Kato, H.; Weissmueller, J.; Markmann, J.: Open porous dealloying-based biomaterials as a novel biomaterial platform. In: Materials Science and Engineering  C. Vol. 88 (2018) 95 - 103. (DOI:  /10.1016/j.msec.2018.03.008)}}
@article{falck_addjoining_a_2018, 
author={Falck, R. and Goushegir, S.M. and dos Santos, J.F. and Amancio-Filho, S.T.},
title={AddJoining: a novel additive manufacturing approach for layered metal-polymer hybrid structures},
year={2018},
journal = {Materials Letters},
volume = {217},
pages = {211 - 214},
doi = {10.1016/j.matlet.2018.01.021},
abstract = {A novel assembling technique based on additive manufacturing and materials joining principles has been introduced for layered metal-polymer hybrid structures. The AddJoining technique produces layered hybrid structures, using polymer 3D printing methods. The feasibility of the technique was demonstrated using fused deposition modeling for single-lap joint configuration. Microstructure and mechanical strength of the joints were studied using two combinations of materials; aluminum 2024-T3 with acrylonitrile butadiene styrene and aluminum 2024-T3 with alternate layers of polyamide-6 and carbon-fiber-reinforced polyamide-6. The latter reached an average ultimate lap-shear strength of 21.9 ± 1.1 MPa. This exploratory investigation showed the potential of AddJoining to produce metal-polymer layered structures.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.matlet.2018.01.021} (DOI). Falck, R.; Goushegir, S.M.; dos Santos, J.F.; Amancio-Filho, S.T.: AddJoining: a novel additive manufacturing approach for layered metal-polymer hybrid structures. In: Materials Letters. Vol. 217 (2018) 211 - 214. (DOI:  /10.1016/j.matlet.2018.01.021)}}
@article{goeritz_retrieval_of_2018, 
author={Goeritz, A. and Berger, S.A. and Gege, P. and Grossart, H.-P. and Nejsrgaard, J.C. and Riedel, S. and Roettgers, R. and Utschig, C.},
title={Retrieval of Water Constituents from Hyperspectral In-Situ Measurements under Variable Cloud Cover—A Case Study at Lake Stechlin (Germany)},
year={2018},
journal = {Remote Sensing},
volume = {10},
number = {2},
pages = {181},
doi = {10.3390/rs10020181},
abstract = {Remote sensing and field spectroscopy of natural waters is typically performed under clear skies, low wind speeds and low solar zenith angles. Such measurements can also be made, in principle, under clouds and mixed skies using airborne or in-situ measurements; however, variable illumination conditions pose a challenge to data analysis. In the present case study, we evaluated the inversion of hyperspectral in-situ measurements for water constituent retrieval acquired under variable cloud cover. First, we studied the retrieval of Chlorophyll-a (Chl-a) concentration and colored dissolved organic matter (CDOM) absorption from in-water irradiance measurements. Then, we evaluated the errors in the retrievals of the concentration of total suspended matter (TSM), Chl-a and the absorption coefficient of CDOM from above-water reflectance measurements due to highly variable reflections at the water surface. In order to approximate cloud reflections, we extended a recent three-component surface reflectance model for cloudless atmospheres by a constant offset and compared different surface reflectance correction procedures. Our findings suggest that in-water irradiance measurements may be used for the analysis of absorbing compounds even under highly variable weather conditions. The extended surface reflectance model proved to contribute to the analysis of above-water reflectance measurements with respect to Chl-a and TSM. Results indicate the potential of this approach for all-weather monitoring.},
note = {Online available at: \url{https://dx.doi.org/10.3390/rs10020181} (DOI). Goeritz, A.; Berger, S.A.; Gege, P.; Grossart, H.-P.; Nejsrgaard, J.C.; Riedel, S.; Roettgers, R.; Utschig, C.: Retrieval of Water Constituents from Hyperspectral In-Situ Measurements under Variable Cloud Cover—A Case Study at Lake Stechlin (Germany). In: Remote Sensing. Vol. 10 (2018) 2, 181. (DOI:  /10.3390/rs10020181)}}
@article{okulov_dealloyingbased_metalpolymer_2018, 
author={Okulov, A.V. and Volegov, A.S. and Weissmueller, J. and Markmann, J. and Okulov, I.V.},
title={Dealloying-based metal-polymer composites for biomedical applications},
year={2018},
journal = {Scripta Materialia},
volume = {146},
pages = {290 - 294},
doi = {10.1016/j.scriptamat.2017.12.022},
abstract = {Here, we developed interpenetrating-phase metal-polymer composites mimicking mechanical behavior of cortical bone and occupying previously unclaimed region at the Ashby diagram in the area of intermediate strength and low stiffness. The composites consist of dealloying-based open porous TixHf100 − x alloys (scaffolds) impregnated by polymer. The scaffolds significantly contribute to strength (215–266 MPa) and stiffness (15.6–20.8 GPa) of the composites while the polymer phase provides their high strain rate sensitivity (0.037–0.044). Tuning scaffolds' connectivity by preloading and/or their chemical composition allows fine optimization of composites' mechanical properties. The results suggest that the composites may provide a basis for promising future implant materials.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.scriptamat.2017.12.022} (DOI). Okulov, A.V.; Volegov, A.S.; Weissmueller, J.; Markmann, J.; Okulov, I.V.: Dealloying-based metal-polymer composites for biomedical applications. In: Scripta Materialia. Vol. 146 (2018) 290 - 294. (DOI:  /10.1016/j.scriptamat.2017.12.022)}}
@article{gialos_investigating_the_2018, 
author={Gialos, A.A. and Zeimpekis, V. and Alexopoulos, N.D. and Kashaev, N. and Riekehr, S. and Karanika, A.},
title={Investigating the impact of sustainability in the production of aeronautical subscale components},
year={2018},
journal = {Journal of Cleaner Production},
volume = {176},
pages = {785 - 799},
doi = {10.1016/j.jclepro.2017.12.151},
abstract = {The aim of this paper is to investigate the impact of sustainability aspects in the production of aeronautical subscale components by comparing the traditional riveted versus the innovative Laser Beam Welding (LBW) process in industrial conditions. We adopt a quantitative assessment methodology for both processes, by taking into account a series of manufacturing scenarios with six multi-dimensional aeronautical subscale components in different annual production rates (mass production). The results reveal that the exploitation of the LBW technology can provide weight savings up to 28%, by exploiting lower density AlCuLi alloys, while the time savings during the manufacturing process can be up to 67%. Furthermore, the total manufacturing cost of the LBW process can be reduced up to 40% for the case of long structures, when compared to the corresponding riveted structures. In terms of environmental friendliness, the LBW process results to increased CO2e emissions by 124% during the manufacturing process when compared to the riveting process. However, this difference is lower than 60% when longer structures with smaller count of stringers are used. Finally, despite the high carbon footprint emission during the manufacturing phase, when the life cycle of aircrafts is assessed, the LBW joining process can contribute to lighter components, resulting to less weighted aircrafts whose engines consume less fuel, contributing in that way to energy and GHG emissions reductions.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jclepro.2017.12.151} (DOI). Gialos, A.A.; Zeimpekis, V.; Alexopoulos, N.D.; Kashaev, N.; Riekehr, S.; Karanika, A.: Investigating the impact of sustainability in the production of aeronautical subscale components. In: Journal of Cleaner Production. Vol. 176 (2018) 785 - 799. (DOI:  /10.1016/j.jclepro.2017.12.151)}}
@article{weissmueller_mechanochemistry_breaks_2018, 
author={Weissmueller, J.},
title={Mechanochemistry breaks with expectations},
year={2018},
journal = {Nature Catalysis},
volume = {1},
number = {1},
pages = {238 - 239},
doi = {10.1038/s41929-018-0061-1},
abstract = {Tensile strain of a solid surface can result in either strengthening or weakening of bonds with adsorbates. Adsorption energies of different adsorbate/site combinations may be shifted in different directions — a striking violation of the Brønsted–Evans–Polanyi relation.},
note = {Online available at: \url{https://dx.doi.org/10.1038/s41929-018-0061-1} (DOI). Weissmueller, J.: Mechanochemistry breaks with expectations. In: Nature Catalysis. Vol. 1 (2018) 1, 238 - 239. (DOI:  /10.1038/s41929-018-0061-1)}}
@article{barbini_influence_of_2018, 
author={Barbini, A. and Carstensen, J. and dos Santos, J.F.},
title={Influence of Alloys Position, Rolling and Welding Directions on Properties of AA2024/AA7050 Dissimilar Butt Weld Obtained by Friction Stir Welding},
year={2018},
journal = {Metals},
volume = {8},
number = {4},
pages = {202},
doi = {10.3390/met8040202},
abstract = {Friction stir welding (FSW) was carried out for the butt joining of dissimilar AA2024-T3 and AA7050-T7651 aluminium alloys with 2-mm thicknesses. A comparison between the position and orientation of different materials was performed by varying the welding speed while keeping the rotational speed constant. Through an analysis of the force and torque produced during welding and a simple analytical model, the results indicate that the heat input was reduced when the AA7050 alloy was located in the advancing side (AS) of the joint. The different material positions influenced the material transportation and the interface in the centre of the stir zone (SZ). The microhardness of both materials was lower when they were in the AS of the joint. The differences in the hardness values were reduced at higher welding speeds when the heat input was decreased. The mechanical performance increased when the lower strength alloy was located in the AS. The material orientation exhibited a small influence when the AA7050 alloy was in the AS and in general on the resulting microhardness for all the cases analysed. The tensile strength values were very similar for both orientations, but an increase in the yield strength could be measured when the materials were oriented in the transverse direction.},
note = {Online available at: \url{https://dx.doi.org/10.3390/met8040202} (DOI). Barbini, A.; Carstensen, J.; dos Santos, J.F.: Influence of Alloys Position, Rolling and Welding Directions on Properties of AA2024/AA7050 Dissimilar Butt Weld Obtained by Friction Stir Welding. In: Metals. Vol. 8 (2018) 4, 202. (DOI:  /10.3390/met8040202)}}
@article{richert_skeletonization_geometrical_2018, 
author={Richert, C. and Huber, N.},
title={Skeletonization, Geometrical Analysis, and Finite Element Modeling of Nanoporous Gold Based on 3D Tomography Data},
year={2018},
journal = {Metals},
volume = {8},
number = {4},
pages = {282},
doi = {10.3390/met8040282},
abstract = {Various modeling approaches simplify and parametrize the complex network structure of nanoporous gold (NPG) for studying the structure–property relationship based on artificially generated structures. This paper presents a computational efficient and versatile finite element method (FEM) beam model that is based on skeletonization and diameter information derived from the original 3D focused ion beam-scanning electron microscope (FIB-SEM) tomography data of NPG. The geometrical skeleton network is thoroughly examined for a better understanding of the NPG structure. A skeleton FEM beam model is derived that can predict the macroscopic mechanical behavior of the material. Comparisons between the mechanical response of this skeleton beam model and a solid FEM model are conducted. Results showed that the biggest-sphere diameter algorithm implemented in the open-source software FIJI, commonly used for geometrical analysis of microstructural data, overestimates the diameter of the curved NPG ligaments. The larger diameters lead to a significant overestimation of macroscopic stiffness and strength by the skeleton FEM beam model. For a parabolic shaped ligament with only 20% variation in its diameter, a factor of more than two was found in stiffness. It is concluded that improved algorithms for image processing are needed that provide accurate diameter information along the ligament axis.},
note = {Online available at: \url{https://dx.doi.org/10.3390/met8040282} (DOI). Richert, C.; Huber, N.: Skeletonization, Geometrical Analysis, and Finite Element Modeling of Nanoporous Gold Based on 3D Tomography Data. In: Metals. Vol. 8 (2018) 4, 282. (DOI:  /10.3390/met8040282)}}
@article{dequeirozcaetano_influence_of_2018, 
author={de Queiroz Caetano, G. and Silva, C.C. and Motta, M.F. and Miranda, H.C. and Farias, J.P. and Bergmann, L.A. and dos Santos, J.F.},
title={Influence of rotation speed and axial force on the friction stir welding of AISI 410S ferritic stainless steel},
year={2018},
journal = {Journal of Materials Processing Technology},
volume = {262},
pages = {430 - 436},
doi = {10.1016/j.jmatprotec.2018.07.018},
abstract = {The Friction Stir Welding process parameters were varied to provide a combination of an acceptable surface finish, absence of cracks, and full tool penetration. Two levels of rotation speed and axial forces from 10 to 30 kN were applied, whilst keeping the welding speed constant at 1 mm/s. One of the defects analyzed was the production of flashes. This can occur due to an increase in axial force and because of the instability in its applications, which implies directly on the formation of volumetric defects along the stir zone. FSW joints without root flaws can be achieved through a correct balance between the axial force and rotation speed, which also allows a greater immersion of the tool probe in the joint. Both rotation speeds using an axial force of around 20 kN proved to be good welding parameters for the FSW process. The welding of the AISI 410S steel (under these conditions) resulted in joints without internal defects and with a good surface finish.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jmatprotec.2018.07.018} (DOI). de Queiroz Caetano, G.; Silva, C.C.; Motta, M.F.; Miranda, H.C.; Farias, J.P.; Bergmann, L.A.; dos Santos, J.F.: Influence of rotation speed and axial force on the friction stir welding of AISI 410S ferritic stainless steel. In: Journal of Materials Processing Technology. Vol. 262 (2018) 430 - 436. (DOI:  /10.1016/j.jmatprotec.2018.07.018)}}
@article{brandstaeter_computational_model_2018, 
author={Brandstaeter, S. and Gizzi, A. and Fuchs, S.L. and Gebauer, A.M. and Aydin, R.C. and Cyron, C.J.},
title={Computational model of gastric motility with active‐strain electromechanics},
year={2018},
journal = {Zeitschrift fuer angewandte Mathematik und Mechanik : ZAMM},
volume = {98},
number = {12},
pages = {2177 - 2197},
doi = {10.1002/zamm.201800166},
abstract = {We present an electro-mechanical constitutive framework for the modeling of gastric motility, including pacemaker electrophysiology and smooth muscle contractility. In this framework, we adopt a phenomenological description of the gastric tissue. Tissue electrophysiology is represented by a set of two minimal two‐variable models and tissue electromechanics by an active‐strain finite elasticity approach. We numerically investigate the implication of the spatial distribution of pacemaker cells on the entrainment and synchronization of the slow waves characterizing gastric motility in health and disease. On simple schematic model geometries, we demonstrate that the proposed computational framework is amenable to large scale in‐silico analyses of the complex gastric motility including the underlying electro‐mechanical coupling.},
note = {Online available at: \url{https://dx.doi.org/10.1002/zamm.201800166} (DOI). Brandstaeter, S.; Gizzi, A.; Fuchs, S.L.; Gebauer, A.M.; Aydin, R.C.; Cyron, C.J.: Computational model of gastric motility with active‐strain electromechanics. In: Zeitschrift fuer angewandte Mathematik und Mechanik : ZAMM. Vol. 98 (2018) 12, 2177 - 2197. (DOI:  /10.1002/zamm.201800166)}}
@article{burkhardt_parameter_development_2018, 
author={Burkhardt, I. and Visone, R. and Riekehr, S. and Rackel, M.W. and Kashaev, N. and Enz, J.},
title={Parameter development and characterization of laser metal deposited high-temperature Ti alloy powders},
year={2018},
journal = {Procedia CIRP},
volume = {74},
pages = {176 - 179},
doi = {10.1016/j.procir.2018.08.088},
abstract = {Powder-based laser metal deposition (LMD) of Ti alloys enables the manufacturing of geometrical complex structures with tailored properties for high-temperature applications. The most important parameters for the LMD-process are the laser power, process velocity, laser focus position, gas flow and powder feed rate. Compared to the predominantly used Ti-6Al-4V, Ti-6Al-2Sn-4Zr-2Mo shows a higher oxidation resistance and a lower creep rate. For determining suitable process conditions, a parameter study using Ti-6Al-2Sn-4Zr-2Mo powder is performed. Subsequent, the parameter transfer to a γ-TiAl alloy is examined. The assessment of the dissimilar-LMD-structures is conducted by visual inspection, radiography inspection, microstructural analysis and hardness measurements.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.procir.2018.08.088} (DOI). Burkhardt, I.; Visone, R.; Riekehr, S.; Rackel, M.W.; Kashaev, N.; Enz, J.: Parameter development and characterization of laser metal deposited high-temperature Ti alloy powders. In: Procedia CIRP. Vol. 74 (2018) 176 - 179. (DOI:  /10.1016/j.procir.2018.08.088)}}
@article{herrnring_precipitation_kinetics_2018, 
author={Herrnring, J. and Kashaev, N. and Klusemann, B.},
title={Precipitation Kinetics of AA6082: An Experimental and Numerical Investigation
},
year={2018},
journal = {Materials Science Forum, THERMEC 2018},
volume = {941},
pages = {1411 - 1417},
doi = {10.4028/www.scientific.net/MSF.941.1411},
abstract = {The development of simulation tools for bridging different scales are essential for understanding complex joining processes. For precipitation hardening, the Kampmann-Wagner numerical model (KWN) is an important method to account for non-isothermal second phase precipitation. This model allows to describe nucleation, growth and coarsening of precipitation hardened aluminum alloys based on a size distribution for every phase which produces precipitations. In particular, this work investigates the performance of a KWN model by [1-3] for Al-Mg-Si-alloys. The model is compared against experimental data from isothermal heat treatments taken partially from [2]. Additionally, the model is used for investigation of the precipitation kinetics for a laser beam welding process, illustrating the time-dependent development of the different parameters related to the precipitation kinetics and the resulting yield strength.},
note = {Online available at: \url{https://dx.doi.org/10.4028/www.scientific.net/MSF.941.1411} (DOI). Herrnring, J.; Kashaev, N.; Klusemann, B.: Precipitation Kinetics of AA6082: An Experimental and Numerical Investigation
. In: Materials Science Forum, THERMEC 2018. Vol. 941 (2018) 1411 - 1417. (DOI:  /10.4028/www.scientific.net/MSF.941.1411)}}
@article{barbini_influence_of_2018, 
author={Barbini, A. and Carstensen, J. and dos Santos, J.F.},
title={Influence of a non-rotating shoulder on heat generation, microstructure and mechanical properties of dissimilar AA2024/AA7050 FSW joints},
year={2018},
journal = {Journal of Materials Science and Technology},
volume = {34},
number = {1},
pages = {119 - 127},
doi = {10.1016/j.jmst.2017.10.017},
abstract = {Friction stir welding (FSW) and stationary shoulder friction stir welding (SSFSW) were carried out for the butt joining of dissimilar AA2024-T3 and AA7050-T7651 aluminium alloys with thicknesses of 2 mm. A comparison between the two processes was performed by varying the welding speed while keeping the rotational speed constant. Through the analysis of the force and torque produced during welding and a simple analytical model, it was possible to show that in SSFSW there is more effective coupling with the tool and the heat produced is more efficiently distributed. This process decreases both the welding area and the diffusion at the interface of the two alloys compared with FSW. The minimum microhardness occurred at the advancing side (AS) at the interface between the thermo-mechanically affected zone (TMAZ) and the stir zone (SZ) in both processes, although the decrease was more gradual in SSFSW. This interface is also where all specimens failed for both welding technologies. An increase in tensile strength was measured in SSFSW compared with standard FSW. Furthermore, it was possible to establish the mechanical performance of the material in the fracture zone using digital image correlation.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jmst.2017.10.017} (DOI). Barbini, A.; Carstensen, J.; dos Santos, J.F.: Influence of a non-rotating shoulder on heat generation, microstructure and mechanical properties of dissimilar AA2024/AA7050 FSW joints. In: Journal of Materials Science and Technology. Vol. 34 (2018) 1, 119 - 127. (DOI:  /10.1016/j.jmst.2017.10.017)}}
@article{fomin_metallurgical_aspects_2018, 
author={Fomin, F. and Froend, M. and Ventzke, V. and Alvarez, P. and Bauer, S. and Kashaev, N.},
title={Metallurgical aspects of joining commercially pure titanium to Ti-6Al-4V alloy in a T-joint configuration by laser beam welding},
year={2018},
journal = {The International Journal of  Advanced Manufacturing Technology},
volume = {97},
number = {5-8},
pages = {2019 - 2031},
doi = {10.1007/s00170-018-1968-z},
abstract = {The present paper focuses on the metallurgical and microstructural characterization of the laser beam-welded T-joints between commercially pure titanium (CP-Ti) and Ti-6Al-4V alloy. The weld regions were comprehensively studied and the mechanisms leading to the final morphology within each weld region were described. The link between microstructural features and local mechanical properties was demonstrated. Owing to different constitution, the responses of the two titanium alloys to thermal cycles imposed by laser welding are completely different. A strong interface with no dilution zone between the two alloys was observed. The cooling rate during the welding process is high enough for diffusionless martensitic transformation in the Ti-6Al-4V part of the fusion zone. In contrast, no evidence of martensite was found in the CP-Ti because of low solute content and, consequently, much higher critical cooling rate. Plausible reason for some controversy found in the literature on the resulting transformation products after laser processing of CP-Ti was given. The present findings might have important industrial implications because careful microstructural characterization revealed the real position of the skin fusion line, which is of great importance for fulfillment of the weld quality criteria.},
note = {Online available at: \url{https://dx.doi.org/10.1007/s00170-018-1968-z} (DOI). Fomin, F.; Froend, M.; Ventzke, V.; Alvarez, P.; Bauer, S.; Kashaev, N.: Metallurgical aspects of joining commercially pure titanium to Ti-6Al-4V alloy in a T-joint configuration by laser beam welding. In: The International Journal of  Advanced Manufacturing Technology. Vol. 97 (2018) 5-8, 2019 - 2031. (DOI:  /10.1007/s00170-018-1968-z)}}
@article{shi_verifying_larchcahn_2018, 
author={Shi, S. and Markmann, J. and Weissmueller, J.},
title={Verifying Larché-Cahn elasticity, a milestone of 20th-century thermodynamics},
year={2018},
journal = {Proceedings of the National Academy of Sciences of the United States of America: PNAS},
volume = {115},
number = {43},
pages = {10914 - 10919},
doi = {10.1073/pnas.1809355115},
abstract = {Many materials phenomena are governed by the interaction between chemistry and mechanics. However, it was only in the second half of the 20th century that the theory of open system elasticity by Francis Larché and John W. Cahn concatenated the fields of solid mechanics and alloy chemistry. As the theory’s central materials descriptors, the open system elastic parameters describe how solids deform under stress when solute can rearrange at equilibrium while the chemical potential is held constant. Here, we report experiments verifying the predictions for these parameters. We study the elasticity of nanoporous Pd-H and Pd-Au-H during load cycles imposed by a dynamic mechanical analyzer. Short diffusion paths afford fast equilibration of H in the local strain gradients that carry the macroscopic elastic deformation. The experiment is in excellent agreement with the theory, confirming a central prediction of one of the key contributions to 20th-century thermodynamics.},
note = {Online available at: \url{https://dx.doi.org/10.1073/pnas.1809355115} (DOI). Shi, S.; Markmann, J.; Weissmueller, J.: Verifying Larché-Cahn elasticity, a milestone of 20th-century thermodynamics. In: Proceedings of the National Academy of Sciences of the United States of America: PNAS. Vol. 115 (2018) 43, 10914 - 10919. (DOI:  /10.1073/pnas.1809355115)}}
@article{fomin_probabilistic_fatiguelife_2018, 
author={Fomin, F. and Horstmann, M. and Huber, N. and Kashaev, N.},
title={Probabilistic fatigue-life assessment model for laser-welded Ti-6Al-4V butt joints in the high-cycle fatigue regime},
year={2018},
journal = {International Journal of Fatigue},
volume = {116},
pages = {22 - 35},
doi = {10.1016/j.ijfatigue.2018.06.012
},
abstract = {The present paper focuses on the effect of inherent welding-induced defects on the high-cycle fatigue behaviour of laser-welded Ti-6Al-4V butt joints. The transition of the crack origin from the surface to the subsurface occurs upon removal of the surface stress concentrators. Under these circumstances, fatigue cracks nucleate at subsurface porosity and show a typical fish-eye pattern of fracture surface. A fatigue-life assessment model has been developed for internally flawed materials based on a fracture-mechanics approach, which takes effects of short-cracks into account. A novel approach for the simplified construction of the cyclic resistance curve of internal cracks is proposed herein. Using statistical methods, the experimentally determined porosity distribution has been incorporated into the model to predict the fatigue scatter range. The presented methodology can potentially be used to achieve a required reliability of the welded joints with respect to fatigue as a design criterion.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.ijfatigue.2018.06.012
} (DOI). Fomin, F.; Horstmann, M.; Huber, N.; Kashaev, N.: Probabilistic fatigue-life assessment model for laser-welded Ti-6Al-4V butt joints in the high-cycle fatigue regime. In: International Journal of Fatigue. Vol. 116 (2018) 22 - 35. (DOI:  /10.1016/j.ijfatigue.2018.06.012
)}}
@article{fomin_surface_modification_2018, 
author={Fomin, F. and Klusemann, B. and Kashaev, N.},
title={Surface modification methods for fatigue properties improvement of laser welded Ti64 butt joints},
year={2018},
journal = {Procedia Structural Integrity},
volume = {13},
pages = {273 - 278},
doi = {10.1016/j.prostr.2018.12.046},
abstract = {Surface and internal defects formed upon laser beam welding (LBW) have been recognized as a serious problem because they cause stress concentration leading to premature failure of a welded component. This paper seeks to remedy these weld imperfections by applying various post-weld treatments and analyzing their effect on the high cycle fatigue (HCF) performance of welded joints. High efficiency of laser-based post-processing techniques after welding such as laser surface remelting (LSR) and laser shock peening (LSP) was demonstrated and compared with conventional approaches. The study reveals that welding porosity determines the internal crack initiation of the surface-treated weldments. Influence of process parameters on porosity level and the HCF properties is presented in detail. Based on an extensive experimental study, practical guidelines needed to mitigate the notch effect from defects and to maximize the fatigue performance of the laser-welded Ti-6Al-4V butt joints are given.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.prostr.2018.12.046} (DOI). Fomin, F.; Klusemann, B.; Kashaev, N.: Surface modification methods for fatigue properties improvement of laser welded Ti64 butt joints. In: Procedia Structural Integrity . Vol. 13 (2018) 273 - 278. (DOI:  /10.1016/j.prostr.2018.12.046)}}
@article{froend_microstructure_and_2018, 
author={Froend, M. and Ventzke, V. and Riekehr, S. and Kashaev, N. and Klusemann, B. and Enz, J.},
title={Microstructure and hardness evolution of laser metal deposited AA5087 wall-structures},
year={2018},
journal = {Procedia CIRP},
volume = {74},
pages = {131 - 135},
doi = {10.1016/j.procir.2018.08.062},
abstract = {Wire-based laser metal deposition enables to manufacture structures with very high deposition rates in comparison to powder-based laser additive manufacturing. However, this advantage is generally accompanied with a high energy input. Thus, an accumulation of heat within the structure can result. In addition, the heat conduction conditions can also change with increasing structure height, leading to inhomogeneous microstructural formation along the part. The present study deals with the evolution of the microstructure and hardness in laser metal deposited AA5087 wall structures. In this regard, two samples processed at adapted parameters for different deposition rates are investigated.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.procir.2018.08.062} (DOI). Froend, M.; Ventzke, V.; Riekehr, S.; Kashaev, N.; Klusemann, B.; Enz, J.: Microstructure and hardness evolution of laser metal deposited AA5087 wall-structures. In: Procedia CIRP. Vol. 74 (2018) 131 - 135. (DOI:  /10.1016/j.procir.2018.08.062)}}
@article{huber_connections_between_2018, 
author={Huber, N.},
title={Connections Between Topology and Macroscopic Mechanical Properties of Three-Dimensional Open-Pore Materials},
year={2018},
journal = {Frontiers in Materials},
volume = {5},
pages = {69},
doi = {10.3389/fmats.2018.00069},
abstract = {This work addresses a number of fundamental questions regarding the topological description of materials characterized by a highly porous three-dimensional structure with bending as the major deformation mechanism. Highly efficient finite-element beam models were used for generating data on the mechanical behavior of structures with different topologies, ranging from highly coordinated bcc to Gibson–Ashby structures. Random cutting enabled a continuous modification of average coordination numbers ranging from the maximum connectivity to the percolation-cluster transition of the 3D network. The computed macroscopic mechanical properties–Young's modulus, yield strength, and Poisson's ratio–combined with the cut fraction, average coordination number, and statistical information on the local coordination numbers formed a database consisting of more than 100 different structures. Via data mining, the interdependencies of topological parameters, and relationships between topological parameters with mechanical properties were discovered. A scaled genus density could be identified, which assumes a linear dependency on the average coordination number. Feeding statistical information about the local coordination numbers of detectable junctions with coordination number of 3 and higher to an artificial neural network enables the determination the average coordination number without any knowledge of the fully connected structure. This parameter serves as a common key for determining the cut fraction, the scaled genus density, and the macroscopic mechanical properties. The dependencies of macroscopic Young's modulus, yield strength, and Poisson's ratio on the cut fraction (or average coordination number) could be represented as master curves, covering a large range of structures from a coordination number of 8 (bcc reference) to 1.5, close to the percolation-cluster transition. The suggested fit functions with a single adjustable parameter agree with the numerical data within a few percent error. Artificial neural networks allow a further reduction of the error by at least a factor of 2. All data for macroscopic Young's modulus and yield strength are covered by a single master curve. This leads to the important conclusion that the relative loss of macroscopic strength due to pinching-off of ligaments corresponds to that of macroscopic Young's modulus. Experimental data in literature support this unexpected finding.},
note = {Online available at: \url{https://dx.doi.org/10.3389/fmats.2018.00069} (DOI). Huber, N.: Connections Between Topology and Macroscopic Mechanical Properties of Three-Dimensional Open-Pore Materials. In: Frontiers in Materials. Vol. 5 (2018) 69. (DOI:  /10.3389/fmats.2018.00069)}}
@article{okulov_phase_formation_2018, 
author={Okulov, I.V. and Boenisch, M. and Okulov, A.V. and Volegov, A.S. and Attar, H. and Ehtemam-Haghighi, S. and Calin, M. and Wang, Z. and Hohenwarter, A. and Kaban, I. and Prashanth, K.G. and Eckert, J.},
title={Phase formation, microstructure and deformation behavior of heavily alloyed TiNb- and TiV-based titanium alloys},
year={2018},
journal = {Materials Science and Engineering  A},
volume = {733},
pages = {80 - 86},
doi = {10.1016/j.msea.2018.07.047},
abstract = {The effect of chemical composition on microstructure and mechanical properties of heavily alloyed beta-titanium Ti-Nb(V)-Cu-Co-Al alloys was studied. The alloys were fabricated by casting into a water-cooled copper crucible employing relatively high cooling rates. The microstructure of these alloys consists of primary micrometer-sized bcc-structured (bcc – body centered cubic) dendrites surrounded by a minor amount of intermetallic phases. The morphology and volume fraction of the intermetallic phases are strongly affected by the alloys’ chemical composition. Particularly, the solubility of Cu and Co in the bcc dendrites of Ti-V-Cu-Co-Al is lower compared to that of Ti-Nb-Cu-Co-Al leading to a higher volume fraction of the intermetallic phase in the latter alloy. The high mechanical strength of the Ti-Nb(V)-Cu-Co-Al alloys (yield strength up to 1430 MPa) is mainly attributed to their multiphase nature and solid solution hardening of the supersaturated bcc-structured dendrites. Moreover, the large compressive plastic deformability supported by pronounced strain-hardening reaches several tens of percent. The alloys exhibit a significant strength asymmetry between compressive and tensile loadings, namely, they are weak and brittle under tensile loading. The tensile brittleness is associated with the lattice distortion in the bcc-structured dendrites as well as crack initiation at the interdendritic precipitates.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.msea.2018.07.047} (DOI). Okulov, I.V.; Boenisch, M.; Okulov, A.V.; Volegov, A.S.; Attar, H.; Ehtemam-Haghighi, S.; Calin, M.; Wang, Z.; Hohenwarter, A.; Kaban, I.; Prashanth, K.G.; Eckert, J.: Phase formation, microstructure and deformation behavior of heavily alloyed TiNb- and TiV-based titanium alloys. In: Materials Science and Engineering  A. Vol. 733 (2018) 80 - 86. (DOI:  /10.1016/j.msea.2018.07.047)}}
@article{li_microstructure_and_2018, 
author={Li, W. and Chu, Q. and Yang, X. and Shen, J. and Vairis, A. and Wang, W.},
title={Microstructure and morphology evolution of probeless friction stir spot welded joints of aluminum alloy},
year={2018},
journal = {Journal of Materials Processing Technology},
volume = {252},
pages = {69 - 80},
doi = {10.1016/j.jmatprotec.2017.09.003},
abstract = {A third generation Al-Li alloy has been successfully welded by probeless friction stir spot welding (P-FSSW). The joints presented symmetrical ‘basin’ shapes and two distinct regions were observed: the stir zone (SZ) and the thermo-mechanically affected zone (TMAZ), which were characterized by recrystallized grains and deformed grains, respectively. In order to study the relationship between the P-FSSWed joint morphology and mechanical strength, a phenomenological model of various geometric features of these joints, including the stir zone width, the stir zone edge angle (SEA) and the hook angle (HA), was established. According to the model, the actual stir zone was described by an ellipse which has its limitation, no matter how to change the welding parameters. The tensile/shear strength was related significantly to the morphology of hook defect, and so was the fracture mode. Additionally, a one-to-one correlation existed between shoulder diameter and sheet thickness to achieve a sound weld, which was useful in manufacture to yield high-quality joints.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jmatprotec.2017.09.003} (DOI). Li, W.; Chu, Q.; Yang, X.; Shen, J.; Vairis, A.; Wang, W.: Microstructure and morphology evolution of probeless friction stir spot welded joints of aluminum alloy. In: Journal of Materials Processing Technology. Vol. 252 (2018) 69 - 80. (DOI:  /10.1016/j.jmatprotec.2017.09.003)}}
@article{mameka_tailoring_the_2018, 
author={Mameka, N. and Luehrs, L. and Heissler, S. and Gliemann, H. and Woell, C.},
title={Tailoring the Strength of Nanoporous Gold by Self-Assembled Monolayers of Alkanethiols},
year={2018},
journal = {ACS Applied Nano Materials},
volume = {1},
number = {12},
pages = {6613 - 6621},
doi = {10.1021/acsanm.8b01368},
abstract = {Because of the large specific surface area, the properties of nanoporous metals and in particular their mechanical properties are sensitive to chemical modifications of their surfaces. Here, we exploit self-assembled monolayers (SAMs) to modify a surface of nanoporous gold and study their effect on plastic behavior. The SAMs investigated here (i) are made from alkanethiols, which consist of a sulfur headgroup that strongly binds to metal substrates, a hydrocarbon chain, and an end group, and (ii) are known to spontaneously self-organize into well-ordered, dense two-dimensional molecular films on the surface of coinage metals. Alkanethiols with various chain lengths and terminal groups were used to prepare SAMs on bulk nanoporous gold, and compression tests were performed on the SAM-modified and nonmodified macroscopic samples. Our experiments reveal a substantial, up to 50%, increase of the flow stress due to thiol adsorption. We attribute the strengthening to the adsorption locking of dislocation end points at the surface, which is mediated by the fairly strong metal–sulfur interaction.},
note = {Online available at: \url{https://dx.doi.org/10.1021/acsanm.8b01368} (DOI). Mameka, N.; Luehrs, L.; Heissler, S.; Gliemann, H.; Woell, C.: Tailoring the Strength of Nanoporous Gold by Self-Assembled Monolayers of Alkanethiols. In: ACS Applied Nano Materials. Vol. 1 (2018) 12, 6613 - 6621. (DOI:  /10.1021/acsanm.8b01368)}}
@article{yang_enhanced_wear_2018, 
author={Yang, J. and Di, S. and Blawert, C. and Lamaka, S.V. and Wang, L. and Fu, B. and Jiang, P. and Wang, L. and Zheludkevich, M.L.},
title={Enhanced Wear Performance of Hybrid Epoxy-Ceramic Coatings on Magnesium Substrates},
year={2018},
journal = {ACS Applied Materials and Interfaces},
volume = {10},
number = {36},
pages = {30741 - 30751},
doi = {10.1021/acsami.8b10612},
abstract = {Epoxy-based polymer was deposited as sealing agent on porous anodized coatings prepared by plasma electrolytic oxidation (PEO) to construct multilayered “soft-hard” coatings on Mg substrates. Different thicknesses and microstructures of the top epoxy layer were achieved by employing different dip-coating strategies. Atomic force microscopy, pull-off tests, and nanoindentation tests were conducted to study the surface roughness, the adhesion strength of the epoxy layer, and the mechanical properties of each component in the hybrid coating system. The micropores and other defects on the anodized layers were sealed by the epoxy polymer, which decreased the surface roughness. The dominant abrasive wear behavior of blank PEO coatings was significantly reduced by the epoxy layers, and the wear mechanism of the hybrid coatings was proposed considering both the microstructure of the hybrid coatings and the mechanical properties of the different components in the hybrid system.},
note = {Online available at: \url{https://dx.doi.org/10.1021/acsami.8b10612} (DOI). Yang, J.; Di, S.; Blawert, C.; Lamaka, S.V.; Wang, L.; Fu, B.; Jiang, P.; Wang, L.; Zheludkevich, M.L.: Enhanced Wear Performance of Hybrid Epoxy-Ceramic Coatings on Magnesium Substrates. In: ACS Applied Materials and Interfaces. Vol. 10 (2018) 36, 30741 - 30751. (DOI:  /10.1021/acsami.8b10612)}}
@article{schnabel_efficient_analysis_2018, 
author={Schnabel, J.E. and Mittelstedt, C.},
title={Efficient analysis of stress concentrations in laminated composite structures with geometric discontinuities},
year={2018},
journal = {PAMM: Proceedings in Applied Mathematics and Mechanics},
volume = {18},
number = {1},
pages = {e201800046},
doi = {10.1002/pamm.201800046},
abstract = {A semi-analytical analysis method for displacements, strains and stresses in laminated composite plates with local reinforcement by patches/doublers is presented. The analysis approach is based on a "global" solution provided by the Classical Laminate Plate Theory (CLPT). Further, a "local" model is introduced which discretizes each laminate ply into several mathematical layers. For each of these mathematical layers an additional displacement field is postulated. These additional
displacement fields capture the localized phenomena close to the free edge of the patch and in the plate-doubler junction but
decay rapidly with increasing distance from these locations, i.e. the CLPT solution is recovered. The model shows excellent agreement with FE analyses for different plate-doubler lay-ups with the benefit of highly reduced computational costs.},
note = {Online available at: \url{https://dx.doi.org/10.1002/pamm.201800046} (DOI). Schnabel, J.E.; Mittelstedt, C.: Efficient analysis of stress concentrations in laminated composite structures with geometric discontinuities. In: PAMM: Proceedings in Applied Mathematics and Mechanics. Vol. 18 (2018) 1, e201800046. (DOI:  /10.1002/pamm.201800046)}}
@article{froend_experimental_investigation_2018, 
author={Froend, M. and Bock, F. and Ventzke, V. and Riekehr, S. and Kashaev, N. and Klusemann, B. and Enz, J.},
title={Experimental Investigation of Temperature Distribution during Wire-Based Laser Metal Deposition of the Al-Mg Alloy 5087
},
year={2018},
journal = {Materials Science Forum, THERMEC 2018},
volume = {941},
pages = {988 - 994},
doi = {10.4028/www.scientific.net/MSF.941.988},
abstract = {Wire-based laser metal deposition enables to manufacture large-scale components with deposition rates significant higher compared to powder-based laser additive manufacturing techniques, which are currently working with deposition rates of only a few hundred gram per hour. However, the wire-based approach requires a significant amount of laser power in the range of several kilowatts instead of only a few hundred watts for powder-based processes. This excessive heat input during laser metal deposition can lead to process instabilities such as a non-uniform material deposition and to a limited processability, respectively. Although, numerous possibilities to monitor temperature evolution during processing exist, there is still a lack of knowledge regarding the relationship between temperature and geometric shape of the deposited structure. Due to changing cooling conditions with increasing distance to the substrate material, producing a wall-like structure results in varying heights of the individual tracks. This presents challenges for the deposition of high wall-like structures and limits the use of constant process parameters. In the present study, the temperature evolution during laser metal deposition of AA5087 using constant process parameters is investigated and a scheme for process parameter adaptions in order to reduce residual stress induced componential distortions is suggested.},
note = {Online available at: \url{https://dx.doi.org/10.4028/www.scientific.net/MSF.941.988} (DOI). Froend, M.; Bock, F.; Ventzke, V.; Riekehr, S.; Kashaev, N.; Klusemann, B.; Enz, J.: Experimental Investigation of Temperature Distribution during Wire-Based Laser Metal Deposition of the Al-Mg Alloy 5087
. In: Materials Science Forum, THERMEC 2018. Vol. 941 (2018) 988 - 994. (DOI:  /10.4028/www.scientific.net/MSF.941.988)}}
@article{burkhardt_development_of_2018, 
author={Burkhardt, I. and Ventzke, V. and Riekehr, S. and Kashaev, N. and Enz, J.},
title={Development of an optimised shielding strategy for laser beam welding of Ti6Al2Sn4Zr2Mo
},
year={2018},
journal = {Materials Science Forum, THERMEC 2018},
volume = {941},
pages = {1404 - 1410},
doi = {10.4028/www.scientific.net/MSF.941.1404},
abstract = {Ti6Al2Sn4Zr2Mo exhibits improved oxidation and creep properties compared to Ti6Al4V. Laser beam welding (LBW) is an approved process to receive narrow weld seams at high welding speeds with low heat input. Almost distortion free complex shaped structures can be joined with optimal parameters. For the optimisation of the LBW process the most relevant parameters are the welding speed, the laser input power and the gas shielding strategy. Using a fibre laser, the laser radiation is attenuated by a welding plume the so-called metal-vapour cloud (MVC). The MVC has a large influence on the laser input power. Therefore, an approach for reducing the MVC by optimising the shielding strategy using an additional gas flow in opposite welding direction is examined. Utilizing high-speed camera records, the effectiveness of the approach is assessed. Welded samples are evaluated by visual and radiographic inspection, metallographic assessment as well as microhardness measurements with regard to weld seam geometry, defects, microstructure and local mechanical properties. The obtained results are correlated to the used laser welding parameters.},
note = {Online available at: \url{https://dx.doi.org/10.4028/www.scientific.net/MSF.941.1404} (DOI). Burkhardt, I.; Ventzke, V.; Riekehr, S.; Kashaev, N.; Enz, J.: Development of an optimised shielding strategy for laser beam welding of Ti6Al2Sn4Zr2Mo
. In: Materials Science Forum, THERMEC 2018. Vol. 941 (2018) 1404 - 1410. (DOI:  /10.4028/www.scientific.net/MSF.941.1404)}}
@article{lemos_residual_stress_2018, 
author={Lemos, G.V.B. and Cunha, P.H.C.P. and Nunes, R.M. and Bergmann, L. and dos Santos, J.F. and Clarke, T.},
title={Residual stress and microstructural features of friction-stir-welded GL E36 shipbuilding steel},
year={2018},
journal = {Materials Science and Technology},
volume = {34},
number = {1},
pages = {95 - 103},
doi = {10.1080/02670836.2017.1361148},
abstract = {The purpose of the present study was to fulfil the knowledge gap concerning residual stresses evaluation of friction stir welded GL E36 shipbuilding steel. Plates of 6 mm thickness were welded using two different welding speeds (1 and 3 mm s−1) at a constant rotational speed of 500 rev min−1. This led to different thermal cycles and the objective is to analyse the resulting microstructures and residual stress states. Therefore, in this work, residual stresses were evaluated by X-ray diffraction; metallography and microhardness testing were performed to support these measurements. Results showed that welds produced with different heat inputs have distinguishable residual stress distributions. Increases in the welding speed led to higher residual stress and microhardness in the stir zone.},
note = {Online available at: \url{https://dx.doi.org/10.1080/02670836.2017.1361148} (DOI). Lemos, G.V.B.; Cunha, P.H.C.P.; Nunes, R.M.; Bergmann, L.; dos Santos, J.F.; Clarke, T.: Residual stress and microstructural features of friction-stir-welded GL E36 shipbuilding steel. In: Materials Science and Technology. Vol. 34 (2018) 1, 95 - 103. (DOI:  /10.1080/02670836.2017.1361148)}}
@article{cipriano_fundamentals_of_2018, 
author={Cipriano, G.P. and Blaga, L.A. and dos Santos, J.F. and Vilaca, P. and Amancio-Filho, S.T.},
title={Fundamentals of Force-Controlled Friction Riveting: Part I - Joint Formation and Heat Development},
year={2018},
journal = {Materials},
volume = {11},
number = {11},
pages = {2294},
doi = {10.3390/ma11112294},
abstract = {This work presents a systematic study on the correlations between process parameters and rivet plastic deformation, produced by force-controlled friction riveting. The 5 mm diameter AA2024 rivets were joined to 13 mm, nominal thickness, polyetherimide plates. A wide range of joint formations was obtained, reflecting the variation in total energy input (24–208 J) and process temperature (319–501 °C). The influence of the process parameters on joint formation was determined, using a central composite design and response surface methodology. Friction time displayed the highest contribution on both rivet penetration (61.9%) and anchoring depth (34.7%), and friction force on the maximum width of the deformed rivet tip (46.5%). Quadratic effects and two-way interactions were significant on rivet anchoring depth (29.8 and 20.8%, respectively). Bell-shaped rivet plastic deformation—high mechanical interlocking—results from moderate energy inputs (~100 J). These geometries are characterized by: rivet penetration depth of 7 to 9 mm; maximum width of the deformed rivet tip of 9 to 12 mm; and anchoring depth higher than 6 mm. This knowledge allows the production of optimized friction-riveted connections and a deeper understanding of the joining mechanisms, further discussed in Part II of this work.},
note = {Online available at: \url{https://dx.doi.org/10.3390/ma11112294} (DOI). Cipriano, G.P.; Blaga, L.A.; dos Santos, J.F.; Vilaca, P.; Amancio-Filho, S.T.: Fundamentals of Force-Controlled Friction Riveting: Part I - Joint Formation and Heat Development. In: Materials. Vol. 11 (2018) 11, 2294. (DOI:  /10.3390/ma11112294)}}
@article{guglielmi_on_a_2018, 
author={Guglielmi, P.O. and Ziehmer, M. and Lilleodden, E.T.},
title={On a novel strain indicator based on uncorrelated misorientation angles for correlating dislocation density to local strength},
year={2018},
journal = {Acta Materialia},
volume = {150},
pages = {195 - 205},
doi = {10.1016/j.actamat.2018.03.009},
abstract = {We present a new method based on uncorrelated misorientation measurements by Electron Backscattered Diffraction (EBSD) to characterize the dislocation density of site-specific areas selected on a bulk material. Gold samples submitted to different degrees of pre-straining are analyzed. A new scalar misorientation parameter called the Characteristic Misorientation Angle (CMA) is derived from uncorrelated misorientation data and compared to the more conventional parameters Grain Average Misorientation (GAM) and Grain Orientation Spread (GOS). We show that CMA is nearly independent of the scan step size and is more sensitive to plastic deformation than GAM and GOS. A coupled effect of local plastic strain and area size is observed on the measured values of CMA. Based on that, values of dislocation density are determined for site-specific areas whose strengths, as defined by the hardness at first pop-in, are subsequently measured by spherical nanoindentation. Results show that the site-specific strength of gold decreases with increasing initial dislocation density. While previous studies have suggested the same trend, the present work offers a new approach to more quantitatively correlate local dislocation densities to the onset of plasticity, without the need for destructive TEM investigations or micro-sample fabrication.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.actamat.2018.03.009} (DOI). Guglielmi, P.O.; Ziehmer, M.; Lilleodden, E.T.: On a novel strain indicator based on uncorrelated misorientation angles for correlating dislocation density to local strength. In: Acta Materialia. Vol. 150 (2018) 195 - 205. (DOI:  /10.1016/j.actamat.2018.03.009)}}
@article{lilleodden_on_the_2018, 
author={Lilleodden, E. and Voorhees, P.},
title={On the topological; morphological; and microstructural characterization of nanoporous metals},
year={2018},
journal = {MRS Bulletin},
volume = {43},
pages = {20 - 26},
doi = {10.1557/mrs.2017.303},
abstract = {The structural characterization of dealloyed nanoporous metals is a fundamental and active area of research, needed for the optimization of these structures for catalytic, electrosensing, biomedical, and mechanical functions. The prediction of properties requires identifying and quantifying salient structural characteristics, while insights into the relevant mechanisms of dealloying and coarsening can be achieved through in situ observations of structural evolution. Three-dimensional structural characterization techniques have advanced such that nanoscale quantification of topology, morphology, and crystallographic parameters are achievable, yet the field is new enough that the assessment and comparison of such parameters of different nanoporous metals are just beginning. Here, we explore the state of the art in structural characterization, focusing on nanoporous gold to exemplify the challenges, the achievements, and the potential associated with establishing an appropriate set of structural parameters for this unique class of materials.},
note = {Online available at: \url{https://dx.doi.org/10.1557/mrs.2017.303} (DOI). Lilleodden, E.; Voorhees, P.: On the topological; morphological; and microstructural characterization of nanoporous metals. In: MRS Bulletin. Vol. 43 (2018) 20 - 26. (DOI:  /10.1557/mrs.2017.303)}}
@article{dovzhenko_residual_stresses_2018, 
author={Dovzhenko, G. and Hanke, S. and Staron, P. and Maawad, E. and Schreyer, A. and Horstmann, M.},
title={Residual stresses and fatigue crack growth in friction surfacing coated Ti-6Al-4V sheets},
year={2018},
journal = {Journal of Materials Processing Technology},
volume = {262},
pages = {104 - 110},
doi = {10.1016/j.jmatprotec.2018.06.029},
abstract = {The relation between the translational stud speed and the residual stress (RS) state of Friction Surfacing (FS) coated 2 mm thick Ti-6Al-4V sheets was studied using synchrotron diffraction. The influence of the RS state on fatigue crack propagation (FCP) was studied using C(T)-100 samples.
It was shown that an active zone of tensile RS is present in the coated region, inducing compressive stresses in the remaining sheet. Higher depositing stud translational speeds show a tendency towards high RS peak values. The deposited material thickness has an influence on the RS distribution.
FCP tests have shown branching cracks deflecting away from the coating, possibly due to the compressive RS around it. Cracks have propagated significantly slower than in uncoated samples. RS measurements on cracked samples have revealed tensile RS peaks at the crack tips with high values of 350 MPa in the direction parallel to the intended crack propagation, which prevent the cracks from reaching the coated region.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jmatprotec.2018.06.029} (DOI). Dovzhenko, G.; Hanke, S.; Staron, P.; Maawad, E.; Schreyer, A.; Horstmann, M.: Residual stresses and fatigue crack growth in friction surfacing coated Ti-6Al-4V sheets. In: Journal of Materials Processing Technology. Vol. 262 (2018) 104 - 110. (DOI:  /10.1016/j.jmatprotec.2018.06.029)}}
@article{wang_study_of_2018, 
author={Wang, L. and Huang, Z. and Wang, H. and Maldar, A. and Yi, S. and Park, J. and Kenesei, P. and Lilleodden, E. and Zeng, X.},
title={Study of slip activity in a Mg-Y alloy by in situ high energy X-ray diffraction microscopy and elastic viscoplastic self-consistent modeling},
year={2018},
journal = {Acta Materialia},
volume = {155},
pages = {138 - 152},
doi = {10.1016/j.actamat.2018.05.065},
abstract = {Slip activity from various slip modes largely determines the yield strength and ductility of Mg alloys. Solid solution elements in Mg can change the slip activity dramatically. In this paper, far-field high energy X-ray diffraction microscopy (FF-HEDM) is employed to study slip activity in a Mg-3wt%Y alloy during an in situ tensile experiment. The specimen was incrementally loaded up to 3% engineering strain along the rolling direction. At each load step, FF-HEDM data were collected to track the crystallographic orientation, center of mass, and stress tensor changes of nearly 1000 grains in the probed volume. By analyzing the change in orientation and stress tensor of individual grains at different load steps, it is possible to identify the activated slip systems and measure their critical resolved shear stress (CRSS) values. Prismatic slip and pyramidal I  slip are found to be very active in this alloy. The estimated CRSS values for basal slip, prismatic slip and pyramidal I  slip are 12 MPa, 38 MPa, and 36 MPa, respectively. These CRSS values were applied in a dislocation-based elastic viscoplastic self-consistent (EVPSC) model that successfully simulated the tensile stress-strain curve from the FF-HEDM experiment. The model also qualitatively predicted the crystal rotation in most of the selected grains, though it underestimated the internal stress and the magnitude of crystal rotation in these grains. Influence of solute Y on the strength and ductility of Mg alloys is discussed.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.actamat.2018.05.065} (DOI). Wang, L.; Huang, Z.; Wang, H.; Maldar, A.; Yi, S.; Park, J.; Kenesei, P.; Lilleodden, E.; Zeng, X.: Study of slip activity in a Mg-Y alloy by in situ high energy X-ray diffraction microscopy and elastic viscoplastic self-consistent modeling. In: Acta Materialia. Vol. 155 (2018) 138 - 152. (DOI:  /10.1016/j.actamat.2018.05.065)}}
@article{kashaev_prospects_of_2018, 
author={Kashaev, N. and Ventzke, V. and Cam, G.},
title={Prospects of laser beam welding and friction stir welding processes for aluminum airframe structural applications},
year={2018},
journal = {Journal of Manufacturing Processes},
volume = {36},
pages = {571 - 600},
doi = {10.1016/j.jmapro.2018.10.005},
abstract = {The present study deals with laser beam welding (LBW) and friction stir welding (FSW) applied to high-strength aluminum alloys used in aircraft industry and displays their advantages compared with the riveting technique regarding structural integrity, weight and material savings. First of all, it is shown with respect to different applications and strength levels which high-strength aluminum alloys represent the state-of-the-art and which aluminum alloys are proposed as substitutes in the future. Furthermore, the respective joining process principles are described and demonstrated on different joint configurations, whereby mechanical and microstructural properties of laser beam- and friction-stir-welded joints are discussed and compared. The current study clearly demonstrates that these two joining techniques are not competing but complementary joining techniques in the aircraft industry.
FSW, as a solid-state joining process, has the advantage that the joining is conducted at temperatures below the melting point of the materials to be joined. Therefore, improved mechanical performance of joints is expected compared to that of fusion joining processes such as LBW. Furthermore, better mechanical properties can be obtained when heat input during joining is reduced by employing stationary shoulder FSW and/or external cooling. On the other hand, LBW offers several advantages such as low distortion, high strength of the joint, and high welding speeds due to its low localized-energy input. Thus, LBW - as a high-speed and easily controllable process - allows the welding of optimized complex geometrical forms in terms of mechanical stiffness, strength, production velocity, and visual quality. Both joining processes have advantages and disadvantages, depending on joint geometries and materials. They both have the potential to reduce the total weight of the structure. The FSW process (particularly lower heat input stationary shoulder FSW process) is more advantageous in producing long-distance straight-line butt joints or overlapped joints of aircraft structures, whereas the high-speed and easily controllable LBW process allows the joining of complex geometrical forms due to its high flexibility, particularly in the new generation high strength Al-alloys (such as AA2198), the strengthening phases of which are more heat resistant.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jmapro.2018.10.005} (DOI). Kashaev, N.; Ventzke, V.; Cam, G.: Prospects of laser beam welding and friction stir welding processes for aluminum airframe structural applications. In: Journal of Manufacturing Processes. Vol. 36 (2018) 571 - 600. (DOI:  /10.1016/j.jmapro.2018.10.005)}}
@article{froend_microstructure_and_2018, 
author={Froend, M. and Ventzke, V. and Riekehr, S. and Kashaev, N. and Klusemann, B. and Enz, J.},
title={Microstructure and microhardness of wire-based laser metal deposited AA5087 using an Ytterbium fibre laser},
year={2018},
journal = {Materials Characterization},
volume = {143},
pages = {59 - 67},
doi = {10.1016/j.matchar.2018.05.022},
abstract = {Wire-based additive manufacturing has been increasingly investigated in recent years. Although it is possible nowadays to manufacture structures that are free from inner defects such as porosity and cracks using wire and arc additive manufacturing, there is still a lack of knowledge regarding wire-based laser metal deposition of aluminium and its alloys. In order to be able to produce locally tailored part properties, it is necessary to understand the process parameter to material property relationships. Using laser energy sources, it becomes possible to analyse in detail the heat input and to observe occurring microstructural evolutions. This work includes a microstructural and mechanical characterization of an AA5087 wall structure. Detailed analyses of the chemical composition, texture, and microhardness of the structure have been performed. The microstructure contains different grain orientations as well as grain shapes and sizes along the structure, resulting in locally different material properties. The results have been analysed and discussed in reference to fundamental theories such as the Hall–Petch and Orowan mechanisms.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.matchar.2018.05.022} (DOI). Froend, M.; Ventzke, V.; Riekehr, S.; Kashaev, N.; Klusemann, B.; Enz, J.: Microstructure and microhardness of wire-based laser metal deposited AA5087 using an Ytterbium fibre laser. In: Materials Characterization. Vol. 143 (2018) 59 - 67. (DOI:  /10.1016/j.matchar.2018.05.022)}}
@article{shi_synthesis_of_2018, 
author={Shi, S. and Markmann, J. and Weissmueller, J.},
title={Synthesis of uniform bulk nanoporous palladium with tunable structure},
year={2018},
journal = {Electrochimica Acta},
volume = {285},
pages = {60 - 69},
doi = {10.1016/j.electacta.2018.07.081},
abstract = {This work presents systematic investigations on the synthesis of hierarchical nanoporous Pd via electrochemical dealloying of CuPd alloys in sulfuric acid. The impact of electrode potential, dealloying temperature, and additional annealing on microstructure and morphology is explored. Dealloying Cu85Pd15 in 1M sulfuric acid at elevated temperature provides a facile strategy to produce bulk nanoporous Pd samples which are uniform, hierarchically nanoporous, and free of macro-scale cracks. The question “Why will one-step template-free dealloying yield a hierarchical and not unimodal nanoporous structure?” is discussed. The impact of passivation and of a percolating Cu-rich cluster on the pore structure is inspected. A structural instability concept for dealloying of dilute master alloys is preferred as the underlying mechanism. Nanoporous Pd with classical, unimodal pore structure and tunable ligament size ranging from 80 to 270 nm emerges when the as-prepared hierarchical nanoporous Pd is annealed. The material of this study may provide a model system that complements nanoporous Au for studies of bulk nanoscale metal networks as functional and structural materials.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.electacta.2018.07.081} (DOI). Shi, S.; Markmann, J.; Weissmueller, J.: Synthesis of uniform bulk nanoporous palladium with tunable structure. In: Electrochimica Acta. Vol. 285 (2018) 60 - 69. (DOI:  /10.1016/j.electacta.2018.07.081)}}
@article{herrnring_multiscale_process_2018, 
author={Herrnring, J. and Staron, P. and Kashaev, N. and Klusemann, B.},
title={Multiscale process simulation of residual stress fields of laser beam welded precipitation hardened AA6082},
year={2018},
journal = {Materialia},
volume = {3},
pages = {243 - 255},
doi = {10.1016/j.mtla.2018.08.010},
abstract = {In this study, a multiscale modelling approach for the determination of residual stresses for the laser beam welded, precipitation hardened aluminium alloy AA6082-T6 is presented and applied. The material behaviour is described by an elasto-visco-plastic material model, specially suited for fusion welding processes. The microstructure evolution during the welding process has a direct influence on the macroscopic mechanical properties. The modelling approach accounts for the change in the microstructure via a Kampmann-Wagner Numerical model which takes into account the kinetics of the precipitates. The macroscopic mechanical properties are determined via classic dislocation theory, which accounts for the interaction between dislocations and precipitates. The temperature field of the welding process is described by a highly efficient semi-analytical approach. The solution of the temperature field in connection with a three dimensional moving heat source is achieved by using the method of Green’s functions. By employing the method of Green’s functions, it is possible to reduce the numerical effort significantly. The results of this modelling approach are compared to temperature, hardness as well as residual stress measurements, obtained from synchrotron X-ray diffraction, for welded sheets to clarify the accuracy of the applied model.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.mtla.2018.08.010} (DOI). Herrnring, J.; Staron, P.; Kashaev, N.; Klusemann, B.: Multiscale process simulation of residual stress fields of laser beam welded precipitation hardened AA6082. In: Materialia. Vol. 3 (2018) 243 - 255. (DOI:  /10.1016/j.mtla.2018.08.010)}}
@article{enz_influence_of_2018, 
author={Enz, J. and Lolos, C. and Riekehr, S. and Ventzke, V. and Kashaev, N.},
title={Influence of different Al-Cu substrates on the properties of laser metal deposited Al coatings},
year={2018},
journal = {Procedia CIRP},
volume = {74},
pages = {127 - 130},
doi = {10.1016/j.procir.2018.08.060},
abstract = {The application of coatings to structures is generally done in order to locally tailor properties. For this purpose, powder-based laser metal deposition (LMD) can be utilized. The resulting properties of the coatings are not only affected by the LMD process parameters, but also by the substrate material. In this regard, the chemical composition as well as its initial microstructure of the substrate has a significant influence. In the present study two Al-Cu alloy substrates, 2139 and 2198, are used for the LMD of pure Al powder. The resulting coatings possess clearly different properties, although the same process parameters are used.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.procir.2018.08.060} (DOI). Enz, J.; Lolos, C.; Riekehr, S.; Ventzke, V.; Kashaev, N.: Influence of different Al-Cu substrates on the properties of laser metal deposited Al coatings. In: Procedia CIRP. Vol. 74 (2018) 127 - 130. (DOI:  /10.1016/j.procir.2018.08.060)}}
@article{reimann_refilling_termination_2017, 
author={Reimann, M. and Goebel, J. and Gartner, T.M. and dos Santos, J.F.},
title={Refilling termination hole in AA 2198–T851 by refill friction stir spot welding
},
year={2017},
journal = {Journal of Materials Processing Technology},
volume = {245},
pages = {157 - 166},
doi = {http://dx.doi.org/10.1016/j.jmatprotec.2017.02.025},
abstract = {Friction stir welding features a joining technology with only few drawbacks. The exit hole inevitably left by the tool is a major disadvantage. In order to eliminate volume defects such as termination holes or voids in friction stir welds, refill friction stir spot welding was used for keyhole repair. The keyhole closure process was employed to 3 mm thick sheets of aluminum-lithium alloy AA 2198-T851. Exit holes with a diameter of 7.5 mm in semi–stationary shoulder bobbin tool friction stir welds were refilled successfully.
To characterize the refilling process characteristic process parameters such as position, force and torque of the tool parts have been monitored. The welds have been analyzed with regards to microstructural features, the local and global mechanical performance as well as the thermal cycle. The properties of the repair welds have been compared to friction stir welded butt joints and keyhole closure welds in bare sheet.
A systematic investigation comparing and combining the two friction based processes has shown that refill friction stir spot welding is able to be applied as keyhole closure technique in sheet material and in semi–stationary shoulder bobbin tool friction stir welds. Defect free welds with known microstructural features were achieved. The mechanical performance of keyhole closure welds using refill friction stir spot welding in semi–stationary shoulder bobbin tool friction stir welds is comparable to the performance of keyhole closure welds in bare sheets. High-strength keyhole closure welds with efficiencies of 78 % in terms of ultimate tensile strength were achieved.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.jmatprotec.2017.02.025} (DOI). Reimann, M.; Goebel, J.; Gartner, T.M.; dos Santos, J.F.: Refilling termination hole in AA 2198–T851 by refill friction stir spot welding
. In: Journal of Materials Processing Technology. Vol. 245 (2017) 157 - 166. (DOI:  10.1016/j.jmatprotec.2017.02.025)}}
@article{schneider_fully_periodic_2017, 
author={Schneider, K. and Klusemann, B. and Bargmann, S.},
title={Fully periodic RVEs for technological relevant composites: not worth the effort!},
year={2017},
journal = {Journal of Mechanics of Materials and Structures},
volume = {12},
number = {4},
pages = {471 - 484},
doi = {http://dx.doi.org/10.2140/jomms.2017.12.471},
abstract = {The setup of a finite element model for homogenization featuring a fully periodic geometry and a fully periodic mesh topology in combination with a high quality discretization is a cumbersome task and might significantly reduce the overall efficiency in multiscale finite element simulations.

In this work, we examine multiple methodologies of setting up finite element models for homogenization purposes that extenuate these difficulties. Approaches resulting in periodic and nonperiodic representative volume element topologies in the microstructural generation process are introduced. Furthermore, we review and analyze various types of boundary conditions that either enforce periodicity or do not require periodicity of the underlying discretization. Approximate periodic boundary conditions are discussed in detail.

The benchmark study proves that a fully periodic topology and mesh discretization with periodic boundary conditions is not necessary in order to identify effective macroscopic material parameters for technologically relevant composites.},
note = {Online available at: \url{http://dx.doi.org/10.2140/jomms.2017.12.471} (DOI). Schneider, K.; Klusemann, B.; Bargmann, S.: Fully periodic RVEs for technological relevant composites: not worth the effort!. In: Journal of Mechanics of Materials and Structures. Vol. 12 (2017) 4, 471 - 484. (DOI:  10.2140/jomms.2017.12.471)}}
@article{froend_fiber_laser_2017, 
author={Froend, M. and Fomin, F. and Riekehr, S. and Alvarez, P. and Zubiri, F. and Bauer, S. and Klusemann, B. and Kashaev, N.},
title={Fiber laser welding of dissimilar titanium (Ti-6Al-4V/cp-Ti) T-joints and their laser forming process for aircraft application},
year={2017},
journal = {Optics and Laser Technology},
volume = {96},
pages = {123 - 131},
doi = {http://dx.doi.org/10.1016/j.optlastec.2017.05.017},
abstract = {The weldability of dissimilar T-joints between commercially pure titanium (cp-Ti) Grade 2 skin and Ti-6Al-4V Grade 5 stringer using a continuous wave 8 kW ytterbium fiber laser as well as the possibility of subsequent laser straightening process of these joints were investigated. Based on the industrial standards ISO 4578:2011 and AWS D17.1:200, process development to compensate inherent angular distortion after welding by laser heating with the same equipment as for welding was carried out. The obtained results were effectively transferred to a 6-stringer-demonstrator with a length up to 500 mm. To investigate the shape and morphology of the welding seam as well as to verify its freedom from defects using the defined process parameters, metallographic transverse cross-sections and X-ray analyses were realized. In addition, the behavior of the welding seam geometry and the bending behavior of the specimens for varied process parameters were elucidated. For the welding process special attention to the shielding conditions and to the local and angular laser beam positioning was payed. To straighten the welded joints, laser straightening parameters inducing no microstructural changes were identified.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.optlastec.2017.05.017} (DOI). Froend, M.; Fomin, F.; Riekehr, S.; Alvarez, P.; Zubiri, F.; Bauer, S.; Klusemann, B.; Kashaev, N.: Fiber laser welding of dissimilar titanium (Ti-6Al-4V/cp-Ti) T-joints and their laser forming process for aircraft application. In: Optics and Laser Technology. Vol. 96 (2017) 123 - 131. (DOI:  10.1016/j.optlastec.2017.05.017)}}
@article{lemos_residual_stress_2017, 
author={Lemos, G.V.B. and Nunes, R.M. and Doll, P. and Bergmann, L. and Strohaecker, T.R. and dos Santos, J.F.},
title={Residual Stress Evaluation in Friction Stir Welds of Inconel 625 - Avaliacao das Tensoes Residuais em Juntas Soldadas de Inconel 625 Obtidas Atraves da Soldagem por Friccao e Mistura Mecanica
},
year={2017},
journal = {Soldagem & Inspecao},
volume = {22},
number = {1},
pages = {35 - 45},
doi = {http://dx.doi.org/10.1590/0104-9224/si2201.05},
abstract = {The use of noble materials is a basic requirement in applications where an aggressive environment such as offshore industry and nuclear energy. In this scenario, the Inconel 625 is often used as clad material in rigid pipes. Thus, nickel superalloys play a fundamental role in the deepwater exploration fields and, therefore, understanding of modern welding methods applied to these alloys and their consequences in the residual stress states is very important. Hence, this work evaluates the residual stress distributions after Friction Stir Welding (FSW) applied on Inconel 625 sheets. FSW was performed with tool rotational speed in the range of 200 to 1200 rpm and welding speed constant. Measurements of superficial residual stresses were investigated by X-ray Diffraction. In addition, macrostructures and heat input were evaluated. Although there are only few reports related to FSW applied on Inconel alloys, probably due to this welding process difficulty, it has been regarded that there is cumulative application of a solid state welding as an excellent alternative for nickel superalloys. The results showed that different welding parameters produced distinctly welded joints and consequently changes in the residual stress distributions. Finally, an increase in the tool rotation speed increased the residual stress in the stir zone.

A utilização de materiais nobres é requisito básico em aplicações onde existe um ambiente agressivo como na indústria do petróleo e nuclear. Neste panorama, a liga Inconel 625 é frequentemente utilizada como material de cladeamento no revestimento interno de dutos rígidos. Assim, as superligas de níquel exercem papel fundamental nos campos de exploração de águas profundas e, por isso, o conhecimento de métodos modernos de soldagem aplicados a estas ligas e suas consequências nos estados de tensões residuais é importante. Portanto, o presente trabalho faz uma avaliação das tensões residuais após a Soldagem por Fricção e Mistura Mecânica (SFMM) em chapas soldadas de Inconel 625. A união das chapas foi realizada com rotação da ferramenta 200 e 1200 rpm e velocidade de soldagem constante (1mm/s). As medições de tensões residuais na superfície das juntas soldadas foram investigadas através da técnica de difração de raios-X. Além disso, foram avaliadas as macroestruturas e o aporte térmico de acordo com os parâmetros de soldagem empregados. Embora não existam muitos trabalhos relacionados ao processo SFMM para ligas de Inconel, provavelmente devido à sua dificuldade de soldagem, tem sido percebido um aumento na aplicação da soldagem no estado sólido como excelente alternativa para as superligas à base de níquel. Os resultados mostraram que diferentes parâmetros de processo produziram juntas soldadas distintas e, consequentemente, variações na distribuição de tensões residuais. Por fim, um aumento na velocidade de rotação da ferramenta ocasionou um aumento nas tensões residuais na zona de mistura.},
note = {Online available at: \url{http://dx.doi.org/10.1590/0104-9224/si2201.05} (DOI). Lemos, G.V.B.; Nunes, R.M.; Doll, P.; Bergmann, L.; Strohaecker, T.R.; dos Santos, J.F.: Residual Stress Evaluation in Friction Stir Welds of Inconel 625 - Avaliacao das Tensoes Residuais em Juntas Soldadas de Inconel 625 Obtidas Atraves da Soldagem por Friccao e Mistura Mecanica
. In: Soldagem & Inspecao. Vol. 22 (2017) 1, 35 - 45. (DOI:  10.1590/0104-9224/si2201.05)}}
@article{santana_process_optimization_2017, 
author={Santana, L.M. and Suhuddin, U.F.H. and Oelscher, M.H. and Strohaecker, T.R. and dos Santos, J.F.},
title={Process Optimization and Microstructure Analysis in Refill Friction Stir Spot Welding of 3-mm-thick Al-Mg-Si Aluminum Alloy},
year={2017},
journal = {The International Journal of  Advanced Manufacturing Technology},
volume = {92},
number = {9-12},
pages = {4213 - 4220},
doi = {http://dx.doi.org/10.1007/s00170-017-0432-9},
abstract = {Novel ultra-high-strength aluminum alloys provide enormous lightweighting potential for modern car body design. However, joining such alloys can be challenging. Refill friction stir spot welding is a solid state joining process that provides fundamental advantages compared to conventional joining technologies when welding aluminum alloys. This work presents refill friction stirspot welding for joining3-mm-thick Al-Mg-Si alloys. The welded joints have been optimized for shear load condition by the design of experiment and analysis of variance. The results show that it is possible to obtain welds of relatively thick Al-Mg-Si alloys with good mechanical properties. Microstructure analyses show that rotational speed and plunge depth play important rolesin the bonded width and hook height, which affect the mechanical performance of the joint.},
note = {Online available at: \url{http://dx.doi.org/10.1007/s00170-017-0432-9} (DOI). Santana, L.M.; Suhuddin, U.F.H.; Oelscher, M.H.; Strohaecker, T.R.; dos Santos, J.F.: Process Optimization and Microstructure Analysis in Refill Friction Stir Spot Welding of 3-mm-thick Al-Mg-Si Aluminum Alloy. In: The International Journal of  Advanced Manufacturing Technology. Vol. 92 (2017) 9-12, 4213 - 4220. (DOI:  10.1007/s00170-017-0432-9)}}
@article{wilmers_interface_elasticity_2017, 
author={Wilmers, J. and McBride, A. and Bargmann, S.},
title={Interface Elasticity Effects in Polymer-Filled Nanoporous Metals},
year={2017},
journal = {Journal of the Mechanics and Physics of Solids},
volume = {99},
pages = {163 - 177},
doi = {http://dx.doi.org/10.1016/j.jmps.2016.11.011},
abstract = {A continuum formulation for electroactive composites made from nanoporous gold and ion-conducting polymer is proposed. A novel extension of surface elasticity theory is developed to account for the high surface-to-volume ratio of nanoporous gold, and to capture the chemoelectromechanical coupling that occurs on the interface between the metal and the polymer. This continuum formulation accounts for the fully non-linear behaviour exhibited by the composite.

The balance of linear momentum, Gauß's flux theorem and a relation for the transport of charge carriers are introduced in the bulk material as well as on the interface to describe the non-linear multiphysics and highly coupled response of the actuator. The resulting system of non-linear equations is solved using the finite element method. A series of numerical examples is presented to elucidate the theory.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.jmps.2016.11.011} (DOI). Wilmers, J.; McBride, A.; Bargmann, S.: Interface Elasticity Effects in Polymer-Filled Nanoporous Metals. In: Journal of the Mechanics and Physics of Solids. Vol. 99 (2017) 163 - 177. (DOI:  10.1016/j.jmps.2016.11.011)}}
@article{elsner_surface_excess_2017, 
author={Elsner, B.A.M. and Mueller, S. and Bargmann, S. and Weissmueller, J.},
title={Surface excess elasticity of gold: Ab initio coefficients and impact on the effective elastic response of nanowires},
year={2017},
journal = {Acta Materialia},
volume = {124},
pages = {468 - 477},
doi = {10.1016/j.actamat.2016.10.066},
abstract = {Predicting the influence of the surface on the effective elastic properties of nanoscale structures and nanomaterials remains a challenge, which we here address on both levels, continuum and atomic. Density Functional Theory (DFT) computation at the atomic level yields the first reliable surface excess elastic parameters for the (111) and (001) surfaces of gold. At the continuum level, we derive closed-form expressions for the effective elastic behavior that can be combined with the DFT-derived excess elastic parameters to obtain the effective axial, torsion, and bending stiffness of circular nanowires with surface excess elasticity. The two approaches use different reference frames, and we emphasize the need for consistent stress definitions and for conversion between the separate stress measures when transferring results between the approaches. We present excess elastic parameters separately for Cauchy and 2nd Piola-Kirchhoff stresses, demonstrating that the conversion substantially modifies their numerical value and may even invert their sign. The results afford an assessment of the contribution of the surface excess elastic parameters to the effective elastic response of nanoscale beams or wires. This assessment sheds doubt on earlier suggestions relating experimental observations of an effective stiffening or softening at small size to the excess elasticity of clean surfaces.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.actamat.2016.10.066} (DOI). Elsner, B.A.M.; Mueller, S.; Bargmann, S.; Weissmueller, J.: Surface excess elasticity of gold: Ab initio coefficients and impact on the effective elastic response of nanowires. In: Acta Materialia. Vol. 124 (2017) 468 - 477. (DOI:  /10.1016/j.actamat.2016.10.066)}}
@article{schimmack_hysteresis_analysis_2017, 
author={Schimmack, M. and Feistauer, E.E. and Amancio-Filho, S.T. and Mercorelli, P.},
title={Hysteresis Analysis and Control of a Metal-Polymer Hybrid Soft Actuator
},
year={2017},
journal = {Energies},
volume = {10},
number = {4},
pages = {508},
doi = {http://dx.doi.org/10.3390/en10040508},
abstract = {The number of applications of stimulus-responsive polymers is growing at an impressive rate. The motivation of this contribution is to use a commercially available low-budget silver-coated polyamide (PA6) as a thermo-responsive metal-polymer hybrid soft actuator. Polyamide is a hygroscopic polymer; therefore, its mechanical and physical-chemical properties are affected by exposition to humidity or immersion in water. The effect of water absorption content on the PA6 and silver-coated PA6 monofilament properties, such as mass change and resistance, were evaluated. Moreover, the influence of swelling and shrinking effects on the surface morphology, caused by variations of moisture and water immersion, was investigated. Based on these variations, the dynamics of the resistance of the hybrid material were analyzed in the context of the proposed hysteresis model. An identification procedure of the hysteresis is presented along with an approximation of the upper and lower bound based on a constrained least square approach. A switching logic algorithm for this hybrid dynamic system is introduced, which makes it possible to structure the non-linear function in a switching mode. Finally, a non-linear integral sliding manifold is proposed and tested to control the resulting force of the actuator.hysteresis model. An identification procedure of the hysteresis is presented along with an approximation of the upper and lower bound based on a constrained least square approach. A switching logic algorithm for this hybrid dynamic system is introduced, which makes it possible to structure the non-linear function in a switching mode. Finally, a non-linear integral sliding manifold is proposed and tested to control the resulting force of the actuator.},
note = {Online available at: \url{http://dx.doi.org/10.3390/en10040508} (DOI). Schimmack, M.; Feistauer, E.E.; Amancio-Filho, S.T.; Mercorelli, P.: Hysteresis Analysis and Control of a Metal-Polymer Hybrid Soft Actuator
. In: Energies. Vol. 10 (2017) 4, 508. (DOI:  10.3390/en10040508)}}
@article{nazarenko_closedform_formulas_2017, 
author={Nazarenko, L. and Bargmann, S. and Stolarski, H.},
title={Closed-form formulas for the effective properties of random particulate nanocomposites with complete Gurtin–Murdoch model of material surfaces},
year={2017},
journal = {Continuum Mechanics and Thermodynamics},
volume = {29},
number = {1},
pages = {77 - 96},
doi = {http://dx.doi.org/10.1007/s00161-016-0521-2},
abstract = {The objective of this work is to present an approach allowing for inclusion of the complete Gurtin–Murdoch material surface equations in methods leading to closed-form formulas defining effective properties of particle-reinforced nanocomposites. Considering that all previous developments of the closed-form formulas for effective properties employ only some parts of the Gurtin–Murdoch model, its complete inclusion constitutes the main focus of this work. To this end, the recently introduced new notion of the energy-equivalent inhomogeneity is generalized to precisely include all terms of the model. The crucial aspect of that generalization is the identification of the energy associated with the last term of the Gurtin–Murdoch equation, i.e., with the surface gradient of displacements. With the help of that definition, the real nanoparticle and its surface possessing its own distinct elastic properties and residual stresses are replaced by an energy-equivalent inhomogeneity with properties incorporating all surface effects. Such equivalent inhomogeneity can then be used in combination with any existing homogenization method. In this work, the method of conditional moments is used to analyze composites with randomly dispersed spherical nanoparticles. Closed-form expressions for effective moduli are derived for both bulk and shear moduli. As numerical examples, nanoporous aluminum is investigated. The normalized bulk and shear moduli of nanoporous aluminum as a function of residual stresses are analyzed and evaluated in the context of other theoretical predictions.},
note = {Online available at: \url{http://dx.doi.org/10.1007/s00161-016-0521-2} (DOI). Nazarenko, L.; Bargmann, S.; Stolarski, H.: Closed-form formulas for the effective properties of random particulate nanocomposites with complete Gurtin–Murdoch model of material surfaces. In: Continuum Mechanics and Thermodynamics. Vol. 29 (2017) 1, 77 - 96. (DOI:  10.1007/s00161-016-0521-2)}}
@article{schnabel_accessing_colony_2017, 
author={Schnabel, J.E. and Bargmann, S.},
title={Accessing Colony Boundary Strengthening of Fully Lamellar TiAl Alloys via Micromechanical Modeling},
year={2017},
journal = {Materials},
volume = {10},
number = {8},
pages = {896},
doi = {http://dx.doi.org/10.3390/ma10080896},
abstract = {In this article, we present a strategy to decouple the relative influences of colony, domain and lamella boundary strengthening in fully lamellar titanium aluminide alloys, using a physics-based crystal plasticity modeling strategy. While lamella and domain boundary strengthening can be isolated in experiments using polysynthetically twinned crystals or mircomechanical testing, colony boundary strengthening can only be investigated in specimens in which all three strengthening mechanisms act simultaneously. Thus, isolating the colony boundary strengthening Hall–Petch coefficient K C KC experimentally requires a sufficient number of specimens with different colony sizes λ C λC but constant lamella thickness λ L λL and domain size λ D λD , difficult to produce even with sophisticated alloying techniques. The here presented crystal plasticity model enables identification of the colony boundary strengthening coefficient K C KC as a function of lamella thickness λ L λL . The constitutive description is based on the model of a polysynthetically twinned crystal which is adopted to a representative volume element of a fully lamellar microstructure. In order to capture the micro yield and subsequent micro hardening in weakly oriented colonies prior to macroscopic yield, the hardening relations of the adopted model are revised and calibrated against experiments with polysynthetically twinned crystals for plastic strains up to 15%.},
note = {Online available at: \url{http://dx.doi.org/10.3390/ma10080896} (DOI). Schnabel, J.E.; Bargmann, S.: Accessing Colony Boundary Strengthening of Fully Lamellar TiAl Alloys via Micromechanical Modeling. In: Materials. Vol. 10 (2017) 8, 896. (DOI:  10.3390/ma10080896)}}
@article{schnabel_freeedge_stress_2017, 
author={Schnabel, J.E. and Yousfi, M. and Mittelstedt, C. and },
title={Free-edge stress fields in cylindrically curved symmetric and unsymmetric cross-ply laminates under bending load},
year={2017},
journal = {Composite Structures},
volume = {180},
pages = {862 - 875},
doi = {10.1016/j.compstruct.2017.08.002},
abstract = {In this paper, an analysis method for the determination of displacement, strain and stress fields in cylindrically curved cross-ply laminates under bending load is presented. The considered cross-ply laminates may be either symmetrically or unsymmetrically laminated and are clamped at one end while the other end is loaded by an evenly distributed bending moment. The analysis method employs a layerwise plane strain approach in the inner regions of the laminate in which the stresses in each layer are represented by adequate formulations for Airy’s stress function. In the regions of the free laminate edges where significant three-dimensional and possibly singular interlaminar stress fields are to be expected, the plane-strain approach is upgraded by a layerwise displacement-based formulation wherein the physical laminate layers are discretized into a number of mathematical layers with respect to the thickness direction. The governing differential equations for the unknown additional displacement functions with respect to the width coordinate in the form of the Euler-Lagrange equations stemming from the underlying variational statement can be solved exactly and eventually lead to an eigenvalue problem that needs to be solved numerically. Usage of continuity conditions between the individual laminate layers and formulation of adequate boundary conditions at the free edges in an integral sense then lead to complete representations for displacements, strains and stresses at every location in the considered laminate. While the analysis approach relies on a discretization of the laminate into a number of mathematical layers with respect to the thickness direction and further requires a numerical solution of a quadratic eigenvalue problem, it provides closed-form analytical solutions concerning the width direction and can thus be classified as being a semi-analytical solution. The presented analysis method is compared to the results of comparative finite element simulations and is shown to be in good agreement, however with only a fraction of the computational effort that is required for according finite element simulations.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.compstruct.2017.08.002} (DOI). Schnabel, J.E.; Yousfi, M.; Mittelstedt, C.; : Free-edge stress fields in cylindrically curved symmetric and unsymmetric cross-ply laminates under bending load. In: Composite Structures. Vol. 180 (2017) 862 - 875. (DOI:  /10.1016/j.compstruct.2017.08.002)}}
@article{dieringa_ultrasound_assisted_2017, 
author={Dieringa, H. and Katsarou, L. and Buzolin, R. and Szakacs, G. and Horstmann, M. and Wolff, M. and Mendis, C. and Vorozhtsov, S. and John, D.St.},
title={Ultrasound Assisted Casting of an AM60 Based Metal Matrix Nanocomposite, Its Properties, and Recyclability
},
year={2017},
journal = {Metals},
volume = {7},
number = {10},
pages = {388},
doi = {http://dx.doi.org/10.3390/met7100388},
abstract = {An AM60 magnesium alloy nanocomposite reinforced with 1 wt % of AlN nanoparticles was prepared using an ultrasound (US) assisted permanent-mould indirect-chill casting process. Ultrasonically generated cavitation and acoustic streaming promoted de-agglomeration of particle clusters and distributed the particles throughout the melt. Significant grain refinement due to nucleation on the AlN nanoparticles was accompanied by an exceptional improvement in properties: yield strength increased by 103%, ultimate tensile strength by 115%, and ductility by 140%. Although good grain refinement was observed, the large nucleation undercooling of 14 K limits further refinement because nucleation is prevented by the formation of a nucleation-free zone around each grain. To assess the industrial applicability and recyclability of the nanocomposite material in various casting processes, tests were performed to determine the effect of remelting on the microstructure. With each remelting, a small percentage of effective AlN nanoparticles was lost, and some grain growth was observed. However, even after the third remelting, excellent strength and ductility was retained. According to strengthening models, enhanced yield strength is mainly attributed to Hall-Petch strengthening caused by the refined grain size. A small additional contribution to strengthening is attributed to Orowan strengthening.},
note = {Online available at: \url{http://dx.doi.org/10.3390/met7100388} (DOI). Dieringa, H.; Katsarou, L.; Buzolin, R.; Szakacs, G.; Horstmann, M.; Wolff, M.; Mendis, C.; Vorozhtsov, S.; John, D.St.: Ultrasound Assisted Casting of an AM60 Based Metal Matrix Nanocomposite, Its Properties, and Recyclability
. In: Metals. Vol. 7 (2017) 10, 388. (DOI:  10.3390/met7100388)}}
@article{hanke_comparative_study_2017, 
author={Hanke, S. and dos Santos, J.F.},
title={Comparative study of severe plastic deformation at elevated temperatures of two aluminium alloys during friction surfacing},
year={2017},
journal = {Journal of Materials Processing Technology},
volume = {247},
pages = {257 - 267},
doi = {http://dx.doi.org/10.1016/j.jmatprotec.2017.04.021},
abstract = {Aluminium alloys 5083 and 6082 were deposited by Friction Surfacing (FS) under the same process conditions. Process characteristics including torque and forces, temperatures and the deposit microstructure were compared. The observed differences are discussed with regard to material strength, thermal softening rate and recrystallization mechanisms.
AA 6082 plasticises faster, reaching ≈30 K higher temperatures, thicker and wider coatings and a higher material efficiency. The specific energy required for plastification is in the same order of magnitude as the activation energy for self-diffusion, emphasising the influence of dynamic recrystallization (DRX) mechanisms. A tendency for lower grain size and larger variations in grain boundary misorientation observed for AA 5083 points towards a shift in the steady-state DRX balance towards dislocation generation, due to the higher Mg content of this alloy. This corresponds to the lower process speeds required for AA 5083. AA 6082 may undergo more localized shear because of its high thermal softening rate and additional loss of strength through dissolution of Mg2Si with increasing temperature. This may contribute to a higher energy and material efficiency for plastification and deposition of AA 6082 by FS.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.jmatprotec.2017.04.021} (DOI). Hanke, S.; dos Santos, J.F.: Comparative study of severe plastic deformation at elevated temperatures of two aluminium alloys during friction surfacing. In: Journal of Materials Processing Technology. Vol. 247 (2017) 257 - 267. (DOI:  10.1016/j.jmatprotec.2017.04.021)}}
@article{kashaev_microstructure_and_2017, 
author={Kashaev, N. and Pugachev, D. and Ventzke, V. and Fomin, F. and Burkhardt, I. and Enz, J. and Riekehr, S.},
title={Microstructure and mechanical performance of autogenously fibre laser beam welded Ti-6242 butt joints},
year={2017},
journal = {Materials Science and Engineering  A},
volume = {694},
pages = {110 - 120},
doi = {http://dx.doi.org/10.1016/j.msea.2017.03.115},
abstract = {This work deals with the effects of laser beam power, focus position and advance speed on the geometry, microstructure and mechanical properties such as the tensile strength and microhardness of autogenously fibre laser beam welded Ti-6Al-2Sn-4Zr-2Mo (denoted as Ti-6242) butt joints used for high temperature applications. The Ti-6242 sheet employed here is characterized by a globular (α+β) microstructure. Laser beam welded butt joints consisted of a martensitic fusion zone, inhomogeneous heat affected zones and equiaxed base materials. The microhardness increased from 330 HV 0.3 in base material to 430 HV 0.3 in fusion zone due to the martensitic transformation. Butt joints showed the base material level of strength in tensile test. The local increase in microhardness provided a shielding effect that protected the Ti-6242 butt joint against mechanical damage during the static tensile load test. The predicted critical total underfill depth that does not reduce the tensile strength of the weld was determined to be 25% of the specimen thickness.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.msea.2017.03.115} (DOI). Kashaev, N.; Pugachev, D.; Ventzke, V.; Fomin, F.; Burkhardt, I.; Enz, J.; Riekehr, S.: Microstructure and mechanical performance of autogenously fibre laser beam welded Ti-6242 butt joints. In: Materials Science and Engineering  A. Vol. 694 (2017) 110 - 120. (DOI:  10.1016/j.msea.2017.03.115)}}
@article{zocollerborba_on_the_2017, 
author={Zocoller Borba, N. and Afonso, C.R.M. and Blaga, L. and dos Santos, J.F. and Canto, L.B. and Amancio-Filho, S.T.},
title={On the Process-Related Rivet Microstructural Evolution, Material Flow and Mechanical Properties of Ti-6Al-4V/GFRP Friction-Riveted Joints},
year={2017},
journal = {Materials},
volume = {10},
number = {2},
pages = {184},
doi = {10.3390/ma10020184},
abstract = {In the current work, process-related thermo-mechanical changes in the rivet microstructure, joint local and global mechanical properties, and their correlation with the rivet plastic deformation regime were investigated for Ti-6Al-4V (rivet) and glass-fiber-reinforced polyester (GF-P) friction-riveted joints of a single polymeric base plate. Joints displaying similar quasi-static mechanical performance to conventional bolted joints were selected for detailed characterization. The mechanical performance was assessed on lap shear specimens, whereby the friction-riveted joints were connected with AA2198 gussets. Two levels of energy input were used, resulting in process temperatures varying from 460 ± 130 °C to 758 ± 56 °C and fast cooling rates (178 ± 15 °C/s, 59 ± 15 °C/s). A complex final microstructure was identified in the rivet. Whereas equiaxial α-grains with β-phase precipitated in their grain boundaries were identified in the rivet heat-affected zone, refined α′ martensite, Widmanstätten structures and β-fleck domains were present in the plastically deformed rivet volume. The transition from equiaxed to acicular structures resulted in an increase of up to 24% in microhardness in comparison to the base material. A study on the rivet material flow through microtexture of the α-Ti phase and β-fleck orientation revealed a strong effect of shear stress and forging which induced simple shear deformation. By combining advanced microstructural analysis techniques with local mechanical testing and temperature measurement, the nature of the complex rivet plastic deformational regime could be determined.},
note = {Online available at: \url{https://dx.doi.org/10.3390/ma10020184} (DOI). Zocoller Borba, N.; Afonso, C.R.M.; Blaga, L.; dos Santos, J.F.; Canto, L.B.; Amancio-Filho, S.T.: On the Process-Related Rivet Microstructural Evolution, Material Flow and Mechanical Properties of Ti-6Al-4V/GFRP Friction-Riveted Joints. In: Materials. Vol. 10 (2017) 2, 184. (DOI:  /10.3390/ma10020184)}}
@article{hanke_degradation_mechanisms_2017, 
author={Hanke, S. and Lemos, G.V.B. and Bergmann, L. and Martinazzi, D. and dos Santos, J.F. and Strohaecker, T.R.},
title={Degradation mechanisms of pcBN tool material during Friction Stir Welding of Ni-base alloy 625},
year={2017},
journal = {Wear},
volume = {A346-A377},
pages = {403 - 408},
doi = {http://dx.doi.org/10.1016/j.wear.2017.01.070},
abstract = {In Friction Stir Welding (FSW), interactions between the plasticized stirred material and the tool significantly affect resulting weld properties. When welding metals with high strength and melting point, the tribological load on the tool is severe, and poses the main limiting factor for the technology's industrial exploitation. Since tool materials are loaded to their limits, it is essential to understand the interactions of specific tool material and welded metal combinations.
In the present study 3.2 mm alloy 625 sheets were joined using a pcBN tool with W-Re binder phase. Wear lead to a change in tool geometry followed by tool fracture. In SEM investigations the welds revealed typical banded structures, composed of small grains and non-metallic phases containing W from the tool material. The tool surface is extensively covered by adhering sheet metal. Further, BN grain pull-outs and appearances of diffusive wear are visible on the worn tool surface.
Tool wear is mainly caused by detachment of BN grains due to thermal softening of the metallic binder phase and dissolution of BN in the hot material in the stirred zone. Using low rotational speeds resulting in lower process temperatures reduces tool wear and results in a homogeneous stirred zone.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.wear.2017.01.070} (DOI). Hanke, S.; Lemos, G.V.B.; Bergmann, L.; Martinazzi, D.; dos Santos, J.F.; Strohaecker, T.R.: Degradation mechanisms of pcBN tool material during Friction Stir Welding of Ni-base alloy 625. In: Wear . Vol. A346-A377 (2017) 403 - 408. (DOI:  10.1016/j.wear.2017.01.070)}}
@article{kashaev_effects_of_2017, 
author={Kashaev, N. and Ventzke, V. and Horstmann, M. and Chupakhin, S. and Riekehr, S. and Falck, R. and Maawad, E. and Staron, P. and Schell, N. and Huber, N.},
title={Effects of laser shock peening on the microstructure and fatigue crack propagation behaviour of thin AA2024 specimens},
year={2017},
journal = {International Journal of Fatigue},
volume = {98},
pages = {223 - 233},
doi = {http://dx.doi.org/10.1016/j.ijfatigue.2017.01.042},
abstract = {Laser shock peening (LSP) was performed on aluminium alloy AA2024 with a thickness of 2.0 mm. Microstructural studies using the electron back scatter diffraction (EBSD) technique were performed to quantify the micro-texture changes in the material through LSP. A residual stress analysis was performed using synchrotron radiation and a hole drilling technique. Fatigue crack propagation (FCP) tests were performed to investigate the retardation effect of LSP residual stresses. Load versus crack opening displacement curves were analysed to obtain the corrected values of load opening levels considering the effects of the residual stresses. Specimens with the LSP treatment reveal a significant retardation of the FCP. The presence of compressive residual stresses caused the crack closure effect, which increased the level of crack opening load and therefore reduced the effective load range. An original methodology to consider LSP-induced residual stresses on the FCP behaviour was proposed.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.ijfatigue.2017.01.042} (DOI). Kashaev, N.; Ventzke, V.; Horstmann, M.; Chupakhin, S.; Riekehr, S.; Falck, R.; Maawad, E.; Staron, P.; Schell, N.; Huber, N.: Effects of laser shock peening on the microstructure and fatigue crack propagation behaviour of thin AA2024 specimens. In: International Journal of Fatigue. Vol. 98 (2017) 223 - 233. (DOI:  10.1016/j.ijfatigue.2017.01.042)}}
@article{ngo_on_the_2017, 
author={Ngo, B.-N.D. and Roschning, B. and Albe, K. and Weissmueller, J. and Markmann, J.},
title={On the origin of the anomalous compliance of dealloying-derived nanoporous gold},
year={2017},
journal = {Scripta Materialia},
volume = {130},
pages = {74 - 77},
doi = {http://dx.doi.org/10.1016/j.scriptamat.2016.11.006},
abstract = {The origin of the anomalously compliant behavior of nanoporous gold is studied by comparing the elasticity obtained from molecular dynamics (MD) and finite element method (FEM) simulations. Both models yield a compliance, which is much higher than the predictions of the Gibson-Ashby scaling relation for metal foams and thus confirm the influence of other microstructural features besides the porosity. The linear elastic FEM simulation also yields a substantially stiffer response than the MD simulation, which reveals that nonlinear elastic behavior contributes decisively to the anomalous compliance of nanoporous gold at small structure size.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.scriptamat.2016.11.006} (DOI). Ngo, B.-N.D.; Roschning, B.; Albe, K.; Weissmueller, J.; Markmann, J.: On the origin of the anomalous compliance of dealloying-derived nanoporous gold. In: Scripta Materialia. Vol. 130 (2017) 74 - 77. (DOI:  10.1016/j.scriptamat.2016.11.006)}}
@article{krekeler_silverrich_clusters_2017, 
author={Krekeler, T. and Strasser, A.V. and Graf, M. and Wang, K. and Hartig, C. and Ritter, M. and Weissmueller, J.},
title={Silver-rich clusters in nanoporous gold},
year={2017},
journal = {Materials Research Letters},
volume = {5},
number = {5},
pages = {314 - 321},
doi = {http://dx.doi.org/10.1080/21663831.2016.1276485},
abstract = {High-resolution elemental mapping in a transmission electron microscope shows that the residual silver in dealloying-made nanoporous gold (NPG) is aggregated in nanoscale clusters. Kinetic Monte Carlo simulation confirms that these regions are buried relics of the master alloy that have never been exposed to corrosion. The surface of as-dealloyed NPG is covered by at least one atomic monolayer of nearly pure gold. The preferential location of silver in the bulk is relevant when interfaces control the material's function, as in catalysis and sensing. Annealing in air homogenizes the alloy by surface diffusion.},
note = {Online available at: \url{http://dx.doi.org/10.1080/21663831.2016.1276485} (DOI). Krekeler, T.; Strasser, A.V.; Graf, M.; Wang, K.; Hartig, C.; Ritter, M.; Weissmueller, J.: Silver-rich clusters in nanoporous gold. In: Materials Research Letters. Vol. 5 (2017) 5, 314 - 321. (DOI:  10.1080/21663831.2016.1276485)}}
@article{husser_size_affected_2017, 
author={Husser, E. and Soyarslan, C. and Bargmann, S.},
title={Size affected dislocation activity in crystals: Advanced surface and grain boundary conditions},
year={2017},
journal = {Extreme Mechanics Letters},
volume = {13},
pages = {36 - 41},
doi = {http://dx.doi.org/10.1016/j.eml.2017.01.007},
abstract = {Extended crystal plasticity theories are well established to study size-dependent hardening of metals. Surface and inner grain boundary conditions play a significant role for crystals at small scales as they affect the dislocation activity and, hence, alter strength and strain hardening behavior. Conventional micro boundary conditions, i.e., microhard and microfree, are unable to capture the underlying physics as they describe ideal and over-simplified surface/interface conditions. In this work, advanced boundary conditions for gradient extended crystal plasticity are introduced to map realistic conditions at external surfaces, interphases, or grain boundaries. They relate the magnitude of plastic slip to surface defect density and slip directions with respect to the surface normal. Characteristic features are highlighted, including the effect of surface yielding and size dependent surface strengthening.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.eml.2017.01.007} (DOI). Husser, E.; Soyarslan, C.; Bargmann, S.: Size affected dislocation activity in crystals: Advanced surface and grain boundary conditions. In: Extreme Mechanics Letters. Vol. 13 (2017) 36 - 41. (DOI:  10.1016/j.eml.2017.01.007)}}
@article{kashaev_fiber_laser_2017, 
author={Kashaev, N. and Pugachev, D. and Riekehr, S. and Ventzke, V.},
title={Fiber Laser Beam Welding of Ti-6242 - Effect of Processing Parameters on Microstructural and Mechanical Properties
},
year={2017},
journal = {Materials Science Forum, THERMEC 2016},
volume = {879},
pages = {903 - 908},
doi = {http://dx.doi.org/10.4028/www.scientific.net/MSF.879.903},
abstract = {The present work investigates the effects of laser beam power, focus position and advance speed on the geometry, microstructure and mechanical properties of fiber laser beam welded Ti-6Al-2Sn-4Zr-2Mo (denoted as Ti-6242) butt joints used for high temperature applications. Detailed microstructural and mechanical studies were performed on welds produced using optimized parameters (a laser beam power of 5 kW, a focus position of 0.0 mm and an advance speed of 6.2 m/min). The Ti-6242 base material is characterized by a globular (α+β) microstructure. The heat input during laser beam welding led to the formation of a martensitic α’-phase fusion zone. The heat affected zone consisted of globular grains and acicular crystallites. These local transformations were connected with a change in the micro-texture, average grain size and β-phase content. Furthermore, the microhardness increased from 330 HV 0.3 to 450 HV 0.3 due to the martensitic transformation. The mechanical behavior of the laser beam welded Ti-6242 butt joint loaded in tension was determined by the properties of the Ti-6242 base material. The local increase in hardness provided a shielding effect that protected the Ti-6242 butt joint against mechanical damage.},
note = {Online available at: \url{http://dx.doi.org/10.4028/www.scientific.net/MSF.879.903} (DOI). Kashaev, N.; Pugachev, D.; Riekehr, S.; Ventzke, V.: Fiber Laser Beam Welding of Ti-6242 - Effect of Processing Parameters on Microstructural and Mechanical Properties
. In: Materials Science Forum, THERMEC 2016. Vol. 879 (2017) 903 - 908. (DOI:  10.4028/www.scientific.net/MSF.879.903)}}
@article{goushegir_influence_of_2017, 
author={Goushegir, S.M. and dos Santos, J.F. and Amancio-Filho, S.T.},
title={Influence of aluminum surface pre-treatments on the bonding mechanisms and mechanical performance of metal-composite single-lap joints},
year={2017},
journal = {Welding in the world},
volume = {61},
number = {6},
pages = {1099 - 1115},
doi = {http://dx.doi.org/10.1007/s40194-017-0509-y},
abstract = {The use of frictional heat for joining thermoplastic-based materials to metals has grown in importance in recent years. Friction spot joining is a relatively new joining technology suitable to join metal-polymer and composite overlap structures. In this work, the influence of various aluminum surface pre-treatments on the bonding mechanisms and mechanical performance of single-lap shear and cross-tensile joints was studied. Mechanical, chemical, and electrochemical pre-treatments were applied to the aluminum surface prior to the joining process. All surface pre-treatments increased the joint strength to some extent, compared with specimens without surface pre-treatments. Some of the treatments (chemical and electrochemical) led to the formation of strong chemical bonding between the aluminum and composite. Phosphoric acid anodizing with additional primer layer showed the best performance in increasing the joint’s strength. The reason was the strong bond formation between the primer layer and the matrix of the composite during the joining cycle. Moreover, the morphology and chemical composition of the aluminum after surface pre-treatments were analyzed in detail to study the correlation between bonding mechanisms and the mechanical performance of the joints. Finally, fracture surface of the joints was analyzed optically and by SEM, demonstrating parts of the composite remained attached to the aluminum after failure.},
note = {Online available at: \url{http://dx.doi.org/10.1007/s40194-017-0509-y} (DOI). Goushegir, S.M.; dos Santos, J.F.; Amancio-Filho, S.T.: Influence of aluminum surface pre-treatments on the bonding mechanisms and mechanical performance of metal-composite single-lap joints. In: Welding in the world. Vol. 61 (2017) 6, 1099 - 1115. (DOI:  10.1007/s40194-017-0509-y)}}
@article{fitseva_influence_of_2017, 
author={Fitseva, V. and Hanke, S. and dos Santos, J.F.},
title={Influence of rotational speed on process characteristics in friction surfacing of Ti-6Al-4V
},
year={2017},
journal = {Materials and Manufacturing Processes},
volume = {32},
number = {5},
pages = {557 - 563},
doi = {http://dx.doi.org/10.1080/10426914.2016.1257799},
abstract = {Friction surfacing process is employed to deposit metallic coatings, whereby similar and dissimilar material combinations can be realized. The process can be applied as a local repair technology, or the coating material can locally modify the surfaces. One advantage of this process is that the coatings are deposited in solid state without reaching the melting range of materials, thereby avoiding dilution with the substrate. The involved severe plastic deformation under high temperatures alters the microstructure of the coating material, leaving it fully dynamically recrystallized. The current work focuses on deposition of Ti-6Al-4V coatings. For that material, the process parameter rotational speed plays a major role in the material’s response during processing. Two different regimes with a threshold at 2000 min−1 exist, upon which the flow behavior of Ti-6Al-4V significantly differs, affecting among others the coating dimensions. Microstructural analysis reveals that the material is deformed in a high temperature β phase, and the high cooling rates (46.4 Ks−1) lead to martensitic transformation. The β grain size differs in the low and high rotational speed regimes. This study shows that metallurgical processes play an important role in friction surfacing, since they influence all relevant process characteristics, including microstructure, material efficiency and process forces.},
note = {Online available at: \url{http://dx.doi.org/10.1080/10426914.2016.1257799} (DOI). Fitseva, V.; Hanke, S.; dos Santos, J.F.: Influence of rotational speed on process characteristics in friction surfacing of Ti-6Al-4V
. In: Materials and Manufacturing Processes. Vol. 32 (2017) 5, 557 - 563. (DOI:  10.1080/10426914.2016.1257799)}}
@article{okulov_dealloyingbased_interpenetratingphase_2017, 
author={Okulov, I.V. and Weissmueller, J. and Markmann, J.},
title={Dealloying-based interpenetrating-phase nanocomposites matching the elastic behavior of human bone
},
year={2017},
journal = {Scientific Reports},
volume = {7},
pages = {20},
doi = {http://dx.doi.org/10.1038/s41598-017-00048-4},
abstract = {The long-term performance of orthopedic implants depends crucially on a close match between the mechanical behavior of bone and of the implant material. Yet, the present man-made materials with the required biocompatibility and strength are substantially stiffer than bone. This mismatch results in stress shielding, which can lead to the loss of bone mass and may even lead to a revision surgery. Here we report a new materials design strategy towards metal-polymer composites that are based on constituents with established biocompatibility and that can be matched to bone. Ti-based nanoporous alloys, prepared by liquid-metal dealloying, are infiltrated with epoxy to form interpenetrating-phase nanocomposites. At up to 260 MPa, their yield strength is technologically interesting for a deformable light-weight material. More importantly, Young’s modulus can be adjusted between 4.4 and 24 GPa, which affords matching to bone. As another parallel to bone, the strength of the composite materials is strain-rate dependent. These findings suggest that the novel composite materials may provide the basis for promising future implant materials.},
note = {Online available at: \url{http://dx.doi.org/10.1038/s41598-017-00048-4} (DOI). Okulov, I.V.; Weissmueller, J.; Markmann, J.: Dealloying-based interpenetrating-phase nanocomposites matching the elastic behavior of human bone
. In: Scientific Reports. Vol. 7 (2017) 20. (DOI:  10.1038/s41598-017-00048-4)}}
@article{okulov_composition_optimization_2017, 
author={Okulov, I.V. and Volegov, A.S. and Attar, H. and Boenisch, M. and Ehtemam-Haghighi, S. and Calin, M. and Eckert, J.},
title={Composition optimization of low modulus and high-strength TiNb-based alloys for biomedical applications},
year={2017},
journal = {Journal of the Mechanical Behavior of Biomedical Materials},
volume = {65},
pages = {866 - 871},
doi = {http://dx.doi.org/10.1016/j.jmbbm.2016.10.013},
abstract = {The effect of chemical composition on microstructure and tensile properties of a series of low modulus Ti-Nb-Cu-Ni-Al alloys was studied. These alloys consist of primary micrometer-sized β-Ti dendrites surrounded by intermetallic phases. The morphology of the intermetallic phases is strongly affected by composition. Due to the composite microstructure, the alloys exhibit a low Young's modulus (77–84 GPa) together with a high yield strength of about 1000 MPa as well as moderate tensile ductility. The results demonstrate that complete substitution of Al by Ti reduces the Young's modulus by 5%. Increasing Nb content at the expense of Ti causes a significant improvement of tensile ductility.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.jmbbm.2016.10.013} (DOI). Okulov, I.V.; Volegov, A.S.; Attar, H.; Boenisch, M.; Ehtemam-Haghighi, S.; Calin, M.; Eckert, J.: Composition optimization of low modulus and high-strength TiNb-based alloys for biomedical applications. In: Journal of the Mechanical Behavior of Biomedical Materials. Vol. 65 (2017) 866 - 871. (DOI:  10.1016/j.jmbbm.2016.10.013)}}
@article{husser_the_role_2017, 
author={Husser, E. and Bargmann, S.},
title={The Role of Geometrically Necessary Dislocations in Cantilever Beam Bending Experiments of Single Crystals},
year={2017},
journal = {Materials},
volume = {10},
number = {3},
pages = {289},
doi = {10.3390/ma10030289},
abstract = {The mechanical behavior of single crystalline, micro-sized copper is investigated in the context of cantilever beam bending experiments. Particular focus is on the role of geometrically necessary dislocations (GNDs) during bending-dominated load conditions and their impact on the characteristic bending size effect. Three different sample sizes are considered in this work with main variation in thickness. A gradient extended crystal plasticity model is presented and applied in a three-dimensional finite-element (FE) framework considering slip system-based edge and screw components of the dislocation density vector. The underlying mathematical model contains non-standard evolution equations for GNDs, crystal-specific interaction relations, and higher-order boundary conditions. Moreover, two element formulations are examined and compared with respect to size-independent as well as size-dependent bending behavior. The first formulation is based on a linear interpolation of the displacement and the GND density field together with a full integration scheme whereas the second is based on a mixed interpolation scheme. While the GND density fields are treated equivalently, the displacement field is interpolated quadratically in combination with a reduced integration scheme. Computational results indicate that GND storage in small cantilever beams strongly influences the evolution of statistically stored dislocations (SSDs) and, hence, the distribution of the total dislocation density. As a particular example, the mechanical bending behavior in the case of a physically motivated limitation of GND storage is studied. The resulting impact on the mechanical bending response as well as on the predicted size effect is analyzed. Obtained results are discussed and related to experimental findings from the literature.},
note = {Online available at: \url{https://dx.doi.org/10.3390/ma10030289} (DOI). Husser, E.; Bargmann, S.: The Role of Geometrically Necessary Dislocations in Cantilever Beam Bending Experiments of Single Crystals. In: Materials. Vol. 10 (2017) 3, 289. (DOI:  /10.3390/ma10030289)}}
@article{goebel_semistationary_shoulder_2017, 
author={Goebel, J. and Reimann, M. and Norman, A. and dos Santos, J.F.},
title={Semi-stationary shoulder bobbin tool friction stir welding of AA2198-T851
},
year={2017},
journal = {Journal of Materials Processing Technology},
volume = {245},
pages = {37 - 45},
doi = {http://dx.doi.org/10.1016/j.jmatprotec.2017.02.011},
abstract = {The aluminum lithium alloy AA2198-T851 has been bobbin tool friction stir welded using a tool concept with one stationary and one rotating shoulder. Defect free welds in 3 mm thick sheet have been produced featuring a high quality surface finish on the stationary side. The macrostructure forms an asymmetrical shape with microstructural characteristics known from standard friction stir welding. Because of only one rotating side a material flow direction towards the stationary shoulder has been observed. A parameter survey shows that a weld pitch of one mm per rotation combined with high pressure between the shoulders lead to good results. Mechanical performance of 82% of base metal ultimate tensile strength and 77% of base metal hardness have been achieved. The fracture analysis indicates two competing fracture modes, one being in the heat affected zone and the other at the borderline of the stirred zone on the advancing side. The first mode forms due to thermal cycle influence, whereas the second location suffers from weak bonding as a result of the thermal cycle and experienced deformation.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.jmatprotec.2017.02.011} (DOI). Goebel, J.; Reimann, M.; Norman, A.; dos Santos, J.F.: Semi-stationary shoulder bobbin tool friction stir welding of AA2198-T851
. In: Journal of Materials Processing Technology. Vol. 245 (2017) 37 - 45. (DOI:  10.1016/j.jmatprotec.2017.02.011)}}
@article{jiao_deformation_mechanisms_2017, 
author={Jiao, J. and Huber, N.},
title={Deformation mechanisms in nanoporous metals: Effect of ligament shape and disorder
},
year={2017},
journal = {Computational Materials Science},
volume = {127},
pages = {194 - 203},
doi = {http://dx.doi.org/10.1016/j.commatsci.2016.10.035},
abstract = {The current work presents a numerical modelling approach for investigating the effect of ligament shape and disorder on the macroscopic mechanical response of nanoporous gold (NPG). The approach starts from a ‘single ligament’ analysis with respect to three fundamental deformation modes, bending, torsion, and compression, that depend on the ligament shape. It can be shown that the predictive capability of the highly computationally efficient beam model is sufficient for a large variation in ligament shapes. Using a representative volume element (RVE) composed of such ligaments, different degrees of disorder are included. For both the single ligament and RVE models, the cylindrical beam serves as a common reference to compare the results when varying the ligament shape. From the comparison of the RVE elastic response with the single ligament results and the further analysis of statistical information from the elements in the RVE, it is found that bending is the major deformation mode for perfectly ordered RVEs, whereas torsion gains importance for increasing RVE disorder. The effect of compression of the ligaments can be neglected in general. It is concluded that the transition to torsion deformation due to disorder is the cause of the strongly reduced lateral expansion during compression deformation of NPG.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.commatsci.2016.10.035} (DOI). Jiao, J.; Huber, N.: Deformation mechanisms in nanoporous metals: Effect of ligament shape and disorder
. In: Computational Materials Science. Vol. 127 (2017) 194 - 203. (DOI:  10.1016/j.commatsci.2016.10.035)}}
@article{suhuddin_microstructure_evolution_2017, 
author={Suhuddin, U.F.H. and Fischer, V. and Kostka, A. and dos Santos, J.F.},
title={Microstructure evolution in refill friction stir spot weld of a dissimilar Al–Mg alloy to Zn-coated steel},
year={2017},
journal = {Science and Technology of Welding and Joining},
volume = {22},
number = {8},
pages = {658 - 665},
doi = {http://dx.doi.org/10.1080/13621718.2017.1300744},
abstract = {In the present study, dissimilar welds of an Al–Mg–Mn alloy and a Zn-coated high-strength low-alloy steel were welded by refill friction stir spot welding. The maximum shear load recorded was approximately 7.8 kN, obtained from the weld produced with a 1600 rev min−1 tool rotational speed. Microstructural analyses showed the formation of a solid–liquid structure of an Al solid solution in Mg–Al-rich Zn liquid, which gives rise to the formation of Zn-rich Al region and microfissuring in some regions during welding. Exposure of steel surface to Mg–Al-rich Zn liquid led to the formation of Fe2Al5 and Fe4Al13 intermetallics. The presence of defective Zn-rich Al regions and Fe–Al intermetallics at the faying surface affects the weld strength.},
note = {Online available at: \url{http://dx.doi.org/10.1080/13621718.2017.1300744} (DOI). Suhuddin, U.F.H.; Fischer, V.; Kostka, A.; dos Santos, J.F.: Microstructure evolution in refill friction stir spot weld of a dissimilar Al–Mg alloy to Zn-coated steel. In: Science and Technology of Welding and Joining. Vol. 22 (2017) 8, 658 - 665. (DOI:  10.1080/13621718.2017.1300744)}}
@article{lemos_progress_in_2017, 
author={Lemos, G.V.B. and Hanke, S. and dos Santos, J.F. and Bergmann, L. and Reguly, A. and Strohaecker, T.R.},
title={Progress in friction stir welding of Ni alloys},
year={2017},
journal = {Science and Technology of Welding and Joining},
volume = {22},
number = {8},
pages = {643 - 657},
doi = {http://dx.doi.org/10.1080/13621718.2017.1288953},
abstract = {In recent years, interest has been increasing in application of Nickel alloys in the oil industry. For subsea engineering, the possibility to weld high-strength materials in an effective manner is essential. Friction Stir Welding (FSW) is alternative to join several materials retaining their properties or even improving them. This fact is relevant for Corrosion-Resistant Alloys (CRA) used in deep-water exploitation of hydrocarbons. Publications up to now have focused on FSW of Inconel® series as alloy 600, 625, and 718. To provide a solid basis for development, this review discusses the crucial points for FSW. The tool materials are described, as well as the joint microstructure and properties achieved. Furthermore, the basics of the corrosion resistance and the early corrosion studies of FSW joints are presented. It is concluded that FSW is a promising process for Ni alloys, but depends on upcoming research regarding tool technology and corrosion investigations.},
note = {Online available at: \url{http://dx.doi.org/10.1080/13621718.2017.1288953} (DOI). Lemos, G.V.B.; Hanke, S.; dos Santos, J.F.; Bergmann, L.; Reguly, A.; Strohaecker, T.R.: Progress in friction stir welding of Ni alloys. In: Science and Technology of Welding and Joining. Vol. 22 (2017) 8, 643 - 657. (DOI:  10.1080/13621718.2017.1288953)}}
@article{okulov_microtonanoscale_deformation_2017, 
author={Okulov, I.V. and Boenisch, M. and Volegov, A.S. and Shakur Shahabi, H. and Wendrock, H. and Gemming, T. and Eckert, J.},
title={Micro-to-nano-scale deformation mechanism of a Ti-based dendritic-ultrafine eutectic alloy exhibiting large tensile ductility},
year={2017},
journal = {Materials Science and Engineering  A},
volume = {682},
pages = {673 - 678},
doi = {http://dx.doi.org/10.1016/j.msea.2016.11.082},
abstract = {Deformation mechanism of a new Ti-16.6Nb-6Co-5.1Cu-6.5Al (at%) alloy is studied using scanning and transmission electron microscopy. The alloy consists of micrometer-sized β-Ti dendrites and an ultrafine-eutectic composed of β-Ti and TiCo phases. The yield strength of the alloy (1.1 GPa) is comparable to that of the metallic glass composites and is coupled with large tensile ductility of about 11%. Transmission electron microscopy analysis reveals that slip lines formed during deformation in the dendrites penetrates the eutectic resulting in formation of a stepped interface and an extra area serving to accommodate shear strains. The β-Ti eutectic component can deform plastically to a high degree supporting deformation of TiCo. The results suggest that microstructural design of the eutectic is important for controlling tensile ductility of dendritic-ultrafine eutectic alloys.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.msea.2016.11.082} (DOI). Okulov, I.V.; Boenisch, M.; Volegov, A.S.; Shakur Shahabi, H.; Wendrock, H.; Gemming, T.; Eckert, J.: Micro-to-nano-scale deformation mechanism of a Ti-based dendritic-ultrafine eutectic alloy exhibiting large tensile ductility. In: Materials Science and Engineering  A. Vol. 682 (2017) 673 - 678. (DOI:  10.1016/j.msea.2016.11.082)}}
@article{wang_local_flow_2017, 
author={Wang, K. and Hartig, C. and Blankenburg, M. and Mueller, M. and Guenther, R. and Weissmueller, J.},
title={Local flow stresses in interpenetrating-phase composites based on nanoporous gold — In situ diffraction},
year={2017},
journal = {Scripta Materialia},
volume = {127},
pages = {151 - 155},
doi = {http://dx.doi.org/10.1016/j.scriptamat.2016.09.026},
abstract = {We report a synchrotron in situ diffraction experiment exploring stress evolution during compression of interpenetrating-phase nanocomposites based on nanoporous gold and polymer. While previous experiments provided indirect indication of local flow conditions based on macroscopic effective flow stress and micromechanics models such as Gibson-Ashby scaling law, the lattice parameter data of our experiment access the flow stress directly. At small structure size we find excellent agreement with previous reports, supporting the match between material and model of those studies. Yet, deviations at larger structure size suggest that coarsening generates defects in metal network structure that are ignored by standard models.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.scriptamat.2016.09.026} (DOI). Wang, K.; Hartig, C.; Blankenburg, M.; Mueller, M.; Guenther, R.; Weissmueller, J.: Local flow stresses in interpenetrating-phase composites based on nanoporous gold — In situ diffraction. In: Scripta Materialia. Vol. 127 (2017) 151 - 155. (DOI:  10.1016/j.scriptamat.2016.09.026)}}
@article{bachmann_numerical_simulation_2017, 
author={Bachmann, M. and Carstensen, J. and Bergmann, L. and dos Santos, J.F. and Wu, C.S. and Rethmeier, M.},
title={Numerical simulation of thermally induced residual stresses in friction stir welding of aluminum alloy 2024-T3 at different welding speeds},
year={2017},
journal = {The International Journal of  Advanced Manufacturing Technology},
volume = {91},
number = {1-4},
pages = {1443 - 1452},
doi = {http://dx.doi.org/10.1007/s00170-016-9793-8},
abstract = {The paper deals with a numerical finite element simulation of the residual stress evolution in friction stir welding of 6 mm thick aluminum alloy AA2024-T3. The transient thermal field during the welding process was calculated with the commercial code COMSOL Multiphysics 5.0. Therefore, a thermal-pseudo-mechanical (TPM) heat source was implemented. A subsequent mechanical simulation was performed with varying hardening models for different welding speeds of 60 and 300 mm/min. The influence of softening of the material, which was due to hardening precipitation dissolution associated to the heating, was also investigated. Experiments in terms of thermocouple measurements as well as Vickers hardness and X-ray measurements of the residual stresses were conducted and compared to numerically obtained results. A qualitatively as well as quantitatively good agreement was found for different applied welding speeds.},
note = {Online available at: \url{http://dx.doi.org/10.1007/s00170-016-9793-8} (DOI). Bachmann, M.; Carstensen, J.; Bergmann, L.; dos Santos, J.F.; Wu, C.S.; Rethmeier, M.: Numerical simulation of thermally induced residual stresses in friction stir welding of aluminum alloy 2024-T3 at different welding speeds. In: The International Journal of  Advanced Manufacturing Technology. Vol. 91 (2017) 1-4, 1443 - 1452. (DOI:  10.1007/s00170-016-9793-8)}}
@article{ma_a_continuum_2017, 
author={Ma, S. and Yuan, H.},
title={A continuum damage model for multi-axial low cycle fatigue of porous sintered metals based on the critical plane concept},
year={2017},
journal = {Mechanics of Materials},
volume = {104},
pages = {13 - 25},
doi = {http://dx.doi.org/10.1016/j.mechmat.2016.09.013},
abstract = {Experimental investigations reveal very different damage mechanisms in porous sintered metals from those of conventional dense materials. Interactions between the inherent porosity and heterogeneous matrix result in complicated deformation behavior and fatigue damage processes. In the present work, the damage evolution in the sintered metal under multi-axial cyclic loading conditions is studied experimentally and computationally. The total damage is divided into the stress-related elastic damage, the plastic damage induced by the plastic deformations and the fatigue damage driven by cyclic loading. To predict the cyclic deformation behavior as well as the fatigue damage evolution, a nonlinear fatigue damage model coupled with the critical plane concept is proposed, embedded into the Ohno–Wang cyclic plasticity and implemented into the FEM software ABAQUS based on an implicit integration algorithm. The proposed damage model is computationally and experimentally verified under multi-axial cyclic loading paths with different strain amplitudes. A good agreement between experimental and computational results shows that the present model is able to describe cyclic mechanical behavior and fatigue damage of porous metals.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.mechmat.2016.09.013} (DOI). Ma, S.; Yuan, H.: A continuum damage model for multi-axial low cycle fatigue of porous sintered metals based on the critical plane concept. In: Mechanics of Materials. Vol. 104 (2017) 13 - 25. (DOI:  10.1016/j.mechmat.2016.09.013)}}
@article{enz_mechanical_properties_2017, 
author={Enz, J. and Kumar, M. and Riekehr, S. and Ventzke, V. and Huber, N. and Kashaev, N.},
title={Mechanical properties of laser beam welded similar and dissimilar aluminum alloys},
year={2017},
journal = {Journal of Manufacturing Processes},
volume = {29},
pages = {272 - 280},
doi = {10.1016/j.jmapro.2017.07.030},
abstract = {Two approaches were used for laser beam welding of similar and dissimilar joints of AA7075 and AA5182 that aim to overcome the weldability problems of high-strength Al-Zn-Mg-Cu alloys. The first approach implies the use of vanadium foil as additional filler material, while the second implies the use of a fiber laser with a large beam diameter and a top-hat beam profile. Although both approaches result in an improved weld quality, in terms of weld appearance, porosity and cracking, the resulting mechanical properties differ considerably. The addition of vanadium leads to a local increase of microhardness in the fusion zone. However, the tensile strength of these joints is lower as for fiber laser welded joints. In direct comparison fiber laser welded joints exhibit also higher formability as the joints welded with vanadium foil. The highest formability is obtained for dissimilar joints with the medium-strength Al-Mg alloy. Due to the unavoidable softening in the weld zone of heat treatable aluminum alloys, the formability of the joints is inferior in comparison to the base materials. In addition, the positive effect of post-weld heat treatment, surface milling and warm forming on the resulting mechanical properties of similar and dissimilar joints is discussed.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.jmapro.2017.07.030} (DOI). Enz, J.; Kumar, M.; Riekehr, S.; Ventzke, V.; Huber, N.; Kashaev, N.: Mechanical properties of laser beam welded similar and dissimilar aluminum alloys. In: Journal of Manufacturing Processes. Vol. 29 (2017) 272 - 280. (DOI:  /10.1016/j.jmapro.2017.07.030)}}
@article{vacchi_effect_of_2017, 
author={Vacchi, G.S. and Plaine, A.H. and Silva, R. and Sordi, V.L. and Suhuddin, U.F.H. and Alcantara, N.G. and Kuri, S.E. and Rovere, C.A.D. and },
title={Effect of friction spot welding (FSpW) on the surface corrosion behavior of overlapping AA6181-T4/Ti-6Al-4V joints},
year={2017},
journal = {Materials and Design},
volume = {131},
pages = {127 - 134},
doi = {10.1016/j.matdes.2017.06.005},
abstract = {The microstructural, mechanical and corrosion behavior of the surface of an AA6181-T4 aluminum alloy overlap welded onto Ti-6Al-4V titanium alloy by friction spot welding (FSpW) was analyzed based on optical microscopy (OM), scanning electron microscopy (SEM), microhardness and potentiodynamic polarization techniques. The results indicated that the FSpW process modified the microstructure of the AA6181-T4 aluminum alloy, as indicated mainly by the size, type and quantity of precipitates in various welding regions. The microhardness tests showed similar hardness values in the stir zone (SZ) and base metal (BM), which was ascribed to the breakdown and homogenization of precipitates in the SZ. On the other hand, the heat affected zone (HAZ) showed the lowest hardness, which was attributed to the coalescence of Mg2Si precipitates caused by the thermal cycle of the welding process. The potentiodynamic polarization tests indicated that the SZ showed the highest pitting potential due to the refined microstructure in this zone. SEM images recorded after potentiodynamic polarization testing indicated that preferential sites for pitting nucleation were regions adjacent to the Al (Fe, Si, Mn, Mg) precipitates, and the mildest corrosive attack was found in the SZ.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.matdes.2017.06.005} (DOI). Vacchi, G.S.; Plaine, A.H.; Silva, R.; Sordi, V.L.; Suhuddin, U.F.H.; Alcantara, N.G.; Kuri, S.E.; Rovere, C.A.D.; : Effect of friction spot welding (FSpW) on the surface corrosion behavior of overlapping AA6181-T4/Ti-6Al-4V joints. In: Materials and Design. Vol. 131 (2017) 127 - 134. (DOI:  /10.1016/j.matdes.2017.06.005)}}
@article{chupakhin_artificial_neural_2017, 
author={Chupakhin, S. and Kashaev, N. and Klusemann, B. and Huber, N.},
title={Artificial neural network for correction of effects of plasticity in equibiaxial residual stress profiles measured by hole drilling},
year={2017},
journal = {The Journal of Strain Analysis for Engineering Design},
volume = {52},
number = {3},
pages = {137 - 151},
doi = {10.1177/0309324717696400},
abstract = {The hole drilling method is a widely known technique for the determination of non-uniform residual stresses in metallic structures by measuring strain relaxations at the material surface caused through the stress redistribution during drilling of the hole. The integral method is a popular procedure for solving the inverse problem of determining the residual stresses from the measured surface strain. It assumes that the residual stress can be approximated by step-wise constant values, and the material behaves elastically so that the superposition principle can be applied. Required calibration data are obtained from finite element simulations, assuming linear elastic material behavior. That limits the method to the measurement of residual stresses well below the yield strength. There is a lack of research regarding effects caused by residual stresses approaching the yield strength and high through-thickness stress gradients as well as the correction of the resulting errors. However, such high residual stresses are often introduced in various materials by processes such as laser shock peening, for example, to obtain life extension of safety relevant components. The aim of this work is to investigate the limitations of the hole drilling method related to the effects of plasticity and to develop an applicable and efficient method for stress correction, capable of covering a wide range of stress levels. For this reason, an axisymmetric model was used for simulating the hole drilling process in ABAQUS involving plasticity. Afterward, the integral method was applied to the relaxation strain data for determining the equibiaxial stress field. An artificial neural network has been used for solving the inverse problem of stress profile correction. Finally, AA2024-T3 specimens were laser peened and the measured stress fields were corrected by means of the trained network. To quantify the stress overestimation in the hole drilling measurement, an error evaluation has been conducted.},
note = {Online available at: \url{https://dx.doi.org/10.1177/0309324717696400} (DOI). Chupakhin, S.; Kashaev, N.; Klusemann, B.; Huber, N.: Artificial neural network for correction of effects of plasticity in equibiaxial residual stress profiles measured by hole drilling. In: The Journal of Strain Analysis for Engineering Design. Vol. 52 (2017) 3, 137 - 151. (DOI:  /10.1177/0309324717696400)}}
@article{mallmann_influence_of_2017, 
author={Mallmann, C. and Simar, A. and Ferrie, E. and Fivel, M. and Lilleodden, E.T.},
title={Influence of Y2O3 nanoparticles on the twinning of single crystalline magnesium},
year={2017},
journal = {Scripta Materialia},
volume = {138},
pages = {79 - 82},
doi = {10.1016/j.scriptamat.2017.05.016},
abstract = {The influence of Y2O3 nanoparticles introduced by Friction Stir Processing on the deformation of magnesium has been studied with microcompression testing of single-crystal pillars oriented favorably for tensile twinning. It was found that the nanoparticles lower the twin nucleation stress and affect the twin morphology, as well as mitigate the size effects usually observed in pure magnesium single-crystals. While single twin nucleation is consistently observed in pure magnesium pillars, multiple twins of identical variants are observed in the pillars with nanoparticles, having nucleated at the Y2O3 particles. Consequently, the resultant twin–twin boundaries lead to an effective hardening.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.scriptamat.2017.05.016} (DOI). Mallmann, C.; Simar, A.; Ferrie, E.; Fivel, M.; Lilleodden, E.T.: Influence of Y2O3 nanoparticles on the twinning of single crystalline magnesium. In: Scripta Materialia. Vol. 138 (2017) 79 - 82. (DOI:  /10.1016/j.scriptamat.2017.05.016)}}
@article{plaine_microstructure_and_2017, 
author={Plaine, A.H. and Suhuddin, U.F.H. and Alcantara, N.G. and dos Santos, J.F.},
title={Microstructure and mechanical behavior of friction spot welded AA6181-T4/Ti6Al4V dissimilar joints},
year={2017},
journal = {The International Journal of  Advanced Manufacturing Technology},
volume = {92},
number = {9-12},
pages = {3703 - 3714},
doi = {10.1007/s00170-017-0439-2},
abstract = {Friction spot welding has become an excellent alternative to produce dissimilar joints in a fast and reliable way. This paper investigates the microstructure and the mechanical behavior of friction spot welded AA6181-T4/Ti6Al4V dissimilar joints produced by two different tool rotational speeds, 2500 and 3000 rpm, previously demonstrated to be the welding parameter with the most influence on the mechanical performance of these joints. Temperature profiles indicated that tool rotational speed directly affects the process temperature and, consequently, the metallurgical reaction taking place at the joint interface. Higher temperatures (3000 rpm condition) resulted in a complex and cracked Ti/Al interface because of the local melting of the aluminum plate. In contrast, by decreasing the process temperature (2500 rpm condition), a continuous thin TiAl3 layer was observed, increasing the lap shear resistance of the joints. Moreover, the local Von Mises strain distribution of a sound joint under lap shear was successfully associated with the different stages of a typical force–displacement curve and used to elucidate the fracture evolution. Lastly, the fatigue behavior of the joints indicated that FSpW dissimilar welds exhibited a better performance than FSpW aluminum similar joints.},
note = {Online available at: \url{https://dx.doi.org/10.1007/s00170-017-0439-2} (DOI). Plaine, A.H.; Suhuddin, U.F.H.; Alcantara, N.G.; dos Santos, J.F.: Microstructure and mechanical behavior of friction spot welded AA6181-T4/Ti6Al4V dissimilar joints. In: The International Journal of  Advanced Manufacturing Technology. Vol. 92 (2017) 9-12, 3703 - 3714. (DOI:  /10.1007/s00170-017-0439-2)}}
@article{staron_in_situ_2017, 
author={Staron, P. and Liu, J. and Riekehr, S. and Schell, N. and Huber, N. and Kashaev, N. and Mueller, M. and Schreyer, A.},
title={In Situ Experiment for Laser Beam Welding of Ti Alloys Using High-Energy X-Rays},
year={2017},
journal = {Materials Science Forum, Mechanical Stress Evaluation by Neutrons and Synchrotron Radiation VIII},
volume = {905},
pages = {114 - 119},
doi = {10.4028/www.scientific.net/MSF.905.114},
abstract = {The laser beam welding (LBW) process has many advantages for industrial production; however, it still has to be optimized for two-phase Ti alloys. Phase transformations and residual stresses play a crucial role for welding these alloys. Specific questions about the development of phase content during fast heating with a laser and rapid cooling can only be addressed with time-resolved in-situ experiments, avoiding artefacts from quenching. Also the residual stress development during cooling depends on the occurring phase transformations. Thus, an LBW chamber employing a fibre laser was developed for use with high-energy X-rays from a synchrotron source. Bead-on-plate welding experiments with 2.5 mm thick samples were carried out at the HZG high-energy materials science beamline (HEMS) at DESY, Hamburg. The first experiments focused on the solid-solid phase transformations in a Ti-6Al-4V alloy. Moreover, residual stresses developing during cooling were studied.},
note = {Online available at: \url{https://dx.doi.org/10.4028/www.scientific.net/MSF.905.114} (DOI). Staron, P.; Liu, J.; Riekehr, S.; Schell, N.; Huber, N.; Kashaev, N.; Mueller, M.; Schreyer, A.: In Situ Experiment for Laser Beam Welding of Ti Alloys Using High-Energy X-Rays. In: Materials Science Forum, Mechanical Stress Evaluation by Neutrons and Synchrotron Radiation VIII. Vol. 905 (2017) 114 - 119. (DOI:  /10.4028/www.scientific.net/MSF.905.114)}}
@article{tier_the_weld_2017, 
author={Tier, M.D. and Rosendo, T.S. and Mazzaferro, J.A. and Mazzaferro, C.P. and dos Santos, J.F. and Strohaecker, T.R.},
title={The weld interface for friction spot welded 5052 aluminium alloy},
year={2017},
journal = {The International Journal of  Advanced Manufacturing Technology},
volume = {90},
number = {1-4},
pages = {267 - 276},
doi = {10.1007/s00170-016-9370-1},
abstract = {Friction Spot Welding (FSpW) is considered to be a competitive technique for producing high quality welds, especially in lightweight alloys. The geometric defects and features originating at the interface between the two welded sheets have an important influence on the mechanical performance of the joint. This work investigates the weld microstructure for FSpW in AA 5052 sheets produced using tool rotational speeds of 900, 1400 or 1900 rpm. OM and SEM were used to analyse the microstructural features of the weld. The mechanical performance was investigated using shear tensile testing, and the fracture mechanisms were assessed by SEM. Three distinct weld interfaces were observed and named as follows: primary bonding, partial bonding and secondary bonding. For welds processed at a lower tool rotational speed (900 rpm), the equivalent bonding ligament is increased, resulting in better joint mechanical performance.},
note = {Online available at: \url{https://dx.doi.org/10.1007/s00170-016-9370-1} (DOI). Tier, M.D.; Rosendo, T.S.; Mazzaferro, J.A.; Mazzaferro, C.P.; dos Santos, J.F.; Strohaecker, T.R.: The weld interface for friction spot welded 5052 aluminium alloy. In: The International Journal of  Advanced Manufacturing Technology. Vol. 90 (2017) 1-4, 267 - 276. (DOI:  /10.1007/s00170-016-9370-1)}}
@article{lopesdovale_influence_of_2017, 
author={Lopes do Vale, N. and Fitseva, V. and Hanke, S. and Urtiga Filho, S.L. and dos Santos, J.F.},
title={Influence of Rotational Speed in the Friction Surfacing of Titanium Grade 1 on Ti-6Al-4V},
year={2017},
journal = {Materials Research : Revista Brasileira de Materiais},
volume = {20},
number = {2},
pages = {830 - 835},
doi = {http://dx.doi.org/10.1590/1980-5373-mr-2016-1011},
abstract = {Titanium Grade 1 was deposited on Ti-6Al-4V, 2 mm thickness, by Friction Surfacing. The process parameters were rotational speed, deposition speed and consumption rate. Only the rotational speed was varied in order to evaluate the influence of this parameter on the coatings generated. The applicability of the process has been described for a large number of materials, although the depositions of titanium alloys are still not widely studied. The objective is to investigate the effects of the rotational speed on the coatings' geometry and microstructural evolution. This investigation has shown that Titanium Grade 1 coatings can be deposited onto a Ti-6Al-4V by Friction Surfacing depending on the rotational speed. The coatings' surface homogeneity was influenced by the rotational speed, being inhomogeneous for the lowest speed. The coatings' thickness and width increased with enhancing this speed. The heat affected zone in the substrate corresponded to the complete thickness under the depositions.},
note = {Online available at: \url{http://dx.doi.org/10.1590/1980-5373-mr-2016-1011} (DOI). Lopes do Vale, N.; Fitseva, V.; Hanke, S.; Urtiga Filho, S.L.; dos Santos, J.F.: Influence of Rotational Speed in the Friction Surfacing of Titanium Grade 1 on Ti-6Al-4V. In: Materials Research : Revista Brasileira de Materiais . Vol. 20 (2017) 2, 830 - 835. (DOI:  10.1590/1980-5373-mr-2016-1011)}}
@article{dorosario_the_stiffness_2017, 
author={do Rosario, J.J. and Berger, J.B. and Lilleodden, E.T. and McMeeking, R.M. and Schneider, G.A.},
title={The stiffness and strength of metamaterials based on the inverse opal architecture},
year={2017},
journal = {Extreme Mechanics Letters},
volume = {12},
pages = {86 - 96},
doi = {10.1016/j.eml.2016.07.006},
abstract = {The inverse opal architecture, a class of mechanical metamaterials recently shown to exhibit high specific strength and modulus, is further investigated here using carefully coupled experiments and finite element modeling. We demonstrate that this architecture can be exploited to achieve optimized specific strength and modulus, while simultaneously offering tunable optical bandgaps and large-area fabrication. Starting with a silica inverse opal structure and adding different thicknesses of titania (10–34 nm) the strength was gradually increased from 41 to 410 MPa and the elastic modulus from 1.7 to 8.3 GPa, within densities of 300–1000 kg m−3. Simulations confirmed that the inverse opal structure can outperform the state-of-the-art octet- and isotropic-truss designs in terms of Young’s, shear and bulk modulus, as well as in structural efficiency (total stiffness). Simulations also predict stresses in the titania coating and in the silica that are on the order of the theoretical tensile yield stresses at failure, indicating that size effects controlling defect population are responsible for the high strengths.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.eml.2016.07.006} (DOI). do Rosario, J.J.; Berger, J.B.; Lilleodden, E.T.; McMeeking, R.M.; Schneider, G.A.: The stiffness and strength of metamaterials based on the inverse opal architecture. In: Extreme Mechanics Letters. Vol. 12 (2017) 86 - 96. (DOI:  /10.1016/j.eml.2016.07.006)}}
@article{juarez_nanoporous_metals_2017, 
author={Juarez, T. and Biener, J. and Weissmueller, J. and Hodge, A.M.},
title={Nanoporous Metals with Structural Hierarchy: A Review},
year={2017},
journal = {Advanced Engineering Materials},
volume = {19},
number = {12},
pages = {1700389},
doi = {10.1002/adem.201700389},
abstract = {Nanoporous (np) metals have generated much interest since they combine several desirable material characteristics, such as high surface area, mechanical size effects, and high conductivity. Most of the research has been focused on np Au due to its relatively straightforward synthesis, chemical stability, and many promising applications in the fields of catalysis and actuation. Other materials, such as np-Cu, Ag, and Pd have also been studied. This review discusses recent advances in the field of np metals, focusing on new research areas that implement and leverage structural hierarchy while using np metals as their base structural constituents. First, we focus on single-element porous metals that are made of np metals at the fundamental level, but synthesized with additional levels of porosity. Second, we discuss the fabrication of composite structures, which use auxiliary materials to enhance the properties of np metals. Important applications of these hierarchical materials, especially in the fields of catalysis and electrochemistry, are also reviewed. Finally, we conclude with a discussion about future opportunities for the advancement and application of np metals.},
note = {Online available at: \url{https://dx.doi.org/10.1002/adem.201700389} (DOI). Juarez, T.; Biener, J.; Weissmueller, J.; Hodge, A.M.: Nanoporous Metals with Structural Hierarchy: A Review. In: Advanced Engineering Materials. Vol. 19 (2017) 12, 1700389. (DOI:  /10.1002/adem.201700389)}}
@article{luehrs_plastic_poissons_2017, 
author={Luehrs, L. and Zandersons, B. and Huber, N. and Weissmueller, J.},
title={Plastic Poisson’s Ratio of Nanoporous Metals: A Macroscopic Signature of Tension–Compression Asymmetry at the Nanoscale},
year={2017},
journal = {Nano Letters},
volume = {17},
number = {10},
pages = {6258 - 6266},
doi = {10.1021/acs.nanolett.7b02950},
abstract = {The suggestion, based on atomistic simulation, of a surface-induced tension−compression asymmetry of the strength and flow stress of small metal bodies so far lacks experimental confirmation. Here, we present the missing experimental evidence. We study the transverse plastic flow of nanoporous gold under uniaxial compression. Performing mechanical tests in electrolyte affords control over the surface state. Specifically, the surface tension, γ, can be varied in situ during plastic flow. We find that decreasing γ leads to an increase of the effective macroscopic plastic Poisson ratio, νP. Finite element simulations of a network with surface tension confirm the notion that νP of nanoporous gold provides a signature for a local tension–compression asymmetry of the nanoscale struts that form the network. We show that γ promotes compression while impeding tensile elongation. Because the transverse strain is partly carried by the elongation of ligaments oriented normal to the load axis, the surface-induced tension–compression asymmetry acts to reduce νP. Our experiment confirms a decisive contribution of the surface tension to small-scale plasticity.},
note = {Online available at: \url{https://dx.doi.org/10.1021/acs.nanolett.7b02950} (DOI). Luehrs, L.; Zandersons, B.; Huber, N.; Weissmueller, J.: Plastic Poisson’s Ratio of Nanoporous Metals: A Macroscopic Signature of Tension–Compression Asymmetry at the Nanoscale. In: Nano Letters. Vol. 17 (2017) 10, 6258 - 6266. (DOI:  /10.1021/acs.nanolett.7b02950)}}
@article{cheng_semiordered_hierarchical_2017, 
author={Cheng, C. and Luehrs, L. and Krekeler, T. and Ritter, M. and Weissmueller, J.},
title={Semiordered Hierarchical Metallic Network for Fast and Large Charge-Induced Strain},
year={2017},
journal = {Nano Letters},
volume = {17},
number = {8},
pages = {4774 - 4780},
doi = {10.1021/acs.nanolett.7b01526},
abstract = {Nanoporous metallic actuators for artificial muscle applications are distinguished by combining the low operating voltage, which is otherwise reserved for polymer-based actuators with interesting values of strain amplitude, strength, and stiffness that are comparable of those of piezoceramics. We report a nanoporous metal actuator with enhanced strain amplitude and accelerated switching. Our 3D macroscopic metallic muscle has semiordered and hierarchical nanoporous structure, in which μm-sized tubes align perpendicular with the sample surface, while nm-sized ligaments consist of the tube walls. This nanoarchitecture combines channels for fast ion transportation with large surface area for charge storage and strain generation. The result is a record reversible strain amplitude of 1.59% with a strain rate of 8.83 × 10–6 s–1 in the field of metallic based actuators. A passive hydroxide layer is self-grown on the metal surface, which not only contributes a supercapacitive layer, but also stabilizes the nanoporous structure against coarsening, which guarantees sustainable actuation beyond ten-thousand cycles.},
note = {Online available at: \url{https://dx.doi.org/10.1021/acs.nanolett.7b01526} (DOI). Cheng, C.; Luehrs, L.; Krekeler, T.; Ritter, M.; Weissmueller, J.: Semiordered Hierarchical Metallic Network for Fast and Large Charge-Induced Strain. In: Nano Letters. Vol. 17 (2017) 8, 4774 - 4780. (DOI:  /10.1021/acs.nanolett.7b01526)}}
@article{graf_nanoporous_gold_2017, 
author={Graf, M. and Roschning, B. and Weissmueller, J.},
title={Nanoporous Gold by Alloy Corrosion: Method-Structure-Property Relationships},
year={2017},
journal = {Journal of the Electrochemical Society},
volume = {164},
number = {4},
pages = {C194 - C200},
doi = {10.1149/2.1681704jes},
abstract = {Nanoporous gold (NPG) made by selective corrosion, or dealloying, serves as a model system for the investigation of electrochemical and mechanical properties of nanomaterials. While various dealloying protocols are in use, it is typically assumed that the structural characteristics are identical and independent of the preparation technique. Yet, reported properties such as strength, Young's modulus, or catalytic behavior can vary widely. Here, we compare the microstructure and the mechanical behavior of NPG structures prepared by three different synthesis protocols reported in the literature. We find that corrosion rates, the content of residual sacrificial metal, the average ligament size and the densification by shrinkage strongly depend on the synthesis protocol and show the consequences on the mechanical properties. We finally deduce different correlations between microstructure and composition for different dealloying routes.},
note = {Online available at: \url{https://dx.doi.org/10.1149/2.1681704jes} (DOI). Graf, M.; Roschning, B.; Weissmueller, J.: Nanoporous Gold by Alloy Corrosion: Method-Structure-Property Relationships. In: Journal of the Electrochemical Society. Vol. 164 (2017) 4,  C194 - C200. (DOI:  /10.1149/2.1681704jes)}}
@article{jalas_electrochemical_tuning_2017, 
author={Jalas, D. and Shao, L.-H. and Canchi, R. and Okuma, T. and Lang, S. and Petrov, A. and Weissmueller, J. and Eich, M.},
title={Electrochemical tuning of the optical properties of nanoporous gold},
year={2017},
journal = {Scientific Reports},
volume = {7},
pages = {44139},
doi = {10.1038/srep44139},
abstract = {Using optical in-situ measurements in an electrochemical environment, we study the electrochemical tuning of the transmission spectrum of films from the nanoporous gold (NPG) based optical metamaterial, including the effect of the ligament size. The long wavelength part of the transmission spectrum around 800 nm can be reversibly tuned via the applied electrode potential. The NPG behaves as diluted metal with its transition from dielectric to metallic response shifted to longer wavelengths. We find that the applied potential alters the charge carrier density to a comparable extent as in experiments on gold nanoparticles. However, compared to nanoparticles, a NPG optical metamaterial, due to its connected structure, shows a much stronger and more broadband change in optical transmission for the same change in charge carrier density. We were able to tune the transmission through an only 200 nm thin sample by 30%. In combination with an electrolyte the tunable NPG based optical metamaterial, which employs a very large surface-to-volume ratio is expected to play an important role in sensor applications, for photoelectrochemical water splitting into hydrogen and oxygen and for solar water purification.},
note = {Online available at: \url{https://dx.doi.org/10.1038/srep44139} (DOI). Jalas, D.; Shao, L.-H.; Canchi, R.; Okuma, T.; Lang, S.; Petrov, A.; Weissmueller, J.; Eich, M.: Electrochemical tuning of the optical properties of nanoporous gold. In: Scientific Reports. Vol. 7 (2017) 44139. (DOI:  /10.1038/srep44139)}}
@article{graf_electrocatalytic_methanol_2017, 
author={Graf, M. and Haensch, M. and Carstens, J. and Wittstock, G. and Weissmueller, J.},
title={Electrocatalytic methanol oxidation with nanoporous gold: microstructure and selectivity},
year={2017},
journal = {Nanoscale},
volume = {9},
number = {45},
pages = {17839 - 17848},
doi = {10.1039/c7nr05124g},
abstract = {The properties of Nanoporous Gold (NPG) obtained by the selective dissolution of Ag from an Au–Ag alloy can be tuned by the details of its fabrication, and specifically the residual Ag content is correlated to the ligament size of the material. We link this correlation to methanol electro-oxidation. Specifically, two different NPG types (obtained by potentiostatic dealloying) are compared with one obtained by free corrosion. They show remarkable differences in activity. Quantitative product analysis reveals that NPG shows nearly selective oxidation of CH3OH to HCOO− when NPG is used as an active electrode in contrast to planar Au. This trend can further be enhanced when applying finer nanoporous structures that are linked to a higher Ag content. X-ray photoelectron spectroscopy (XPS) reveals changes in the nature of residual Ag from which we conclude that Ag is not a passive component in the methanol oxidation process.},
note = {Online available at: \url{https://dx.doi.org/10.1039/c7nr05124g} (DOI). Graf, M.; Haensch, M.; Carstens, J.; Wittstock, G.; Weissmueller, J.: Electrocatalytic methanol oxidation with nanoporous gold: microstructure and selectivity. In: Nanoscale. Vol. 9 (2017) 45, 17839 - 17848. (DOI:  /10.1039/c7nr05124g)}}
@article{huang_a_new_2017, 
author={Huang, Y. and Lv, Z. and Wan, L. and Shen, J. and dos Santos, J.F.},
title={A new method of hybrid friction stir welding assisted by friction surfacing for joining dissimilar Ti/Al alloy},
year={2017},
journal = {Materials Letters},
volume = {207},
pages = {172 - 175},
doi = {10.1016/j.matlet.2017.07.081},
abstract = {A new method of friction surfacing assisted hybrid friction stir welding (FS-HFSW) technique was developed to improve the joint efficiency and avoid the pin abrasion for joining of dissimilar Ti/Al joints. The FSW tool with enlarged head and concave end-face was designed to broaden the lap width and promote material flow. The maximum tensile load reached 12.2 kN, representing 85.3% of the parent Al alloy, with a ductile fracture locating at the heat affected zone of base Al. The excellent bonding of Ti and Al was based on the combined effects of nanoscale TiAl3 IMCs layer and complex mechanical inter-locking.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.matlet.2017.07.081} (DOI). Huang, Y.; Lv, Z.; Wan, L.; Shen, J.; dos Santos, J.F.: A new method of hybrid friction stir welding assisted by friction surfacing for joining dissimilar Ti/Al alloy. In: Materials Letters. Vol. 207 (2017) 172 - 175. (DOI:  /10.1016/j.matlet.2017.07.081)}}
@article{druecker_influence_of_2017, 
author={Druecker, S. and Wilmers, J. and Bargmann, S.},
title={Influence of the microstructure on effective mechanical properties of carbon nanotube composites},
year={2017},
journal = {Coupled Systems Mechanics},
volume = {6},
number = {1},
pages = {1 - 15},
doi = {10.12989/csm.2017.6.1.001 },
abstract = {Despite the exceptional mechanical properties of individual carbon nanotubes (CNTs), the effective properties of CNT-reinforced composites remain below expectations. The composite’s microstructure has been identified as a key factor in explaining this discrepancy. In this contribution, a method for generating representative volume elements of aligned CNT sheets is presented. The model captures material characteristics such as random waviness and entanglement of individual nanotubes. Thus it allows studying microstructural effects on the composite’s effective properties. Simulations investigating the strengthening effect of the application of a pre-stretch on the CNTs are carried out and found to be in very good agreement with experimental values. They highlight the importance of the nanotube’s waviness and entanglement for the mechanical behavior of the composite. The presented representative volume elements are the first to accurately capture the waviness and entanglement of CNT sheets for realistically high volume fractions.},
note = {Online available at: \url{https://dx.doi.org/10.12989/csm.2017.6.1.001 } (DOI). Druecker, S.; Wilmers, J.; Bargmann, S.: Influence of the microstructure on effective mechanical properties of carbon nanotube composites. In: Coupled Systems Mechanics. Vol. 6 (2017) 1, 1 - 15. (DOI:  /10.12989/csm.2017.6.1.001 )}}
@article{shi_actuation_by_2017, 
author={Shi, S. and Markmann, J. and Weissmueller, J.},
title={Actuation by hydrogen electrosorption in hierarchical nanoporous palladium
},
year={2017},
journal = {Philosophical Magazine},
volume = {97},
number = {19},
pages = {1571 - 1587},
doi = {10.1080/14786435.2017.1311428},
abstract = {We report a strategy for preparing macroscopic samples of nanoporous (np-) Pd by electrochemical dealloying. Starting out with the master alloy , single-step dealloying in 1 M at C provides a hierarchical network structure with two well-defined ligament sizes, 35 and 10 nm. The material is distinguished by its uniform microstructure and its excellent mechanical deformability. Thereby, it may provide an alternative to dealloying-made nanoporous gold as a model system for nanoscale functional materials. Our study exemplifies this by exploring actuation through electrochemically controlled hydrogen sorption. Hydrogen underpotential deposition, bulk sorption isotherms and the concentration strain coefficient are found to agree closely with previous studies of H adsorption on planar surfaces and of hydrogen absorption in bulk, respectively. The actuation strain reaches amplitudes up to 4.0%. Even though each strain cycle brings the np-Pd-H through the phase transformation, the strain amplitude remains stable during much more than 1000 cycles. Furthermore, in view of the macroscopic sample size in all three dimensions, the switching time for actuation is remarkably fast.},
note = {Online available at: \url{https://dx.doi.org/10.1080/14786435.2017.1311428} (DOI). Shi, S.; Markmann, J.; Weissmueller, J.: Actuation by hydrogen electrosorption in hierarchical nanoporous palladium
. In: Philosophical Magazine. Vol. 97 (2017) 19, 1571 - 1587. (DOI:  /10.1080/14786435.2017.1311428)}}
@article{ovri_temperature_dependence_2017, 
author={Ovri, H. and Lilleodden, E.T.},
title={Temperature dependence of plastic instability in Al alloys: A nanoindentation study},
year={2017},
journal = {Materials and Design},
volume = {125},
pages = {69 - 75},
doi = {10.1016/j.matdes.2017.03.071},
abstract = {An elevated temperature nanoindentation based method for characterizing the thermal dependence of plastic instability and assessing the activation energies associated with the phenomenon in Al alloys is presented in this work. The method exploits the nanoscale force–displacement resolution capabilities of the Nanoindenter, precludes the ambiguities inherent in the uniaxial testing based methods and offers increased reliability because of the statistical significance of the data achieved. The activation energies estimated for an Al—Mg and an Al—Li alloy with the proposed method were found to be 0.59 ± 0.07 eV and 0.72 ± 0.01 eV, respectively, and are consistent with values derived with other methods. The rate controlling mechanisms associated with these activation energies are described in terms of existing models for plastic instability in these alloy systems.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.matdes.2017.03.071} (DOI). Ovri, H.; Lilleodden, E.T.: Temperature dependence of plastic instability in Al alloys: A nanoindentation study. In: Materials and Design. Vol. 125 (2017) 69 - 75. (DOI:  /10.1016/j.matdes.2017.03.071)}}
@article{graf_xray_studies_2017, 
author={Graf, M. and Ngo, B.-N.D. and Weissmueller, J. and Markmann, J.},
title={X-Ray Studies of Nanoporous Gold: Powder Diffraction by Large Crystals with Small Holes},
year={2017},
journal = {Arxiv.org, Condensed Matter, Materials Science},
pages = {1708.07789},
abstract = {X-ray diffraction studies of nanoporous gold face the poorly understood diffraction scenario where large coherent crystals are riddled with nanoscale holes. Theoretical considerations derived in this study show that the ligament size of the porous network influences the scattering despite being quasi single crystalline. Virtual diffraction of artificially generated samples confirms the results but also shows a loss of long-range coherency and the appearance of microstrain due to thermal relaxation. Subsequently, a large set of laboratory X-ray investigations of nanoporous gold fabricated by different approaches and synthesis parameters reveal a clear correlation between ligament size and size of the coherent scattering domains as well as extremely high microstrains in samples with ligament sizes below 10 nm.},
note = {Graf, M.; Ngo, B.-N.D.; Weissmueller, J.; Markmann, J.: X-Ray Studies of Nanoporous Gold: Powder Diffraction by Large Crystals with Small Holes. In: Arxiv.org, Condensed Matter, Materials Science. (2017) 1708.07789.}}
@article{reimann_microstructure_and_2017, 
author={Reimann, M. and Goebel, J. and dos Santos, J.F.},
title={Microstructure and mechanical properties of keyhole repair welds in AA 7075-T651 using refill friction stir spot welding},
year={2017},
journal = {Materials and Design},
volume = {132},
pages = {283 - 294},
doi = {10.1016/j.matdes.2017.07.013},
abstract = {To develop a suitable keyhole closure process in high-strength AlZnMg(Cu) alloys, refill friction stir spot welding was used to perform repair welds of through holes of 7.5 mm diameter in AA 7075-T651 plates with 6 mm thickness. The thermal cycle and the evolution of microstructural features were investigated in detail. The mechanical performance of the welds was studied based on the changes in microstructure and temperature exposure caused by the welding process.
Thermal cycle measurements revealed high heating rates and peak temperatures of up to 540 °C in the weld center. Leftover grains from the base metal that did not recrystallize were determined in the stirred zone of the weld center. The welds showed a W-shaped hardness distribution with a lowest hardness of 70% of base metal values in the heat affected zone. Under quasi-static loading, two failure modes were determined, with mode 1 failure occurring in the heat affected zone and mode 2 failure occurring in the outer regions of the stirred zone with crack initiation in the lower portions of the weld. Post-weld natural aging was proven to be highly significant for the mechanical properties of the welds and is effective for up to 4 weeks after welding.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.matdes.2017.07.013} (DOI). Reimann, M.; Goebel, J.; dos Santos, J.F.: Microstructure and mechanical properties of keyhole repair welds in AA 7075-T651 using refill friction stir spot welding. In: Materials and Design. Vol. 132 (2017) 283 - 294. (DOI:  /10.1016/j.matdes.2017.07.013)}}
@article{wang_a_nanoporous_2017, 
author={Wang, K. and Stenner, C. and Weissmueller, J.},
title={A nanoporous gold-polypyrrole hybrid nanomaterial for actuation},
year={2017},
journal = {Sensors and Actuators  B},
volume = {248},
pages = {622 - 629},
doi = {10.1016/j.snb.2017.04.025},
abstract = {We discuss actuation with a hybrid nanomaterial that is made by electro-polymerizing pyrrole on the internal surfaces of dealloying-derived nanoporous gold and then letting aqueous electrolyte be imbibed in the remaining pore space. In this way, active polypyrrole films are contacted by two separate but individually contiguous conduction paths, providing efficient transport of ions in the electrolyte channels and of electrons in the metal skeleton. The metal skeleton also serves to enhance the mechanical behavior of the actuator. Actuation exploits the dimension changes of the polymer when ions are exchanged with the electrolyte in a pseudo-capacitive way, at potentials negative of the classic oxidation/reduction of polypyrrole. Our experiments with millimeter-size bulk samples indicate fast switching and substantially larger strain amplitude than nanoporous metal actuators.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.snb.2017.04.025} (DOI). Wang, K.; Stenner, C.; Weissmueller, J.: A nanoporous gold-polypyrrole hybrid nanomaterial for actuation. In: Sensors and Actuators  B. Vol. 248 (2017) 622 - 629. (DOI:  /10.1016/j.snb.2017.04.025)}}
@article{pohlmeinhardt_hydrogen_embrittlement_2017, 
author={Pohl Meinhardt, C. and Scheid, A. and dos Santos, J.F. and Bergmann, L.A. and Borges, Favaro, M. and Fortis Kwietniewski, C.E.},
title={Hydrogen embrittlement under cathodic protection of friction stir welded UNS S32760 super duplex stainless steel},
year={2017},
journal = {Materials Science and Engineering  A},
volume = {706},
pages = {48 - 56},
doi = {10.1016/j.msea.2017.08.117},
abstract = {Hydrogen Induced Stress Cracking (HISC) resistance of super duplex stainless steels is basically controlled by the material's microstructure. Friction stir welding is a low heat input joining process that has the potential to maintain the base metal original resistance to HISC since it does not significantly alter the proportion of ferrite and austenite. This work evaluated the susceptibility to HISC under cathodic protection of friction stir welded super duplex stainless steel UNS S32760. Microstructure evaluation revealed a recommended proportion of ferrite and austenite phases as well a refinement of the overall stir zone microstructure. Fracture toughness tests in synthetic sea water under cathodic protection of − 895 mVsce indicated that the microstructure of the stir zone is actually less sensitive to HISC than the microstructure of the base metal.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.msea.2017.08.117} (DOI). Pohl Meinhardt, C.; Scheid, A.; dos Santos, J.F.; Bergmann, L.A.; Borges, Favaro, M.; Fortis Kwietniewski, C.E.: Hydrogen embrittlement under cathodic protection of friction stir welded UNS S32760 super duplex stainless steel. In: Materials Science and Engineering  A. Vol. 706 (2017) 48 - 56. (DOI:  /10.1016/j.msea.2017.08.117)}}
@article{proenca_friction_riveting_2017, 
author={Proenca, B.C. and Blaga, L. and dos Santos, J.F. and Canto, L.B. and Amancio Filho, S.T.},
title={Friction riveting (‘FricRiveting’) of 6056 T6 aluminium alloy and polyamide 6: influence of rotational speed on the formation of the anchoring zone and on mechanical performance},
year={2017},
journal = {Welding International},
volume = {31},
number = {7},
pages = {509 - 518},
doi = {10.1080/09507116.2016.1218627},
abstract = {Metal-polymer hybrid structures can be used as an alternative solution for reducing weight and fuel consumption in the transport industry, which aims to minimise the emission of harmful gases that have a greenhouse effect. Friction riveting is a relatively new technique for joining metal-polymer hybrid structures. The process is based on the generation of frictional heat between the components, resulting in the plastic deformation of the end of the metal rivet, which is anchored inside the polymer component. This study assessed the technical feasibility of joining AA 6056 T6 and PA6, focusing on the influence of the rotational speed of the rivet on the mechanical performance of the joints. The maximum temperature reached during the process increased with the rotational speed, from 291 ± 6 °C with 10,000 rev/min to 375 ± 5 °C with 15,000 rev/min. The use of higher rotational speeds led to the tip of the rivet undergoing plastic deformation during the friction phase. This produced mechanically stronger joints, because the metal rivet was anchored more securely in the polymer block. The AA 6056 T6-PA6 joints perform well in terms of tensile strength, reaching 85% of the tensile strength of the metal rivet. We therefore confirmed that it is possible to join AA 6056 T6 and PA6 using the technique of friction riveting, and that rotational speed directly affects the tensile strength of the joints.},
note = {Online available at: \url{https://dx.doi.org/10.1080/09507116.2016.1218627} (DOI). Proenca, B.C.; Blaga, L.; dos Santos, J.F.; Canto, L.B.; Amancio Filho, S.T.: Friction riveting (‘FricRiveting’) of 6056 T6 aluminium alloy and polyamide 6: influence of rotational speed on the formation of the anchoring zone and on mechanical performance. In: Welding International. Vol. 31 (2017) 7, 509 - 518. (DOI:  /10.1080/09507116.2016.1218627)}}
@article{mameka_on_the_2017, 
author={Mameka, N. and Markmann, J. and Weissmueller, J.},
title={On the impact of capillarity for strength at the nanoscale},
year={2017},
journal = {Nature Communications},
volume = {8},
pages = {1976},
doi = {10.1038/s41467-017-01434-2},
abstract = {The interior of nanoscale crystals experiences stress that compensates for the capillary forces and that can be large, in the order of 1 GPa. Various studies have speculated on whether and how this surface-induced stress affects the stability and plasticity of small crystals. Yet, experiments have so far failed to discriminate between the surface contribution and other, bulk-related size effects. To clarify the issue, here we study the variation of the flow stress of a nanomaterial while distinctly different variations of the two capillary parameters, surface tension, and surface stress, are imposed under control of an applied electric potential. Our theory qualifies the suggested impact of surface stress as not forceful and instead predicts a significant contribution of the surface energy, as measured by the surface tension. The predictions for the combined potential-dependence and size-dependence of the flow stress are quantitatively supported by the experiment. Previous suggestions, favoring the surface stress as the relevant capillary parameter, are not consistent with our experiment.},
note = {Online available at: \url{https://dx.doi.org/10.1038/s41467-017-01434-2} (DOI). Mameka, N.; Markmann, J.; Weissmueller, J.: On the impact of capillarity for strength at the nanoscale. In: Nature Communications. Vol. 8 (2017) 1976. (DOI:  /10.1038/s41467-017-01434-2)}}
@article{chu_study_of_2017, 
author={Chu, Q. and Li, W.Y. and Yang, X.W. and Shen, J.J. and Li, Y.B. and Wang, W.B.},
title={Study of process/structure/property relationships in probeless friction stir spot welded AA2198 Al-Li alloy},
year={2017},
journal = {Welding in the World},
volume = {61},
number = {2},
pages = {291 - 298},
doi = {10.1007/s40194-017-0423-3},
abstract = {Probeless friction stir spot welding (probeless FSSW) is a useful variant of conventional friction stir spot welding (FSSW), where there is no probe at the end of the tool shoulder. In this study, AA2198-T8 aluminum-lithium alloy has been successfully welded by probeless FSSW. The variations of geometric features of probeless FSSWed joints: stir zone width, stir zone edge angle and hook angle, and their effects on the joint mechanical properties were studied quantitatively. Results show that the width of stir zone is constrained by shoulder diameter, and the ratio of the width to shoulder diameter approaches 0.9. With the increase of stir zone depth, the stir zone edge angle approaches 45° eventually during the welding process. Additionally, the hook defect can be found among all of the probeless FSSWed joints due to the upward material flow of the lower sheet. When the hook angle is around 90°, the tensile/shear strength reaches a relatively higher value. The fracture mode changes from shear fracture to plug fracture when hook angle transforms from obtuse to acute.},
note = {Online available at: \url{https://dx.doi.org/10.1007/s40194-017-0423-3} (DOI). Chu, Q.; Li, W.Y.; Yang, X.W.; Shen, J.J.; Li, Y.B.; Wang, W.B.: Study of process/structure/property relationships in probeless friction stir spot welded AA2198 Al-Li alloy. In: Welding in the World. Vol. 61 (2017) 2, 291 - 298. (DOI:  /10.1007/s40194-017-0423-3)}}
@article{enz_frische_forschung_2017, 
author={Enz, J.},
title={Frische Forschung - LASERSTRAHLSCHWEISSEN vON HOCHLEGIERTEN ALUMINIUM-ZINK-LEGIERUNGEN},
year={2017},
journal = {Laser Community - Das Laser-Magazin von TRUMPF},
volume = {25},
pages = {19},
note = {Enz, J.: Frische Forschung - LASERSTRAHLSCHWEISSEN vON HOCHLEGIERTEN ALUMINIUM-ZINK-LEGIERUNGEN. In: Laser Community - Das Laser-Magazin von TRUMPF. Vol. 25 (2017) 19.}}
@article{fomin_influence_of_2017, 
author={Fomin, F. and Kashaev, N.},
title={Influence of Porosity on the High Cycle Fatigue Behaviour of Laser Beam Welded Ti-6Al-4V Butt Joints},
year={2017},
journal = {Procedia Structural Integrity},
volume = {7},
pages = {415 - 422},
doi = {10.1016/j.prostr.2017.11.107},
abstract = {Surface defects and internal discontinuities are inevitable results of the laser beam welding (LBW) process regardless of the material used. Comprehensive understanding of the fatigue degradation caused by these defects is of major concern for the introduction of LBW into manufacturing or repair processes. The present paper focuses on the effect of inherent welding-induced material flaws on the high cycle fatigue behaviour of the laser welded Ti-6Al-4V butt joints. If the surface quality of the welded joint is sufficiently high, the transition of the crack origin from the surface to the subsurface occurs. The mechanisms of internal fatigue crack formation and growth at the early stages were studied. A typical fish-eye pattern of fracture surface was observed in close proximity to the crack origin. The model based on fracture mechanics for durability prediction in the presence of randomly distributed porosity was developed. The link between theory, modelling and experiment was successfully demonstrated.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.prostr.2017.11.107} (DOI). Fomin, F.; Kashaev, N.: Influence of Porosity on the High Cycle Fatigue Behaviour of Laser Beam Welded Ti-6Al-4V Butt Joints. In: Procedia Structural Integrity . Vol. 7 (2017) 415 - 422. (DOI:  /10.1016/j.prostr.2017.11.107)}}
@article{jiao_effect_of_2017, 
author={Jiao, J. and Huber, N.},
title={Effect of nodal mass on macroscopic mechanical properties of nanoporous metals},
year={2017},
journal = {International Journal of Mechanical Sciences},
volume = {134},
pages = {234 - 243},
doi = {10.1016/j.ijmecsci.2017.10.011},
abstract = {The current work investigates the effect of the nodal mass on the macroscopic mechanical behavior of nanoporous metals using the Finite Element Method. A nodal corrected beam modeling concept is introduced that allows local incorporation of the effective elastoplastic mechanical behavior of the nodal mass in the nodal area of a representative volume element (RVE). The calibration to the corresponding Finite Element solid model is achieved by integrating additional geometry and material parameters to the so-called nodal areas in the beam model. With this technique an excellent prediction can be achieved over a large range of deformation for different types of RVEs. From the results of the nodal corrected beam model, modified leading constants are determined in the scaling laws for Young's modulus and yield strength. The effect of the nodal correction is also studied with respect to various randomization levels. Finally, the ligament size dependent strength is analyzed by applying the proposed model to experimental data. It could be shown that the nodal correction improves the overall agreement with literature data, particularly for such data points that are related to samples with a high solid fraction.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.ijmecsci.2017.10.011} (DOI). Jiao, J.; Huber, N.: Effect of nodal mass on macroscopic mechanical properties of nanoporous metals. In: International Journal of Mechanical Sciences. Vol. 134 (2017) 234 - 243. (DOI:  /10.1016/j.ijmecsci.2017.10.011)}}
@article{soyarslan_thermomechanical_formulation_2016, 
author={Soyarslan, C. and Bargmann, S.},
title={Thermomechanical formulation of ductile damage coupled to nonlinear isotropic hardening and multiplicative viscoplasticity},
year={2016},
journal = {Journal of the Mechanics and Physics of Solids},
volume = {91},
pages = {334 - 358},
doi = {http://dx.doi.org/10.1016/j.jmps.2016.03.002},
abstract = {In this paper, we present a thermomechanical framework which makes use of the internal variable theory of thermodynamics for damage-coupled finite viscoplasticity with nonlinear isotropic hardening. Damage evolution, being an irreversible process, generates heat. In addition to its direct effect on material's strength and stiffness, it causes deterioration of the heat conduction. The formulation, following the footsteps of [Simo, J.C., Miehe, Ch. [1992]: “Associative coupled thermoplasticity at finite strains: Formulation, numerical analysis and implementation”, Computer Methods in Applied Mechanics and Engineering, Vol. 98, 41–104.], introduces inelastic entropy as an additional state variable. Given a temperature dependent damage dissipation potential, we show that the evolution of inelastic entropy assumes a split form relating to plastic and damage parts, respectively. The solution of the thermomechanical problem is based on the so-called isothermal split. This allows the use of the model in 2D and 3D example problems involving geometrical imperfection triggered necking in an axisymmetric bar and thermally triggered necking of a 3D rectangular bar.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.jmps.2016.03.002} (DOI). Soyarslan, C.; Bargmann, S.: Thermomechanical formulation of ductile damage coupled to nonlinear isotropic hardening and multiplicative viscoplasticity. In: Journal of the Mechanics and Physics of Solids. Vol. 91 (2016) 334 - 358. (DOI:  10.1016/j.jmps.2016.03.002)}}
@article{ma_anisotropic_constitutive_2016, 
author={Ma, S. and Scheider, I. and Bargmann, S.},
title={Anisotropic constitutive model incorporating multiple damage mechanisms for multiscale simulation of dental enamel},
year={2016},
journal = {Journal of the Mechanical Behavior of Biomedical Materials},
volume = {62},
pages = {515 - 533},
doi = {http://dx.doi.org/10.1016/j.jmbbm.2016.05.033},
abstract = {An anisotropic constitutive model is proposed in the framework of finite deformation to capture several damage mechanisms occurring in the microstructure of dental enamel, a hierarchical bio-composite. It provides the basis for a homogenization approach for an efficient multiscale (in this case: multiple hierarchy levels) investigation of the deformation and damage behavior. The influence of tension–compression asymmetry and fiber–matrix interaction on the nonlinear deformation behavior of dental enamel is studied by 3D micromechanical simulations under different loading conditions and fiber lengths. The complex deformation behavior and the characteristics and interaction of three damage mechanisms in the damage process of enamel are well captured. The proposed constitutive model incorporating anisotropic damage is applied to the first hierarchical level of dental enamel and validated by experimental results. The effect of the fiber orientation on the damage behavior and compressive strength is studied by comparing micro-pillar experiments of dental enamel at the first hierarchical level in multiple directions of fiber orientation. A very good agreement between computational and experimental results is found for the damage evolution process of dental enamel.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.jmbbm.2016.05.033} (DOI). Ma, S.; Scheider, I.; Bargmann, S.: Anisotropic constitutive model incorporating multiple damage mechanisms for multiscale simulation of dental enamel. In: Journal of the Mechanical Behavior of Biomedical Materials. Vol. 62 (2016) 515 - 533. (DOI:  10.1016/j.jmbbm.2016.05.033)}}
@article{andre_influence_of_2016, 
author={Andre, N.M. and Goushegir, S.M. and dos Santos, J.F. and Canto, L.B. and Amancio Filho, S.T.},
title={Influence of the Interlayer Film Thickness on the Mechanical Performance of AA2024-T3/CF-PPS Hybrid Joints Produced by Friction Spot Joining - Influencia da Espessura do Filme Polimerico Intermediario na Resistencia Mecanica de Juntas Hibridas de Alumínio 2024-T3 e CF-PPS Produzidas por Uniao Pontual por Friccao},
year={2016},
journal = {Soldagem & Inspecao},
volume = {21},
number = {1},
pages = {2 - 15},
doi = {http://dx.doi.org/10.1590/0104-9224/SI2101.02},
abstract = {Friction Spot Joining (FSpJ) is an innovative friction-based joining technique for metal-polymer hybrid structures. Friction spot joints of aluminum alloy 2024-T3 and carbon-fiber reinforced poly(phenylene sulfide) composite laminate (CF-PPS) were produced with an additional PPS film interlayer. Two different film thicknesses were investigated in this study: 100 and 500 µm. Lap shear testing demonstrated that the joints produced with 100 µm film (2093 ± 180 N) were stronger than the joints with 500 µm (708 ± 69 N). Additionally, the fracture surface analysis revealed a larger bonding area for the joints with 100 µm film (53 ± 2 mm2) as compared to the joints with 500 µm film (40 ± 1 mm2). Considering the low thermal conductivity of PPS, the thinnest film is more likely to soften by the frictional heat during the joining process. Hence, the low viscosity of the molten PPS favors the wettability of the parts’ surface. Microstructural analyses proved that the metallic nub formation and the interdiffusion of PPS chains between film and composite matrix are also favored for thinner film use. Thus, superior adhesion between the partners is achieved. Therefore, it was concluded that the addition of the thinnest film interlayer leads to stronger joints.

Resumo
A União Pontual por Fricção (FSpJ) é uma técnica inovadora para união de estruturas híbridas metal-polímero e baseia-se na geração de calor por fricção. Juntas de alumínio 2024-T3 e compósito laminado de poli(sulfeto de fenileno) com fibra de carbono (CF-PPS) foram produzidas com filme intermediário de PPS. Duas espessuras de filme foram investigadas: 100 e 500 µm. Ensaios de cisalhamento sob tração demonstraram que as juntas com filmes de 100 µm são mais resistentes (2093 ± 180 N) em relação às juntas com filme de 500 µm (708 ± 69 N). Adicionalmente, as superfícies de fratura das juntas revelaram áreas de união maiores para as juntas com filmes de 100 µm (53 ± 2 contra 40 ± 1 mm2). Para o filme mais fino, a extensão do amolecimento devido ao calor friccional é maior. Consequentemente, a baixa viscosidade atingida com a fusão do polímero favorece a molhabilidade das superfícies dos componentes da junta pelo PPS amolecido, resultando em melhor adesão entre as partes. Ademais, análises microestruturais demonstraram que a formação do cerne metálico e a interdifusão das moléculas de PPS entre compósito e filme também são favorecidas. Portanto, concluiu-se que a adição do filme mais fino produziu juntas mais resistentes.},
note = {Online available at: \url{http://dx.doi.org/10.1590/0104-9224/SI2101.02} (DOI). Andre, N.M.; Goushegir, S.M.; dos Santos, J.F.; Canto, L.B.; Amancio Filho, S.T.: Influence of the Interlayer Film Thickness on the Mechanical Performance of AA2024-T3/CF-PPS Hybrid Joints Produced by Friction Spot Joining - Influencia da Espessura do Filme Polimerico Intermediario na Resistencia Mecanica de Juntas Hibridas de Alumínio 2024-T3 e CF-PPS Produzidas por Uniao Pontual por Friccao. In: Soldagem & Inspecao. Vol. 21 (2016) 1, 2 - 15. (DOI:  10.1590/0104-9224/SI2101.02)}}
@article{feistauer_ultrasonic_joining_2016, 
author={Feistauer, E.E. and Guimaraes, R.P.M. and Ebel, T. and dos Santos, J.F. and Amancio-Filho, S.T.},
title={Ultrasonic joining: A novel direct-assembly technique for metal-composite hybrid structures},
year={2016},
journal = {Materials Letters},
volume = {170},
pages = {1 - 4},
doi = {http://dx.doi.org/10.1016/j.matlet.2016.01.137},
abstract = {Ultrasonic joining (U-Joining) is a new direct assembly technique developed by Helmholtz-Zentrum Geesthacht that uses ultrasonic energy to join fiber-reinforced thermoplastics to surface-structured metallic parts produced by metal injection molding. Ultrasonic vibration and pressure create frictional heat at the materials interface, which softens the composite matrix and allows the reinforcement (structured on the surface of the metallic part) to penetrate the composite. As a result, a metal-composite hybrid joint with improved out-of-plane strength is achieved. In this work, the features of U-Joining are briefly introduced, and the feasibility of the technique is demonstrated with Ti-6Al-4V/glass-fiber-reinforced polyetherimide joints. Optical microscopy reveals that a close contact between metal and composite was achieved after U-joining. Lap shear testing of six-pin joints showed an improvement in strength of up to 5.5 times (2011±530 N) that of pin-less reference joints (368±29 N).},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.matlet.2016.01.137} (DOI). Feistauer, E.E.; Guimaraes, R.P.M.; Ebel, T.; dos Santos, J.F.; Amancio-Filho, S.T.: Ultrasonic joining: A novel direct-assembly technique for metal-composite hybrid structures. In: Materials Letters. Vol. 170 (2016) 1 - 4. (DOI:  10.1016/j.matlet.2016.01.137)}}
@article{maawad_influence_of_2016, 
author={Maawad, E. and Gan, W. and Hofmann, M. and Ventzke, V. and Riekehr, S. and Brokmeier, H.-G. and Kashaev, N. and Mueller, M.},
title={Influence of crystallographic texture on the microstructure, tensile properties and residual stress state of laser-welded titanium joints},
year={2016},
journal = {Materials and Design},
volume = {101},
pages = {137 - 145},
doi = {http://dx.doi.org/10.1016/j.matdes.2016.03.148},
abstract = {Preferred grain orientations (crystallographic texture) of base materials could influence on mechanical properties, microstructure and residual stresses of welded joints. This should be considered for design purposes, in particular for materials having non-cubic crystal structures. A multitude of experiments have been carried out in this field of study without considering the crystallographic texture based anisotropy of base materials. In the present work, commercially pure titanium (CP-Ti) rolled sheets were laser welded along various directions with respect to the sample orientations, namely rolling direction (RD), transverse direction (TD) and 45° to RD. Three-dimensional strain profiles and the local texture around the weld were measured by neutron diffraction. Furthermore, grain orientation mapping within the base material, the heat-affected zone and the fusion zone was investigated using the electron back-scatter diffraction (EBSD) technique. The results revealed that tensile properties of the samples are different, while no significant statistical differences in residual stresses were observed.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.matdes.2016.03.148} (DOI). Maawad, E.; Gan, W.; Hofmann, M.; Ventzke, V.; Riekehr, S.; Brokmeier, H.-G.; Kashaev, N.; Mueller, M.: Influence of crystallographic texture on the microstructure, tensile properties and residual stress state of laser-welded titanium joints. In: Materials and Design. Vol. 101 (2016) 137 - 145. (DOI:  10.1016/j.matdes.2016.03.148)}}
@article{kashaev_effect_of_2016, 
author={Kashaev, N. and Ventzke, V. and Fomichev, V. and Fomin, F. and Riekehr, S.},
title={Effect of Nd:YAG laser beam welding on weld morphology and mechanical properties of Ti–6Al–4V butt joints and T-joints},
year={2016},
journal = {Optics and Lasers in Engineering},
volume = {86},
pages = {172 - 180},
doi = {http://dx.doi.org/10.1016/j.optlaseng.2016.06.004},
abstract = {A Nd:YAG single-sided laser beam welding process study for Ti–6Al–4V butt joints and T-joints was performed to investigate joining techniques with regard to the process-weld morphology relationship. An alloy compatible filler wire was used to avoid underfills and undercuts. The quality of the butt joints and T-joints was characterized in terms of weld morphology, microstructure and mechanical properties. Joints with regular shapes, without visible cracks, pores, and geometrical defects were achieved. Tensile tests revealed high joint integrity in terms of strength and ductility for both the butt joint and T-joint geometries. Both the butt joints and T-joints showed base material levels of strength. The mechanical performance of T-joints was also investigated using pull-out tests. The performance of the T-joints in such tests was sensitive to the shape and morphology of the welds. Fracture always occurred in the weld without any plastic deformation in the base material outside the weld.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.optlaseng.2016.06.004} (DOI). Kashaev, N.; Ventzke, V.; Fomichev, V.; Fomin, F.; Riekehr, S.: Effect of Nd:YAG laser beam welding on weld morphology and mechanical properties of Ti–6Al–4V butt joints and T-joints. In: Optics and Lasers in Engineering. Vol. 86 (2016) 172 - 180. (DOI:  10.1016/j.optlaseng.2016.06.004)}}
@article{ma_continuum_damage_2016, 
author={Ma, S. and Scheider, I. and Bargmann, S.},
title={Continuum damage modeling and simulation of hierarchical dental enamel},
year={2016},
journal = {Modelling and Simulation in Materials Science Engineering},
volume = {24},
number = {4},
pages = {045014},
doi = {http://dx.doi.org/10.1088/0965-0393/24/4/045014},
abstract = {Dental enamel exhibits high fracture toughness and stiffness due to a complex hierarchical and graded microstructure, optimally organized from nano- to macro-scale. In this study, a 3D representative volume element (RVE) model is adopted to study the deformation and damage behavior of the fibrous microstructure. A continuum damage mechanics model coupled to hyperelasticity is developed for modeling the initiation and evolution of damage in the mineral fibers as well as protein matrix. Moreover, debonding of the interface between mineral fiber and protein is captured by employing a cohesive zone model. The dependence of the failure mechanism on the aspect ratio of the mineral fibers is investigated. In addition, the effect of the interface strength on the damage behavior is studied with respect to geometric features of enamel. Further, the effect of an initial flaw on the overall mechanical properties is analyzed to understand the superior damage tolerance of dental enamel. The simulation results are validated by comparison to experimental data from micro-cantilever beam testing at two hierarchical levels. The transition of the failure mechanism at different hierarchical levels is also well reproduced in the simulations.},
note = {Online available at: \url{http://dx.doi.org/10.1088/0965-0393/24/4/045014} (DOI). Ma, S.; Scheider, I.; Bargmann, S.: Continuum damage modeling and simulation of hierarchical dental enamel. In: Modelling and Simulation in Materials Science Engineering. Vol. 24 (2016) 4, 045014. (DOI:  10.1088/0965-0393/24/4/045014)}}
@article{andre_friction_spot_2016, 
author={Andre, N.M. and Goushegir, S.M. and dos Santos, J.F. and Canto, L.B. and Amancio-Filho, S.T.},
title={Friction Spot Joining of aluminum alloy 2024-T3 and carbon-fiber-reinforced poly(phenylene sulfide) laminate with additional PPS film interlayer: Microstructure, mechanical strength and failure mechanisms},
year={2016},
journal = {Composites / B},
volume = {94},
pages = {197 - 208},
doi = {http://dx.doi.org/10.1016/j.compositesb.2016.03.011},
abstract = {Friction Spot Joining is an innovative friction-based joining technique for metal–polymer hybrid structures. In this work, aluminum alloy 2024-T3 and CF-PPS friction-spot joints were produced with additional PPS film interlayer. The joints were investigated in terms of the microstructure, mechanical performance under quasi-static loading and failure mechanisms. Macro- and micro-mechanical interlocking as well as adhesion forces were identified to dictate bonding mechanisms in the FSp joint with film interlayer. The ultimate lap shear force of the joints (2700 ± 115 N up to 3070 ± 165 N) were 20%–55% higher than the corresponding joints without interlayer, due to the larger bonding area, better load distribution and improved micro-mechanical interlocking. The failure analysis of the joints revealed a mixture of adhesive-cohesive failure, whereas cohesive failure was dominant.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.compositesb.2016.03.011} (DOI). Andre, N.M.; Goushegir, S.M.; dos Santos, J.F.; Canto, L.B.; Amancio-Filho, S.T.: Friction Spot Joining of aluminum alloy 2024-T3 and carbon-fiber-reinforced poly(phenylene sulfide) laminate with additional PPS film interlayer: Microstructure, mechanical strength and failure mechanisms. In: Composites / B. Vol. 94 (2016) 197 - 208. (DOI:  10.1016/j.compositesb.2016.03.011)}}
@article{soyarslan_a_thermomechanically_2016, 
author={Soyarslan, C. and Turtuk, I.C. and Deliktas, B. and Bargmann, S.},
title={A Thermomechanically Consistent Constitutive Theory for Modeling Micro-Void and/or Micro-Crack Driven Failure in Metals at Finite Strains},
year={2016},
journal = {International Journal of Applied Mechanics},
volume = {8},
number = {1},
pages = {1650009},
doi = {http://dx.doi.org/10.1142/S1758825116500095},
abstract = {Within a continuum approximation, we present a thermomechanical finite strain plasticity
model which incorporates the blended effects of micro-heterogeneities in the form of
micro-cracks and micro-voids. The former accounts for cleavage-type of damage without
any volume change whereas the latter is a consequence of plastic void growth. Limiting
ourselves to isotropy, for cleavage damage a scalar damage variable d ∈ [0, 1] is
incorporated. Its conjugate variable, the elastic energy release rate, and evolution law
follow the formal steps of thermodynamics of internal variables requiring postulation
of an appropriate damage dissipation potential. The growth of void volume fraction f
is incorporated using a Gurson-type porous plastic potential postulated at the effective
stress space following continuum damage mechanics principles. Since the growth
of microvoids is driven by dislocation motion around voids the dissipative effects corresponding
to the void growth are encapsulated in the plastic flow. Thus, the void volume
fraction is used as a dependent variable using the conservation of mass. The predictive
capability of the model is tested through uniaxial tensile tests at various temperatures
Θ ∈ [−125◦C,125◦C]. It is shown, via fracture energy plots, that temperature driven
ductile-brittle transition in fracture mode is well captured. With an observed ductilebrittle
transition temperature around −50◦C, at lower temperatures fracture is brittle
dominated by d whereas at higher temperatures it is ductile dominated by f.},
note = {Online available at: \url{http://dx.doi.org/10.1142/S1758825116500095} (DOI). Soyarslan, C.; Turtuk, I.C.; Deliktas, B.; Bargmann, S.: A Thermomechanically Consistent Constitutive Theory for Modeling Micro-Void and/or Micro-Crack Driven Failure in Metals at Finite Strains. In: International Journal of Applied Mechanics. Vol. 8 (2016) 1, 1650009. (DOI:  10.1142/S1758825116500095)}}
@article{alexopoulos_laser_beam_2016, 
author={Alexopoulos, N.D. and Gialos, A.A. and Zeimpekis, V. and Velonaki, Z. and Kashaev, N. and Riekehr, S. and Karanika, A.},
title={Laser beam welded structures for a regional aircraft: weight, cost and carbon footprint savings},
year={2016},
journal = {Journal of Manufacturing Systems},
volume = {39},
pages = {38 - 52},
doi = {http://dx.doi.org/10.1016/j.jmsy.2016.02.002},
abstract = {Laser beam welded structures offer great opportunities for the lightweight design of fuselage structures in order to reduce structural weight for increased fuel efficiency. Our main objective is to validate and demonstrate that laser beam welding (LBW) technology provides the best opportunities in terms of weight reduction, production time and energy consumption for manufacturing aircraft components. To this end, a comparison in terms of energy, process time, cost and carbon footprint is assessed against the ‘conventional’ manufacturing process of riveting, to prove that LBW is actually an environmental friendly process. Manufacturing of a four-stringer stiffened flat subscale component was the case of the present work that was called in the Clean Sky Eco-Design Airframe (EDA) project as the B1 demonstrator (742 mm × 384 mm). The LBW process has been broken down into several sub-processes and activities according to the Activity Based Costing (ABC) methodology and the weight reduction, production time and energy consumption results were compared against the respective of the riveting process. It was proved that for the specific subscale LBW component, it consumes half the energy and can be processed in less than half the time needed (in serial processing of the component) with riveting. Manufacturing of the component with the LBW process (door to door approach) is more environmentally friendly, since it produces 53% less CO2e emissions than the respective riveted process. This is a clear advantage to this manufacturing process in order to assure a sustainable life cycle of the final product.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.jmsy.2016.02.002} (DOI). Alexopoulos, N.D.; Gialos, A.A.; Zeimpekis, V.; Velonaki, Z.; Kashaev, N.; Riekehr, S.; Karanika, A.: Laser beam welded structures for a regional aircraft: weight, cost and carbon footprint savings. In: Journal of Manufacturing Systems. Vol. 39 (2016) 38 - 52. (DOI:  10.1016/j.jmsy.2016.02.002)}}
@article{zocollerborba_influence_of_2016, 
author={Zocoller Borba, N. and Blaga, L. and dos Santos, J.F. and Canto, L.B. and Amancio-Filho, S.T.},
title={Influence of Rotational Speed on the Microstructure and Mechanical Performance of Friction-Riveted Thermosetting Composite Joints - Influencia da Velocidade de Rotacao do Rebite na Microestrutura e no Desempenho Mecanico de Juntas de Composito Termofixo Rebitadas por Friccao},
year={2016},
journal = {Soldagem & Inspecao},
volume = {21},
number = {1},
pages = {30 - 43},
doi = {http://dx.doi.org/10.1590/0104-9224/SI2101.04},
abstract = {Facing the actual demand for efficient joining technologies for multi-materials structures, Friction Riveting was shown to be an alternative joining technology for thermoset composite profiles in civil infrastructure. This process is based on plasticizing and deforming the tip of a rotating metallic rivet within a polymeric component through frictional heating. The feasibility of friction-riveted hybrid joints of Ti-6Al-4V/glass-fiber reinforced thermoset polyester was already demonstrated in a separate work. This paper complements this study by analyzing the rivet rotational speed effect on the process temperature, joint microstructure and the local and global mechanical properties of the joint. Joints were produced using two different levels of rotational speed: 9000 rpm and 10000 rpm (the other parameters were kept constant). The results showed process temperatures (655-765 °C) up to 96% higher than the onset decomposition temperature of the polyester matrix (370 °C); this led to severe degradation of the composite in the joint area. The increase in rotational speed, and therefore in heat generation, led to a statistically insignificant increase of the rivet penetration depth and the rivet diameter widening. However, the extension of the degraded composite area increased 47% which was responsible to deteriorate in 50% the joint tensile strength (from 4.0 ± 1.2 kN to 2.0 ± 0.7 kN). Moreover, the microhardness map of the joined rivet evidenced possible phase transformations in the alloy, favoring the material hardening by increasing in rotational speed. However, no correlations could be established between the changes in hardness and the joint tensile strength since the joints majority failure by full rivet pull-out. Thereby, for the improvement of friction-riveted Ti-6Al-4V/ glass-fiber reinforced thermoset polyester joints, the optimization of rotational speed is essential. This can guarantee the formation of efficient anchored joints and wider rivet tip deformation, concomitantly with the minimizing of the extension of the matrix degradation and finally leading to better tensile strength of the joints.

A Rebitagem por Fricção tem se demonstrado como alternativa para união de perfis de compósito termofixo aplicados na construção civil, frente às necessidades atuais por tecnologias eficientes de união de estruturas multimateriais. Nesse processo, a extremidade de um rebite metálico é plastificada e forjada dentro de um componente polimérico, via calor friccional. Sua viabilidade técnica já foi demonstrada para juntas de Ti-6Al-4V/poliéster termofixo reforçado com fibra de vidro. Este artigo tem como objetivo complementar esse estudo através da análise do efeito da velocidade de rotação do rebite na temperatura do processo, microestrutura e propriedades mecânicas locais e globais das juntas. Foram fabricadas juntas com dois níveis de velocidade de rotação: 9000 rpm e 10000 rpm (os demais parâmetros foram mantidos constantes). Temperaturas do processo (655-765 °C) superiores em 96% da temperatura de início de decomposição da matriz de poliéster (370 °C) foram atingidas, desencadeando degradação polimérica acentuada na região de união. O aumento da velocidade de rotação e, portanto, do aporte térmico, não contribuiu estatisticamente para o aumento na profundidade de penetração e na largura da extremidade deformada do rebite. Porém, a extensão da área polimérica degradada aumentou em 47%, a qual resultou em redução proporcional de 50% da resistência à tração das juntas (de 4,0 ± 1,2 kN para 2,0 ± 0,7 kN). Adicionalmente, mapas de microdureza no rebite evidenciaram possíveis transformações de fase da liga que favoreceram seu endurecimento, com o aumento da velocidade de rotação. Contudo, nenhuma correlação pôde ser evidenciada entre a dureza e o desempenho mecânico das juntas sob tração, já que as amostras falharam majoritariamente por arrancamento completo do rebite da placa de compósito. Portanto, no desenvolvimento de juntas rebitadas por fricção de Ti-6Al-4V/ poliéster termofixo reforçado com fibra de vidro, a otimização da velocidade de rotação é essencial para se obter suficiente deformação plástica do rebite e minimizar a extensão da degradação da matriz de poliéster, garantindo um satisfatório desempenho mecânico sob tração das juntas.},
note = {Online available at: \url{http://dx.doi.org/10.1590/0104-9224/SI2101.04} (DOI). Zocoller Borba, N.; Blaga, L.; dos Santos, J.F.; Canto, L.B.; Amancio-Filho, S.T.: Influence of Rotational Speed on the Microstructure and Mechanical Performance of Friction-Riveted Thermosetting Composite Joints - Influencia da Velocidade de Rotacao do Rebite na Microestrutura e no Desempenho Mecanico de Juntas de Composito Termofixo Rebitadas por Friccao. In: Soldagem & Inspecao. Vol. 21 (2016) 1, 30 - 43. (DOI:  10.1590/0104-9224/SI2101.04)}}
@article{reimann_keyhole_closure_2016, 
author={Reimann, M. and Gartner, T. and Suhuddin, U. and Goebel, J. and dos Santos, J.F.},
title={Keyhole closure using friction spot welding in aluminum alloy 6061–T6},
year={2016},
journal = {Journal of Materials Processing Technology},
volume = {237},
pages = {12 - 18},
doi = {http://dx.doi.org/10.1016/j.jmatprotec.2016.05.013},
abstract = {A new approach to refill keyholes using the friction spot welding (FSpW) technology was developed. Keyholes with a diameter of 7.5 mm in aluminum alloy 6061–T6 rolled sheets were filled with a cylindrical plug of the same material. Afterwards, the FSpW process joins the plug to the surrounding workpiece resulting in a sealed keyhole.

Microstructural analysis and mechanical testing of keyhole closures have been performed. The mechanical properties have been determined in terms of microhardness, tensile strength, yield strength and elongation at fracture. Design of experiments and analysis of variance techniques were employed to evaluate the influence of the gas shielding, post-weld heat treatments and the plug itself on the properties of the welds.

The experimental results demonstrate that the proposed method is suitable to refill keyholes in AA 6061–T6 and produce flawless joints with a superior surface appearance. The welds show high strength and hardness, especially when heat treatments are applied. The high strength of the welds were achieved at the expense of elongation at fracture, which is caused by a strengthened zone in the center of the welds.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.jmatprotec.2016.05.013} (DOI). Reimann, M.; Gartner, T.; Suhuddin, U.; Goebel, J.; dos Santos, J.F.: Keyhole closure using friction spot welding in aluminum alloy 6061–T6. In: Journal of Materials Processing Technology. Vol. 237 (2016) 12 - 18. (DOI:  10.1016/j.jmatprotec.2016.05.013)}}
@article{enz_laser_weldability_2016, 
author={Enz, J. and Riekehr, S. and Ventzke, V. and Huber, N. and Kashaev, N.},
title={Laser Weldability of High-Strength Al-Zn Alloys and Its Improvement by the Use of an Appropriate Filler Material},
year={2016},
journal = {Metallurgical and Materials Transactions  A},
volume = {47},
number = {6},
pages = {2830 - 2841},
doi = {http://dx.doi.org/10.1007/s11661-016-3446-2},
abstract = {Heat-treatable Al-Zn alloys are promising candidates for use as structural lightweight materials in automotive and aircraft applications. This is mainly due to their high strength-to-density ratio in comparison to conventionally employed Al alloys. Laser beam welding is an efficient method for producing joints with high weld quality and has been established in the industry for many years. However, it is well known that aluminum alloys with a high Zn content or, more precisely, with a high (Zn + Mg + Cu) content are difficult to fusion weld due to the formation of porosity and hot cracks. The present study concerns the laser weldability of these hard-to-weld Al-Zn alloys. In order to improve weldability, it was first necessary to understand the reasons for weldability problems and to identify crucial influencing factors. Based on this knowledge, it was finally possible to develop an appropriate approach. For this purpose, vanadium was selected as additional filler material. Vanadium exhibits favorable thermophysical properties and, thereby, can improve the weldability of Al-Zn alloys. The effectiveness of the approach was verified by its application to several Al-Zn alloys with differing amounts of (Zn + Mg + Cu).},
note = {Online available at: \url{http://dx.doi.org/10.1007/s11661-016-3446-2} (DOI). Enz, J.; Riekehr, S.; Ventzke, V.; Huber, N.; Kashaev, N.: Laser Weldability of High-Strength Al-Zn Alloys and Its Improvement by the Use of an Appropriate Filler Material. In: Metallurgical and Materials Transactions  A. Vol. 47 (2016) 6, 2830 - 2841. (DOI:  10.1007/s11661-016-3446-2)}}
@article{ekh_a_framework_2016, 
author={Ekh, M. and Bargmann, S.},
title={A framework for geometrically non-linear gradient extended crystal plasticity coupled to heat conduction and damage},
year={2016},
journal = {Multiscale and Multiphysics Mechanics},
volume = {1},
number = {2},
pages = {171 - 188},
doi = {http://dx.doi.org/10.12989/mmm.2016.1.2.171},
abstract = {Gradient enhanced theories of crystal plasticity enjoy great research interest. The focus of this work is on thermodynamically consistent modeling of grain size dependent hardening effects. In this contribution, we develop a model framework for damage coupled to gradient enhanced crystal thermoplasticity. The damage initiation is directly linked to the accumulated plastic slip. The theoretical setting is that of finite strains. Numerical results on single-crystalline metal showing the development of damage conclude the paper.},
note = {Online available at: \url{http://dx.doi.org/10.12989/mmm.2016.1.2.171} (DOI). Ekh, M.; Bargmann, S.: A framework for geometrically non-linear gradient extended crystal plasticity coupled to heat conduction and damage. In: Multiscale and Multiphysics Mechanics. Vol. 1 (2016) 2, 171 - 188. (DOI:  10.12989/mmm.2016.1.2.171)}}
@article{mameka_nanoporous_gold_2016, 
author={Mameka, N. and Wang, K. and Markmann, J. and Lilleodden, E.T. and Weissmueller, J.},
title={Nanoporous Gold - Testing Macro-scale Samples to Probe Small-scale Mechanical Behavior},
year={2016},
journal = {Materials Research Letters},
volume = {4},
number = {1},
pages = {27 - 36},
doi = {http://dx.doi.org/10.1080/21663831.2015.1094679},
abstract = {Nanoporous gold made by dealloying exemplifies how the exciting mechanical properties of nanoscale objects can be exploited in designing materials from which macroscopic things can be formed. The homogeneous microstructure and the possibility of adjusting the ligament size, L, between few and few hundred nm, along with the high deformability and reproducible mechanical behavior predestine the material for model studies of small-scale plasticity using reliable macroscopic testing schemes on mm- or cm-size samples. Such experiments tend to agree with the Gibson-Ashby scaling relation for strength versus solid fraction, while suggesting an essentially scaling of the local strength of the ligaments. By contrast, the elastic compliance is dramatically enhanced compared to the Gibson-Ashby relation for the stiffness. Contrary to intuition, the anomalously compliant behavior of the nanomaterial goes along with a trend for more stiffness at smaller L. This article discusses surface excess elasticity, nonlinear elastic behavior and specifically shear instability of the bulk, network connectivity, and the surface chemistry as relevant issues which deserve further study.},
note = {Online available at: \url{http://dx.doi.org/10.1080/21663831.2015.1094679} (DOI). Mameka, N.; Wang, K.; Markmann, J.; Lilleodden, E.T.; Weissmueller, J.: Nanoporous Gold - Testing Macro-scale Samples to Probe Small-scale Mechanical Behavior. In: Materials Research Letters. Vol. 4 (2016) 1, 27 - 36. (DOI:  10.1080/21663831.2015.1094679)}}
@article{effertz_fatigue_life_2016, 
author={Effertz, P.S. and Infante, V. and Quintino, L. and Suhuddin, U. and Hanke, S. and dos Santos, J.F.},
title={Fatigue life assessment of friction spot welded 7050-T76 aluminium alloy using Weibull distribution},
year={2016},
journal = {International Journal of Fatigue},
volume = {87},
pages = {381 - 390},
doi = {http://dx.doi.org/10.1016/j.ijfatigue.2016.02.030},
abstract = {Friction spot welding is a solid state welding process suitable to obtain spot like-joints in overlap configuration. The process is particularly useful to weld lightweight materials in similar and dissimilar combinations, and therefore an interesting alternative to other joining techniques (rivets, resistance welding, etc.). Optimum process parameters have been defined using the Taguchi method by maximizing the response variable (the lap shear strength). A study of the fatigue life was carried out on specimens welded with the above mentioned optimized process parameters. Fatigue tests were performed using a stress ratio of R = 0.10. Two-parameter Weibull distribution was used to analyze statistically the fatigue life for the joined overlapped sheets. Subsequently, the Weibull plots were drawn, as well as S–N curves considering different reliability levels. The results show that for a relatively low load, corresponding to 10% of the maximum supported by the joint, the number of cycles surpasses 1 × 106, hence infinite life of the service component can be attributed. Fatigue fracture surfaces were investigated for the highest and lowest loads tested using scanning electron microscope (SEM).},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.ijfatigue.2016.02.030} (DOI). Effertz, P.S.; Infante, V.; Quintino, L.; Suhuddin, U.; Hanke, S.; dos Santos, J.F.: Fatigue life assessment of friction spot welded 7050-T76 aluminium alloy using Weibull distribution. In: International Journal of Fatigue. Vol. 87 (2016) 381 - 390. (DOI:  10.1016/j.ijfatigue.2016.02.030)}}
@article{roschning_scaling_laws_2016, 
author={Roschning, B. and Huber, N.},
title={Scaling laws of nanoporous gold under uniaxial compression: Effects of structural disorder on the solid fraction, elastic Poisson's ratio, Young's modulus and yield strength},
year={2016},
journal = {Journal of the Mechanics and Physics of Solids},
volume = {92},
pages = {55 - 71},
doi = {http://dx.doi.org/10.1016/j.jmps.2016.02.018},
abstract = {In this work the relationship between the structural disorder and the macroscopic mechanical behavior of nanoporous gold under uniaxial compression was investigated, using the finite element method. A recently proposed model based on a microstructure consisting of four-coordinated spherical nodes interconnected by cylindrical struts, whose node positions are randomly displaced from the lattice points of a diamond cubic lattice, was extended. This was done by including the increased density as result of the introduced structural disorder. Scaling equations for the elastic Poisson's ratio, the Young's modulus and the yield strength were determined as functions of the structural disorder and the solid fraction. The extended model was applied to identify the elastic-plastic behavior of the solid phase of nanoporous gold. It was found, that the elastic Poisson's ratio provides a robust basis for the calibration of the structural disorder. Based on this approach, a systematic study of the size effect on the yield strength was performed and the results were compared to experimental data provided in literature. An excellent agreement with recently published results for polymer infiltrated samples of nanoporous gold with varying ligament size was found.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.jmps.2016.02.018} (DOI). Roschning, B.; Huber, N.: Scaling laws of nanoporous gold under uniaxial compression: Effects of structural disorder on the solid fraction, elastic Poisson's ratio, Young's modulus and yield strength. In: Journal of the Mechanics and Physics of Solids. Vol. 92 (2016) 55 - 71. (DOI:  10.1016/j.jmps.2016.02.018)}}
@article{lu_plasma_electrolytic_2016, 
author={Lu, X. and Blawert, C. and Huang, Y. and Ovri, H. and Zheludkevich, M.L. and Kainer, K.U.},
title={Plasma electrolytic oxidation coatings on Mg alloy with addition of SiO2 particles},
year={2016},
journal = {Electrochimica Acta},
volume = {187},
pages = {20 - 33},
doi = {http://dx.doi.org/10.1016/j.electacta.2015.11.033},
abstract = {The addition of particles into plasma electrolytic oxidation (PEO) electrolyte provides a possibility to produce functionalized coatings with a wider range of compositions and new phases. In this study, nano- and micro-sized SiO2 particles were in-situ incorporated into phosphate-based coatings and the effect of these particles on the microstructure, composition and properties of the coatings was investigated. It was observed that the size and the melting point of the particles have a synergistic effect on the uptake and incorporation mode. The uptake of the nanoparticles occurred mainly via discharge channels and open pores, while micro-sized particles were mainly absorbed via the coating surface. Different particle properties result in reactive and inert incorporation for the nano- and micro-sized SiO2 particles, respectively. The results show that particle additions improve the wear resistance of PEO coating, although corrosion resistance is slightly reduced. Due to superior wear performance and degradability, PEO coatings with reactively incorporated nanoparticles on Mg alloy might be suitable for bio-medical application.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.electacta.2015.11.033} (DOI). Lu, X.; Blawert, C.; Huang, Y.; Ovri, H.; Zheludkevich, M.L.; Kainer, K.U.: Plasma electrolytic oxidation coatings on Mg alloy with addition of SiO2 particles. In: Electrochimica Acta. Vol. 187 (2016) 20 - 33. (DOI:  10.1016/j.electacta.2015.11.033)}}
@article{soyarslan_modeling_of_2016, 
author={Soyarslan, C. and Guelcimen, B. and Bargmann, S. and Haehner, P.},
title={Modeling of fracture in small punch tests for small- and large-scale yielding conditions at various temperatures},
year={2016},
journal = {International Journal of Mechanical Sciences},
volume = {106},
pages = {266 - 285},
doi = {http://dx.doi.org/10.1016/j.ijmecsci.2015.12.007},
abstract = {We present a systematic numerical study on temperature dependent fracture mode change in small punch tests. Following Needleman and Tvergaard (2000), we model the material as thermo-inelastic, where the ductile fracture mode, by void nucleation, growth and coalescence is accounted for by Gurson׳s porous metal plasticity (Gurson, 1977). The brittle fracture mode by cleavage is accounted for by Ritchie–Knott–Rice׳s deterministic maximum principal stress criterion (Ritchie et al., 1973). The well-known problem of mesh dependence associated with softening material behavior is remedied by using an integral type nonlocal formulation similar to that presented in Tvergaard and Needleman (1995). Two length scales are incorporated into the constitutive relations: the ductile fracture length scale is based on the average inclusion distance and associated with the nonlocal evolution equation for the porosity. The brittle fracture length scale is based on the average grain size and associated with the material region at which the maximum principal stress is averaged out. The material model is used to simulate small punch tests at View the MathML source−196°C, View the MathML source−158°C and View the MathML source25°C of notched and unnotched specimens of P91 steel representative for small- and large-scale yielding conditions, respectively. The simulated fracture modes and patterns show a very good agreement with experiments: for View the MathML source−196°C brittle fracture propagating normal to the maximum (tensile) principal stress prevails. For View the MathML source25°C ductile fracture is governed by shear localization with voidage. The simulations also show that the deformation energy is considerably higher for the upper shelf tests compared to the lower shelf tests.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.ijmecsci.2015.12.007} (DOI). Soyarslan, C.; Guelcimen, B.; Bargmann, S.; Haehner, P.: Modeling of fracture in small punch tests for small- and large-scale yielding conditions at various temperatures. In: International Journal of Mechanical Sciences. Vol. 106 (2016) 266 - 285. (DOI:  10.1016/j.ijmecsci.2015.12.007)}}
@article{sopu_structureproperty_relationships_2016, 
author={Sopu, D. and Soyarslan, C. and Sarac, B. and Bargmann, S. and Stoica, M. and Eckert, J.},
title={Structure-property relationships in nanoporous metallic glasses},
year={2016},
journal = {Acta Materialia},
volume = {106},
pages = {199 - 207},
doi = {http://dx.doi.org/10.1016/j.actamat.2015.12.026},
abstract = {We investigate the influence of various critical structural aspects such as pore density, distribution, size and number on the deformation behavior of nanoporous Cu64 Zr36 glass. By using molecular dynamics and finite element simulations an effective strategy to control the strain localization in nanoporous heterostructures is provided. Depending on the pore distribution in the heterostructure, upon tensile loading the nanoporous glass showed a clear transition from a catastrophic fracture to localized deformation in one dominant shear band, and ultimately to homogeneous plastic flow mediated by a pattern of multiple shear bands. The change in the fracture mechanism from a shear band slip to necking-like homogeneous flow is quantitative interpreted by calculating the critical shear band length. Finally, we identify the most effective heterostructure with enhanced ductility as compared to the monolithic bulk metallic glass. The heterostructure with a fraction of pores of about 3% distributed in such a way that the pores do not align along the maximum shear stress direction shows higher plasticity while retaining almost the same strength as the monolithic glass. Our results provide clear evidence that the mechanical properties of nanoporous glassy materials can be tailored by carefully controlling the design parameters.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.actamat.2015.12.026} (DOI). Sopu, D.; Soyarslan, C.; Sarac, B.; Bargmann, S.; Stoica, M.; Eckert, J.: Structure-property relationships in nanoporous metallic glasses. In: Acta Materialia. Vol. 106 (2016) 199 - 207. (DOI:  10.1016/j.actamat.2015.12.026)}}
@article{plaine_process_parameter_2016, 
author={Plaine, A.H. and Gonzalez, A.R. and Suhuddin, U.F.H. and dos Santos, J.F. and Alcantara, N.G.},
title={Process parameter optimization in friction spot welding of AA5754 and Ti6Al4V dissimilar joints using response surface methodology},
year={2016},
journal = {The International Journal of  Advanced Manufacturing Technology},
volume = {85},
number = {5},
pages = {1575 - 1583},
doi = {http://dx.doi.org/10.1007/s00170-015-8055-5},
abstract = {This study shows experimental and numerical results of friction spot welding of AA5754 and Ti6Al4V alloys. The determination of proper welding parameters plays an important role for the weld strength. Experimental tests, conducted according to combinations of process parameters such as tool rotational speed (RS) and dwell time (DT), were investigated with response surface methodology using a 3k factorial design of experiments. Sound joints with elevated shear strength were achieved and the influence of the main process parameters on joint strength evaluated. DT was the parameter with the largest influence on the joint shear resistance (58.9 %), followed by its interaction with RS (38.1 %). Higher strength was correlated to the thickness and morphology of the joint interface. A numerical model for predicting lap shear strength was successfully developed and used to optimize welding parameters in order to produce high-performance joints with less energy consumption and high efficiency.},
note = {Online available at: \url{http://dx.doi.org/10.1007/s00170-015-8055-5} (DOI). Plaine, A.H.; Gonzalez, A.R.; Suhuddin, U.F.H.; dos Santos, J.F.; Alcantara, N.G.: Process parameter optimization in friction spot welding of AA5754 and Ti6Al4V dissimilar joints using response surface methodology. In: The International Journal of  Advanced Manufacturing Technology. Vol. 85 (2016) 5, 1575 - 1583. (DOI:  10.1007/s00170-015-8055-5)}}
@article{plaine_interface_formation_2016, 
author={Plaine, A.H. and Suhuddin, U.F.H. and Afonso, C.R.M. and Alcantara, N.G. and dos Santos, J.F.},
title={Interface formation and properties of friction spot welded joints of AA5754 and Ti6Al4V alloys},
year={2016},
journal = {Materials and Design},
volume = {93},
pages = {224 - 231},
doi = {http://dx.doi.org/10.1016/j.matdes.2015.12.170},
abstract = {This study aims to understand the influence of dwell time on the microstructure of the interface and lap shear strength of friction spot welded joints of AA5754 and Ti6Al4V alloys. The interface reaction layer consists mainly of TiAl3 intermetallic compound. It was noticed that dwell time significantly influences the diffusion process during the friction spot welding, thereby modifying the thickness of the interface and thus affecting the mechanical performance of the joints. Minimizing or optimizing the brittle TiAl3 phase was demonstrated to be the key issue to achieve high strength Ti/Al dissimilar joints. The intermetallic compound growth kinetics was also examined showing that an incubation time of approximately 2.7 s is necessary before it nucleates at the Ti/Al interface and grows laterally to form a continuous layer. Afterwards, the TiAl3 layer grows toward the Al during thickening with a corresponding growth rate of k = 2.92 × 10− 7 m/s. These results are critical to understand the microstructure–properties relationship and contribute with additional improvements on the joint performance.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.matdes.2015.12.170} (DOI). Plaine, A.H.; Suhuddin, U.F.H.; Afonso, C.R.M.; Alcantara, N.G.; dos Santos, J.F.: Interface formation and properties of friction spot welded joints of AA5754 and Ti6Al4V alloys. In: Materials and Design. Vol. 93 (2016) 224 - 231. (DOI:  10.1016/j.matdes.2015.12.170)}}
@article{soyarslan_variants_of_2016, 
author={Soyarslan, C. and Richter, H. and Bargmann, S.},
title={Variants of Lemaitre’s damage model and their use in formability prediction of metallic materials},
year={2016},
journal = {Mechanics of Materials},
volume = {92},
pages = {58 - 79},
doi = {http://dx.doi.org/10.1016/j.mechmat.2015.08.009},
abstract = {Taking Lemaitre’s damage model (Lemaitre, 1996) as the point of departure, we present two successive enhancements to meet the requirements of formability prediction for today’s modern steels. The first extension is a quasi-unilateral damage evolution which, after a spectral decomposition of the stress tensor, scales the elastic energy release rate due to compressive principal stress components. The second one is inspired by a recent multiplicative modification of triaxiality dependent Oyane’s fracture criterion with a shear stress dependent term, following (Lou et al., 2012)]. For plane stress states, the former modification allows, besides correcting the pathological symmetry of the fracture strain with respect to vanishing stress triaxiality ratio, i.e. η=0,η=0,hindering fracture under uniaxial compression since the altered fracture strain curve shows an asymptotic behavior at η=−1/3η=−1/3. Depending on the selected parameters, the latter modification permits one to further modify this curve to give account for two local minima in the vicinity of generalized shear points within the triaxiality interval [−1/3,2/3][−1/3,2/3]. From a formability prediction perspective, as a consequence of the former modification, premature failure prediction of the conventional Lemaitre’s damage model in many compression dominated metal forming operations is remedied. The latter modification permits modeling shear dominated fracture. Moreover, for each variant, closed form expressions for the isochronous fracture surfaces associated with linear strain paths are derived and resulting surface plots at various spaces are compared. It is shown that only shear modification together with quasi-unilateral enhancement lets model show enough flexibility during parameter calibration for the experimental data. Finally, handled calibrations are compared with those of the existing fracture criteria frequently used in the literature to highlight relative strengths of the current proposal.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.mechmat.2015.08.009} (DOI). Soyarslan, C.; Richter, H.; Bargmann, S.: Variants of Lemaitre’s damage model and their use in formability prediction of metallic materials. In: Mechanics of Materials. Vol. 92 (2016) 58 - 79. (DOI:  10.1016/j.mechmat.2015.08.009)}}
@article{bargmann_materials_based_2016, 
author={Bargmann, S. and Soyarslan, C. and Husser, E. and Konchakova, N.},
title={Materials based design of structures: computational modeling of the mechanical behavior of gold-polymer nanocomposites},
year={2016},
journal = {Mechanics of Materials},
volume = {94},
pages = {53 - 65},
doi = {http://dx.doi.org/10.1016/j.mechmat.2015.11.008},
abstract = {The impact of small scale geometric confinement on deformation mechanisms is subject of intense research in materials sciences nowadays. Nanoporous metals have a microstructure with an extremely high volume-specific surface content. Due to a very high local strength and a relatively regular interconnection of the nanoconstituents as well as a low mass density, nanoporous metals are very good candidates for strong and light-weight structural materials.

The modeling of a modern nanocomposite material of gold-polymer is in the focus of the contribution. A gradient extended crystal plasticity theory is applied to the computation of the mechanical response of the metal part of the composite and an elastic-viscoplastic continuum model is used for the simulation of the polymer material. The gradient hardening contribution is included into the crystal plasticity model in order to study the influence of the ligament size. Numerical results of the deformation of the gold-polymer nanocomposite under compression are presented. Simulation results are compared to the corresponding experimental data.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.mechmat.2015.11.008} (DOI). Bargmann, S.; Soyarslan, C.; Husser, E.; Konchakova, N.: Materials based design of structures: computational modeling of the mechanical behavior of gold-polymer nanocomposites. In: Mechanics of Materials. Vol. 94 (2016) 53 - 65. (DOI:  10.1016/j.mechmat.2015.11.008)}}
@article{enz_fibre_laser_2016, 
author={Enz, J. and Riekehr, S. and Ventzke, V. and Huber, N. and Kashaev, N.},
title={Fibre laser welding of high-alloyed Al–Zn–Mg–Cu alloys},
year={2016},
journal = {Journal of Materials Processing Technology},
volume = {237},
pages = {155 - 162},
doi = {http://dx.doi.org/10.1016/j.jmatprotec.2016.06.002},
abstract = {The theoretical fundamentals of laser weldability of metals are surveyed and relevant thermophysical parameters are identified – such as vapour pressure, keyhole pressure, beam irradiance, surface tension and viscosity. The derived approach for improving the laser weldability implies the use of a Yb fibre laser with an initial large beam diameter, a top-hat beam profile and a high laser power, which enables the formation of a large and stable keyhole during deep penetration welding. For validating the effectiveness of the developed approach, it is applied to various high-alloyed and hard-to-weld Al–Zn–Mg–Cu alloys. Defect-free welds are obtained even for AA7034 – the alloy with the highest (Zn + Mg + Cu) content commercially available. As reference, the same alloys are welded by using a conventional Nd:YAG laser with a small beam diameter, a Gaussian beam profile and medium laser power. The laser weldability deteriorates with increasing (Zn + Mg + Cu) content in terms of porosity and excess of penetration. The obtained results highlight the importance of the laser system used on the laser weldability of Al–Zn–Mg–Cu alloys.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.jmatprotec.2016.06.002} (DOI). Enz, J.; Riekehr, S.; Ventzke, V.; Huber, N.; Kashaev, N.: Fibre laser welding of high-alloyed Al–Zn–Mg–Cu alloys. In: Journal of Materials Processing Technology. Vol. 237 (2016) 155 - 162. (DOI:  10.1016/j.jmatprotec.2016.06.002)}}
@article{steglich_mechanismbased_modelling_2016, 
author={Steglich, D. and Tian, X. and Besson, J.},
title={Mechanism-based modelling of plastic deformation in magnesium alloys},
year={2016},
journal = {European Journal of Mechanics  A},
volume = {55},
pages = {289 - 303},
doi = {http://dx.doi.org/10.1016/j.euromechsol.2015.09.011},
abstract = {The plastic deformation of two different rolled magnesium sheets (AZ31 and ZE10) under quasi-static tensile and compressive loading conditions at room temperature is studied. Beside glide by dislocation motion, deformation twinning leads to evolving flow stress asymmetry and evolving plastic anisotropy in these alloys. These mechanisms cause a significant change in the shape of the yield surface with accumulated plastic deformation which cannot be described by traditional hardening concepts. A phenomenological plasticity model in which the primary deformation mechanisms, slip and (extension) twinning, are treated separately is developed here and incorporated in the finite element framework. Deformations caused by these mechanisms are modelled by a symmetric and an asymmetric plastic potential, respectively. The hardening functions are coupled to account for the latent hardening. The necessary input for model parameter calibration is provided by mechanical tests along different orientations of the rolled sheets. Tensile tests of notched samples and shear tests are furthermore incorporated in the parameter optimisation strategy, which is based on minimising the difference between experimental behaviour and FE prediction over the entire deformation range up to failure. The model accounts for the characteristic tension-compression asymmetry and the evolution of strain anisotropy. Both, the convex-up and the concave-down shaped stress–strain response are predicted. The computational model is exemplified by studying the evolution of the plastic multipliers during a shear test. It is shown that despite its phenomenological character, the model predicts the dominant deformation mechanism present at monotonous loading of the magnesium sheets investigated.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.euromechsol.2015.09.011} (DOI). Steglich, D.; Tian, X.; Besson, J.: Mechanism-based modelling of plastic deformation in magnesium alloys. In: European Journal of Mechanics  A. Vol. 55 (2016) 289 - 303. (DOI:  10.1016/j.euromechsol.2015.09.011)}}
@article{druecker_finite_element_2016, 
author={Druecker, S. and Steglich, D. and Merckelbach, L. and Werner, A. and Bargmann, S.},
title={Finite element damage analysis of an underwater glider–ship collision},
year={2016},
journal = {Journal of Marine Science and Technology},
volume = {21},
number = {2},
pages = {261 - 270},
doi = {http://dx.doi.org/10.1007/s00773-015-0349-7},
abstract = {Underwater gliders, which are profiling autonomous underwater vehicles designed to make oceanographic measurements, are increasingly used in the coastal ocean. As they regularly surface for data transmission, gliders increasingly pose a risk for fast ships. In order to estimate the extent of damage due to collision, 3D finite element simulations of collisions between a glider and a high-speed craft with a glass-fiber reinforced plastic hull are performed. Different collision scenarios such as impact locations, angles of attack and speeds are examined. The results are compared to an analytical solution based on simplifying assumptions. Although both methods reveal consistent results, it is shown that finite element simulations are required to account for the 3D shape of the ship. The results indicate that at ship velocities exceeding 7.5 m/s (14.6 kt) the glider penetrates the ship’s hull causing severe damage to its structure.},
note = {Online available at: \url{http://dx.doi.org/10.1007/s00773-015-0349-7} (DOI). Druecker, S.; Steglich, D.; Merckelbach, L.; Werner, A.; Bargmann, S.: Finite element damage analysis of an underwater glider–ship collision. In: Journal of Marine Science and Technology. Vol. 21 (2016) 2, 261 - 270. (DOI:  10.1007/s00773-015-0349-7)}}
@article{luehrs_elastic_and_2016, 
author={Luehrs, L. and Soyarslan, C. and Markmann, J. and Bargmann, S. and Weissmueller, J.},
title={Elastic and plastic Poisson’s ratios of nanoporous gold},
year={2016},
journal = {Scripta Materialia},
volume = {110},
pages = {65 - 69},
doi = {http://dx.doi.org/10.1016/j.scriptamat.2015.08.002},
abstract = {We explore the elastic and plastic Poisson’s ratios, νEνE and νPνP, of nanoporous gold, using digital image correlation during compression experiments including load/unload segments. The two coefficients differ significantly, with νEνE independent of the ligament size, L  , and with a trend for View the MathML sourceνP∝L at not too large L  . Disorder in the network of ligaments may explain why νEνE is smaller than predicted by lattice-based models. Finite element simulations, based on the Deshpande–Fleck constitutive law, validate the data analysis. The constitutive law captures work-hardening and transverse flow of nanoporous gold in good agreement with the experiment.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.scriptamat.2015.08.002} (DOI). Luehrs, L.; Soyarslan, C.; Markmann, J.; Bargmann, S.; Weissmueller, J.: Elastic and plastic Poisson’s ratios of nanoporous gold. In: Scripta Materialia. Vol. 110 (2016) 65 - 69. (DOI:  10.1016/j.scriptamat.2015.08.002)}}
@article{goushegir_xps_analysis_2016, 
author={Goushegir, S.M. and Scharnagl, N. and dos Santos, J.F. and Amancio-Filho, S.T.},
title={XPS analysis of the interface between AA2024-T3 / CF-PPS friction spot joints},
year={2016},
journal = {Surface and Interface Analysis :SIA},
volume = {48},
number = {8},
pages = {706 - 711},
doi = {http://dx.doi.org/10.1002/sia.5816},
abstract = {Friction spot joining (FSpJ) is an advanced, alternative technology suitable for joining metal-composite overlap structures. In this paper, the principles of the FSpJ technique are briefly described. Furthermore, the influence of aluminum surface pretreatments (conversion coating and phosphoric acid anodizing) on the adhesion between aluminum alloy AA2024-T3 and carbon-fiber-reinforced poly(phenylene sulfide) (CF-PPS) friction spot joints was examined. X-ray photoelectron spectroscopy (XPS) was used to investigate the changes in the chemical composition of the aluminum after surface pretreatments, as well as chemical bond formation at the interface between the aluminum and composite. The joints were mechanically loaded until failure, and the fracture surface of the joints were analyzed on the aluminum side. XPS results showed evidence of Al–C and Zr–C bond formation at the interface for the selected surface pretreatments in the course of the joining cycle. Chemical bond formation was confirmed through the analysis of C1s and Al2p regions in which the appearance of new peaks with different binding energies compared with the aluminum and composite were identified.},
note = {Online available at: \url{http://dx.doi.org/10.1002/sia.5816} (DOI). Goushegir, S.M.; Scharnagl, N.; dos Santos, J.F.; Amancio-Filho, S.T.: XPS analysis of the interface between AA2024-T3 / CF-PPS friction spot joints. In: Surface and Interface Analysis :SIA. Vol. 48 (2016) 8, 706 - 711. (DOI:  10.1002/sia.5816)}}
@article{richtertrummer_fatigue_crack_2016, 
author={Richter-Trummer, V. and Zhang, X. and Irving, P.E. and Pacchione, M. and Beltrao, M. and dos Santos, J.F.},
title={Fatigue Crack Growth Behaviour in Friction Stir Welded Aluminium–Lithium Alloy Subjected to Biaxial Loads},
year={2016},
journal = {Experimental Techniques},
volume = {40},
number = {3},
pages = {921 - 935},
doi = {http://dx.doi.org/10.1111/ext.12116},
abstract = {In this article, biaxial load fatigue crack growth tests are reported. Specimens were made of an advanced aluminium–lithium alloy AA2198-T8 joined by the friction stir welding process, capable of producing advanced integral metallic structures that can offer significant cost and weight savings over the current joining methods. Two material rolling directions are considered in relation to the welding and crack growth direction. Welding-induced initial distortion was measured before the experiment for better result interpretation. Test specimens are representative of two different weld orientations, that is longitudinal weld parallel to the material rolling direction and circumferential weld perpendicular to the material rolling direction for investigating the inherent material anisotropy of aluminium–lithium alloys. In all tests, the fatigue crack was initiated in the thermo-mechanical process zone of the weld and propagated parallel to the weld joint line. It is shown that the rolling direction of the selected aluminium alloy strongly affects the crack growth path. The specimens welded orthogonally to the rolling direction exhibit a shorter fatigue crack growth life than the specimens welded parallel to the rolling direction.},
note = {Online available at: \url{http://dx.doi.org/10.1111/ext.12116} (DOI). Richter-Trummer, V.; Zhang, X.; Irving, P.E.; Pacchione, M.; Beltrao, M.; dos Santos, J.F.: Fatigue Crack Growth Behaviour in Friction Stir Welded Aluminium–Lithium Alloy Subjected to Biaxial Loads. In: Experimental Techniques. Vol. 40 (2016) 3, 921 - 935. (DOI:  10.1111/ext.12116)}}
@article{plaine_fatigue_behavior_2016, 
author={Plaine, A.H. and Suhuddin, U.F.H. and Alcantara, N.G. and dos Santos, J.F.},
title={Fatigue behavior of friction spot welds in lap shear specimens of AA5754 and Ti6Al4V alloys},
year={2016},
journal = {International Journal of Fatigue},
volume = {91},
pages = {149 - 157},
doi = {http://dx.doi.org/10.1016/j.ijfatigue.2016.06.005},
abstract = {The fatigue behavior of single friction spot welded AA5754 and Ti6Al4V dissimilar joints was investigated based on experimental observations. Fatigue tests were performed in a constant amplitude load control servo-hydraulic machine with a load ratio of R = 0.1 at room temperature. Two-parameter Weibull distribution was used to analyze statistically the fatigue data for the joined overlapped sheets. Weibull graphics were plotted for each stress amplitude value. Subsequently, S–N curves were drawn for different reliability levels (10%, 50%, 90% and 99%) for the benefit of designers. A fatigue limit of 25 MPa was determined for the AA5754/Ti6Al4V joints (at survival level of 50%), corresponding to 15% of the maximum average static fracture load. Two different types of fatigue failure modes were observed for the specimens. Under high cyclic loads, the failure occurred in the upper Al sheet because of the higher stress concentration at the notch tip leading to crack initiation followed by its propagation through the thickness toward the joint surface and, subsequently, along the specimen width direction. Under low cyclic loads, “through weld” failure was observed as the crack rapidly propagated along the interfacial surface until a critical point at which the remaining cross section could no longer sustain the shear overload and failed. A fatigue crack growth mechanism based on the paths of the dominant fatigue cracks was then proposed and used to explain the fatigue fracture evolution under different loading conditions.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.ijfatigue.2016.06.005} (DOI). Plaine, A.H.; Suhuddin, U.F.H.; Alcantara, N.G.; dos Santos, J.F.: Fatigue behavior of friction spot welds in lap shear specimens of AA5754 and Ti6Al4V alloys. In: International Journal of Fatigue. Vol. 91 (2016) 149 - 157. (DOI:  10.1016/j.ijfatigue.2016.06.005)}}
@article{goushegir_failure_and_2016, 
author={Goushegir, S.M. and dos Santos, J.F. and Amancio-Filho, S.T.},
title={Failure and fracture micro-mechanisms in metal-composite single lap joints produced by welding-based joining techniques},
year={2016},
journal = {Composites / A},
volume = {81},
pages = {121 - 128},
doi = {http://dx.doi.org/10.1016/j.compositesa.2015.11.001},
abstract = {Welding-based joining technologies have been recently developed for metal-composite lightweight structures. In this work, the welding-based joining technology, friction spot joining, was selected to study the failure and fracture micro-mechanisms of an aluminum-composite single lap joint. Failure analysis suggested that the radial cracks nucleate at the periphery of the bonding area and propagate rapidly until failure of the so-called adhesion zone. Upon further loading the cracks propagate into the transition and plastically deformed zones leading to a reduction of the stiffness of the joint. The findings of the fractography demonstrated a mixed brittle-ductile fracture. Three zones were identified on the fracture surfaces: a smooth and featureless area demonstrating brittle fracture, a quasi-smooth area representing a mixture of ductile and brittle fractures and finally a zone with a highly rough surface implying ductile fracture of the composite part. Further, fiber pull-out and breakage were identified as additional fracture micro-mechanisms.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.compositesa.2015.11.001} (DOI). Goushegir, S.M.; dos Santos, J.F.; Amancio-Filho, S.T.: Failure and fracture micro-mechanisms in metal-composite single lap joints produced by welding-based joining techniques. In: Composites / A. Vol. 81 (2016) 121 - 128. (DOI:  10.1016/j.compositesa.2015.11.001)}}
@article{schneider_automatic_threedimensional_2016, 
author={Schneider, K. and Klusemann, B. and Bargmann, S.},
title={Automatic three-dimensional geometry and mesh generation of periodic representative volume elements for matrix-inclusion composites},
year={2016},
journal = {Advances in Engineering Software},
volume = {99},
pages = {177 - 188},
doi = {http://dx.doi.org/10.1016/j.advengsoft.2016.06.001},
abstract = {This paper introduces an efficient method to automatically generate and mesh a periodic three-dimensional microstructure for matrix-inclusion composites. Such models are of major importance in the field of computational micromechanics for homogenization purposes utilizing unit cell models. The main focus of this contribution is on the creation of cubic representative volume elements (RVEs) featuring a periodic geometry and a periodic mesh topology suitable for the application of periodic boundary conditions in the framework of finite element simulations. Our method systematically combines various meshing tools in an extremely efficient and robust algorithm. The RVE generation itself follows a straightforward random sequential absorption approach resulting in a randomized periodic microstructure. Special emphasis is placed on the discretization procedure to maintain a high quality mesh with as few elements as possible, thus, manageable for computer simulations applicable to high volume concentrations, high number of inclusions and complex inclusion geometries. Examples elucidate the ability of the proposed approach to efficiently generate large RVEs with a high number of anisotropic inclusions incorporating extreme aspect ratios but still maintaining a high quality mesh and a low number of elements.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.advengsoft.2016.06.001} (DOI). Schneider, K.; Klusemann, B.; Bargmann, S.: Automatic three-dimensional geometry and mesh generation of periodic representative volume elements for matrix-inclusion composites. In: Advances in Engineering Software. Vol. 99 (2016) 177 - 188. (DOI:  10.1016/j.advengsoft.2016.06.001)}}
@article{stenner_piezoelectric_gold_2016, 
author={Stenner, C. and Shao, L.-H. and Mameka, N. and Weissmueller, J.},
title={Piezoelectric Gold: Strong Charge-Load Response in a Metal-Based Hybrid Nanomaterial},
year={2016},
journal = {Advanced Functional Materials},
volume = {26},
number = {28},
pages = {5174 - 5181},
doi = {http://dx.doi.org/10.1002/adfm.201600938},
abstract = {Impregnating the pores of nanoporous gold with aqueous electrolyte yields a hybrid nanomaterial with two separate and interpenetrating charge transport paths, electronic conduction in the metal and ionic conduction in the electrolyte. As the two paths are capacitively connected, space-charge layers along the internal interfaces are coupled to electric potential differences between the paths and can be controlled or detected thereby. The present experiments show that the space charge couples to mechanical deformation of the hybrid material, so that external loading generates an electric current. The electric signal originates from charge displacement along the entire internal interface; the signal is particularly robust since the interface area is large. The charge transfer in response to load constitutes a piezoelectric response, yet the mechanism is quite different to classic piezoelectricity. The analysis in this work predicts links between electromechanical coupling parameters for strain sensing and actuation, which are in excellent agreement with the experiment.},
note = {Online available at: \url{http://dx.doi.org/10.1002/adfm.201600938} (DOI). Stenner, C.; Shao, L.-H.; Mameka, N.; Weissmueller, J.: Piezoelectric Gold: Strong Charge-Load Response in a Metal-Based Hybrid Nanomaterial. In: Advanced Functional Materials. Vol. 26 (2016) 28, 5174 - 5181. (DOI:  10.1002/adfm.201600938)}}
@article{schnoor_nanostructured_mwcntpolypyrrole_2016, 
author={Schnoor, T.I.W. and Vainio, U. and Shao, l.-H. and Lilleodden, E.T. and Mueller, M. and Schreyer, A. and Schulte, K. and Fiedler, B.},
title={Nanostructured MWCNT/Polypyrrole Actuators with Anisotropic Strain Response},
year={2016},
journal = {Advanced Engineering Materials},
volume = {18},
number = {4},
pages = {597 - 607},
doi = {10.1002/adem.201500287},
abstract = {Conducting polymers (CP) as an active material in electrochemical actuators are often likened to “artificial muscles”. To transfer the isotropic change of volume in the CP component into an anisotropic actuation as in a natural muscle, different design approaches, mostly bilayer or triple layer bending devices, have been studied. Herein, we report a novel actuator design with an almost linear strain response, consisting of nanostructured aligned multi‐walled carbon nanotube arrays in which each MWCNT is individually coated with a thin layer of polypyrrole.},
note = {Online available at: \url{https://dx.doi.org/10.1002/adem.201500287} (DOI). Schnoor, T.I.W.; Vainio, U.; Shao, l.-H.; Lilleodden, E.T.; Mueller, M.; Schreyer, A.; Schulte, K.; Fiedler, B.: Nanostructured MWCNT/Polypyrrole Actuators with Anisotropic Strain Response. In: Advanced Engineering Materials. Vol. 18 (2016) 4, 597 - 607. (DOI:  /10.1002/adem.201500287)}}
@article{liu_phase_transformations_2016, 
author={Liu, J. and Staron, P. and Riekehr, S. and Stark, A. and Schell, N. and Huber, N. and Schreyer, A. and Mueller, M. and Kashaev, N.},
title={Phase Transformations During Solidification of a Laser-Beam-Welded TiAl Alloy—An In Situ Synchrotron Study
},
year={2016},
journal = {Metallurgical and Materials Transactions  A},
volume = {47},
number = {12},
pages = {5761 - 5770},
doi = {http://dx.doi.org/10.1007/s11661-016-3726-x},
abstract = {An in situ highly time-resolved, high-energy X-ray diffraction investigation was carried out to observe the phase transformations of a TiAl alloy during laser beam welding. The diffraction patterns are recorded every 0.1 seconds by a fast area two-dimensional detector and plotted according to time, yielding the solidification pathway, the solid phase volume fraction, and the lattice parameter variation of different phases during the solidification and cooling process. Moreover, it is the first study that can demonstrate that the α phase without any Burgers orientation relationship, the so-called non-Burgers α, precipitates appear earlier than the Burgers α. The non-Burgers α grains are found to nucleate on the primary borides.},
note = {Online available at: \url{http://dx.doi.org/10.1007/s11661-016-3726-x} (DOI). Liu, J.; Staron, P.; Riekehr, S.; Stark, A.; Schell, N.; Huber, N.; Schreyer, A.; Mueller, M.; Kashaev, N.: Phase Transformations During Solidification of a Laser-Beam-Welded TiAl Alloy—An In Situ Synchrotron Study
. In: Metallurgical and Materials Transactions  A. Vol. 47 (2016) 12, 5761 - 5770. (DOI:  10.1007/s11661-016-3726-x)}}
@article{azevedo_friction_stir_2016, 
author={Azevedo, J. and Quintino, L. and Infante, V. and Miranda, R.M. and dos Santos, J.F.},
title={Friction Stir Welding of Shipbuilding Steel with Primer},
year={2016},
journal = {Soldagem & Inspecao},
volume = {21},
number = {1},
pages = {16 - 29},
doi = {http://dx.doi.org/10.1590/0104-9224/SI2101.03},
abstract = {Friction Stir Welding has proven its merits for welding of aluminium alloys and is focused in expanding its material database to steel and titanium and also to assess new joint configurations. The use of welded structures in shipbuilding industry has a long tradition and continuously seeks for innovation in terms of materials and processes maintaining, or even, reducing costs. Several studies have been performed in the past years on FSW of steel. However, just recently were reported defect-free welds, free of martensite with stable parameters in steel without Primer. FSW of steel with primer has not been addressed. This work aims to fulfil a knowledge gap related to the use of friction stir for welding shipbuilding steel by analysing the effect of welding parameters on the metallurgical characteristics and mechanical properties of welds obtained with an innovative FSW tool in joining steel plates with a primer. Welds were performed in 4mm thick GL-A36 steel plates painted with a zinc based primer followed by a detailed microscopic, chemical and mechanical analysis. The results that matching fatigue properties are obtained using this technique, in FSW of shipbuilding steel with Primer.},
note = {Online available at: \url{http://dx.doi.org/10.1590/0104-9224/SI2101.03} (DOI). Azevedo, J.; Quintino, L.; Infante, V.; Miranda, R.M.; dos Santos, J.F.: Friction Stir Welding of Shipbuilding Steel with Primer. In: Soldagem & Inspecao. Vol. 21 (2016) 1, 16 - 29. (DOI:  10.1590/0104-9224/SI2101.03)}}
@article{goncalves_improvement_of_2016, 
author={Goncalves, J. and dos Santos, J.F. and Canto, L.B. and Amancio Filho, S.T.},
title={Improvement of friction spot welding (FSpW) to join polyamide 6 and polyamide 66/carbon fibre laminate},
year={2016},
journal = {Welding International},
volume = {30},
number = {4},
pages = {247 - 254},
doi = {10.1080/09507116.2015.1096466},
abstract = {Friction spot welding is an innovative technique developed and patented in 2005 by the research centre Helmholtz Zentrum Geesthacht. Advantages of the process include fast joining cycles, low operational costs and good mechanical performance. It was originally developed to weld lightweight metals and has been continuously improved to weld polymers. There are only a few studies on friction spot welding of thermoplastics, and the welding of polymeric composites by Friction spot welding (FSpW) is still unpublished. This study demonstrated the technical feasibility of welding a polyamide 6 (PA6) plate over a carbon fibre polyamide 66 laminate (CF-PA66) by FSpW. The thermal history, the surface finish, the microstructure of the weld region and the mechanical shear strength of PA6/CF-PA66 lap joints were investigated. The increase in the diameter of the clamping ring – originally designed for welding lightweight metals – led to the selection of welding parameters that result in high heat input, resulting in an increased welded area and lower notch left by the tool in the sample that improved the surface finish of the weld. This optimisation resulted in a PA6/CF-PA66 joint with lap shear strength of 35 MPa (2196 N), with fracture occurring mainly in the top plate of PA6.},
note = {Online available at: \url{https://dx.doi.org/10.1080/09507116.2015.1096466} (DOI). Goncalves, J.; dos Santos, J.F.; Canto, L.B.; Amancio Filho, S.T.: Improvement of friction spot welding (FSpW) to join polyamide 6 and polyamide 66/carbon fibre laminate. In: Welding International. Vol. 30 (2016) 4, 247 - 254. (DOI:  /10.1080/09507116.2015.1096466)}}
@article{huang_materialflow_behavior_2016, 
author={Huang, Y. and Wang, Y. and Wan, L. and Liu, H. and Shen, J. and dos Santos, J.F. and Zhou, L. and Feng, J.},
title={Material-flow behavior during friction-stir welding of 6082-T6 aluminum alloy},
year={2016},
journal = {The International Journal of  Advanced Manufacturing Technology},
volume = {87},
number = {1},
pages = {1115 - 1123},
doi = {http://dx.doi.org/10.1007/s00170-016-8603-7},
abstract = {Material-flow behavior during friction-stir welding of 6082-T6 aluminum alloy has been visualized by marker insert technique. Four stacked layers were evolved in welding nugget zone (WNZ) in the transverse section. The material-flow behavior in vertical direction was detected by observing the distribution of Cu foil fragments and Al-Cu intermetallic compounds. The downward and upward flows encounter each other at the advancing side in the material depositing process, changing the morphology of WNZ. A conceptual balanced-flow model and a plastic material-flow model were used to describe the material-flow behavior, and the origin of the downward material flow in the advancing side was discussed. The excess-material flow derived by the welding tool due to the existence of the tilt angle is crucial to the weld formation.},
note = {Online available at: \url{http://dx.doi.org/10.1007/s00170-016-8603-7} (DOI). Huang, Y.; Wang, Y.; Wan, L.; Liu, H.; Shen, J.; dos Santos, J.F.; Zhou, L.; Feng, J.: Material-flow behavior during friction-stir welding of 6082-T6 aluminum alloy. In: The International Journal of  Advanced Manufacturing Technology. Vol. 87 (2016) 1, 1115 - 1123. (DOI:  10.1007/s00170-016-8603-7)}}
@article{fitseva_the_role_2016, 
author={Fitseva, V. and Hanke, S. and dos Santos, J.F. and Stemmer, P. and Gleising, B.},
title={The role of process temperature and rotational speed in the microstructure evolution of Ti-6Al-4V friction surfacing coatings},
year={2016},
journal = {Materials and Design},
volume = {110},
pages = {112 - 123},
doi = {http://dx.doi.org/10.1016/j.matdes.2016.07.132},
abstract = {Friction surfacing is a solid state technique for depositing metallic coatings. Coating materials are thermo-mechanically processed at high temperatures during deposition. The high degree of deformation involved leads to a dynamically recrystallised fine grained microstructure. For Ti-6Al-4V, the microstructure and mechanical properties of coatings generated by friction surfacing have not been studied yet. The current work focuses on investigating effects of rotational speed on microstructure, grain size evolution and mechanical properties of the coating material.

Various rotational speeds in a wide range, exceeding the range of deformation used in many other severe plastic deformation processes, were used to generate Ti-6Al-4V coatings by friction surfacing. Their influence on the thermal cycle and consequently on microstructure formation was revealed. The β grain size is related to the rotational speed and thermal cycle. Grain refinement at low rotational speed was observed, while higher rotational speeds and corresponding increase in maximum temperature led to grain coarsening. Although the peak temperature dominates the grain size evolution, dynamic recrystallisation during friction surfacing counteracts this effect, reducing the grain size by one order of magnitude. The coatings exhibit a hardness ascent about 15% due to martensite formation, high dislocation density and oxide precipitations.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.matdes.2016.07.132} (DOI). Fitseva, V.; Hanke, S.; dos Santos, J.F.; Stemmer, P.; Gleising, B.: The role of process temperature and rotational speed in the microstructure evolution of Ti-6Al-4V friction surfacing coatings. In: Materials and Design. Vol. 110 (2016) 112 - 123. (DOI:  10.1016/j.matdes.2016.07.132)}}
@article{steyskal_electrochemically_tunable_2016, 
author={Steyskal, E.-M. and Qi, Z. and Poelt, P. and Albu, M. and Weissmueller, J. and Wuerschum, R.},
title={Electrochemically Tunable Resistance of Nanoporous Platinum Produced by Dealloying},
year={2016},
journal = {Langmuir},
volume = {32},
number = {31},
pages = {7757 - 7764},
doi = {http://dx.doi.org/10.1021/acs.langmuir.6b01734},
abstract = {The extremely high surface-to-volume ratio of nanoporous platinum (np-Pt) produced by dealloying was applied for tuning electrical resistance by surface charging. In the as-dealloyed state, a characteristic sign-inversion of the charging-induced resistance variation occurs, which can be associated with the electronic structure of PtO. After electrochemical reduction, the relative resistance variations of np-Pt of up to 58% could be generated by electrochemically induced adsorption and desorption, which was 1 order of magnitude larger compared with that of cluster-assembled nanocrystalline Pt. Although the maximum resistance variation was also higher than that of dealloyed nanoporous gold (np-Au), the resistance variation related to the imposed charge was reduced owing to the higher bulk resistance of Pt compared with that of Au. The sign-inversion behavior of the resistance could be recovered by re-oxidation.},
note = {Online available at: \url{http://dx.doi.org/10.1021/acs.langmuir.6b01734} (DOI). Steyskal, E.-M.; Qi, Z.; Poelt, P.; Albu, M.; Weissmueller, J.; Wuerschum, R.: Electrochemically Tunable Resistance of Nanoporous Platinum Produced by Dealloying. In: Langmuir. Vol. 32 (2016) 31, 7757 - 7764. (DOI:  10.1021/acs.langmuir.6b01734)}}
@article{wang_kink_formation_2016, 
author={Wang, L. and Sabisch, J. and Lilleodden, E.T.},
title={Kink formation and concomitant twin nucleation in Mg–Y},
year={2016},
journal = {Scripta Materialia},
volume = {111},
pages = {68 - 71},
doi = {10.1016/j.scriptamat.2015.08.016},
abstract = {During in situ tensile loading of a Mg–2.5 wt%Y alloy, a large kink band was observed. The orientation of the kink band varies continuously with a maximum misorientation angle of 18° with respect to the matrix grain. The formation of the kink band is accompanied by the nucleation of numerous 











{101¯2}
twins at the kink boundaries. A mechanistic model is proposed to account for this unique kink band and concomitant twin nucleation via dissociation of basal dislocations. This mechanism is aided by the presence of Y, which suppresses 
{101¯2}twinning and simultaneously decreases the stacking fault energy.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.scriptamat.2015.08.016} (DOI). Wang, L.; Sabisch, J.; Lilleodden, E.T.: Kink formation and concomitant twin nucleation in Mg–Y. In: Scripta Materialia. Vol. 111 (2016) 68 - 71. (DOI:  /10.1016/j.scriptamat.2015.08.016)}}
@article{prashanth_mechanical_and_2016, 
author={Prashanth, K.G. and Zhuravleva, K. and Okulov, I.V. and Calin, M. and Eckert, J. and Gebert, A.},
title={Mechanical and Corrosion Behavior of New Generation Ti-45Nb Porous Alloys Implant Devices},
year={2016},
journal = {Technologies},
volume = {4},
number = {4},
pages = {33},
doi = {http://dx.doi.org/10.3390/technologies4040033},
abstract = {Strategies to improve the mechanical compatibility of Ti-based materials for hard tissue implant applications are directed towards significant stiffness reduction by means of the adjustment of suitable β-phases and porous device architectures. In the present study, the effect of different compaction routes of the gas-atomized β-Ti-45Nb powder on the sample architecture, porosity, and on resulting mechanical properties in compression was investigated. Green powder compacted and sintered at 1000 °C had a porosity varying between 8% and 12%, strength between 260 and 310 MPa, and Young’s modulus ranging between 18 and 21 GPa. Hot pressing of the powder without or with subsequent sintering resulted in microporosity varying between 1% and 3%, ultimate strength varying between 635 and 735 MPa, and Young’s modulus between 55 and 69 GPa. Samples produced with NaCl space-holder by hot-pressing resulted in a macroporosity of 45% and a high strength of ˃200 MPa, which is higher than the strength of a human cortical bone. Finally, the corrosion tests were carried out to prove that the presence of residual NaCl traces will not influence the performance of the porous implant in the human body.},
note = {Online available at: \url{http://dx.doi.org/10.3390/technologies4040033} (DOI). Prashanth, K.G.; Zhuravleva, K.; Okulov, I.V.; Calin, M.; Eckert, J.; Gebert, A.: Mechanical and Corrosion Behavior of New Generation Ti-45Nb Porous Alloys Implant Devices. In: Technologies. Vol. 4 (2016) 4, 33. (DOI:  10.3390/technologies4040033)}}
@article{klusemann_fourthorder_straingradient_2016, 
author={Klusemann, B. and Bargmann, S. and Estrin, Y.},
title={Fourth-order strain-gradient phase mixture model for nanocrystalline fcc materials},
year={2016},
journal = {Modelling and Simulation in Materials Science Engineering},
volume = {24},
number = {8},
pages = {085016},
doi = {http://dx.doi.org/10.1088/0965-0393/24/8/085016},
abstract = {The proposed modeling approach for nanocrystalline materials is an extension of the local phase mixture model introduced by Kim et al (2000 Acta Mater. 48 493–504). Local models cannot account for any non-uniformities or strain patterns, i.e. such models describe the behavior correctly only as long as it is homogeneous. In order to capture heterogeneities, the phase mixture model is augmented with gradient terms of higher order, namely second and fourth order. Different deformation mechanisms are assumed to operate in grain interior and grain boundaries concurrently. The deformation mechanism in grain boundaries is associated with diffusional mass transport along the boundaries, while in the grain interior dislocation glide as well as diffusion controlled mechanisms are considered. In particular, the mechanical response of nanostructured polycrystals is investigated. The model is capable of correctly predicting the transition of flow stress from Hall–Petch behavior in conventional grain size range to an inverse Hall–Petch relation in the nanocrystalline grain size range. The consideration of second- and fourth-order strain gradients allows non-uniformities within the strain field to represent strain patterns in combination with a regularization effect. Details of the numerical implementation are provided.},
note = {Online available at: \url{http://dx.doi.org/10.1088/0965-0393/24/8/085016} (DOI). Klusemann, B.; Bargmann, S.; Estrin, Y.: Fourth-order strain-gradient phase mixture model for nanocrystalline fcc materials. In: Modelling and Simulation in Materials Science Engineering. Vol. 24 (2016) 8, 085016. (DOI:  10.1088/0965-0393/24/8/085016)}}
@article{nazarenko_lurie_solution_2016, 
author={Nazarenko, L. and Bargmann, S. and Stolarski, H.},
title={Lurie solution for spherical particle and spring layer model of interphases: Its application in analysis of effective properties of composites},
year={2016},
journal = {Mechanics of Materials},
volume = {96},
pages = {39 - 52},
doi = {http://dx.doi.org/10.1016/j.mechmat.2016.01.011},
abstract = {A new approach to the determination of equivalent inhomogeneity for spherical particles and the spring layer model of their interphases with the matrix material is developed. To validate this approach the effective properties of random composites containing spherical inhomogeneities surrounded by an interphase material of constant thickness are evaluated. The properties of equivalent inhomogeneity, incorporating only properties of the original inhomogeneity and its interphase, are determined employing a new approach based on the exact Lurie's solution for spheres. This constitutes the central aspect of the proposed approach being in contrast with some existing definitions of equivalent inhomogeneity whose properties dependent also on the properties of the matrix. With the equivalent inhomogeneity specified as proposed here, the effective properties of the material with interphases can be found using any method applicable to analysis of the materials with perfect interfaces (i.e., without interphases) and any properties of the matrix. In this work, the method of conditional moments is employed to this end. The choice of that method is motivated by the method's solid formal foundations, its potential applicability to inhomogeneities other than spheres and to anisotropic materials. The resulting effective properties of materials with randomly distributed spherical particles are presented in the closed-form and are in excellent agreement with values reported in technical literature, which are based on both formally exact and approximate methods.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.mechmat.2016.01.011} (DOI). Nazarenko, L.; Bargmann, S.; Stolarski, H.: Lurie solution for spherical particle and spring layer model of interphases: Its application in analysis of effective properties of composites. In: Mechanics of Materials. Vol. 96 (2016) 39 - 52. (DOI:  10.1016/j.mechmat.2016.01.011)}}
@article{chupakhin_effect_of_2016, 
author={Chupakhin, S. and Kashaev, N. and Huber, N.},
title={Effect of elasto-plastic material behaviour on determination of residual stress profiles using the hole drilling method},
year={2016},
journal = {Journal of Strain Analysis for Engineering Design},
volume = {51},
number = {8},
pages = {572 - 581},
doi = {http://dx.doi.org/10.1177/0309324716663940},
abstract = {The hole drilling method is a well-known technique for the determination of non-uniform residual stress profiles by measuring relaxation distortions caused by the presence of the hole. The integral method, an inverse calculation technique on which the hole drilling method is based, assumes linear elastic material behaviour and is therefore limited to the measurement of residual stresses below 60% of the yield strength. The aim of this study is to investigate the effects of elastic–plastic material behaviour on the determined non-uniform residual stress profile when the residual stresses exceed the given 60% limit. To this end, compressive residual stress profiles, as they are typically induced by laser shock peening, are investigated using finite element simulations followed by an analysis with the integral method. The obtained results from the analysis are compared to the applied residual stress profiles. An evaluation of the deviation between these two profiles provides detailed insight into the expected error as a function of hole drilling depth and the ratio of residual stress magnitude to yield strength. As an additional benefit of the presented approach, it also provides an indication of the range of depth at which the non-uniform residual stress profile should be corrected to reduce measurement error.},
note = {Online available at: \url{http://dx.doi.org/10.1177/0309324716663940} (DOI). Chupakhin, S.; Kashaev, N.; Huber, N.: Effect of elasto-plastic material behaviour on determination of residual stress profiles using the hole drilling method. In: Journal of Strain Analysis for Engineering Design. Vol. 51 (2016) 8, 572 - 581. (DOI:  10.1177/0309324716663940)}}
@article{liu_phase_transformation_2016, 
author={Liu, J. and Staron, P. and Riekehr, S. and Stark, A. and Schell, N. and Huber, N. and Schreyer, A. and Mueller, M. and Kashaev, N.},
title={Phase Transformation and Residual Stress in a Laser Beam Spot-Welded TiAl-Based Alloy},
year={2016},
journal = {Metallurgical and Materials Transactions  A},
volume = {47},
number = {12},
pages = {5750 - 5760},
doi = {http://dx.doi.org/10.1007/s11661-016-3745-7},
abstract = {The microstructure, chemical composition, residual stress, and lattice parameter evolution of the welding zone (WZ) and heat-affected zone (HAZ) of a laser-beam-welded TiAl-based alloy were investigated. It was found that both α2 and γ phases remain highly restrained in the WZ edge, and the stresses are relieved in the HAZ. A grain refinement mechanism is proposed, which works by heating the material to the β or α + β phase field for a short time. The lamellar colonies are refined by the Nb-enriched segregations.},
note = {Online available at: \url{http://dx.doi.org/10.1007/s11661-016-3745-7} (DOI). Liu, J.; Staron, P.; Riekehr, S.; Stark, A.; Schell, N.; Huber, N.; Schreyer, A.; Mueller, M.; Kashaev, N.: Phase Transformation and Residual Stress in a Laser Beam Spot-Welded TiAl-Based Alloy. In: Metallurgical and Materials Transactions  A. Vol. 47 (2016) 12, 5750 - 5760. (DOI:  10.1007/s11661-016-3745-7)}}
@article{soyarslan_the_effect_2016, 
author={Soyarslan, C. and Klusemann, B. and Bargmann, S.},
title={The effect of yield surface curvature change by cross hardening on forming limit diagrams of sheets},
year={2016},
journal = {International Journal of Mechanical Sciences},
volume = {117},
pages = {53 - 66},
doi = {http://dx.doi.org/10.1016/j.ijmecsci.2016.07.028},
abstract = {The paper aims at clarification of the role of reduction in yield locus curvature on forming limit diagrams. To this end, a cross-hardening model showing a reduction of yield surface curvature is used which accounts for dynamic and latent hardening effects associated with dislocation motion during loading. The model's three-dimensional tensorial as well as reduced plane-stress vector formulations are given. The first quadrants of forming limit diagrams are numerically produced using finite element models of the Marciniak-Kuczyński test with spatially correlated random defect distribution as localization triggering mechanism. The effect of cross hardening is investigated in detail. It is demonstrated that for plane strain loading path there occurs no difference in localization predictions of the models with and without cross hardening whereas for biaxial strain paths a delayed localization is observed in the cross hardening model as compared to the one without cross hardening effects. This is in accordance with the relative bluntness of the yield surface at the points of load path change towards localization. These results are complemented by Nakazima test simulations where similar observations are made.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.ijmecsci.2016.07.028} (DOI). Soyarslan, C.; Klusemann, B.; Bargmann, S.: The effect of yield surface curvature change by cross hardening on forming limit diagrams of sheets. In: International Journal of Mechanical Sciences. Vol. 117 (2016) 53 - 66. (DOI:  10.1016/j.ijmecsci.2016.07.028)}}
@article{feistauer_performance_of_2016, 
author={Feistauer, E. and Bergmann, L. and dos Santos, J.F.},
title={Performance of friction stir welded tailor welded blanks in AA5059 and AA6082 alloys for marine applications},
year={2016},
journal = {Key Engineering Materials, Aluminium Constructions: Sustainability, Durability and Structural Advantages},
volume = {710},
pages = {91 - 96},
doi = {10.4028/www.scientific.net/KEM.710.91},
abstract = {Tailor welded blank (TWB) concepts in aluminum alloys, welded by friction stir welding (FSW), are an attractive solution to reduce structural weight of structures applied on the transportation sector. In the present work the mechanical performance and microstructural features of dissimilar friction stir welded TWBs were assessed. Welds were produced with alloys of particular interest to the shipbuilding sector (AA6082 and AA5083, with a thickness combination of 6 and 8 mm respectively) and the effect of rotational speed on the weld properties was investigated. A digital image correlation system (DIC) was used to characterize the local strain fields during the quasi-static tensile tests. Microstructure analysis revealed the presence of a remnant oxide line (ROL) at the stir zone. Moreover, the rotational speed directly affected the ROL distribution and consequently the mechanical properties of the welds. The TWB produced with low rotation speed and high force (600 rpm and 20kN) has shown the highest mechanical performance and failed at the thermo-mechanical affected zone of the AA6082 plate. The micromechanisms of fracture were assessed by SEM and revealed a ductile fracture with large amounts of dimples spread out on the fracture surface.},
note = {Online available at: \url{https://dx.doi.org/10.4028/www.scientific.net/KEM.710.91} (DOI). Feistauer, E.; Bergmann, L.; dos Santos, J.F.: Performance of friction stir welded tailor welded blanks in AA5059 and AA6082 alloys for marine applications. In: Key Engineering Materials, Aluminium Constructions: Sustainability, Durability and Structural Advantages. Vol. 710 (2016) 91 - 96. (DOI:  /10.4028/www.scientific.net/KEM.710.91)}}
@article{wang_global_and_2016, 
author={Wang, F.F. and Li, W.Y. and Shen, J. and Zhang, Z.H. and Li, J.L. and dos Santos, J.F.},
title={Global and local mechanical properties and microstructure of Bobbin tool friction-stir-welded Al–Li alloy},
year={2016},
journal = {Science and Technology of Welding and Joining},
volume = {21},
number = {6},
pages = {479 - 483},
doi = {http://dx.doi.org/10.1080/13621718.2015.1132128},
abstract = {AA2198–T851 sheets were welded by bobbin tool friction stir welding using a rotational speed of 800 rpm and welding speed of 42 mm min−1. The microstructure and precipitates within the joint were characterised by transmission electron microscopy. The global and local mechanical behaviour was determined using a digital image correlation system. Specific attention was given to the relationship between the local microstructure and properties across the joint, which govern the global strength and ductility of the welds. A lower global elongation of the joint is caused by the premature strain localisation in the softened zone.},
note = {Online available at: \url{http://dx.doi.org/10.1080/13621718.2015.1132128} (DOI). Wang, F.F.; Li, W.Y.; Shen, J.; Zhang, Z.H.; Li, J.L.; dos Santos, J.F.: Global and local mechanical properties and microstructure of Bobbin tool friction-stir-welded Al–Li alloy. In: Science and Technology of Welding and Joining. Vol. 21 (2016) 6, 479 - 483. (DOI:  10.1080/13621718.2015.1132128)}}
@article{abibe_on_the_2016, 
author={Abibe, A.B. and Sonego, M. and dos Santos, J.F. and Canto, L.B. and Amancio-Filho, S.T.},
title={On the feasibility of a friction-based staking joining method for polymer–metal hybrid structures},
year={2016},
journal = {Materials and Design},
volume = {92},
pages = {632 - 642},
doi = {http://dx.doi.org/10.1016/j.matdes.2015.12.087},
abstract = {The increased use of hybrid structures to reduce weight currently faces the limitations of traditional joining methods. Consequently there is a niche for development of new joining techniques, which can reduce or overcome some of the existing limitations. This paper presents for the first time the new Friction-based Injection Clinching Joining technique (F-ICJ), describing the microstructure and changes in local properties of joints between polyetherimide (PEI) and aluminum alloy 6082-T6. A shear layer around the rotating tool composes a polymer thermomechanically affected zone (PTMAZ), which presents pores as a result of evolution of gaseous products. The PTMAZ shows decreases of 8% to 12% in local strength compared to the base material, as measured by microhardness. Ultimate forces of 1419 ± 43 N in lap shear and 430 ± 44 N in cross tensile were achieved for F-ICJ joints. These levels are similar to ultrasonic staking joints of the same material combination, but the hollow design of F-ICJ stakes accounts for improved strength-to-weight ratio (18% in lap shear, 21% in cross tensile). Although the F-ICJ process currently requires longer cycles (7.5 s) than state-of-the-art ultrasonic staking (2.8–2.9 s), generated results indicate that the F-ICJ process is a competitive staking joining method with potential for improvement.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.matdes.2015.12.087} (DOI). Abibe, A.B.; Sonego, M.; dos Santos, J.F.; Canto, L.B.; Amancio-Filho, S.T.: On the feasibility of a friction-based staking joining method for polymer–metal hybrid structures. In: Materials and Design. Vol. 92 (2016) 632 - 642. (DOI:  10.1016/j.matdes.2015.12.087)}}
@article{goushegir_friction_spot_2016, 
author={Goushegir, S.M.},
title={Friction spot joining (FSpJ) of aluminum-CFRP hybrid structures},
year={2016},
journal = {Welding in the World},
volume = {60},
number = {6},
pages = {1073 - 1093},
doi = {http://dx.doi.org/10.1007/s40194-016-0368-y},
abstract = {The employment of various materials (such as lightweight metal alloys and composites) with distinct physicochemical properties in the automotive and aerospace industries has opened a new field of research into the joining of dissimilar materials. Several alternative methods have recently been developed for joining metal-composite multi-material structures. Friction spot joining (FSpJ) is an innovative technique within welding-based joining technologies suitable for metal-composite structures. This work aims to address and overview different aspects of FSpJ. Case-study overlap joints using aluminum alloy AA2024-T3 and carbon-fiber-re-inforced poly(phenylene sulfide) (CF-PPS) were produced. Peak temperatures of up to 474 °C were recorded during the process. Such temperatures are well below thermal decomposition of PPS, and extensive thermal degradation of PPS was not detected by thermal analysis in this work. Microstructure analysis was performed showing usual metallurgical phenomena (recovery and dynamic re-crystallization) taking place with friction-based aluminum joining. Microstructural changes caused an alteration to the local mechanical properties as confirmed by microhardness and nanohardness measurements. Moreover, microstructural analysis of the composite part revealed the formation of a small number of volumetric defects such as pores and fiber-matrix debonding. Bonding mechanisms at the interface were studied into details by microscopy analysis and X-ray photoelectron spectroscopy. The influence of various aluminum surface pre-treatments on the bonding mechanisms and mechanical performance of single-lap shear joints was studied. In addition, fatigue life of the joints was investigated using an exponential model to obtain S-N curves. Finally, the quasi-static strength of the friction spot joints was compared with the state-of-the-art adhesive bonding. Friction spot joints showed 50 % stronger joints than adhesively bonded joints, indicating the potential of the technique to be used for joining lightweight metals to composite materials.},
note = {Online available at: \url{http://dx.doi.org/10.1007/s40194-016-0368-y} (DOI). Goushegir, S.M.: Friction spot joining (FSpJ) of aluminum-CFRP hybrid structures. In: Welding in the World. Vol. 60 (2016) 6, 1073 - 1093. (DOI:  10.1007/s40194-016-0368-y)}}
@article{hu_nanoporous_gold_2016, 
author={Hu, K. and Ziehmer, M. and Wang, K. and Lilleodden, E.T.},
title={Nanoporous gold: 3D structural analyses of representative volumes and their implications on scaling relations of mechanical behaviour},
year={2016},
journal = {Philosophical Magazine},
volume = {96},
number = {32-34},
pages = {3322 - 3335},
doi = {http://dx.doi.org/10.1080/14786435.2016.1222087},
abstract = {We present a quantitative study of the salient structural parameters identified from so-called ‘representative volumes’ of the bicontinuous nanoporous gold (NPG) network, and examine the validity of self-similarity in describing its evolution. The approach is based on 3D-focused ion beam tomography applied to as-dealloyed and isothermally annealed NPG samples. After identifying sufficiently large representative volumes, we show that the ligament width distributions coarsen in a sufficiently self-similar, time-invariant manner, while the scaled connectivity density shows a self-similar ligament network topology. Using these critical parameters, namely mean ligament diameter and connectivity density, the Gibson–Ashby scaling laws for the mechanical response of cellular materials are revisited. The inappropriateness of directly applying the Gibson–Ashby model to NPG is demonstrated by comparing finite element method compression simulations of both the NPG reconstruction and that of the Gibson–Ashby solid model; rather than the solid volume fraction, we show that an effective load-bearing ring structure governs mechanical behaviour.},
note = {Online available at: \url{http://dx.doi.org/10.1080/14786435.2016.1222087} (DOI). Hu, K.; Ziehmer, M.; Wang, K.; Lilleodden, E.T.: Nanoporous gold: 3D structural analyses of representative volumes and their implications on scaling relations of mechanical behaviour. In: Philosophical Magazine. Vol. 96 (2016) 32-34, 3322 - 3335. (DOI:  10.1080/14786435.2016.1222087)}}
@article{steglich_texturebased_forming_2016, 
author={Steglich, D. and Jeong, Y.},
title={Texture-based forming limit prediction for Mg sheet alloys ZE10 and AZ31},
year={2016},
journal = {International Journal of Mechanical Sciences},
volume = {117},
pages = {102 - 114},
doi = {http://dx.doi.org/10.1016/j.ijmecsci.2016.08.013},
abstract = {A viscoplastic self-consistent crystal plasticity model was employed to study the formability of two magnesium sheet alloys, i.e., AZ31 and ZE10 at 200 °C°C. The flow stress-strain curves obtained by uniaxial tension tests at various strain rates and the crystallographic texture obtained from X-ray diffraction were used to calibrate the model. The crystal plasticity model was incorporated with the Marciniak-Kuczyński model in order to address the forming limits of the magnesium sheets. A good agreement of the model predictions with the experimental data obtained by Nakajima tests was achieved. The model was further studied to quantify the effects of the sample orientation with respect to laboratory axes, the amount of pre-strain applied to the sheet prior to forming, and the initial crystallographic texture. The resulting forming limit diagrams demonstrate the optimal choice of sample orientation and crystallographic texture that can lead to a significant improvement in forming limit strains.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.ijmecsci.2016.08.013} (DOI). Steglich, D.; Jeong, Y.: Texture-based forming limit prediction for Mg sheet alloys ZE10 and AZ31. In: International Journal of Mechanical Sciences. Vol. 117 (2016) 102 - 114. (DOI:  10.1016/j.ijmecsci.2016.08.013)}}
@article{mcbride_thermoelastic_modelling_2016, 
author={McBride, A. and Bargmann, S. and Pond, D. and Limbert, G.},
title={Thermoelastic modelling of the skin at finite deformations},
year={2016},
journal = {Journal of Thermal Biology},
volume = {62 B},
pages = {201 - 209},
doi = {http://dx.doi.org/10.1016/j.jtherbio.2016.06.017},
abstract = {The modelling and computation of the coupled thermal and mechanical response of human skin at finite deformations is considered. The model extends current thermal models to account for thermally- and mechanically-induced deformations. Details of the solution of the highly nonlinear system of governing equations using the finite element method are presented. A representative numerical example illustrates the importance of considering the coupled response for the problem of a rigid, hot indenter in contact with the skin.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.jtherbio.2016.06.017} (DOI). McBride, A.; Bargmann, S.; Pond, D.; Limbert, G.: Thermoelastic modelling of the skin at finite deformations. In: Journal of Thermal Biology. Vol. 62 B (2016) 201 - 209. (DOI:  10.1016/j.jtherbio.2016.06.017)}}
@article{klusemann_modeling_of_2016, 
author={Klusemann, B.},
title={Modeling of microstructural pattern formation in crystal plasticity},
year={2016},
journal = {PAMM: Proceedings in Applied Mathematics and Mechanics},
volume = {16},
number = {1},
pages = {361 - 362},
doi = {http://dx.doi.org/10.1002/pamm.201610169},
abstract = {The mechanical behavior of most materials is dictated by a present or emergent underlying microstructure which is a direct result of different, even competing physical mechanisms occurring at lower length scales. In this work, energetic microstructure interaction via different non-convex contributions to the free energy in metals is modeled. For this purpose rate dependent gradient extended crystal plasticity models at the glide-system level are formulated. The non-convex energy serves as the driving force for the emergent microstructure. The competition between the kinetics and the relaxation of the free energy is an essential feature of the model. Non-convexity naturally arises in finite-deformation single-slip crystal plasticity and the results of the gradient model for this case are compared with an effective laminate model based on energy relaxation. Similarities as well as essential differences are observed and explained.},
note = {Online available at: \url{http://dx.doi.org/10.1002/pamm.201610169} (DOI). Klusemann, B.: Modeling of microstructural pattern formation in crystal plasticity. In: PAMM: Proceedings in Applied Mathematics and Mechanics. Vol. 16 (2016) 1, 361 - 362. (DOI:  10.1002/pamm.201610169)}}
@article{tian_process_optimization_2016, 
author={Tian, Y. and Robson, J.D. and Riekehr, S. and Kashaev, N. and Wang, L. and Lowe, T. and Karanika, A.},
title={Process Optimization of Dual-Laser Beam Welding of Advanced Al-Li Alloys Through Hot Cracking Susceptibility Modeling},
year={2016},
journal = {Metallurgical and Materials Transactions  A},
volume = {47},
number = {7},
pages = {3533 - 3544},
doi = {http://dx.doi.org/10.1007/s11661-016-3509-4},
abstract = {Laser welding of advanced Al-Li alloys has been developed to meet the increasing demand for light-weight and high-strength aerospace structures. However, welding of high-strength Al-Li alloys can be problematic due to the tendency for hot cracking. Finding suitable welding parameters and filler material for this combination currently requires extensive and costly trial and error experimentation. The present work describes a novel coupled model to predict hot crack susceptibility (HCS) in Al-Li welds. Such a model can be used to shortcut the weld development process. The coupled model combines finite element process simulation with a two-level HCS model. The finite element process model predicts thermal field data for the subsequent HCS hot cracking prediction. The model can be used to predict the influences of filler wire composition and welding parameters on HCS. The modeling results have been validated by comparing predictions with results from fully instrumented laser welds performed under a range of process parameters and analyzed using high-resolution X-ray tomography to identify weld defects. It is shown that the model is capable of accurately predicting the thermal field around the weld and the trend of HCS as a function of process parameters.},
note = {Online available at: \url{http://dx.doi.org/10.1007/s11661-016-3509-4} (DOI). Tian, Y.; Robson, J.D.; Riekehr, S.; Kashaev, N.; Wang, L.; Lowe, T.; Karanika, A.: Process Optimization of Dual-Laser Beam Welding of Advanced Al-Li Alloys Through Hot Cracking Susceptibility Modeling. In: Metallurgical and Materials Transactions  A. Vol. 47 (2016) 7, 3533 - 3544. (DOI:  10.1007/s11661-016-3509-4)}}
@article{ziehmer_a_principle_2016, 
author={Ziehmer, M. and Hu, K. and Wang, K. and Lilleodden, E.T.},
title={A principle curvatures analysis of the isothermal evolution of nanoporous gold: Quantifying the characteristic length-scales},
year={2016},
journal = {Acta Materialia},
volume = {120},
pages = {24 - 31},
doi = {http://dx.doi.org/10.1016/j.actamat.2016.08.028},
abstract = {A study of the isothermal evolution of a nanoporous gold (npg) microstructure after dealloying has been performed. In order to adequately characterize its complex three-dimensional bicontinuous ligament-ring structure, an analysis of the scaled principle curvatures κ1 and κ2 based on representative volumes of meshed 3D reconstructions was applied. Five npg samples, as obtained from an electrolytical dealloying process, with different mean ligament diameters ranging from ca. 25 nm (as-dealloyed) to ca. 420 nm (from annealing at 300° C) were analyzed. The results indicate that ligament surface flattening effects lead to small but distinct morphological changes during the investigated early and mid-stages of coarsening, visible in the scaled κ1- and κ2- marginal distributions. Thus, strictly speaking, self-similar evolution of npg cannot be confirmed, but dependent on the specific application, the evolution might be seen as “sufficiently” self-similar. Moreover, it is shown that the inverse mean principle curvatures from the marginal distributions can be used to identify the mean sizes of the two salient structural features, namely the ligaments and the rings. Both inverse mean principle curvatures scale linearly with the mean ligament diameter. Thus, for the material used in this study, one parameter is sufficient to characterize its microstructure. Finally, it is shown that rings resembling the ones from the real samples can be generated computationally by applying modified torus parameterizations. Surprisingly, a calculation of the curvature distribution of only one ”average” ring is sufficient to approximate the scaled kappa distributions accumulated from the ring distributions of the real samples.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.actamat.2016.08.028} (DOI). Ziehmer, M.; Hu, K.; Wang, K.; Lilleodden, E.T.: A principle curvatures analysis of the isothermal evolution of nanoporous gold: Quantifying the characteristic length-scales. In: Acta Materialia. Vol. 120 (2016) 24 - 31. (DOI:  10.1016/j.actamat.2016.08.028)}}
@article{ovri_new_insights_2015, 
author={Ovri, H. and Lilleodden, E.T.},
title={New insights into plastic instability in precipitation strengthened Al–Li alloys},
year={2015},
journal = {Acta Materialia},
volume = {89},
pages = {88 - 97},
doi = {http://dx.doi.org/10.1016/j.actamat.2015.01.065},
abstract = {A mechanistic model that describes the microscopic mechanisms underlying plastic instability in precipitation strengthened Al–Li based alloy systems is proposed in this work. The model is based on experimental observations from high resolution nanoindentation tests and transmission electron microscopy (TEM) based methods, including in situ TEM tensile straining. These experiments show that dynamic strain aging (DSA), which is widely accepted as the underlying mechanism for plastic instability, cannot sufficiently account for the occurrence of plastic instability in Al–Li based alloy systems. It is proposed that an altogether different mechanism controls plastic instability, namely a diffusion-controlled pseudo-locking mechanism that accompanies order hardening. This mechanism does not require the concurrent operation of DSA by Li, which may be a nonviable mechanism given the low binding energy of Li to dislocation cores, for plastic instability to occur.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.actamat.2015.01.065} (DOI). Ovri, H.; Lilleodden, E.T.: New insights into plastic instability in precipitation strengthened Al–Li alloys. In: Acta Materialia. Vol. 89 (2015) 88 - 97. (DOI:  10.1016/j.actamat.2015.01.065)}}
@article{deng_electrocapillary_coupling_2015, 
author={Deng, Q. and Gosslar, D.-H. and Smetanin, M. and Weissmueller, J.},
title={Electrocapillary coupling at rough surfaces},
year={2015},
journal = {Physical Chemistry Chemical Physics},
volume = {17},
number = {17},
pages = {11725 - 11731},
doi = {http://dx.doi.org/10.1039/c5cp00167f},
abstract = {We investigate the impact of the surface roughness on the experimental value of the electrocapillary coupling coefficient, ς. This quantity relates the response of electrode potential, E, to tangential elastic strain, e, and also measures the variation of the surface stress, f, with the superficial charge density, q. We combine experiments measuring the apparent coupling coefficient ςeff for gold thin film electrodes in weakly adsorbing electrolyte with data for the surface roughness determined by atomic force microscopy and by the capacitance ratio method. We find that even moderate roughness has a strong impact on the value of ςeff. Analyzing the mechanics of corrugated surfaces affords a correction scheme yielding values of ς that are invariant with roughness and that agree with expectations for the true coupling coefficient on ideal, planar surfaces. The correction is simple and readily applied to experiments measuring ςeff from surface stress changes in cantilever bending studies or from the potential variation in dynamic electro-chemo-mechanical analysis.},
note = {Online available at: \url{http://dx.doi.org/10.1039/c5cp00167f} (DOI). Deng, Q.; Gosslar, D.-H.; Smetanin, M.; Weissmueller, J.: Electrocapillary coupling at rough surfaces. In: Physical Chemistry Chemical Physics. Vol. 17 (2015) 17, 11725 - 11731. (DOI:  10.1039/c5cp00167f)}}
@article{steglich_prediction_of_2015, 
author={Steglich, D. and Tian, X.},
title={Prediction of Crashworthiness for extruded Magnesium Materials},
year={2015},
journal = {Key Engineering Materials, Material Forming ESAFORM 2015},
volume = {651-653},
pages = {1009 - 1014},
doi = {http://dx.doi.org/10.4028/www.scientific.net/KEM.651-653.1009},
abstract = {To assess the crashworthiness of simple wrought magnesium structures, the axial deformation behaviour of different square tubes produced from magnesium alloys AZ31 and ZE10 were numerically investigated under quasi-static compressive loading conditions. Finite-element simulations were conducted to predict and assess the plastic buckling and crush behaviour. The necessary data to determine parameters for the plastic potential were taken from compression tests conducted along different orientations. The yield function Hill48 was selected, despite its inability to capture the strength differential effect. The modelling approach pursued is justified by considering the mechanical loading conditions, the fabrication process of the profiles and its implication on strain anisotropy, balancing achievable accuracy and computational efforts. The simulation results revealed that the material work hardening rates evidenced in uniaxial compression tests influenced the buckling modes as well as the energy dissipation.},
note = {Online available at: \url{http://dx.doi.org/10.4028/www.scientific.net/KEM.651-653.1009} (DOI). Steglich, D.; Tian, X.: Prediction of Crashworthiness for extruded Magnesium Materials. In: Key Engineering Materials, Material Forming ESAFORM 2015. Vol. 651-653 (2015) 1009 - 1014. (DOI:  10.4028/www.scientific.net/KEM.651-653.1009)}}
@article{krohn_influence_of_2015, 
author={Krohn, H. and Hanke, S. and Beyer, M. and dos Santos, J.F.},
title={Influence of external cooling configuration on friction surfacing of AA6082 T6 over AA2024 T351},
year={2015},
journal = {Manufacturing Letters},
volume = {5},
pages = {17 - 20},
doi = {http://dx.doi.org/10.1016/j.mfglet.2015.04.004},
abstract = {Friction surfacing is a solid-state surface engineering technology. Previous studies have shown that underwater friction surfacing has some advantages in efficiency and homogeneity of the deposited material. To use these advantages a water spray cooling system was implemented to achieve a more flexible process. This concept has been investigated by depositing Al alloy AA6082 T6 on AA2024 T351 substrate. The efficiency of the process was increased from 19% to 31% without influencing the properties of the deposited material. Temperature measurements revealed that the intensity and chosen location of cooling also affect the process characteristics and allow modifying the coating geometry.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.mfglet.2015.04.004} (DOI). Krohn, H.; Hanke, S.; Beyer, M.; dos Santos, J.F.: Influence of external cooling configuration on friction surfacing of AA6082 T6 over AA2024 T351. In: Manufacturing Letters. Vol. 5 (2015) 17 - 20. (DOI:  10.1016/j.mfglet.2015.04.004)}}
@article{steglich_experimental_and_2015, 
author={Steglich, D. and Mekonen, M.N. and Bohlen, J.},
title={Experimental and Numerical Formability Analysis of AZ31 and ZE10 Sheets},
year={2015},
journal = {Materials Today: Proceedings},
volume = {2},
number = {S1},
pages = {S 125 - S 130},
doi = {http://dx.doi.org/10.1016/j.matpr.2015.05.029},
abstract = {Experimentally and numerically obtained mechanical responses of Nakazima-type sheet forming tests for the magnesium alloys ZE10 and AZ31 at elevated temperature (200°C) are explored. The results from the experiments reveal sufficient ductility at the prescribed test temperature allowing sheet forming processes. The material's anisotropy as well as the distortional character of hardening is confirmed. Differences in the mechanical response between the two materials in terms of strain paths during the forming experiments are quantified. The corresponding numerical responses are obtained employing a suitable plasticity model based on tensor transforms. In addition, for predicting limit conditions of the forming process, the localisation criterion by Marciniak and Kuczynski is adopted. The constitutive model together with the localisation criterion is implemented in a finite element framework based on a fully implicit time integration scheme. The observed differential hardening during plastic deformation is predicted. The reasonably good agreement between the responses of the model and the respective experiments indicate the predictive capabilities of the implemented model for the considered magnesium alloys. The influence of the model parameter identification strategy is demonstrated.
© 2014 The Authors. Published by Elsevier Ltd.
Selection and peer-review under responsibility of the Conference Committee of Conference MEFORM 2015, Light Metals – Forming Technologies and Further. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.matpr.2015.05.029} (DOI). Steglich, D.; Mekonen, M.N.; Bohlen, J.: Experimental and Numerical Formability Analysis of AZ31 and ZE10 Sheets. In: Materials Today: Proceedings. Vol. 2 (2015) S1, S 125 - S 130. (DOI:  10.1016/j.matpr.2015.05.029)}}
@article{goushegir_influence_of_2015, 
author={Goushegir, S.M. and dos Santos, J.F. and Amancio-Filho, S.T.},
title={Influence of process parameters on mechanical performance and bonding area of AA2024/carbon-fiber-reinforced poly(phenylene sulfide) friction spot single lap joints},
year={2015},
journal = {Materials and Design},
volume = {83},
pages = {431 - 442},
doi = {http://dx.doi.org/10.1016/j.matdes.2015.06.044},
abstract = {The effects of friction spot joining process parameters on the bonding area and mechanical performance
of single lap joints were investigated using full-factorial design of experiments and analysis of variance.
On one hand, the main process parameters with significant influence on the bonding area were joining
pressure, tool rotational speed and joining time. On the other hand, tool rotational speed and joining
pressure displayed the highest influence on the lap shear strength of the joints followed by tool plunge
depth, whereas the joining time was not statistically significant. The interaction between the rotational
speed and joining time was the only interaction with a significant effect on the mechanical performance.
Joints with ultimate lap shear forces varying between 1698 ± 92 N and 2310 ± 155 N were obtained. It
was observed that generally a larger bonding area as a result of higher heat input leads to an increased
mechanical performance of the joints. The generated regression model by the analysis of variance was
used to identify an optimized set of parameters for increasing the lap shear strength of the joints to
2280 ± 88 N. Furthermore, the process temperature was monitored, which varied in the range of
370–474 C.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.matdes.2015.06.044} (DOI). Goushegir, S.M.; dos Santos, J.F.; Amancio-Filho, S.T.: Influence of process parameters on mechanical performance and bonding area of AA2024/carbon-fiber-reinforced poly(phenylene sulfide) friction spot single lap joints. In: Materials and Design. Vol. 83 (2015) 431 - 442. (DOI:  10.1016/j.matdes.2015.06.044)}}
@article{shen_crystallographic_texture_2015, 
author={Shen, J. and Wang, F. and Suhuddin, U.F.H. and Hu, S. and Li, W. and dos Santos, J.F.},
title={Crystallographic Texture in Bobbin Tool Friction-Stir-Welded Aluminum},
year={2015},
journal = {Metallurgical and Materials Transactions  A},
volume = {46},
number = {7},
pages = {2809 - 2813},
doi = {http://dx.doi.org/10.1007/s11661-015-2948-7},
abstract = {Bobbin tool friction-stir welding was used to join 3.2-mm-thick AA2198. The textural results show that four sub zones are formed vertically in the stirred zone. The materials in upper and lower two zones underwent negative and positive shears, respectively; they are uniformly recognized as dominate C and minor A simple shear components.},
note = {Online available at: \url{http://dx.doi.org/10.1007/s11661-015-2948-7} (DOI). Shen, J.; Wang, F.; Suhuddin, U.F.H.; Hu, S.; Li, W.; dos Santos, J.F.: Crystallographic Texture in Bobbin Tool Friction-Stir-Welded Aluminum. In: Metallurgical and Materials Transactions  A. Vol. 46 (2015) 7, 2809 - 2813. (DOI:  10.1007/s11661-015-2948-7)}}
@article{ngo_anomalous_compliance_2015, 
author={Ngo, B.-N.D. and Stukowski, A. and Mameka, N. and Markmann, J. and Albe, K. and Weissmueller, J.},
title={Anomalous compliance and early yielding of nanoporous gold},
year={2015},
journal = {Acta Materialia},
volume = {93},
pages = {144 - 155},
doi = {http://dx.doi.org/10.1016/j.actamat.2015.04.021},
abstract = {We present a study of the elastic and plastic behavior of nanoporous gold in compression, focusing on molecular dynamics simulation and inspecting experimental data for verification. Both approaches agree on an anomalously high elastic compliance in the early stages of deformation, along with a quasi immediate onset of plastic yielding even at the smallest load. Already before the first loading, the material undergoes spontaneous plastic deformation under the action of the capillary forces, requiring no external load. Plastic deformation under compressive load is accompanied by dislocation storage and dislocation interaction, along with strong strain hardening. Dislocation-starvation scenarios are not supported by our results. The stiffness increases during deformation, but never approaches the prediction by the relevant Gibson–Ashby scaling law. Microstructural disorder affects the plastic deformation behavior and surface excess elasticity might modify elastic response, yet we relate the anomalous compliance and the immediate yield onset to an atomistic origin: the large surface-induced prestress induces elastic shear that brings some regions in the material close to the shear instability of the generalized stacking fault energy curve. These regions are elastically highly compliant and plastically weak.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.actamat.2015.04.021} (DOI). Ngo, B.-N.D.; Stukowski, A.; Mameka, N.; Markmann, J.; Albe, K.; Weissmueller, J.: Anomalous compliance and early yielding of nanoporous gold. In: Acta Materialia. Vol. 93 (2015) 144 - 155. (DOI:  10.1016/j.actamat.2015.04.021)}}
@article{ovri_microstructural_influences_2015, 
author={Ovri, H. and Jaegle, E.A. and Stark, A. and Lilleodden, E.T.},
title={Microstructural influences on strengthening in a naturally aged and overaged Al-Cu-Li-Mg based alloy},
year={2015},
journal = {Materials Science and Engineering  A},
volume = {637},
pages = {162 - 169},
doi = {http://dx.doi.org/10.1016/j.msea.2015.04.039},
abstract = {A combination of transmission electron microscopy, atom probe tomography and high-energy X-ray diffraction was employed to investigate the influence of local microstructural changes on strengthening in a commercial Al-Li-Cu based alloy, AA2198, in the stretched and naturally aged, and overaged states. Strengthening in the stretched and naturally aged temper was shown to be governed by a combination of Cu-Cu clusters, δ′/β′ phase and solution strengthening. This is in contrast to another report which suggest that strength in this temper is only due to Cu-rich clusters [Decreus B et. al. Acta Mater 61 (2013) 2207]. On the other hand, although large volume fractions of equilibrium phases such as TB, and θ were present in the overaged temper, its strengthening was largely governed by order hardening, which is the strengthening mechanism associated with the δ′/β′ phase. The δ′/β′ phase remained in the matrix even after extensive overaging.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.msea.2015.04.039} (DOI). Ovri, H.; Jaegle, E.A.; Stark, A.; Lilleodden, E.T.: Microstructural influences on strengthening in a naturally aged and overaged Al-Cu-Li-Mg based alloy. In: Materials Science and Engineering  A. Vol. 637 (2015) 162 - 169. (DOI:  10.1016/j.msea.2015.04.039)}}
@article{dieringa_twinroll_casting_2015, 
author={Dieringa, H. and Das, S. and Eskin, D. and Fan, Z. and Katsarou, L. and Horstmann, M. and Kurz, G. and Mendis, C. and Hort, N. and Kainer, K.U.},
title={Twin-roll Casting after Intensive Melt Shearing and Subsequent Rolling of an AM30 Magnesium Alloy with Addition of CaO and SiC},
year={2015},
journal = {Materials Science Forum, Light Metals Technology 2015},
volume = {828-829},
pages = {35 - 40},
doi = {10.4028/www.scientific.net/MSF.828-829.35},
abstract = {Intensive melt shearing is a process that can be used for mixing ceramic particles into magnesium melt. It applies shear stress to the melt and can de-agglomerate nanoparticle additions to magnesium melts without the use of electromagnetic fields or ultrasound. A wrought magnesium alloy AM30 was selected for processing with intensive melt shearing and subsequent twin-roll
casting. AM30 with additions of CaO and SiC were also processed by this route and the hardness and microstructure were investigated. Sheets were rolled and their tensile strength was determined.
The work was done as part of the European Union research project ExoMet. Its target includes the
production of high-performance magnesium-based materials by exploring novel grain refinement
and nanoparticle addition in conjunction with melt treatment by means of external fields.},
note = {Online available at: \url{https://dx.doi.org/10.4028/www.scientific.net/MSF.828-829.35} (DOI). Dieringa, H.; Das, S.; Eskin, D.; Fan, Z.; Katsarou, L.; Horstmann, M.; Kurz, G.; Mendis, C.; Hort, N.; Kainer, K.U.: Twin-roll Casting after Intensive Melt Shearing and Subsequent Rolling of an AM30 Magnesium Alloy with Addition of CaO and SiC. In: Materials Science Forum, Light Metals Technology 2015. Vol. 828-829 (2015) 35 - 40. (DOI:  /10.4028/www.scientific.net/MSF.828-829.35)}}
@article{kashaev_assessment_of_2015, 
author={Kashaev, N. and Ventzke, V. and Riekehr, S. and Dorn, F. and Horstmann, M.},
title={Assessment of alternative joining techniques for Ti–6Al–4V/CFRP hybrid joints regarding tensile and fatigue strength},
year={2015},
journal = {Materials and Design},
volume = {81},
pages = {73 - 81},
doi = {http://dx.doi.org/10.1016/j.matdes.2015.04.051},
abstract = {CFRP and titanium joints are used in the aerospace industry. These materials are usually joined by titanium rivets which are inserted into holes drilled through both materials. Conventional riveted hybrid joints of CFRP and titanium parts fail under quasi static loading due to the uneven load distribution at the titanium rivets. Under cyclic loading, the fatigue failure occurs mainly in the titanium part because of the higher notch sensitivity. The aim of this work is the comparison of different joining concepts in terms of stiffness, strength and fatigue limit. First, laser riveting, here titanium pins are Nd:YAG laser beam welded to the Ti–6Al–4V parts. Second, conventional riveted hybrid joint is combined with adhesive bonding. Third, surface structuring of the Ti–6Al–4V parts is used to enhance friction in the riveted joint. Tensile and fatigue tests as well as fractographical examinations are performed to establish the process–property–performance relationship of the hybrid joints. Laser riveting leads to higher stiffness but equal strength, when compared to conventional riveted joints. Fatigue life is improved by the implementation of adhesive bonding and surface structuring.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.matdes.2015.04.051} (DOI). Kashaev, N.; Ventzke, V.; Riekehr, S.; Dorn, F.; Horstmann, M.: Assessment of alternative joining techniques for Ti–6Al–4V/CFRP hybrid joints regarding tensile and fatigue strength. In: Materials and Design. Vol. 81 (2015) 73 - 81. (DOI:  10.1016/j.matdes.2015.04.051)}}
@article{nazarenko_energyequivalent_inhomogeneity_2015, 
author={Nazarenko, L. and Bargmann, S. and Stolarski, H.},
title={Energy-equivalent inhomogeneity approach to analysis of effective properties of nanomaterials with stochastic structure},
year={2015},
journal = {International Journal of Solids and Structures},
volume = {59},
pages = {183 - 197},
doi = {http://dx.doi.org/10.1016/j.ijsolstr.2015.01.026},
abstract = {A mathematical model based on the method of conditional moments combined with a new notion of the energy-equivalent inhomogeneity is presented and applied in the investigation of the effective properties of a material with randomly distributed nanoparticles. The surface effect is introduced via Gurtin–Murdoch equations describing the properties of the matrix/nanoparticle interface. The real system, consisting of the inhomogeneities and their surfaces possessing different properties and, possibly, residual stresses, is replaced by energy-equivalent inhomogeneities with modified bulk properties which incorporate the surface effects. The effective stiffness tensor of the material with so defined equivalent inhomogeneities is determined by the method of conditional moments. Closed-form expressions for the effective moduli of a composite consisting of a matrix and randomly distributed spherical inhomogeneities are derived for both the bulk and the shear moduli. Dependence of those moduli on the radius of nanoparticles is included in these expressions exhibiting analytically the nature of the size-dependence in nanomaterials. As numerical examples, nanoporous aluminum and nanoporous gold are investigated. The dependence of the normalized bulk and shear moduli of nanoporous aluminum (for two sets of surface properties) on the pore volume fraction (for different radii of nanopores) and on the radius of nanopores (for fixed volume fraction of nanopores) are compared to and discussed in the context of other theoretical predictions. Further, the normalized effective Young’s modulus of nanoporous gold as a function of void volume fraction for various ligament radii is analyzed.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.ijsolstr.2015.01.026} (DOI). Nazarenko, L.; Bargmann, S.; Stolarski, H.: Energy-equivalent inhomogeneity approach to analysis of effective properties of nanomaterials with stochastic structure. In: International Journal of Solids and Structures. Vol. 59 (2015) 183 - 197. (DOI:  10.1016/j.ijsolstr.2015.01.026)}}
@article{enz_singlesided_laser_2015, 
author={Enz, J. and Khomenko, V. and Riekehr, S. and Ventzke, V. and Huber, N. and Kashaev, N.},
title={Single-sided laser beam welding of a dissimilar AA2024–AA7050 T-joint},
year={2015},
journal = {Materials and Design},
volume = {76},
pages = {110 - 116},
doi = {http://dx.doi.org/10.1016/j.matdes.2015.03.049},
abstract = {In the aircraft industry double-sided laser beam welding of skin–stringer joints is an approved method for producing defect-free welds. But due to limited accessibility – as for the welding of skin–clip joints – the applicability of this method is limited. Therefore single-sided laser beam welding of T-joints becomes necessary. This also implies a reduction of the manufacturing effort. However, the main obstacle for the use of single-sided welding of T-joints is the occurrence of weld defects. An additional complexity represents the combination of dissimilar and hard-to-weld aluminium alloys – like Al–Cu and Al–Zn alloys. These alloys offer a high strength-to-density ratio, but are also associated with distinct weldability problems especially for fusion welding techniques like laser beam welding. The present study demonstrates how to overcome the weldability problems during single-sided laser beam welding of a dissimilar T-joint made of AA2024 and AA7050. For this purpose a high-power fibre laser with a large beam diameter is used. Important welding parameters are identified and adjusted for achieving defect-free welds. The obtained joints are compared to double-sided welded joints made of typical aircraft aluminium alloys. In this regard single-sided welded joints showed the expected differing weld seam appearance, but comparable mechanical properties.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.matdes.2015.03.049} (DOI). Enz, J.; Khomenko, V.; Riekehr, S.; Ventzke, V.; Huber, N.; Kashaev, N.: Single-sided laser beam welding of a dissimilar AA2024–AA7050 T-joint. In: Materials and Design. Vol. 76 (2015) 110 - 116. (DOI:  10.1016/j.matdes.2015.03.049)}}
@article{coratella_application_of_2015, 
author={Coratella, S. and Sticchi, M. and Toparli, M.B. and Fitzpatrick, M.E. and Kashaev, N.},
title={Application of the eigenstrain approach to predict the residual stress distribution in laser shock peened AA7050-T7451 samples},
year={2015},
journal = {Surface and Coatings Technology},
volume = {273},
pages = {39 - 49},
doi = {http://dx.doi.org/10.1016/j.surfcoat.2015.03.026},
abstract = {Laser Shock Peening allows the introduction of deep compressive residual stresses into metallic components. It is applicable to most metal alloys used for aerospace applications. The method is relatively expensive in application, and therefore development studies often rely heavily on Finite Element Modeling to simulate the entire process, with a high computational cost. A different approach has been used recently, the so-called eigenstrain approach. The present study looks at the feasibility of applying the eigenstrain method for prediction of the residual stress in a sample that contains curved surface features. The eigenstrain is determined from a simple geometry sample, and applied to the more complex geometry to predict the residual stress after laser shock peening. In particular the prediction of residual stress at a curved edge, and for different values of material thickness, have been studied. The research has demonstrated that the eigenstrain approach gives promising results in predicting residual stresses when only the thickness is altered, but when the geometry of the peened surface is altered the eigenstrain method seems to slightly overestimate the residual stresses. This highlights a limitation of the eigenstrain method where the change in geometry means that the inelastic strain field as a consequence of a treatment – in this case laser shock peening – no longer has similitude.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.surfcoat.2015.03.026} (DOI). Coratella, S.; Sticchi, M.; Toparli, M.B.; Fitzpatrick, M.E.; Kashaev, N.: Application of the eigenstrain approach to predict the residual stress distribution in laser shock peened AA7050-T7451 samples. In: Surface and Coatings Technology. Vol. 273 (2015) 39 - 49. (DOI:  10.1016/j.surfcoat.2015.03.026)}}
@article{guglielmi_mechanical_characterization_2015, 
author={Guglielmi, P.O. and Herbert, E.G. and Tartivel, L. and Behl, M. and Lendlein, A. and Huber, N. and Lilleodden, E.T.},
title={Mechanical characterization of oligo(ethylene glycol)-based hydrogels by dynamic nanoindentation experiments},
year={2015},
journal = {Journal of the Mechanical Behavior of Biomedical Materials},
volume = {46},
pages = {1 - 10},
doi = {http://dx.doi.org/10.1016/j.jmbbm.2015.02.009},
abstract = {Oligo(ethylene glycol)-based (OEG) hydrogel samples of varying cross-link densities and degrees of swelling were characterized through dynamic nanoindentation testing. Experiments were performed using a non-standard nanoindentation method, which was validated on a standard polystyrene sample. This method maximizes the capability of the instrument to measure the stiffness and damping of highly compliant, viscoelastic materials. Experiments were performed over the frequency range of 1 to 50 Hz, using a 1 mm diameter flat punch indenter. A hydration method was adopted to avoid sample dehydration during testing. Values of storage modulus (E′)(E′) ranged from 3.5 to 8.9 MPa for the different OEG-hydrogel samples investigated. Samples with higher OEG concentrations showed greater scatter in the modulus measurements and it is attributed to inhomogeneities in these materials. The (E′)(E′) values did not show a strong variation over frequency for any of the samples. Values of loss modulus (E″)(E″) were two orders of magnitude lower than the storage modulus, resulting in very low values of loss factor (E″/E′E″/E′<0.1). These are characteristics of strong gels, which present negligible viscous properties.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.jmbbm.2015.02.009} (DOI). Guglielmi, P.O.; Herbert, E.G.; Tartivel, L.; Behl, M.; Lendlein, A.; Huber, N.; Lilleodden, E.T.: Mechanical characterization of oligo(ethylene glycol)-based hydrogels by dynamic nanoindentation experiments. In: Journal of the Mechanical Behavior of Biomedical Materials. Vol. 46 (2015) 1 - 10. (DOI:  10.1016/j.jmbbm.2015.02.009)}}
@article{wilmers_a_continuum_2015, 
author={Wilmers, J. and Bargmann, S.},
title={A continuum mechanical model for the description of solvent induced swelling in polymeric glasses: thermomechanics coupled with diffusion},
year={2015},
journal = {European Journal of Mechanics  A},
volume = {53},
pages = {10 - 18},
doi = {http://dx.doi.org/10.1016/j.euromechsol.2015.03.002},
abstract = {The problem of interest is the numerical modelling of Case II diffusion in polymeric glasses. Case II diffusion is characterised by a strong coupling between diffusion and deformation and is highly temperature dependent. In this work, a general continuum mechanical framework describing a three-way coupling of thermomechanics and diffusion is adapted to the description of Case II diffusion.
Numerical studies are carried out to examine the capability of the model and the nature of the coupling. It is shown that the model is well suited for the description of solvent induced swelling as it predicts all characteristic properties of Case II diffusion.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.euromechsol.2015.03.002} (DOI). Wilmers, J.; Bargmann, S.: A continuum mechanical model for the description of solvent induced swelling in polymeric glasses: thermomechanics coupled with diffusion. In: European Journal of Mechanics  A. Vol. 53 (2015) 10 - 18. (DOI:  10.1016/j.euromechsol.2015.03.002)}}
@article{thamburaja_the_plastic_2015, 
author={Thamburaja, P. and Klusemann, B. and Adibi, S. and Bargmann, S.},
title={The plastic yield and flow behavior in metallic glasses},
year={2015},
journal = {Applied Physics Letters},
volume = {106},
number = {5},
pages = {051903},
doi = {http://dx.doi.org/10.1063/1.4907398},
abstract = {Metallic glasses have vast potential applications as components in microelectronics- and nanoelectronics-type devices. The design of such components through computer simulations requires the input of a faithful set of continuum-based constitutive equations. However, one long-standing controversial issue in modeling the plastic behavior of metallic glasses at the continuum level is the use of the most appropriate plastic yield criterion and flow rule. Guided by a series of molecular dynamics simulations conducted at low-homologous temperatures under homogeneous deformations, we quantitatively prove that the continuum plastic behavior in metallic glasses is most accurately described by a von Mises-type plastic yield criterion and flow rule.},
note = {Online available at: \url{http://dx.doi.org/10.1063/1.4907398} (DOI). Thamburaja, P.; Klusemann, B.; Adibi, S.; Bargmann, S.: The plastic yield and flow behavior in metallic glasses. In: Applied Physics Letters. Vol. 106 (2015) 5, 051903. (DOI:  10.1063/1.4907398)}}
@article{scheider_damage_modeling_2015, 
author={Scheider, I. and Xiao, T. and Yilmaz, E. and Schneider, G.A. and Huber, N. and Bargmann, S.},
title={Damage modeling of small-scale experiments on dental enamel with hierarchical microstructure},
year={2015},
journal = {Acta Biomaterialia},
volume = {15},
pages = {244 - 253},
doi = {http://dx.doi.org/10.1016/j.actbio.2014.11.036},
abstract = {Dental enamel is a highly anisotropic and heterogeneous material, which exhibits an optimal reliability with respect to the various loads occurring over years. In this work, enamel’s microstructure of parallel aligned rods of mineral fibers is modeled and mechanical properties are evaluated in terms of strength and toughness with the help of a multiscale modeling method. The established model is validated by comparing it with the stress–strain curves identified by microcantilever beam experiments extracted from these rods. Moreover, in order to gain further insight in the damage-tolerant behavior of enamel, the size of crystallites below which the structure becomes insensitive to flaws is studied by a microstructural finite element model. The assumption regarding the fiber strength is verified by a numerical study leading to accordance of fiber size and flaw tolerance size, and the debonding strength is estimated by optimizing the failure behavior of the microstructure on the hierarchical level above the individual fibers. Based on these well-grounded properties, the material behavior is predicted well by homogenization of a representative unit cell including damage, taking imperfections (like microcracks in the present case) into account.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.actbio.2014.11.036} (DOI). Scheider, I.; Xiao, T.; Yilmaz, E.; Schneider, G.A.; Huber, N.; Bargmann, S.: Damage modeling of small-scale experiments on dental enamel with hierarchical microstructure. In: Acta Biomaterialia. Vol. 15 (2015) 244 - 253. (DOI:  10.1016/j.actbio.2014.11.036)}}
@article{gerstein_characterization_of_2015, 
author={Gerstein, G. and Klusemann, B. and Bargmann, S. and Schaper, M.},
title={Characterization of the Microstructure Evolution in IF-Steel and AA6016 during Plane-Strain Tension and Simple Shear},
year={2015},
journal = {Materials},
volume = {8},
number = {1},
pages = {285 - 301},
doi = {http://dx.doi.org/10.3390/ma8010285},
abstract = {In the current work, the evolutions of grain and dislocation microstructures are investigated on the basis of plane strain tension and simple shear tests for an interstitial free steel (DC06) and a 6000 series aluminum alloy (AA6016-T4). Both materials are commonly-used materials in the automobile industry. The focus of this contribution is on the characterization and comparison of the microstructure formation in DC06 and AA6016-T4. Our observations shed light on the active mechanisms at the micro scale governing the macroscopic response. This knowledge is of great importance to understand the physical deformation mechanisms, allowing the control and design of new, tailor-made materials with the desired material behavior.},
note = {Online available at: \url{http://dx.doi.org/10.3390/ma8010285} (DOI). Gerstein, G.; Klusemann, B.; Bargmann, S.; Schaper, M.: Characterization of the Microstructure Evolution in IF-Steel and AA6016 during Plane-Strain Tension and Simple Shear. In: Materials. Vol. 8 (2015) 1, 285 - 301. (DOI:  10.3390/ma8010285)}}
@article{steglich_experimental_and_2015, 
author={Steglich, D. and Tian, X. and Bohlen, J. and Riekehr, S. and Kashaev, N. and Kainer, K.U. and Huber, N.},
title={Experimental and numerical crushing analyses of thin-walled magnesium profiles},
year={2015},
journal = {International Journal of Crashworthiness},
volume = {20},
number = {2},
pages = {177 - 190},
doi = {http://dx.doi.org/10.1080/13588265.2014.996319},
abstract = {In order to assess the crashworthiness of simple magnesium structures the axial deformation behaviour of different hollow rectangular profiles produced from wrought magnesium alloys Mg–3wt.%Al–1wt.%Zn–0.3wt.%Mn and Mg–1wt.%Zn–0.4wt.%rare earth mischmetal were investigated under quasi-static compressive loading conditions. Laser beam welding was applied to build the crush configurations from plane rolled sheets; indirect extrusion was used to manufacture seamless profiles. Numerical simulations were conducted to predict and assess the crush behaviour. The simulation results revealed that the material work hardening rates evidenced in uniaxial compression tests together with the cross section influenced the buckling modes as well as the energy dissipation. The performance of the magnesium profiles in terms of dissipated specific energy is better than that of aluminium profiles for small compressive displacements. However, for large displacements, shear-compressive failure limited the crush displacement and hence the energy dissipation. The weld itself did not influence the failure and the energy dissipation of the respective structure. For the alloy and process development of wrought magnesium, prospective improvements towards higher dissipated energy can be realised by increasing not only the strength but also the hardening rate of the material.},
note = {Online available at: \url{http://dx.doi.org/10.1080/13588265.2014.996319} (DOI). Steglich, D.; Tian, X.; Bohlen, J.; Riekehr, S.; Kashaev, N.; Kainer, K.U.; Huber, N.: Experimental and numerical crushing analyses of thin-walled magnesium profiles. In: International Journal of Crashworthiness. Vol. 20 (2015) 2, 177 - 190. (DOI:  10.1080/13588265.2014.996319)}}
@article{cornec_numerical_prediction_2015, 
author={Cornec, A. and Kabir, M.R. and Huber, N.},
title={Numerical prediction of the stress–strain response of a lamellar GammaTiAl polycrystal using a two-scale modelling approach},
year={2015},
journal = {Materials Science and Engineering  A},
volume = {620},
pages = {273 - 285},
doi = {http://dx.doi.org/10.1016/j.msea.2014.10.018},
abstract = {An advanced model incorporating a two-scale structural description with integrated constitutive formulations of crystal plasticity was adopted to describe the mechanical behaviour of a γTiAl polycrystal with grains of staggered (γ/α2)-phase lamellae. The numerical model assembles a polycrystalline compound of 64 lamellar grains generated from periodic unit cells (PUC) taking relevant phase configurations. The representative parameter set for the crystal plasticity are estimated by modelling the lamellar deformation and fitting the compression and tension test results in two steps: firstly, the fundamental parameters were identified for a poly-synthetically twinned single crystal (PST) under compression, and secondly, these PST parameters were adjusted to the γTiAl polycrystal consisting of fully lamellar grains. Numerical results show that the compression–tension anomaly in the stress–strain curves can be successfully described by a ‘high-grade’ PUC model including six domain variants of the γ-phase occurring in the lamellae. Using a PUC model with simplified mapping of lamellar microstructure, the prediction quality remains unsatisfactory with respect to the observed compression and tension anomaly and the crystal parameters are found to be inconsistent. Differently aligned lamellar grains in polycrystalline cubic model are predicted, which showed that the global stress–strain curves are weakly affected by different local alignments (or textures) of the grains, whereas, the single grain analyses show strong variations in local stress–strain curves. The simulated nature of local variations in grain scale stress–strain behaviour accords with the independent results from instrumented indentation testing of the same lamellar polycrystal.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.msea.2014.10.018} (DOI). Cornec, A.; Kabir, M.R.; Huber, N.: Numerical prediction of the stress–strain response of a lamellar GammaTiAl polycrystal using a two-scale modelling approach. In: Materials Science and Engineering  A. Vol. 620 (2015) 273 - 285. (DOI:  10.1016/j.msea.2014.10.018)}}
@article{proenca_friction_riveting_2015, 
author={Proenca, B.C. and Blaga, L. and dos Santos, J.F. and Canto, L.B. and Amancio Filho, S.T.},
title={Friction Riveting of Aluminum Alloy 6056 T6 and Polyamide 6: Role of the Rotation Speed on the Formation of the Anchoring Zone and Mechanical Performance - Rebitagem por Friccao (“FricRiveting”) de Liga de Alumínio 6056 T6 e Poliamida 6: Influencia da Velocidade de Rotacao na Formacao da Zona de Ancoragem e no Desempenho Mecanico},
year={2015},
journal = {Soldagem & Inspecao},
volume = {20},
number = {4},
pages = {489 - 500},
doi = {http://dx.doi.org/10.1590/0104-9224/SI2004.15},
abstract = {Hybrid metal-polymer structures are an alternative solution to reduce weight and fuel consumption in the transportation industry in order to minimize the emission of noxious gases in regard to the greenhouse effect. Friction Riveting is a relatively new technique for joining metal-polymer hybrid structures. The process relies on the generation of frictional heat between the components causing the plastic deformation of the metallic rivet and its anchoring in the polymer component. This study evaluated the technical feasibility of friction-riveted AA 6056 T6 and PA6 joints, and the influence of the rotational speed (RS) on the maximum process temperature and on the mechanical performance of the joints. The maximum temperature reached increased with the rotational speed, from 291 ± 6 °C at 10000 rev/min to 375 ± 5 °C at 15000 rev/min. The use of greater rotational speeds induced the plastic deformation of the tip of the metallic rivet during the frictional phase. This led to mechanically stronger joints due to the larger anchoring of the metallic rivet within the polymeric plate. The AA 6056 T6-PA6 joints had good tensile strength, achieving 85% of the metallic rivet’s tensile strength. Therefore, the feasibility of friction-riveted AA 6056 T6-PA6 joints was proven. Furthermore, it was shown that the rotational speed influences directly the rivet anchoring and thus the tensile strength of the joints.},
note = {Online available at: \url{http://dx.doi.org/10.1590/0104-9224/SI2004.15} (DOI). Proenca, B.C.; Blaga, L.; dos Santos, J.F.; Canto, L.B.; Amancio Filho, S.T.: Friction Riveting of Aluminum Alloy 6056 T6 and Polyamide 6: Role of the Rotation Speed on the Formation of the Anchoring Zone and Mechanical Performance - Rebitagem por Friccao (“FricRiveting”) de Liga de Alumínio 6056 T6 e Poliamida 6: Influencia da Velocidade de Rotacao na Formacao da Zona de Ancoragem e no Desempenho Mecanico. In: Soldagem & Inspecao. Vol. 20 (2015) 4, 489 - 500. (DOI:  10.1590/0104-9224/SI2004.15)}}
@article{schaefer_ultrafine_sanding_2015, 
author={Schaefer, H. and Hess, C. and Tobergte, H. and Volf, A. and Ichilmann, S. and Eickmeier, H. and Voss, B. and Kashaev, N. and Nordmann, J. and Akram, W. and Hartmann-Azanza, B. and Steinhart, M.},
title={Ultrafine Sanding Paper: A Simple Tool for Creating Small Particles},
year={2015},
journal = {Small},
volume = {11},
number = {8},
pages = {931 - 935},
doi = {http://dx.doi.org/10.1002/smll.201303930},
abstract = {A top-down approach, i.e., creating small particles by mechanical force starting from bulk materials, probably presents the most logical approach to particle size reduction and, therefore, top-down techniques are among the first to achieve small particles. A new solvent-free, amazingly simple approach is reported, suitable to achieve nanoparticles and sub-micro particles.},
note = {Online available at: \url{http://dx.doi.org/10.1002/smll.201303930} (DOI). Schaefer, H.; Hess, C.; Tobergte, H.; Volf, A.; Ichilmann, S.; Eickmeier, H.; Voss, B.; Kashaev, N.; Nordmann, J.; Akram, W.; Hartmann-Azanza, B.; Steinhart, M.: Ultrafine Sanding Paper: A Simple Tool for Creating Small Particles. In: Small. Vol. 11 (2015) 8, 931 - 935. (DOI:  10.1002/smll.201303930)}}
@article{esteves_friction_spot_2015, 
author={Esteves, J.V. and Goushegir, S.M. and dos Santos, J.F. and Canto, L.B. and Hage, E.Jr. and Amancio-Filho, S.T.},
title={Friction spot joining of aluminum AA6181-T4 and carbon fiber-reinforced poly(phenylene sulfide): Effects of process parameters on the microstructure and mechanical strength},
year={2015},
journal = {Materials and Design},
volume = {66 B},
pages = {437 - 445},
doi = {http://dx.doi.org/10.1016/j.matdes.2014.06.070},
abstract = {Friction spot joining is an alternative technique to produce metal-composite overlap joints. The main process parameters are tool rotational speed, plunge depth, joining time and joining force. In this study, the individual effect of the process parameters on the microstructure and mechanical strength of hybrid AA6181-T4/CF-PPS double lap joints was investigated using Taguchi method and analysis of variance (ANOVA). Produced joints presented mechanical performance from 2107 N to 3523 N. Joints failed by brittle fracture at the interface between aluminum alloy and composite, with displacement-at-peak load values from 0.7 mm to 0.9 mm. Tool rotational speed was the parameter with the largest influence on the joint shear resistance, followed by the joining time, plunge depth and joining force. Higher strength was correlated to the extension of the bonding area and macro-mechanical interlocking related to the formation of a metallic indentation (metallic nub) slightly inserted into the composite. Larger bonding areas were shown to be related to higher heat input (as a result of longer joining times and intermediate rotational speeds) leading to larger consolidated polymeric layers at the metal-composite interface. Higher macro-mechanical interlocking was obtained at larger plunge depths. Joining force was shown to be related to crevice and pore filling of the metal surface by supporting spreading of the molten polymer. Higher joining forces led to better wetting of the interface, increasing adhesive forces and joint mechanical performance. Nevertheless excessive joining forces caused squeezing flow of the molten layer reducing joint strength, since a large adhesive area was lost.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.matdes.2014.06.070} (DOI). Esteves, J.V.; Goushegir, S.M.; dos Santos, J.F.; Canto, L.B.; Hage, E.Jr.; Amancio-Filho, S.T.: Friction spot joining of aluminum AA6181-T4 and carbon fiber-reinforced poly(phenylene sulfide): Effects of process parameters on the microstructure and mechanical strength. In: Materials and Design. Vol. 66 B (2015) 437 - 445. (DOI:  10.1016/j.matdes.2014.06.070)}}
@article{sticchi_review_of_2015, 
author={Sticchi, M. and Schnubel, D. and Kashaev, N. and Huber, N.},
title={Review of Residual Stress Modification Techniques for Extending the Fatigue Life of Metallic Aircraft Components},
year={2015},
journal = {Applied Mechanics Reviews},
volume = {67},
number = {1},
pages = {010801},
doi = {http://dx.doi.org/10.1115/1.4028160},
abstract = {A major challenge for the aircraft industry in the future will be the development of effective strategies for maintaining and extending the service life of a growing fleet of aging aircraft. In this context, residual-stress-based approaches for extending the fatigue life of aircraft components are believed to have great potential for providing cost-effective solutions. This paper reviews residual-stress-based life extension techniques and published work on the use of these techniques in aerospace applications. The techniques reviewed include cold expansion, shot peening, laser shock peening, deep rolling and heating. Comparisons of the various techniques with regard to current applications and limitations are given.},
note = {Online available at: \url{http://dx.doi.org/10.1115/1.4028160} (DOI). Sticchi, M.; Schnubel, D.; Kashaev, N.; Huber, N.: Review of Residual Stress Modification Techniques for Extending the Fatigue Life of Metallic Aircraft Components. In: Applied Mechanics Reviews. Vol. 67 (2015) 1, 010801. (DOI:  10.1115/1.4028160)}}
@article{soyarslan_lode_parameter_2015, 
author={Soyarslan, C. and Richter, H. and Bargmann, S.},
title={Lode Parameter Dependence and Quasi-Unilateral Effects in Continuum Damage Mechanics: Models and Applications in Metal Forming},
year={2015},
journal = {Key Engineering Materials, Material Forming ESAFORM 2015},
volume = {651-653},
pages = {187 - 192},
doi = {http://dx.doi.org/10.4028/www.scientific.net/KEM.651-653.187},
abstract = {This work concerns with two successive modifications of the Lemaitre’s damage model to
meet the requirements of formability prediction for today’s modern steels. The first one is the quasiunilateral
damage evolution which modifies the damage driving force by scaling the elastic energy
release rate due to compressive principal stress components. The second one is the shear modification
by which the damage rate is multiplied by a normalized maximum shear stress dependent factor.
With the assumption of non-rotating principal axes of deformation, proportional strain paths and rigid
plasticity, closed form expressions for the isochronous fracture surfaces are derived for each model
variant and resulting surface plots at various spaces are compared. The findings show that the former
modification not only remedies the pathological reflective symmetry of the fracture surface across
the  plane with vanishing stress triaxiality ratio, but also allows hindering fracture under uniaxial
compression. The latter modification by adding a direct Lode parameter dependence to the damage
evolution function allows prediction of premature fracture at generalized shear stress states, a condition
observed for certain advanced high strength metallic sheets. Parameter calibration is realized for
each model variant using the experimental data from the literature. It is shown that the fracture model
with both the shear modification and the quasi-unilateral enhancement shows the best fitting quality.
Finally, the models are implemented as user subroutines for ABAQUS/EXPLICIT and used in prediction
of initiation and propagation of cracks for a series of deep-drawing punch tests. A good agreement
with the outputs reported in the literature is observed in terms of the shear damage occurrence zones
as well as corresponding punch force-displacement diagrams.},
note = {Online available at: \url{http://dx.doi.org/10.4028/www.scientific.net/KEM.651-653.187} (DOI). Soyarslan, C.; Richter, H.; Bargmann, S.: Lode Parameter Dependence and Quasi-Unilateral Effects in Continuum Damage Mechanics: Models and Applications in Metal Forming. In: Key Engineering Materials, Material Forming ESAFORM 2015. Vol. 651-653 (2015) 187 - 192. (DOI:  10.4028/www.scientific.net/KEM.651-653.187)}}
@article{qi_porous_gold_2015, 
author={Qi, Z. and Vainio, U. and Kornowski, A. and Ritter, M. and Weller, H. and Jin, H. and Weissmueller, J.},
title={Porous Gold with a Nested-Network Architecture and Ultrafine Structure},
year={2015},
journal = {Advanced Functional Materials},
volume = {25},
number = {17},
pages = {2530 - 2536},
doi = {http://dx.doi.org/10.1002/adfm.201404544},
abstract = {A preparation strategy is developed for monolithic samples of nanoporous gold with a hierarchical structure comprising two nested networks of solid “ligaments” on distinctly different structural length scales. The electrochemical dealloying protocol achieves a large retention of less noble element in a first corrosion step, thereby allowing an extra corrosion step which forms a separate structural hierarchy level. The beneficial impact of adding Pt to the Ag–Au master alloys that are more conventionally used in dealloying approaches to nanoporous gold is demonstrated. At ≈6 nm, the lower hierarchy level ligament size emerges extremely small. Furthermore, Pt favors the retention of Ag during the first dealloying step even when the master alloy has a high Au content. The high Au content reduces the corrosion-induced shrinkage, mitigating crack formation during preparation and favoring the formation of high-quality macroscopic (mm-sized) samples. The corrosion effectively carves out the nanoscale hierarchical ligament structure from the parent crystals tens of micrometers in size. This is revealed by X-ray as well as electron backscatter diffraction, which shows that the porous crystallites inherit the highly ordered, macroscopic crystal lattice structure of the master alloy.},
note = {Online available at: \url{http://dx.doi.org/10.1002/adfm.201404544} (DOI). Qi, Z.; Vainio, U.; Kornowski, A.; Ritter, M.; Weller, H.; Jin, H.; Weissmueller, J.: Porous Gold with a Nested-Network Architecture and Ultrafine Structure. In: Advanced Functional Materials. Vol. 25 (2015) 17, 2530 - 2536. (DOI:  10.1002/adfm.201404544)}}
@article{wang_nanoporousgoldbased_composites_2015, 
author={Wang, K. and Kobler, A. and Kuebel, C. and jelitto, H. and Schneider, G. and Weissmueller, J.},
title={Nanoporous-gold-based composites: toward tensile ductility},
year={2015},
journal = {NPG Asia Materials},
volume = {7},
pages = {e187},
doi = {http://dx.doi.org/10.1038/am.2015.58},
abstract = {We report on mechanical tests on interpenetrating-phase nanocomposite materials made by vacuum impregnation of nanoscale metal networks with a polymer. The metal component is nanoporous gold made by dealloying, whereas two epoxy resins and polyurethane are explored as the polymer component. The composites are strong and deformable in compression. Although previous observations invariably indicate tensile brittleness for nanoporous gold, composite samples made from cm-sized nanoporous samples enable macroscopic tensile and four-point bending tests that show ductility. This implies that the high strength of individual metal objects such as nanowires can now be incorporated into a strong and ductile material from which macroscopic things can be formed. In fact, a rule-of-mixture-type analysis of the stresses carried by the metal phase suggests quantitative agreement with data reported from separate experiments on small-scale gold nanostructures.},
note = {Online available at: \url{http://dx.doi.org/10.1038/am.2015.58} (DOI). Wang, K.; Kobler, A.; Kuebel, C.; jelitto, H.; Schneider, G.; Weissmueller, J.: Nanoporous-gold-based composites: toward tensile ductility. In: NPG Asia Materials. Vol. 7 (2015) e187. (DOI:  10.1038/am.2015.58)}}
@article{soyarslan_a_directional_2015, 
author={Soyarslan, C. and Klusemann, B. and Bargmann, S.},
title={A directional modification of the Levkovitch–Svendsen cross-hardening model based on the stress deviator},
year={2015},
journal = {Mechanics of Materials},
volume = {86},
pages = {21 - 30},
doi = {http://dx.doi.org/10.1016/j.mechmat.2015.03.003},
abstract = {In the original Levkovitch–Svendsen cross-hardening model parallel and orthogonal projections required for the yield surface evolution with respective dynamic and latent hardening effects are associated with the unit plastic flow direction View the MathML sourcenp=Ėp/|Ėp|. This work gives a detailed investigation regarding the consequences and proposes the use of the so–called radial direction ns=[S-X]/|S-X|ns=[S-X]/|S-X| instead where S=dev(σ)S=dev(σ). It is shown that for an initially plastically anisotropic material under load paths with proportional stresses the original model brings a continuous directional change in the plastic strains. Eventually, even if the dynamic hardening component is bypassed, the material model predicts additional strengthening in loading direction due to latent hardening. In this undesired response, the broken coaxiality of the stress deviator and plastic strain rate tensor with initial anisotropy is the cause. This entanglement of isotropic/kinematic hardening and latent hardening creates difficulties – especially in the parameter identification even for the simplest uniaxial loading. The introduced modification to the model remedies this undesired feature and, hence, makes it possible to isolate the hardening sources during parameter identification stage. The discussions are supported by analytically and numerically derived yield loci for various scenarios. Our analytical studies allow definition of critical material parameter limits for the latent hardening parameter slsl in terms of the initial anisotropy and the constant stress deviator ratio.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.mechmat.2015.03.003} (DOI). Soyarslan, C.; Klusemann, B.; Bargmann, S.: A directional modification of the Levkovitch–Svendsen cross-hardening model based on the stress deviator. In: Mechanics of Materials. Vol. 86 (2015) 21 - 30. (DOI:  10.1016/j.mechmat.2015.03.003)}}
@article{andrade_microstructure_of_2015, 
author={Andrade, T.C. and Silva, C.C. and Miranda, H.C.de and Motta, M.F. and Farias, J.P. and Bergman, L.A. and dos Santos, J.F.},
title={Microstructure of AISI 410S Ferritic Stainless Steel and AISI 304L Austenitic Stainless Steel Dissimilar Weld Joined by FSW Process - Microestrutura de uma Solda Dissimilar entre o Aço Inoxidável Ferrítico AISI 410S e o Aço Inoxidável Austenítico AISI 304L Soldado pelo Processo FSW},
year={2015},
journal = {Soldagem & Inspecao},
volume = {20},
number = {4},
pages = {467 - 478},
doi = {http://dx.doi.org/10.1590/0104-9224/SI2004.13},
abstract = {This study aims to investigate the microstructure formed in dissimilar welding between AISI 410S ferritic stainless steel and AISI 304L austenitic stainless steels plates by friction stir welding process. The welding was performed setting the following parameters: rotation 450 rpm; welding speed of 1.0 mm/s; and axial force 40 kN. The AISI 410S was positioned on the advancing side while the AISI 304L steel was positioned in the retracting side. The analysis consisted of metallographic preparation and microstructural characterization by optical microscopy and scanning electron microscopy. For AISI 410S ferritic stainless steel was found martensite formation in association with ferrite in the stir zone (SZ), thermomechanically affected zone (TMAZ) and heat-affected zone (HAZ). The characteristics of the FSW welding process for the ferritic stainless steel resulted in grain refining, whether in the SZ, TMAZ and HAZ. In the austenitic stainless steel side, the same behavior was not found.

O presente trabalho visa investigar a microestrutura formada na soldagem dissimilar entre chapas de aços inoxidáveis ferríticos AISI 410S e aços inoxidáveis austeníticos AISI 304L pelo processo friction stir welding. A soldagem foi realizada com o ajuste dos seguintes parâmetros: rotação 450 rpm; velocidade de soldagem de 1,0 mm/s; e força axial 40 kN. O aço AISI 410S foi posicionado no lado de avanço enquanto que o aço AISI 304L foi posicionado no lado de retrocesso. A análise consistiu de preparação metalográfica e caracterização microestrutural por microscopia ótica e microscopia eletrônica de varredura. Para o aço AISI 410S foi observada a formação de martensita associada com ferrita na zona de mistura (ZM), zona termomecanicamente afetada (ZTMA) e na zona afetada pelo calor (ZAC). As características do processo de soldagem FSW resultaram num refino de grão para o aço inoxidável ferrítico, posicionado no lado de avanço, tanto na ZM quanto nas ZTMA e ZAC. O mesmo comportamento não foi observado para o lado austenítico.},
note = {Online available at: \url{http://dx.doi.org/10.1590/0104-9224/SI2004.13} (DOI). Andrade, T.C.; Silva, C.C.; Miranda, H.C.de; Motta, M.F.; Farias, J.P.; Bergman, L.A.; dos Santos, J.F.: Microstructure of AISI 410S Ferritic Stainless Steel and AISI 304L Austenitic Stainless Steel Dissimilar Weld Joined by FSW Process - Microestrutura de uma Solda Dissimilar entre o Aço Inoxidável Ferrítico AISI 410S e o Aço Inoxidável Austenítico AISI 304L Soldado pelo Processo FSW. In: Soldagem & Inspecao. Vol. 20 (2015) 4, 467 - 478. (DOI:  10.1590/0104-9224/SI2004.13)}}
@article{dorosrio_selfassembled_ultra_2015, 
author={do Rosário, J. and Lilleodden, E. and Waleczek, M. and Kubin, R. and Petrov, A. and Dyachenko, P. and Sabisch, J. and Nielsch, K. and Huber, N. and Eich, M. and Schneider, G.},
title={Self‐Assembled Ultra High Strength, Ultra Stiff Mechanical Metamaterials Based on Inverse Opals},
year={2015},
journal = {Advanced Engineering Materials},
volume = {17},
number = {10},
pages = {1420 - 1424},
doi = {10.1002/adem.201500118},
abstract = {Inverse opals are presented as a class of mechanical metamaterials. Pure silica and titania coated silica inverse opals show high strength‐ and modulus‐to‐weight ratios, even outperforming many optimized strut‐based microfabricated ceramic materials. Micropillars were fabricated out of self‐assembled layers and tested under compression. Their high performance is due to its arch‐like structure, where stresses are smoothly directed into the regions of higher material mass, thereby mitigating the stress concentration at the pore perimeter, as confirmed by numerical simulations.},
note = {Online available at: \url{https://dx.doi.org/10.1002/adem.201500118} (DOI). do Rosário, J.; Lilleodden, E.; Waleczek, M.; Kubin, R.; Petrov, A.; Dyachenko, P.; Sabisch, J.; Nielsch, K.; Huber, N.; Eich, M.; Schneider, G.: Self‐Assembled Ultra High Strength, Ultra Stiff Mechanical Metamaterials Based on Inverse Opals. In: Advanced Engineering Materials. Vol. 17 (2015) 10, 1420 - 1424. (DOI:  /10.1002/adem.201500118)}}
@article{lu_influence_of_2015, 
author={Lu, J. and Huber, N. and Kashaev, N.},
title={Influence of the geometry on the fatigue performance of crenellated fuselage panels},
year={2015},
journal = {Ciencia & Tecnologia dos Materiais},
volume = {27},
number = {2},
pages = {100 - 107},
doi = {http://dx.doi.org/10.1016/j.ctmat.2015.06.003},
abstract = {Crenellation is a novel local engineering technique aimed at improving the fatigue performance of the airframe structures without increasing the weight. In this concept, a systematic thickness variation is applied to the fuselage skin to retard the fatigue crack growth. In order to achieve the best retardation effect, it is necessary optimize the crenellation geometry. As a result, a parameter study characterizing three independent geometric aspects of the crenellations was performed: the crenellation ratio c, the periodic length λ and a position parameter. The study was based on a FEA model validated by experiments. It is expected to give a sufficiently accurate prediction on fatigue life of different crenellation patterns. The obtained knowledge concerning the impact of those geometrical factors could provide guidance for future crenellation designs for industrial applications.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.ctmat.2015.06.003} (DOI). Lu, J.; Huber, N.; Kashaev, N.: Influence of the geometry on the fatigue performance of crenellated fuselage panels. In: Ciencia & Tecnologia dos Materiais. Vol. 27 (2015) 2, 100 - 107. (DOI:  10.1016/j.ctmat.2015.06.003)}}
@article{mcbride_a_computational_2015, 
author={McBride, A. and Bargmann, S. and Reddy, B.D.},
title={A computational investigation of a model of single-crystal gradient thermoplasticity that accounts for the stored energy of cold work and thermal annealing},
year={2015},
journal = {Computational Mechanics},
volume = {55},
number = {4},
pages = {755 - 769},
doi = {http://dx.doi.org/10.1007/s00466-015-1134-5},
abstract = {A theory of single-crystal gradient thermoplasticity that accounts for the stored energy of cold work and thermal annealing has recently been proposed by Anand et al. (Int J Plasticity 64:1–25, 2015). Aspects of the numerical implementation of the aforementioned theory using the finite element method are detailed in this presentation. To facilitate the implementation, a viscoplastic regularization of the plastic evolution equations is performed. The weak form of the governing equations and their time-discrete counterparts are derived. The theory is then elucidated via a series of three-dimensional numerical examples where particular emphasis is placed on the role of the defect-flow relations. These relations govern the evolution of a measure of the glide and geometrically necessary dislocation densities which is associated with the stored energy of cold work.},
note = {Online available at: \url{http://dx.doi.org/10.1007/s00466-015-1134-5} (DOI). McBride, A.; Bargmann, S.; Reddy, B.D.: A computational investigation of a model of single-crystal gradient thermoplasticity that accounts for the stored energy of cold work and thermal annealing. In: Computational Mechanics. Vol. 55 (2015) 4, 755 - 769. (DOI:  10.1007/s00466-015-1134-5)}}
@article{enz_laser_weldbability_2015, 
author={Enz, J. and Riekehr, S. and Ventzke, V. and Kashaev, N.},
title={Laser Weldbability of different Al-Zn alloys and its improvement},
year={2015},
journal = {Materials Science Forum, Light Metals Technology 2015},
volume = {828-829},
pages = {389 - 394},
doi = {http://dx.doi.org/10.4028/www.scientific.net/MSF.828-829.389},
abstract = {Weld defects - such as porosity and hot cracking - occur especially during the laser beam welding of high-alloyed Al-Zn alloys. This significantly limits the application range of these promising high-strength alloys. In the present study the laser weldability of Al-Zn alloys was investigated regarding welding parameters and chemical composition of the alloys. In addition, the novel approach of the Helmholtz-Zentrum Geesthacht for overcoming the weldability problems was applied to the different Al-Zn alloys in order to assess its capability. It was shown that the laser weldability of Al-Zn alloys deteriorates with an increasing amount of Zn, Mg and Cu. The variation of laser welding parameters did not lead to any improvement of weldability. Only the use of a V foil as additional filler material resulted in promising welding results even for high-alloyed Al-Zn alloys.},
note = {Online available at: \url{http://dx.doi.org/10.4028/www.scientific.net/MSF.828-829.389} (DOI). Enz, J.; Riekehr, S.; Ventzke, V.; Kashaev, N.: Laser Weldbability of different Al-Zn alloys and its improvement. In: Materials Science Forum, Light Metals Technology 2015. Vol. 828-829 (2015) 389 - 394. (DOI:  10.4028/www.scientific.net/MSF.828-829.389)}}
@article{kitzler_the_electrochemomechanical_2015, 
author={Kitzler, T. and Maawad, E. and Toebbens, D.M. and Ziehmer, M. and Markmann, J.},
title={The Electro-Chemo-Mechanical Coupling in Lithium Alloy Electrodes and Its Origins},
year={2015},
journal = {Journal of the Electrochemical Society},
volume = {162},
number = {14},
pages = {A2684 - A2691},
doi = {http://dx.doi.org/10.1149/2.0461514jes},
abstract = {A method to identify and separate the influence of changes in the surface stress from the bulk stress in a model lithium-ion battery electrode during electrochemical cycling was developed. The strategy for this separation is based on the different influence of surface and bulk stresses on the coupling between electrode potential and mechanical strain as measured by dynamic electro-chemo-mechanical analysis and the coupling between the transferred electric charge and the elastic strain as determined by wide angle X-ray scattering. Using both methods, it was possible to uncover the behavior of an apparent surface stress evoked by the bulk stress due to grain boundary alloying of lithium in a gold film. Additionally, the analysis allowed for a determination of a range in surface stress due to underpotential deposition of one monolayer of lithium as the interval between −3.1 to −1.9 N/m.},
note = {Online available at: \url{http://dx.doi.org/10.1149/2.0461514jes} (DOI). Kitzler, T.; Maawad, E.; Toebbens, D.M.; Ziehmer, M.; Markmann, J.: The Electro-Chemo-Mechanical Coupling in Lithium Alloy Electrodes and Its Origins. In: Journal of the Electrochemical Society. Vol. 162 (2015) 14, A2684 - A2691. (DOI:  10.1149/2.0461514jes)}}
@article{lu_crenellation_patterns_2015, 
author={Lu, J. and Kashaev, N. and Huber, N.},
title={Crenellation Patterns for Fatigue Crack Retardation in Fuselage Panels Optimized via Genetic Algorithm},
year={2015},
journal = {Procedia Engineering},
volume = {114},
pages = {248 - 254},
doi = {http://dx.doi.org/10.1016/j.proeng.2015.08.065},
abstract = {Crenellation is a promising technique to effectively improve the fatigue life of fuselage panels. It systematically varies the thickness of the fuselage skin at a constant structural weight. In the design of the crenellation patterns, the schemes of redistributing the skin material between different thickened and thinned regions can be innumerable. In order to select the optimum design from the huge searching space, a genetic algorithm was used in this study, which was coupled with FEM simulations used to predict the fatigue life of different crenellation designs. To accelerate the optimization process, a progressively refined searching approach and an old-individual-filtering technique were used. The suggested approach leads to both a reduced computational cost and improved solution quality.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.proeng.2015.08.065} (DOI). Lu, J.; Kashaev, N.; Huber, N.: Crenellation Patterns for Fatigue Crack Retardation in Fuselage Panels Optimized via Genetic Algorithm. In: Procedia Engineering. Vol. 114 (2015) 248 - 254. (DOI:  10.1016/j.proeng.2015.08.065)}}
@article{liu_in_situ_2015, 
author={Liu, J. and Staron, P. and Riekehr, S. and Stark, A. and Schell, N. and Huber, N. and Schreyer, A. and Mueller, M. and Kashaev, N.},
title={In situ study of phase transformations during laser-beam welding of a TiAl alloy for grain refinement and mechanical property optimization},
year={2015},
journal = {Intermetallics},
volume = {62},
pages = {27 - 35},
doi = {http://dx.doi.org/10.1016/j.intermet.2015.03.003},
abstract = {In situ time-resolved X-ray diffraction by synchrotron radiation was used to monitor the phase transformations and grain-refining processes during laser-beam welding of a γ-TiAl-based alloy. The heating rate plays an important role of grain refinement. A high heating rate suppresses solid–solid phase transformations. The superheated γ grains serve as heterogeneous nuclei for β grains on subsequent solidification and refine the lamellar colonies. At low heating rate, diffusion-based transformations are observed on heating and coarse lamellae are formed after welding. The refined lamellar colonies improve the mechanical properties.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.intermet.2015.03.003} (DOI). Liu, J.; Staron, P.; Riekehr, S.; Stark, A.; Schell, N.; Huber, N.; Schreyer, A.; Mueller, M.; Kashaev, N.: In situ study of phase transformations during laser-beam welding of a TiAl alloy for grain refinement and mechanical property optimization. In: Intermetallics. Vol. 62 (2015) 27 - 35. (DOI:  10.1016/j.intermet.2015.03.003)}}
@article{sievers_continuum_modeling_2015, 
author={Sievers, C. and Mosler, J.},
title={Continuum modeling of material interfaces and surfaces based on molecular statics computations},
year={2015},
journal = {PAMM: Proceedings in Applied Mathematics and Mechanics},
volume = {15},
number = {1},
pages = {359 - 360},
doi = {http://dx.doi.org/10.1002/pamm.201510170},
abstract = {The effective macroscopic properties of a broad variety of different materials are defined by the properties of the involved material interfaces and surfaces. However, in contrast to classical bulk materials, the mechanical properties of material interfaces can usually only be determined indirectly. For that purpose, two different approaches are presented which allow to compute macroscopic properties of material interfaces based on molecular statics computations. While the first of those is based on the principle of energy equivalence, the second one relies on the principle of stress equivalence. The advantages and disadvantages of both frameworks are analyzed.},
note = {Online available at: \url{http://dx.doi.org/10.1002/pamm.201510170} (DOI). Sievers, C.; Mosler, J.: Continuum modeling of material interfaces and surfaces based on molecular statics computations. In: PAMM: Proceedings in Applied Mathematics and Mechanics. Vol. 15 (2015) 1, 359 - 360. (DOI:  10.1002/pamm.201510170)}}
@article{deng_less_noble_2015, 
author={Deng, Q. and Gopal, V, Weissmueller, J.},
title={Less Noble or More Noble: How Strain Affects the Binding of Oxygen on Gold},
year={2015},
journal = {Angewandte Chemie},
volume = {127},
number = {44},
pages = {13173 - 13177},
doi = {http://dx.doi.org/10.1002/ange.201504715},
abstract = {Many heterogeneous catalysts exploit strained active layers to modulate reactivity and/or selectivity. It is therefore significant that density functional theory, as well as experimental approaches, find that tensile strain makes the gold surface more binding for oxygen, in other words, less noble. We show that this behavior does not apply when re-structuring of the gold surface is allowed to occur simultaneously with the adsorption of oxygen. In situ cantilever-bending studies show the surface stress to increase when oxygen species adsorb on a (111)-textured gold surface in aqueous H2SO4. This implies a positive sign of the electrocapillary coupling parameter and, hence, a trend for weaker oxygen binding in response to tensile strain. These conflicting findings indicate that different electrosorption processes, and specifically oxygen species adsorption on the bulk-terminated surface, exhibit fundamentally different coupling between the chemistry and the mechanics of the surface.},
note = {Online available at: \url{http://dx.doi.org/10.1002/ange.201504715} (DOI). Deng, Q.; Gopal, V, Weissmueller, J.: Less Noble or More Noble: How Strain Affects the Binding of Oxygen on Gold. In: Angewandte Chemie. Vol. 127 (2015) 44, 13173 - 13177. (DOI:  10.1002/ange.201504715)}}
@article{plaine_the_optimization_2015, 
author={Plaine, A.H. and Gonzalez, A.R. and Suhuddin, U.F.H. and dos Santos, J.F. and Alcantara, N.G.},
title={The optimization of friction spot welding process parameters in AA6181-T4 and Ti6Al4V dissimilar joints},
year={2015},
journal = {Materials and Design},
volume = {83},
pages = {36 - 41},
doi = {http://dx.doi.org/10.1016/j.matdes.2015.05.082},
abstract = {Friction spot welding is a relatively new solid-state joining process able to produce overlap joints between similar and dissimilar materials. In this study, the effect of the process parameters on the lap shear strength of AA6181-T4/Ti6Al4V single joints was investigated using full-factorial design of experiment and analyses of variance. Sound joints with lap shear strength from 4769 N to 6449 N were achieved and the influence of the main process parameters on joint performance was evaluated. Tool rotational speed was the parameter with the largest influence on the joint shear resistance, followed by its interaction with dwell time. Based on the experimental results following response surface methodology, a mathematical model to predict lap shear strength was developed using a second order polynomial function. The initial prediction results indicated that the established model could adequately estimate joint strength within the range of welding parameters being used. The model was then used to optimize welding parameters in order satisfy engineering demands.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.matdes.2015.05.082} (DOI). Plaine, A.H.; Gonzalez, A.R.; Suhuddin, U.F.H.; dos Santos, J.F.; Alcantara, N.G.: The optimization of friction spot welding process parameters in AA6181-T4 and Ti6Al4V dissimilar joints. In: Materials and Design. Vol. 83 (2015) 36 - 41. (DOI:  10.1016/j.matdes.2015.05.082)}}
@article{ma_computational_investigation_2015, 
author={Ma, S. and Yuan, H.},
title={Computational investigation of multi-axial damage modeling for porous sintered metals with experimental verification
},
year={2015},
journal = {Engineering Fracture Mechanics},
volume = {149},
pages = {89 - 110},
doi = {http://dx.doi.org/10.1016/j.engfracmech.2015.09.049},
abstract = {The experimental investigation shows that the damage process in sintered metals starts in almost zero loading and can be divided into three stages: the elastic stage, the secondary stage and finally the tertiary stage. A phenomenological continuum damage model is introduced to predict the inelastic behavior of the sintered material and the damage process. The numerical implicit integration algorithm is developed and implemented into ABAQUS. The proposed damaged model is computationally and experimentally verified under multi-axial loading conditions. It is confirmed that the proposed damage model is able to properly describe the mechanical behavior and the damage evolution under most different loading configurations.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.engfracmech.2015.09.049} (DOI). Ma, S.; Yuan, H.: Computational investigation of multi-axial damage modeling for porous sintered metals with experimental verification
. In: Engineering Fracture Mechanics. Vol. 149 (2015) 89 - 110. (DOI:  10.1016/j.engfracmech.2015.09.049)}}
@article{goncalves_friction_spot_2015, 
author={Goncalves, J. and dos Santos, J.F. and Canto, L.B. and Amancio-Filho, S.T.},
title={Friction spot welding of carbon fiber-reinforced polyamide 66 laminate},
year={2015},
journal = {Materials Letters},
volume = {159},
pages = {509 - 509},
doi = {http://dx.doi.org/10.1016/j.matlet.2015.08.036},
abstract = {Friction spot welding (FSpW) is an innovative technique developed by the Helmholtz Zentrum Geesthacht (WO/2001/036144). FSpW uses the friction between a rotating tool and workpieces to generate enough heat to cause macromolecular interdiffusion across the interface of the joining partners to create the weld. In this work, the feasibility of FSpW on carbon fiber-reinforced polyamide 66 laminate (CF-PA66) was evaluated through lap shear testing and optical microscopy. CF-PA66 welds with good surface finishing, an absence of degradation flaws and an average lap-shear strength of 26.8±0.8 MPa were achieved. These welds have comparable mechanical performance to state-of-the-art ultrasonic welds, which indicates the potential of the FSpW process for fiber-reinforced polymer composites.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.matlet.2015.08.036} (DOI). Goncalves, J.; dos Santos, J.F.; Canto, L.B.; Amancio-Filho, S.T.: Friction spot welding of carbon fiber-reinforced polyamide 66 laminate. In: Materials Letters. Vol. 159 (2015) 509 - 509. (DOI:  10.1016/j.matlet.2015.08.036)}}
@article{hanke_sliding_wear_2015, 
author={Hanke, S. and Fischer, A. and dos Santos, J.F.},
title={Sliding wear behaviour of a Cr-base alloy after microstructure alterations induced by friction surfacing},
year={2015},
journal = {Wear},
volume = {338-339},
pages = {332 - 338},
doi = {http://dx.doi.org/10.1016/j.wear.2015.07.010},
abstract = {Friction surfacing is a method suitable to generate a wide variety of metallic coatings by means of frictional heating and severe shear deformation. It is a solid-state joining method, and therefore may be applied to non-fusion weldable as well as non-deformable brittle materials, as Cr-based alloys are. In the present study coatings of Cr60Ni40 alloy are generated onto Nimonic 80A substrates. Microstructural investigations of the coating material are carried out and compared to the usual cast state. The wear behaviour of the coatings as well as the cast material is examined under reciprocating sliding against 52100 ball bearing steel by means of a ball-on-flat test rig, lubricated with silicone oil to prevent oxidation. In this tribological system, wear takes place by abrasion with microploughing being the predominant submechanism, surface fatigue as well as adhesion by materials transfer of Cr60Ni40 from the flats to the steel balls. White etching layers form on Cr60Ni40 underneath the worn surfaces, which show cracks and delaminations. The amount of wear of all coatings is within the same magnitude compared to the cast state but slightly smaller. This can be explained by the distinctly finer microstructure (grain boundary strengthening) and a high degree of supersaturation of the solid solutions (solid solution strengthening) within the coatings. The results of this study show that it is possible to generate coatings of brittle alloys like Cr60Ni40 by friction surfacing, which show a slightly better wear behaviour under reciprocating sliding. Thus, in combination with a ductile substrate, these coatings are likely to extend the range of applicability of such high-temperature wear and corrosion resistant alloys.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.wear.2015.07.010} (DOI). Hanke, S.; Fischer, A.; dos Santos, J.F.: Sliding wear behaviour of a Cr-base alloy after microstructure alterations induced by friction surfacing. In: Wear . Vol. 338-339 (2015) 332 - 338. (DOI:  10.1016/j.wear.2015.07.010)}}
@article{suhuddin_friction_spot_2015, 
author={Suhuddin, U. and Piccolo, D. and Fischer, V. and dos Santos, J.F.},
title={Friction Spot Welding of Similar AA5754 to AA5754 Aluminum Alloys and Dissimilar AA5754 Aluminum to AZ31 Magnesium Alloys},
year={2015},
journal = {Advanced Materials Research, Advanced Materials Research and Production},
volume = {1112},
pages = {485 - 488},
doi = {http://dx.doi.org/10.4028/www.scientific.net/AMR.1112.485},
abstract = {Friction spot welding is a solid-state spot welding process developed and patented by Helmholtz-Zentrum Geesthacht, Germany. A non-consumable rotating tool consisting of two rotating parts, a pin and a sleeve, and one stationary clamping ring is used to join two or more similar/dissimilar sheets of materials in lap configuration. The result is a spot welded lap connection with minimal material loss and a flat surface without keyhole. The present work presents a summary of results from studies in similar AA5754 to AA5754 Al alloys and dissimilar AA5754 Al to AZ31 Mg alloys.},
note = {Online available at: \url{http://dx.doi.org/10.4028/www.scientific.net/AMR.1112.485} (DOI). Suhuddin, U.; Piccolo, D.; Fischer, V.; dos Santos, J.F.: Friction Spot Welding of Similar AA5754 to AA5754 Aluminum Alloys and Dissimilar AA5754 Aluminum to AZ31 Magnesium Alloys. In: Advanced Materials Research, Advanced Materials Research and Production. Vol. 1112 (2015) 485 - 488. (DOI:  10.4028/www.scientific.net/AMR.1112.485)}}
@article{wang_effect_of_2015, 
author={Wang, F.F. and Li, W.Y. and Shen, J.J. and Hu, S.Y. and Li, J.L. and dos Santos, J.F. and Huber, N.},
title={Effect of tool rotational speed on the microstructure and mechanical properties of bobbin tool friction stir welding of Al-Li alloy},
year={2015},
journal = {Materials and Design},
volume = {86},
pages = {933 - 940},
doi = {http://dx.doi.org/10.1016/j.matdes.2015.07.096},
abstract = {A third-generation Al-Li alloy AA2198 has been successfully welded by bobbin tool friction stir welding. The stirred zone, displaying an hourglass shape, consists of recrystallized Al grains and precipitates remaining in solution. Joint line remnants have been found in all etched welds. Symmetrical hardness profiles have been obtained in the thickness direction, which indicates that the joints have homogenous through-thickness mechanical properties. As the rotational speed increases, the grain size of the stirred zone increases, whereas the density of strengthening particles decreases; the joint line remnants become compressed remarkably in the shoulder-dominated zone while less changes occur in the probe-dominated zone; the softest region shrinks and shifts outward, the average hardness of the stirred zone increases and the hardness profile along the cross section of the joint changes from the U-shaped to W-shaped. The tensile strength of the joint initially increases with rotational speed and then decreases with the maximal strength efficiency reaching 80%; three fracture modes have been observed and cracking initiates at the joint line remnant propagating towards the heat-affected zone, and finally to the border between the thermal-mechanically affected zone and stirred zone.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.matdes.2015.07.096} (DOI). Wang, F.F.; Li, W.Y.; Shen, J.J.; Hu, S.Y.; Li, J.L.; dos Santos, J.F.; Huber, N.: Effect of tool rotational speed on the microstructure and mechanical properties of bobbin tool friction stir welding of Al-Li alloy. In: Materials and Design. Vol. 86 (2015) 933 - 940. (DOI:  10.1016/j.matdes.2015.07.096)}}
@article{altmeyer_microstructure_and_2015, 
author={Altmeyer, J. and Suhuddin, U.F.H. and dos Santos, J.F. and Amancio-Filho, S.T.},
title={Microstructure and mechanical performance of metal-composite hybrid joints produced by FricRiveting},
year={2015},
journal = {Composites / B},
volume = {81},
pages = {130 - 140},
doi = {http://dx.doi.org/10.1016/j.compositesb.2015.06.015},
abstract = {The mechanical performance and microstructure of friction riveted metallic-insert joints made of polyether ether ketone composite reinforced with 30% short carbon fibers and titanium grade 3 was studied. The metallic-insert joints reached a maximal pull-out tensile force of 10.6 kN, which corresponds to 100% of the titanium base material strength. It was shown the pull-out force increased as the rivet tip widened. Frictional heat during the process was mainly generated by the friction between the tip of the rivet and the composite substrate in the friction zone. Microstructural analyses of the metallic part of the joint revealed the presence of different microstructural zones: a friction zone, and two thermomechanically affected zones 1 and 2. Based on the composite morphology, the composite part of the joint was categorized into three different zones: the stir zone, a thermomechanically affected zone and a heat-affected zone. A study of the material flow showed that the flow of the composite was strongly affected by the rotation and axial movement of the rivet.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.compositesb.2015.06.015} (DOI). Altmeyer, J.; Suhuddin, U.F.H.; dos Santos, J.F.; Amancio-Filho, S.T.: Microstructure and mechanical performance of metal-composite hybrid joints produced by FricRiveting. In: Composites / B. Vol. 81 (2015) 130 - 140. (DOI:  10.1016/j.compositesb.2015.06.015)}}
@article{fitseva_friction_surfacing_2015, 
author={Fitseva, V. and Krohn, H. and Hanke, S. and dos Santos, J.F.},
title={Friction surfacing of Ti–6Al–4V: Process characteristics and deposition behaviour at various rotational speeds},
year={2015},
journal = {Surface and Coatings Technology},
volume = {278},
pages = {56 - 63},
doi = {http://dx.doi.org/10.1016/j.surfcoat.2015.07.039},
abstract = {By the process of friction surfacing, coatings are generated from metallic materials at temperatures below their melting range. The high degree of deformation while depositing leads to grain refinement in the microstructure, which has a positive effect on the mechanical properties of the layer. The applicability of the process has been described for a large number of materials. The deposition of Ti–6Al–4V has been reported in one publication but was not systematically studied. Therefore, the main aims of the present work are to define the process parameter fields for the deposition of Ti–6Al–4V leading to flash and defect free coatings and associate them with geometric features of the deposited layer.

This investigation has shown that Ti–6Al–4V coatings can be effectively deposited onto a Ti–6Al–4V substrate by friction surfacing. A wide range of process parameters was established in which coatings of high quality have been obtained. The consumption rate control has been implemented as an efficient mode for the deposition of Ti–6Al–4V coatings. Temperature measurements at the coating interface have been accomplished showing that the coating material has been deformed in the β-phase. Furthermore, the homogeneity of the coating surface has been established to be a function of the rotational speed. The coatings exhibited a defect-free bond at the interface with the substrate. Two process parameter ranges with respect to the flash formation have been established. One of them enables flash-free coatings and the other generates coatings with flash formation on the retreating side, which can be controlled by the rotational and deposition speeds. Moreover, an increase in the rotational speed has been shown to lead to an increase in the coating thickness and width as well as an increase in the deposition efficiency up to 39 %.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.surfcoat.2015.07.039} (DOI). Fitseva, V.; Krohn, H.; Hanke, S.; dos Santos, J.F.: Friction surfacing of Ti–6Al–4V: Process characteristics and deposition behaviour at various rotational speeds. In: Surface and Coatings Technology. Vol. 278 (2015) 56 - 63. (DOI:  10.1016/j.surfcoat.2015.07.039)}}
@article{sticchi_a_parametric_2015, 
author={Sticchi, M. and Staron, P. and Sano, Y. and Meixer, M. and Klaus, M. and Rebelo-Kornmeier, J. and Huber, N. and Kashaev, N.},
title={A parametric study of laser spot size and coverage on the laser shock peening induced residual stress in thin aluminium samples},
year={2015},
journal = {The Journal of Engineering},
volume = {2015},
number = {13},
pages = {97 - 105},
doi = {http://dx.doi.org/10.1049/joe.2015.0106 },
abstract = {Laser Shock Peening is a fatigue enhancement treatment using laser energy to induce compressive Residual Stresses (RS) in the outer layers of metallic components. This work describes the variations of introduced RS-field with peen size and coverage for thin metal samples treated with under-water-LSP. The specimens under investigation were of aluminium alloy AA2024-T351, AA2139-T3, AA7050-T76 and AA7075-T6, with thickness 1.9 mm. The RS were measured by using Hole Drilling with Electronic Speckle Pattern Interferometry and X-ray Diffraction. Of particular interest are the effects of the above mentioned parameters on the zero-depth value, which gives indication of the amount of RS through the thickness, and on the value of the surface compressive stresses, which indicates the magnitude of induced stresses. A 2D-axisymmetrical Finite Element model was created for a preliminary estimation of the stress field trend. From experimental results, correlated with numerical and analytical analysis, the following conclusions can be drawn: increasing the spot size the zero-depth value increases with no significant change of the maximum compressive stress; the increase of coverage leads to significant increase of the compressive stress; thin samples of Al-alloy with low Hugoniot Elastic Limit (HEL) reveal deeper compression field than alloy with higher HEL value.},
note = {Online available at: \url{http://dx.doi.org/10.1049/joe.2015.0106 } (DOI). Sticchi, M.; Staron, P.; Sano, Y.; Meixer, M.; Klaus, M.; Rebelo-Kornmeier, J.; Huber, N.; Kashaev, N.: A parametric study of laser spot size and coverage on the laser shock peening induced residual stress in thin aluminium samples. In: The Journal of Engineering. Vol. 2015 (2015) 13,  97 - 105. (DOI:  10.1049/joe.2015.0106 )}}
@article{butzke_thermomechanical_modeling_2015, 
author={Butzke, J.-E. and Bargmann, S.},
title={Thermomechanical modeling of polysynthetically twinned TiAl crystals},
year={2015},
journal = {Philosophical Magazine},
volume = {95},
number = {24},
pages = {2607 - 2626},
doi = {http://dx.doi.org/10.1080/14786435.2015.1070968},
abstract = {In the present paper, a thermomechanically coupled hyperelastic-plastic model is set up to predict the yield stress of polysynthetically twinned TiAl crystals as a function of temperature, load angle,  content, lamellar thickness and domain size. The elastic deformation is modelled in terms of the Helmholtz free energy density, and the deformation in the plastic regime is mapped by crystal plasticity theory. The yield stress temperature anomaly of intermetallics is incorporated in the model via the critical resolved shear stresses. The numerical results show a very good agreement with experimental results for a wide range of microstructural parameters and temperatures.},
note = {Online available at: \url{http://dx.doi.org/10.1080/14786435.2015.1070968} (DOI). Butzke, J.-E.; Bargmann, S.: Thermomechanical modeling of polysynthetically twinned TiAl crystals. In: Philosophical Magazine. Vol. 95 (2015) 24, 2607 - 2626. (DOI:  10.1080/14786435.2015.1070968)}}
@article{kashaev_microstructure_and_2015, 
author={Kashaev, N. and Ventzke, V. and Horstmann, M. and Riekehr, S. and Yashin, G. and Stutz, L. and Beck, W.},
title={Microstructure and Mechanical Properties of Laser Beam Welded Joints between Fine-Grained and Standard Ti-6Al-4V Sheets Subjected to Superplastic Forming},
year={2015},
journal = {Advanced Engineering Materials},
volume = {17},
number = {3},
pages = {374 - 382},
doi = {http://dx.doi.org/10.1002/adem.201400202},
abstract = {A fine-grained Ti–6Al–4V sheet that has been developed for superplastic forming (SPF) was joined to a standard Ti–6Al–4V sheet using a Nd:YAG laser and alloy compatible filler wire. The microstructural and mechanical properties of dissimilar laser beam welded butt joints were investigated to determine their behavior under static and cyclic loads and for SPF. The filler wire affected the heat input and reduced the increase in the hardness within the fusion zone compared to that in the heat-affected zone. The laser beam welding process activated local microstructure transformations that were associated with local changes in the microtexture, the β content, and the grain size. The mechanical behavior of a dissimilar laser beam welded butt joint under a static tensile load was controlled by the properties of the standard Ti–6Al–4V sheet. Laser beam welded specimens showed inferior fatigue behavior. Removing the geometrical notches did not significantly improve the fatigue behavior because local microstructural and microtextural changes still created metallurgical notches. SPF was observed in the fine-grained Ti–6Al–4V sheet without crack formation in the heat-affected zones or the fusion zone. The welding seam of the dissimilar fine-grained-standard butt joint was resistant to SPF.},
note = {Online available at: \url{http://dx.doi.org/10.1002/adem.201400202} (DOI). Kashaev, N.; Ventzke, V.; Horstmann, M.; Riekehr, S.; Yashin, G.; Stutz, L.; Beck, W.: Microstructure and Mechanical Properties of Laser Beam Welded Joints between Fine-Grained and Standard Ti-6Al-4V Sheets Subjected to Superplastic Forming. In: Advanced Engineering Materials. Vol. 17 (2015) 3, 374 - 382. (DOI:  10.1002/adem.201400202)}}
@article{riekehr_mechanical_properties_2015, 
author={Riekehr, S. and Ravasi, R. and Enz, J. and Ventzke, V. and Kashaev, N.},
title={Mechanical Properties of Fibre Laser Welded AZ31B Sheets and their Dependence on the Spot-Size},
year={2015},
journal = {Materials Science Forum, Light Metals Technology 2015},
volume = {828-829},
pages = {298 - 304},
doi = {http://dx.doi.org/10.4028/www.scientific.net/MSF.828-829.298},
abstract = {In the present work the mechanical behaviour of laser beam welded AZ31B alloy was studied, by changing systematically the spot size of the used fibre laser system between 200 µm and 1000 µm at different power levels between 2 kW and 8 kW. Maximum welding velocities with respect to imperfections were determined. The characterization of the obtained welds - in terms of Vickers hardness, UTS, Af and weld width, resp. weld area - was correlated with the micro-texture in dependence of the different Focus Spot Diameters and Laser Beam Power levels as well as the resulting cooling rates. Highest UTS of 94% of the base material was achieved with 200 µm Focus Spot Diameter and Laser Beam Power of 4 kW at welding velocity of 100 mm/s. By increasing the Focus Spot Diameter to 600 µm, the tensile strength was reduced to 86 % of the actual strength of the base material.},
note = {Online available at: \url{http://dx.doi.org/10.4028/www.scientific.net/MSF.828-829.298} (DOI). Riekehr, S.; Ravasi, R.; Enz, J.; Ventzke, V.; Kashaev, N.: Mechanical Properties of Fibre Laser Welded AZ31B Sheets and their Dependence on the Spot-Size. In: Materials Science Forum, Light Metals Technology 2015. Vol. 828-829 (2015) 298 - 304. (DOI:  10.4028/www.scientific.net/MSF.828-829.298)}}
@article{kainer_challenges_and_2015, 
author={Kainer, K.U. and Hoppe, R. and Bohlen, J. and Kurz, G. and Yi, S. and Letzig, D.},
title={Challenges and Solutions in the Development of Magnesium Sheet for Sustainable Vehicle Concepts},
year={2015},
journal = {Materials Science Forum, Light Metals Technology 2015},
volume = {828-829},
pages = {15 - 22},
doi = {http://dx.doi.org/10.4028/www.scientific.net/MSF.828-829.15},
abstract = {Magnesium as the lightest structural metal offers significant potential weight saving compared with steel and aluminium. Cast magnesium components are widely used, e.g. as engine blocks or gear box housings. To open more opportunities for weight saving, it is necessary to widen the application fields to wrought products, such as large thin walled components for which sheets as semi-finished products are needed. The production and processing of magnesium sheets material is currently hampered by the limited formability of magnesium and high costs. The use of the twin-roll casting (TRC) as a cost-effective manufacturing process and the development of new calcium-containing alloys are leading to a decisive reduction of those obstacles.},
note = {Online available at: \url{http://dx.doi.org/10.4028/www.scientific.net/MSF.828-829.15} (DOI). Kainer, K.U.; Hoppe, R.; Bohlen, J.; Kurz, G.; Yi, S.; Letzig, D.: Challenges and Solutions in the Development of Magnesium Sheet for Sustainable Vehicle Concepts. In: Materials Science Forum, Light Metals Technology 2015. Vol. 828-829 (2015) 15 - 22. (DOI:  10.4028/www.scientific.net/MSF.828-829.15)}}
@article{schaefer_oxidized_mild_2015, 
author={Schaefer, H. and Kuepper, K. and Wollschlaeger, J. and Kashaev, N. and Hardege, J. and Walder, L. and Beladi-Mousavi, S.M. and Hartmann-Azanza, B. and Steinhart, M. and Sadaf, S. and Dorn, F.},
title={Oxidized Mild Steel S235: An Efficient Anode for Electrocatalytically Initiated Water Splitting},
year={2015},
journal = {ChemSusChem},
volume = {8},
number = {18},
pages = {3099 - 3110},
doi = {http://dx.doi.org/10.1002/cssc.201500666},
abstract = {The surface of steel S235 was oxidized by Cl2 gas and checked for its electrocatalytic efficiency regarding oxygen formation in aqueous solution. If exposed to humid Cl2 gas for 110 min, steel S235 became an electrocatalyst that exhibits an overpotential for the oxygen evolution reaction (OER) of 462 mV at 1 mA cm−2 at pH 7. The OER activity of the same sample at pH 13 was moderate (347 mV overpotential at 2.0 mA cm−2 current density) in comparison with OER electrocatalysts developed recently. Potential versus time plots measured at a constant current demonstrate the sufficient stability of all samples under catalysis conditions at pH 7 and 13 for tens of hours. High-resolution X-ray photoelectron spectra could be reasonably resolved with the proviso that Fe2O3, FeO(OH), MnO(OH), and Mn2O3 are the predominant Fe and Mn species on the surface of the oxidized steel S235.},
note = {Online available at: \url{http://dx.doi.org/10.1002/cssc.201500666} (DOI). Schaefer, H.; Kuepper, K.; Wollschlaeger, J.; Kashaev, N.; Hardege, J.; Walder, L.; Beladi-Mousavi, S.M.; Hartmann-Azanza, B.; Steinhart, M.; Sadaf, S.; Dorn, F.: Oxidized Mild Steel S235: An Efficient Anode for Electrocatalytically Initiated Water Splitting. In: ChemSusChem. Vol. 8 (2015) 18, 3099 - 3110. (DOI:  10.1002/cssc.201500666)}}
@article{larrayozizcara_characterization_and_2014, 
author={Larrayoz Izcara, X. and Guirao Blank, A. and Pyczak, F. and Staron, P. and Schumann, S. and Huber, N.},
title={Characterization and modeling of the influence of artificial aging on the microstructural evolution of age-hardenable AlSi10Mg(Cu) aluminum alloys},
year={2014},
journal = {Materials Science and Engineering  A},
volume = {610},
pages = {46 - 53},
doi = {http://dx.doi.org/10.1016/j.msea.2014.04.031},
abstract = {A comprehensive analysis of the effect of the artificial aging on the Mg2Si precipitation distribution of the age-hardenable AlSi10Mg(Cu) aluminum alloy from T6 to T7 condition is presented considering the influence of temperature and time of the aging conditions. A complete quantitative characterization of the strengthening distributions covering a broad range of aging conditions was obtained using the small angle neutron scattering (SANS) technique, complemented with high-resolution transmission electron microscopy (HTEM). This information was successfully used to fit Robson׳s precipitation model for the prediction of the precipitation distribution as a function of time and temperature. Based on the measured precipitation behavior a sigmoidal function of the interfacial energy was added to Robson׳s model. As a result a unique set of modeling parameters was obtained for the whole precipitation process and range of temperatures considered. Robson׳s model is shown to be a powerful tool for predicting the evolution of these nanometer-scale particles in industrial and complex aging processes, which are critical for designing new components based on the material requirements.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.msea.2014.04.031} (DOI). Larrayoz Izcara, X.; Guirao Blank, A.; Pyczak, F.; Staron, P.; Schumann, S.; Huber, N.: Characterization and modeling of the influence of artificial aging on the microstructural evolution of age-hardenable AlSi10Mg(Cu) aluminum alloys. In: Materials Science and Engineering  A. Vol. 610 (2014) 46 - 53. (DOI:  10.1016/j.msea.2014.04.031)}}
@article{ventzke_prozessentwicklung_zum_2014, 
author={Ventzke, V. and Riekehr, S. and Horstmann, M. and Kashaev, N. and Brokmeier, H.-G. and Huber, N.},
title={Prozessentwicklung zum Rotationsreibschweißen der Gamma-TiAl-Feingusslegierung Ti-47Al-3.5(Mn+Cr+Nb)-0.8(B+Si) mit Ti6Al4V: Teil: 2 - The Development of the Rotational Friction Welding Process for the Welding of Gamma-TiAl-Casting Alloy Ti-47Al-3.5(Mn+Cr+Nb)-0.8(B+Si) to Ti6Al4V: Part: 2},
year={2014},
journal = {Practical Metallography - Praktische Metallographie},
volume = {51},
number = {6},
pages = {401 - 424},
abstract = {Gegenstand der vorliegenden Arbeit ist die Prozessentwicklung zum Rotationsreibschweißen der γ-TiAl-Feingusslegierung Ti-47Al-3,5(Mn+Cr+Nb)-0,8(B+Si) mit der Ti-Baislegierung Ti6Al4V sowie die Charakterisierung der mechanischen und mikrostrukturellen Eigenschaften der artfremden Reibschweißverbindungen. Wegen Bindefehlern ist die prozessbegleitende Durchführung von Vor- und Nachwärmebehandlungen notwendig, um diese zu reduzieren. Das mechanische Verhalten der Reibschweißverbindungen unter Zugbeanspruchung bei Raumtemperatur wird durch die Grundwerkstoffeigenschaften der intermetallischen γ-TiAl-Feingusslegierung bestimmt und nicht durch die Bindezone. Bei der einsatzrelevanten Temperatur von 700 °C trat wegen superplastischer Verformung auf der Ti6Al4V-Seite kein Bruchversagen der artfremden Reibschweißverbindung ein.

This article reports on the development of the rotational friction welding process for the welding of γ-TiAl- casting alloy Ti-47Al-3.5(Mn+Cr+Nb)-0.8(B+Si) to Ti6Al4V base metal and on the characterisation of the mechanical and microstructural properties of dissimilar metal friction welding. Pre- and post welding heat treatment is necessary in order to reduce the occurrence of bonding defects. The mechanical behaviour of friction welded joints under tensile loading at room temperature is primarily determined by the properties of the inter-metallic γTiAl- casting alloy base metal and not by the bonding zone itself. At the relevant service temperature of 700 °C, failure by fracture does not take place on the Ti6Al4V side of the dissimilar metal friction welded joint due to the super-plastic deformation of this alloy.},
note = {Ventzke, V.; Riekehr, S.; Horstmann, M.; Kashaev, N.; Brokmeier, H.-G.; Huber, N.: Prozessentwicklung zum Rotationsreibschweißen der Gamma-TiAl-Feingusslegierung Ti-47Al-3.5(Mn+Cr+Nb)-0.8(B+Si) mit Ti6Al4V: Teil: 2 - The Development of the Rotational Friction Welding Process for the Welding of Gamma-TiAl-Casting Alloy Ti-47Al-3.5(Mn+Cr+Nb)-0.8(B+Si) to Ti6Al4V: Part: 2. In: Practical Metallography - Praktische Metallographie. Vol. 51 (2014) 6, 401 - 424.}}
@article{shen_eutectic_structures_2014, 
author={Shen, J. and Suhuddin, U.F.H. and Barbosa, M.E.B. and dos Santos, J.F.},
title={Eutectic structures in friction spot welding joint of aluminum alloy to copper},
year={2014},
journal = {Applied Physics Letters},
volume = {104},
number = {19},
pages = {191901},
doi = {http://dx.doi.org/10.1063/1.4876238},
abstract = {A dissimilar joint of AA5083 Al alloy and copper was produced by friction spot welding. The Al-MgCuAl2 eutectic in both coupled and divorced manners were found in the weld. At a relatively high temperature, mass transport of Cu due to plastic deformation, material flow, and atomic diffusion, combined with the alloy system of AA5083 are responsible for the ternary eutectic melting.},
note = {Online available at: \url{http://dx.doi.org/10.1063/1.4876238} (DOI). Shen, J.; Suhuddin, U.F.H.; Barbosa, M.E.B.; dos Santos, J.F.: Eutectic structures in friction spot welding joint of aluminum alloy to copper. In: Applied Physics Letters. Vol. 104 (2014) 19, 191901. (DOI:  10.1063/1.4876238)}}
@article{feistauer_mechanical_behaviour_2014, 
author={Feistauer, E.E. and Bergmann, L.A. and Barreto, L.S. and dos Santos, J.F.},
title={Mechanical behaviour of dissimilar friction stir welded tailor welded blanks in Al–Mg alloys for Marine applications},
year={2014},
journal = {Materials and Design},
pages = {323 - 332},
doi = {http://dx.doi.org/10.1016/j.matdes.2014.02.042},
abstract = {Tailor welded blanks (TWB) in Al alloys are an attractive structural solution for application in the shipbuilding sector, mainly due to reductions in weight and lower production costs. In the present study, the global and local mechanical properties of dissimilar friction stir welded TWB were assessed. The joints were manufactured with dissimilar Al–Mg alloys and thicknesses (6 and 8 mm) of particular interest to the shipbuilding sector (AA5083 and AA5059). A digital image correlation system (DIC) linked to a tensile test system was used to characterise the local strain fields, and true stress–strain curves were generated for several TWB sub-zones. Microhardness and DIC analyses showed that the stir zone of the TWB presented overmatching in relation to the weakest base material, and that the joints displayed excellent overall mechanical performance that was comparable to the AA5059 base material in terms of strength and ductility. The fatigue strength was evaluated by means of tension–tension fatigue tests, and the TWB joints reached the fatigue keen with a stress range of 70 MPa.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.matdes.2014.02.042} (DOI). Feistauer, E.E.; Bergmann, L.A.; Barreto, L.S.; dos Santos, J.F.: Mechanical behaviour of dissimilar friction stir welded tailor welded blanks in Al–Mg alloys for Marine applications. In: Materials and Design. (2014) 323 - 332. (DOI:  10.1016/j.matdes.2014.02.042)}}
@article{mameka_electrical_stiffness_2014, 
author={Mameka, N. and Markmann, J. and Jin, H.-J. and Weissmueller, J.},
title={Electrical stiffness modulation—confirming the impact of surface excess elasticity on the mechanics of nanomaterials},
year={2014},
journal = {Acta Materialia},
volume = {76},
pages = {272 - 280},
doi = {http://dx.doi.org/10.1016/j.actamat.2014.04.067},
abstract = {Local variations in the stiffness at surfaces may affect the elastic response of nanostructures, yet experiments disagree on the magnitude and even sign of the surface excess elastic constants. The present study reports the variation in the effective macroscopic stiffness of bulk samples of nanoporous gold when the surface state is modulated under potential control in an electrochemical environment. Using in situ experiments in a dynamic mechanical analyzer to measure the storage and loss moduli, we show that adsorption of ⩽1⩽1 atomic monolayer of oxygen species as well as a capacitively controlled excess of electrons at the surface stiffen the material, while oxygen desorption/electron depletion enhance the compliance. Relative changes in the effective stiffness of up to 8% imply the variation of a surface excess elastic constant of the order of 60 N m−1, much larger than the absolute value of that constant deduced from previous atomistic simulation studies of clean surfaces. Since the electrode potential affects exclusively the surface, our observations provide conclusive evidence for the impact of local stiffness variation at surfaces on the effective elastic response of nanostructures.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.actamat.2014.04.067} (DOI). Mameka, N.; Markmann, J.; Jin, H.-J.; Weissmueller, J.: Electrical stiffness modulation—confirming the impact of surface excess elasticity on the mechanics of nanomaterials. In: Acta Materialia. Vol. 76 (2014) 272 - 280. (DOI:  10.1016/j.actamat.2014.04.067)}}
@article{huetsch_increased_room_2014, 
author={Huetsch, L.L. and Huetsch, J. and Herzberg, K. and dos Santos, J.F. and Huber, N.},
title={Increased Room Temperature Formability of Mg AZ31 by High Speed Friction Stir Processing},
year={2014},
journal = {Materials and Design},
volume = {54},
pages = {980 - 988},
doi = {http://dx.doi.org/10.1016/j.matdes.2013.08.108},
abstract = {The aim of this work is to investigate the formability at room temperature of the Mg alloy AZ31 by friction stir processing. Defect-free process zones were created using process speeds of up to 10 m/min, the resulting microstructure and grain size were analyzed. Microstructural zones with varying texture were identified by electron backscatter diffraction. Tensile tests supported by digital image correlation analysis revealed different deformation behavior and enhanced ductility in the thermo mechanically affected zone which was associated with the variation in grain size and texture. Finally, the sheet forming behavior of the processed material was investigated, using the Nakajima test method with Hasek specimen geometries. Forming limit diagrams for several process conditions reveal a continuous increase in formability with increasing processing speed. Additionally, the local anisotropy was analyzed by comparison of the R values at the point of highest strain, to quantify the impact of processing on formability.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.matdes.2013.08.108} (DOI). Huetsch, L.L.; Huetsch, J.; Herzberg, K.; dos Santos, J.F.; Huber, N.: Increased Room Temperature Formability of Mg AZ31 by High Speed Friction Stir Processing. In: Materials and Design. Vol. 54 (2014) 980 - 988. (DOI:  10.1016/j.matdes.2013.08.108)}}
@article{kashaev_fatigue_fatigue_2014, 
author={Kashaev, N. and Riekehr, S. and Horstmann, M. and Ventzke, V.},
title={Fatigue, Fatigue Crack Propagation and Mechanical Fracture Behaviour of Laser Beam-Welded AZ31 Magnesium Sheets},
year={2014},
journal = {Materials Science Forum, Thermec 2013},
volume = {783-786},
pages = {2310 - 2315},
doi = {http://dx.doi.org/10.4028/www.scientific.net/MSF.783-786.2310},
abstract = {Weight reduction is the main driving force in automotive and aircraft structural design.
As a result, magnesium alloys, with their high potential for lightweight construction, have attracted
a considerable amount of industrial attention. The determining criterion for the structural
applications of magnesium alloys is the availability of efficient joining technologies for the
construction of lightweight structures and the availability of reliable data for the assessment of their
damage tolerance behaviour. Laser beam welding (LBW), as a high-speed and easily controllable
process, allows the welding of complex geometric forms that are optimised in terms of mechanical
stiffness, strength, production velocity and visual quality. The work accomplished in this study
addresses the challenges of the LBW process for typical joint configurations using the magnesium
alloy AZ31HP: butt joints, T joints and overlap joints. LBW processes were developed for use with
a 3.3-kW Nd:YAG laser to optimise the mechanical performance of such joints with respect to
tensile strength, fatigue, fatigue crack propagation and mechanical fracture behaviour. The
relationships between the LBW process and the microstructural and mechanical properties of welds
were established. Compared to state-of-the-art aerospace alloys, AZ31HP demonstrates that
magnesium alloys have potential for use in structural applications, with AZ31HP being comparable
to AA2024T351 and AA6061T6. Welded AZ31HP exhibits better crack resistance than the base
material, so fully welded integral structures made from magnesium alloys can be used in
lightweight construction.},
note = {Online available at: \url{http://dx.doi.org/10.4028/www.scientific.net/MSF.783-786.2310} (DOI). Kashaev, N.; Riekehr, S.; Horstmann, M.; Ventzke, V.: Fatigue, Fatigue Crack Propagation and Mechanical Fracture Behaviour of Laser Beam-Welded AZ31 Magnesium Sheets. In: Materials Science Forum, Thermec 2013. Vol. 783-786 (2014) 2310 - 2315. (DOI:  10.4028/www.scientific.net/MSF.783-786.2310)}}
@article{steglich_mechanical_testing_2014, 
author={Steglich, D. and Tian, X. and Bohlen, J. and Kuwabara, T.},
title={Mechanical Testing of Thin Sheet Magnesium Alloys in Biaxial Tension and Uniaxial Compression},
year={2014},
journal = {Experimental Mechanics},
volume = {54},
number = {7},
pages = {1247 - 1258},
doi = {http://dx.doi.org/10.1007/s11340-014-9892-0},
abstract = {Tension and compression experiments on magnesium rolled sheets and extruded products of AZ31 (Mg + 3%Al + 1%Zn) and ZE10 (Mg + 1%Zn + 0.3%Ce based misc metal) were performed at room temperature. The tests were conducted along the longitudinal and the transverse direction to quantify the in-plane anisotropy. Samples built from adhesively-bonded layers of sheets were used for in-plane as well as through-thickness compression testing. It was verified that this simple testing method leads to identical results as using comb-like dies and equi-biaxial bulge testing, respectively. In the case of uniaxial loading, the longitudinal and transverse strain components were measured using independent extensometers. R-values were calculated from these signals. The mechanical responses were correlated to the microstructure and the texture. The recorded differences between tensile and compressive response reveal the strength differential effect of the materials. The distortional character of the plastic behaviour is evidenced through their responses to equi-biaxial tensile loading. Significant differences in the compressive responses of the two alloys were identified by comparing the respective hardening rates.},
note = {Online available at: \url{http://dx.doi.org/10.1007/s11340-014-9892-0} (DOI). Steglich, D.; Tian, X.; Bohlen, J.; Kuwabara, T.: Mechanical Testing of Thin Sheet Magnesium Alloys in Biaxial Tension and Uniaxial Compression. In: Experimental Mechanics. Vol. 54 (2014) 7, 1247 - 1258. (DOI:  10.1007/s11340-014-9892-0)}}
@article{altmeyer_effect_of_2014, 
author={Altmeyer, J. and dos Santos, J.F. and Amancio-Filho, S.T.},
title={Effect of the friction riveting process parameters on the joint formation and performance of Ti alloy/short-fibre reinforced polyether ether ketone joints},
year={2014},
journal = {Materials and Design},
volume = {60},
pages = {164 - 176},
doi = {http://dx.doi.org/10.1016/j.matdes.2014.03.042},
abstract = {The feasibility of friction riveting on short carbon fibre-reinforced thermoplastic polymers was investigated in this work. A design of experiments (DoE) was used to investigate the impact of rotational speed, friction time, friction pressure and forging pressure on joint formation and performance. The joint formation was studied using the mushrooming efficiency, the rivet penetration depth and the mechanical energy input. The tensile pull-out force was used to describe the mechanical performance of the investigated metallic-insert joints made of grade 3 titanium and short carbon fibre-reinforced polyether ether ketone (PEEK). All samples were scanned with X-rays before any mechanical testing to acquire the dimensions of the anchored rivet inside the reinforced polymer, elucidating their correlations with the mechanical performance. The DoE model can be used to tailor joint formation and performance. A parameter-set that improves the pull-out performance was determined using an analysis of variance. The analysis revealed that high rotational speed, friction time and forging pressure caused high pull-out forces. The metallic-insert joints reached high pull-out tensile strength between 6.3 kN and 10.7 kN. The dimensions of the deformed metallic rivet were correlated with the mechanical performance of the joint: the larger the widening of the rivet tip, the higher the pull out force was. Furthermore, widening of the rivet tip by 70% led to the maximal tensile pull-out force (10.7 kN), corresponding to the base material strength of the titanium rivet (10.7 kN). At this threshold value (70%), the failure mode also changed from failure mode III (pull-out of rivet) to failure mode I (rivet failure).},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.matdes.2014.03.042} (DOI). Altmeyer, J.; dos Santos, J.F.; Amancio-Filho, S.T.: Effect of the friction riveting process parameters on the joint formation and performance of Ti alloy/short-fibre reinforced polyether ether ketone joints. In: Materials and Design. Vol. 60 (2014) 164 - 176. (DOI:  10.1016/j.matdes.2014.03.042)}}
@article{husser_computational_modeling_2014, 
author={Husser, E. and Lilleodden, E.T. and Bargmann, S.},
title={Computational modeling of intrinsically induced strain gradients during compression of c-axis-oriented magnesium single crystal},
year={2014},
journal = {Acta Materialia},
volume = {71},
pages = {206 - 219},
doi = {http://dx.doi.org/10.1016/j.actamat.2014.02.017},
abstract = {A finite-deformation strain gradient crystal plasticity model is implemented in a three-dimensional finite-element framework in order to analyze the deformation behavior and the stress–strain response of magnesium single crystals under c -axis orientation. The potential-based and thermodynamically consistent material model is formulated in a non-local and non-linear inelastic context in which dislocation densities are introduced via plastic strain gradients. Experiments have shown that the internal length scale of the microstructure starts to affect the overall stress–strain response when the sample size decreases to the micron scale. As a consequence, strain gradients develop, leading to an additional energetic-like hardening effect which results in an increase of the macroscopic strength with decreasing crystal size. In the case of uniaxial compression of c  -axis-oriented single-crystal micropillars, the model is able to predict the discrete dislocation glide in terms of a band-shaped slip zone. Two different pillar sample sizes are taken into account in order to investigate the intrinsic size effect during plastic deformation where the crystallographic orientation leads to the activation of pyramidal {112¯2}〈112¯3〉 slip systems as reported in various experimental studies. The interaction of those slip systems is expressed in terms of latent hardening and excess dislocation development. A comparison between numerical results and corresponding experimental data is presented.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.actamat.2014.02.017} (DOI). Husser, E.; Lilleodden, E.T.; Bargmann, S.: Computational modeling of intrinsically induced strain gradients during compression of c-axis-oriented magnesium single crystal. In: Acta Materialia. Vol. 71 (2014) 206 - 219. (DOI:  10.1016/j.actamat.2014.02.017)}}
@article{ventzke_prozessentwicklung_zum_2014, 
author={Ventzke, V. and Riekehr, S. and Horstmann, M. and Kashaev, N. and Brokmeier, H.-G. and Huber, N.},
title={Prozessentwicklung zum Rotationsreibschweißen der Gamma-TiAl-Feingusslegierung Ti-47Al-3.5(Mn+Cr+Nb)-0.8(B+Si) mit Ti6Al4V: Teil: 1 - The Development of the Rotational Friction Welding Process for the Welding of Gamma-TiAl-Casting Alloy Ti-47Al-3.5(Mn+Cr+Nb)-0.8(B+Si) to Ti6Al4V: Part: 1},
year={2014},
journal = {Practical Metallography - Praktische Metallographie},
volume = {51},
number = {5},
pages = {321 - 352},
doi = {10.3139/147.110266},
abstract = {Gegenstand der vorliegenden Arbeit ist die Prozessentwicklung zum Rotationsreibschweißen der γ-TiAl-Feingusslegierung Ti-47Al-3,5(Mn+Cr+Nb)-0,8(B+Si) mit der Ti-Baislegierung Ti6Al4V sowie die Charakterisierung der mechanischen und mikrostrukturellen Eigenschaften der artfremden Reibschweißverbindungen. Wegen Bindefehlern ist die prozessbegleitende Durchführung von Vor- und Nachwärmebehandlungen notwendig, um diese zu reduzieren. Das mechanische Verhalten der Reibschweißverbindungen unter Zugbeanspruchung bei Raumtemperatur wird durch die Grundwerkstoffeigenschaften der intermetallischen γ-TiAl-Feingusslegierung bestimmt und nicht durch die Bindezone. Bei der einsatzrelevanten Temperatur von 700 °C trat wegen superplastischer Verformung auf der Ti6Al4V-Seite kein Bruchversagen der artfremden Reibschweißverbindung ein.

This article reports on the development of the rotational friction welding process for the welding of γ-TiAl- casting alloy Ti-47Al-3.5(Mn+Cr+Nb)-0.8(B+Si) to Ti6Al4V base metal and on the characterisation of the mechanical and microstructural properties of dissimilar metal friction welding. Pre- and post welding heat treatment is necessary in order to reduce the occurrence of bonding defects. The mechanical behaviour of friction welded joints under tensile loading at room temperature is primarily determined by the properties of the inter-metallic γTiAl- casting alloy base metal and not by the bonding zone itself. At the relevant service temperature of 700 °C, failure by fracture does not take place on the Ti6Al4V side of the dissimilar metal friction welded joint due to the super-plastic deformation of this alloy.},
note = {Online available at: \url{https://dx.doi.org/10.3139/147.110266} (DOI). Ventzke, V.; Riekehr, S.; Horstmann, M.; Kashaev, N.; Brokmeier, H.-G.; Huber, N.: Prozessentwicklung zum Rotationsreibschweißen der Gamma-TiAl-Feingusslegierung Ti-47Al-3.5(Mn+Cr+Nb)-0.8(B+Si) mit Ti6Al4V: Teil: 1 - The Development of the Rotational Friction Welding Process for the Welding of Gamma-TiAl-Casting Alloy Ti-47Al-3.5(Mn+Cr+Nb)-0.8(B+Si) to Ti6Al4V: Part: 1. In: Practical Metallography - Praktische Metallographie. Vol. 51 (2014) 5, 321 - 352. (DOI:  /10.3139/147.110266)}}
@article{enz_laser_welding_2014, 
author={Enz, J. and Riekehr, S. and Ventzke, V. and Sotirov, N. and Kashaev, N.},
title={Laser Welding of High-Strength Aluminium Alloys for the Sheet Metal Forming Process},
year={2014},
journal = {Procedia CIRP},
volume = {18},
pages = {203 - 208},
doi = {http://dx.doi.org/10.1016/j.procir.2014.06.132},
abstract = {Laser beam welding of similar and dissimilar joints made of 7075-T6 and 5182-O sheets is conducted. A new approach of the
Helmholtz-Zentrum Geesthacht is used to solve the problems of weldability and softening. The microstructural characteristics and
the mechanical properties of the joints are evaluated. With this information it is possible to initially assess the formability of the
tailored blanks. Finally the formability of the welds will be validated via a sheet metal forming process. Owing to the good
formability of the base materials, the results obtained for the welded joints are compared with base material properties.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.procir.2014.06.132} (DOI). Enz, J.; Riekehr, S.; Ventzke, V.; Sotirov, N.; Kashaev, N.: Laser Welding of High-Strength Aluminium Alloys for the Sheet Metal Forming Process. In: Procedia CIRP. Vol. 18 (2014) 203 - 208. (DOI:  10.1016/j.procir.2014.06.132)}}
@article{wilmers_simulation_of_2014, 
author={Wilmers, J. and Bargmann, S.},
title={Simulation of non-classical diffusion in polymers},
year={2014},
journal = {Heat and Mass Transfer},
volume = {50},
number = {11},
pages = {1543 - 1552},
doi = {http://dx.doi.org/10.1007/s00231-014-1365-6},
abstract = {The present contribution is concerned with the computational modelling of non-classical diffusion in amorphous polymers. Special attention is paid to the limiting case of Case II diffusion. Application of the dual-phase-lag concept to Fick’s first law leads to a description of Case II behaviour. The change in material properties during the glass transition is explicitly accounted for by a concentration dependent formulation of the material parameters. The proposed model is well suited for modelling the sharp diffusion front and linear uptake kinetics associated with Case II diffusion. Application of a concentration dependent diffusion coefficient reduces the concentration gradient behind the front to a minimum. For the solution procedure, a finite element scheme in space and a finite difference method in time are applied. Three-dimensional numerical results are presented for classical Fickian and non-classical Case II diffusion. This paper adds to the basic understanding of the computational modelling of the Case II diffusion phenomenon.},
note = {Online available at: \url{http://dx.doi.org/10.1007/s00231-014-1365-6} (DOI). Wilmers, J.; Bargmann, S.: Simulation of non-classical diffusion in polymers. In: Heat and Mass Transfer. Vol. 50 (2014) 11, 1543 - 1552. (DOI:  10.1007/s00231-014-1365-6)}}
@article{zhong_crack_mitigation_2014, 
author={Zhong, Y. and Markmann, J. and Jin, H.-J. and Ivanisenko, Y. and Kurmanaeva, L. and Weissmueller, J.},
title={Crack Mitigation during Dealloying of Au25Cu75},
year={2014},
journal = {Advanced Engineering Materials},
volume = {16},
number = {4},
pages = {389 - 398},
doi = {http://dx.doi.org/10.1002/adem.201300211},
abstract = {The suggested use of nanoporous gold for functional and structural applications requires uniform and specifically crack-free monolithic bodies, ideally with a structure size in the range of 10 nm or below. Here we investigate electrochemical dealloying of two different starting alloys, Au25Ag75 and Au25Cu75, as pathways towards that goal. With an emphasis on the processes that lead to crack formation, we discuss the role of the parameters (i) lattice parameter change, (ii) dealloying potential and rate, and (iii) thermo-mechanical treatment of the master alloys. The Cu-based alloys are found to give superior homogeneity at very small structure sizes, provided that intermediate temperature treatments are avoided. A complete suppression of crack formation was achieved by application of a dealloying potential of 1.1 V versus Ag/AgCl, at a ligament size of 11 nm.},
note = {Online available at: \url{http://dx.doi.org/10.1002/adem.201300211} (DOI). Zhong, Y.; Markmann, J.; Jin, H.-J.; Ivanisenko, Y.; Kurmanaeva, L.; Weissmueller, J.: Crack Mitigation during Dealloying of Au25Cu75. In: Advanced Engineering Materials. Vol. 16 (2014) 4, 389 - 398. (DOI:  10.1002/adem.201300211)}}
@article{dethlefs_hybrid_friction_2014, 
author={Dethlefs, A. and Roos, A. and dos Santos, J.F. and Wimmer, G.},
title={Hybrid Friction Diffusion Bonding of Aluminium Tube-to-Tube-Sheet Connections in Coil-Wound Heat Exchangers},
year={2014},
journal = {Materials and Design},
volume = {60},
pages = {7 - 12},
doi = {http://dx.doi.org/10.1016/j.matdes.2014.03.049},
abstract = {The present study presents and evaluates an application of a new solid-state bonding process, hybrid friction diffusion bonding (HFDB). HFDB is used to fabricate tube-to-tube-sheet connections for aluminium coil-wound heat exchangers. An industry-applicable process variant is developed, and its feasibility is demonstrated by gas leak tightness tests and tensile pull-out tests. The joints meet the requirements of industrial applications. Furthermore, the process is characterised by the thermal field development in the weld area and the applied process forces. The microstructure of the joint is investigated, and dynamic recrystallization is assumed to be the primary grain refinement mechanism in the thermo-mechanically affected zone.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.matdes.2014.03.049} (DOI). Dethlefs, A.; Roos, A.; dos Santos, J.F.; Wimmer, G.: Hybrid Friction Diffusion Bonding of Aluminium Tube-to-Tube-Sheet Connections in Coil-Wound Heat Exchangers. In: Materials and Design. Vol. 60 (2014) 7 - 12. (DOI:  10.1016/j.matdes.2014.03.049)}}
@article{gandra_friction_surfacing_2014, 
author={Gandra, J. and Krohn, H. and Miranda, R.M. and Vilaca, P. and Quintino, L. and dos Santos, J.F.},
title={Friction surfacing - A review},
year={2014},
journal = {Journal of Materials Processing Technology},
volume = {214},
number = {5},
pages = {1062 - 1093},
doi = {http://dx.doi.org/10.1016/j.jmatprotec.2013.12.008},
abstract = {Friction surfacing (FS) is a solid state technology with increasing applications in the context of localized surface engineering. FS has been investigated mainly for producing fine grained coatings, which exhibit superior wear and corrosion properties. Since no bulk melting takes place, this process allows dissimilar joining of materials that would be otherwise incompatible or difficult to deposit by fusion based methods. Several studies also emphasize its energy efficiency and low environmental impact as key advantages when compared with other alternative technologies. Main applications include repair of worn or damaged surfaces through building up or crack sealing. It has also been applied to enhance surface properties at specific areas in the manufacturing of parts and tools. A wide range of material combinations have been deposited by FS, mainly alloy and stainless steels. Aluminium, magnesium and titanium alloys have also been investigated, including the production of metal matrix composites.

Starting with a brief introduction, this review presents a detailed description of the thermo-mechanical and microstructural transformations as well as process modelling approaches. The material combinations investigated so far and the effect of process parameters are also addressed. An overview of the main technologic and equipment advances is presented, including: computational optimization models, surface preparation, gas protection, post-processing methods, pre-heating and cooling. An assessment of the material deposition rate and the specific energy consumption is also provided, comparing friction surfacing to mainstream electric arc, laser and thermal spraying based processes. Based on current process advantages and disadvantages, an outlook on future research and development is provided.

Friction surfacing has a significant potential for further industrial applications and is being developed as a practicable alternative to mainstream coating processes. The present review paper provides a broad overview throughout the fundamentals of FS and the most relevant technology developments, establishing both a theoretical and technical basis for new researchers and industrial practitioners searching for new coating alternatives.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.jmatprotec.2013.12.008} (DOI). Gandra, J.; Krohn, H.; Miranda, R.M.; Vilaca, P.; Quintino, L.; dos Santos, J.F.: Friction surfacing - A review. In: Journal of Materials Processing Technology. Vol. 214 (2014) 5, 1062 - 1093. (DOI:  10.1016/j.jmatprotec.2013.12.008)}}
@article{huetsch_the_influence_2014, 
author={Huetsch, J. and Lilleodden, E.T.},
title={The influence of focused-ion beam preparation technique on microcompression investigations: Lathe vs. annular milling},
year={2014},
journal = {Scripta Materialia},
volume = {77},
pages = {49 - 51},
doi = {http://dx.doi.org/10.1016/j.scriptamat.2014.01.016},
abstract = {Two commonly used focused ion beam (FIB) milling techniques were employed for Mg micropillar fabrication to investigate the influence of the individual FIB technique on the microcompression testing method. Results from lathe milled pillars show that the relatively high ion exposure of this technique relative to annular milling greatly affects both stress–strain response and deformation morphology; stresses reached are up to four times higher than for the annular milled pillars and cracking of a surface layer is observed.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.scriptamat.2014.01.016} (DOI). Huetsch, J.; Lilleodden, E.T.: The influence of focused-ion beam preparation technique on microcompression investigations: Lathe vs. annular milling. In: Scripta Materialia. Vol. 77 (2014) 49 - 51. (DOI:  10.1016/j.scriptamat.2014.01.016)}}
@article{trinidad_processing_of_2014, 
author={Trinidad, J. and Marco, I. and Arruebarrena, G. and Wendt, J. and Letzig, D. and Saenz de Argandona, E. and Goodall, R.},
title={Processing of Magnesium Porous Structures by Infiltration Casting for Biomedical Applications},
year={2014},
journal = {Advanced Engineering Materials},
volume = {16},
number = {2},
pages = {241 - 247},
doi = {http://dx.doi.org/10.1002/adem.201300236},
abstract = {Magnesium and its alloys are currently considered to be a promising metallic biomaterial. The interest in magnesium alloys arises from their biocompatibility, bioabsorbility, and especially from their mechanical properties, which are more compatible to those of human bone than the mechanical properties of other metallic biomaterials, such as stainless steel and titanium. A medical application in which magnesium is gaining interest is regenerative medicine where scaffolds are used to create tissues from cells. For its application in regenerative medicine, the scaffolds have to present a 3D open-cell structure. The main purpose of the present research is to set up the fabrication procedure necessary to manufacture porous magnesium scaffolds; for this the replication (infiltration) process has been used and adapted to process magnesium alloys, processing five different biodegradable magnesium alloys (AZ91E, WE43, ZM20, ZWM200, and ZXM200).},
note = {Online available at: \url{http://dx.doi.org/10.1002/adem.201300236} (DOI). Trinidad, J.; Marco, I.; Arruebarrena, G.; Wendt, J.; Letzig, D.; Saenz de Argandona, E.; Goodall, R.: Processing of Magnesium Porous Structures by Infiltration Casting for Biomedical Applications. In: Advanced Engineering Materials. Vol. 16 (2014) 2, 241 - 247. (DOI:  10.1002/adem.201300236)}}
@article{nazarenko_influence_of_2014, 
author={Nazarenko, L. and Bargmann, S. and Stolarski, H.},
title={Influence of Interfaces on Effective Properties of Nanomaterials with Stochastically Distributed Spherical Inclusions},
year={2014},
journal = {International Journal of Solids and Structures},
volume = {51},
number = {5},
pages = {954 - 966},
doi = {http://dx.doi.org/10.1016/j.ijsolstr.2013.11.024},
abstract = {The method of conditional moments is generalized to include evaluation of the effective elastic properties of particulate nanomaterials and to investigate the size effect in those materials. Determining the effective constants necessitates finding a stochastically averaged solution to the fundamental equations of linear elasticity coupled with surface/interface conditions (Gurtin-Murdoch model). To obtain such a solution the system of governing stochastic differential equations is first transformed to an equivalent system of stochastic integral equations. Using statistical averaging, the boundary-value problem is then converted to an infinite system of linear algebraic equations. A two-point approximation is considered and the stress fluctuations within the inclusions are neglected in order to obtain a finite system of algebraic equations in terms of component-average strains. Closed-form expressions are derived for the effective moduli of a composite consisting of a matrix and randomly distributed spherical inhomogeneities. As a numerical example a nanoporous material is investigated assuming a model in which the interface effects influence only the bulk modulus of the material. In that model the resulting shear modulus is the same as for the material without surface effects. Dependence of the bulk moduli on the radius of nanopores and on the pore volume fraction is analyzed. The results are compared to, and discussed in the context of other theoretical predictions.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.ijsolstr.2013.11.024} (DOI). Nazarenko, L.; Bargmann, S.; Stolarski, H.: Influence of Interfaces on Effective Properties of Nanomaterials with Stochastically Distributed Spherical Inclusions. In: International Journal of Solids and Structures. Vol. 51 (2014) 5, 954 - 966. (DOI:  10.1016/j.ijsolstr.2013.11.024)}}
@article{kupka_a_combined_2014, 
author={Kupka, D. and Huber, N. and Lilleodden, E.T.},
title={A combined experimental-numerical approach for elasto-plastic fracture of individual grain boundaries},
year={2014},
journal = {Journal of the Mechanics and Physics of Solids},
volume = {64},
pages = {455 - 467},
doi = {http://dx.doi.org/10.1016/j.jmps.2013.12.004},
abstract = {The parameters for a crystal plasticity finite element constitutive law were calibrated for the aluminum–lithium alloy 2198 using micro-column compression testing on single crystalline volumes. The calibrated material model was applied to simulations of micro-cantilever deflection tests designed for micro-fracture experiments on single grain boundaries. It was shown that the load–displacement response and the local deformation of the grains, which was measured by digital image correlation, were predicted by the simulations. The fracture properties of individual grain boundaries were then determined in terms of a traction–separation-law associated with a cohesive zone. This combination of experiments and crystal plasticity finite element simulations allows the investigation of the fracture behavior of individual grain boundaries in plastically deforming metals.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.jmps.2013.12.004} (DOI). Kupka, D.; Huber, N.; Lilleodden, E.T.: A combined experimental-numerical approach for elasto-plastic fracture of individual grain boundaries. In: Journal of the Mechanics and Physics of Solids. Vol. 64 (2014) 455 - 467. (DOI:  10.1016/j.jmps.2013.12.004)}}
@article{kashaev_fatigue_and_2014, 
author={Kashaev, N. and Chupakhin, S. and Enz, J. and Ventzke, V. and Groth, A. and Horstmann, M. and Riekehr, S.},
title={Fatigue and Fatigue Crack Propagation of Laser Beam-Welded AA2198 Joints and Integral Structures},
year={2014},
journal = {Advanced Materials Research, 11th International Fatigue Congress},
volume = {891-892},
pages = {1457 - 1462},
doi = {http://dx.doi.org/10.4028/www.scientific.net/AMR.891-892.1457},
abstract = {To meet the future demands of the aerospace industry with respect to safety, productivity, weight, and cost, new materials and joining concepts have being developed. Recent developments in the metallurgical field now make it possible to use laser-weldable Al-alloys of the 2xxx series such as AA2198 with a high structural efficiency index due to their high strength and low density. AA2198 holds the promise of providing a breakthrough response to the challenges of lightweight design in aircraft applications. Laser beam welding as an efficient joining technology for fuselage structures is already established in the aircraft industry for lower fuselage panels because the welded panels provide a higher buckling strength and lower weight compared with the classical riveted designs. The key factor for the application of laser-welded AA2198 structures is the availability of reliable data for the assessment of their damage tolerance behavior. In the research presented, the mechanical properties with regard to fatigue and fatigue crack propagation of laser beamwelded AA2198 joints and four-stringer panels were investigated. It was found that the fatigue endurance limit of laser beamwelded AA2198T3 is approximately 25 % below the endurance limit of the base material. With regard to the fatigue crack propagation behavior, the laser beam welded four-stringer panels with T-joints show a fatigue life increased by a factor of 1.7 compared with the base material. This work shows that high-quality laser beam welds of AA2198 can be produced on a large scale using the laser beam welding facilities of the Helmholtz-Zentrum Geesthacht.},
note = {Online available at: \url{http://dx.doi.org/10.4028/www.scientific.net/AMR.891-892.1457} (DOI). Kashaev, N.; Chupakhin, S.; Enz, J.; Ventzke, V.; Groth, A.; Horstmann, M.; Riekehr, S.: Fatigue and Fatigue Crack Propagation of Laser Beam-Welded AA2198 Joints and Integral Structures. In: Advanced Materials Research, 11th International Fatigue Congress. Vol. 891-892 (2014) 1457 - 1462. (DOI:  10.4028/www.scientific.net/AMR.891-892.1457)}}
@article{huber_scaling_laws_2014, 
author={Huber, N. and Viswanath, R.N. and Mameka, N. and Markmann, J. and Weissmueller, J.},
title={Scaling laws of nanoporous metals under uniaxial compression},
year={2014},
journal = {Acta Materialia},
volume = {67},
pages = {252 - 265},
doi = {http://dx.doi.org/10.1016/j.actamat.2013.12.003},
abstract = {This study is motivated by discrepancies between recent experimental compression test data of nanoporus gold and the scaling laws for strength and elasticity by Gibson and Ashby. We present a systematic theoretical investigation of the relationship between microstructure and macroscopic behaviour of nanoporous metals. The microstructure is modelled by four-coordinated spherical nodes interconnected by cylindrical struts. The node positions are randomly displaced from the lattice points of a diamond lattice. We report scaling laws for Young’s modulus and yield strength, which depend on the extension of nodal connections between the ligaments and the solid fraction. A comparison with the scaling laws of Gibson and Ashby revealed a significant deviation for the yield stress. The model was applied for identifying a continuum constitutive law for the solid fraction. Matching the model’s predicted macroscopic stress–strain behaviour to experimental data for the flow stress at large compression strain requires the incorporation of work hardening in the constitutive law. Furthermore, the amount of disorder of the node positions is decisive in matching the model results to the experimental observations of an anomalously low stiffness and an almost complete lack of transverse plastic strain.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.actamat.2013.12.003} (DOI). Huber, N.; Viswanath, R.N.; Mameka, N.; Markmann, J.; Weissmueller, J.: Scaling laws of nanoporous metals under uniaxial compression. In: Acta Materialia. Vol. 67 (2014) 252 - 265. (DOI:  10.1016/j.actamat.2013.12.003)}}
@article{deng_mechanical_modulation_2014, 
author={Deng, Q. and Smetanin, M. and Weissmueller, J.},
title={Mechanical modulation of reaction rates in electrocatalysis},
year={2014},
journal = {Journal of Catalysis},
volume = {309},
pages = {351 - 361},
doi = {http://dx.doi.org/10.1016/j.jcat.2013.10.008},
abstract = {Many modern catalyst materials exploit a strained surface layer as the active component. Here, we explore how the catalytic activity is affected by changes in the lattice parameter, focusing on the hydrogen evolution reaction on Au and Pt electrodes in H2SO4 as a model process. We present a lock-in technique that allows the modulation of the reaction current to be followed in situ while a small cyclic elastic strain is imposed on the electrode material. We find that tensile strain enhances the exchange current density and the reactivity at low overpotential, ΔE, whereas the trend is inverted and the reactivity diminished at higher ΔE. We introduce kinetic rate equations for Heyrowsky and Tafel kinetics, allowing for strain dependence of the hydrogen adsorption enthalpy as well as the activation enthalpy. The results link the reactivity modulation to electrocapillary coupling coefficients that are open to investigation by experiment or ab initio computation. The inversion in sign of the coupling as the function of ΔE emerges in agreement with experiment.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.jcat.2013.10.008} (DOI). Deng, Q.; Smetanin, M.; Weissmueller, J.: Mechanical modulation of reaction rates in electrocatalysis. In: Journal of Catalysis. Vol. 309 (2014) 351 - 361. (DOI:  10.1016/j.jcat.2013.10.008)}}
@article{bargmann_continuum_mechanical_2014, 
author={Bargmann, S. and Favata, A.},
title={Continuum mechanical modeling of laser-pulsed heating in polycrystals: A multi-physics problem of coupling diffusion, mechanics, and thermal waves},
year={2014},
journal = {Zeitschrift fuer angewandte Mathematik und Mechanik : ZAMM},
volume = {94},
number = {6},
pages = {487 - 498},
doi = {http://dx.doi.org/10.1002/zamm.201300116},
abstract = {This contribution introduces a geometrically nonlinear, continuum thermomechanical framework for pulsed laser heating in crystalline matter: a physical process which is characterized by a non-Fourier like heat propagation and defect diffusion. The key objective of this work is to derive the highly nonlinear and strongly coupled system of governing equations describing the multi-physical behavior from fundamental balance principles. A general form for the Helmholtz energy is proposed and the resulting constitutive laws are derived from logical, thermodynamically consistent argumentation. The approach adopted to derive the governing equations is not entirely specific to laser induced heating, rather it encompasses a wide range of applications wherein heat conduction, species diffusion, and finite elastic effects are coupled. The present theory is thus applicable to the generality of models for thermal and mechanical waves: an area of increasing research interest. A numerical example is presented for the fully coupled, nonlinear and transient theory.},
note = {Online available at: \url{http://dx.doi.org/10.1002/zamm.201300116} (DOI). Bargmann, S.; Favata, A.: Continuum mechanical modeling of laser-pulsed heating in polycrystals: A multi-physics problem of coupling diffusion, mechanics, and thermal waves. In: Zeitschrift fuer angewandte Mathematik und Mechanik : ZAMM. Vol. 94 (2014) 6, 487 - 498. (DOI:  10.1002/zamm.201300116)}}
@article{xue_switchable_imbibition_2014, 
author={Xue, Y. and Markmann, J. and Duan, H. and Weissmueller, J. and Huber, P.},
title={Switchable imbibition in nanoporous gold},
year={2014},
journal = {Nature Communications},
volume = {5},
pages = {4237},
doi = {http://dx.doi.org/10.1038/ncomms5237},
abstract = {Spontaneous imbibition enables the elegant propelling of nano-flows because of the dominance of capillarity at small length scales. The imbibition kinetics are, however, solely determined by the static host geometry, the capillarity, and the fluidity of the imbibed liquid. This makes active control particularly challenging. Here we show for aqueous electrolyte imbibition in nanoporous gold that the fluid flow can be reversibly switched on and off through electric potential control of the solid–liquid interfacial tension, that is, we can accelerate the imbibition front, stop it, and have it proceed at will. Simultaneous measurements of the mass flux and the electrical current allow us to document simple scaling laws for the imbibition kinetics, and to explore the charge transport in the metallic nanopores. Our findings demonstrate that the high electric conductivity along with the pathways for fluid/ionic transport render nanoporous gold a versatile, accurately controllable electrocapillary pump and flow sensor for minute amounts of liquids with exceptionally low operating voltages.},
note = {Online available at: \url{http://dx.doi.org/10.1038/ncomms5237} (DOI). Xue, Y.; Markmann, J.; Duan, H.; Weissmueller, J.; Huber, P.: Switchable imbibition in nanoporous gold. In: Nature Communications. Vol. 5 (2014) 4237. (DOI:  10.1038/ncomms5237)}}
@article{bargmann_a_revised_2014, 
author={Bargmann, S. and Favata, A. and Podio-Guidugli, P.},
title={A Revised Exposition of the GreenNaghdi Theory of Heat Propagation},
year={2014},
journal = {Journal of Elasticity},
volume = {114},
number = {2},
pages = {143 - 154},
doi = {http://dx.doi.org/10.1007/s10659-013-9431-8},
abstract = {We offer a revised exposition of the three types of heat-propagation theories proposed by Green and Naghdi. Those theories, which make use of the notion of thermal displacement and allow for heat waves, are at variance with the standard Fourier theory; they have attracted considerable interest, and have been applied in a number of disparate physical circumstances, where heat propagation is coupled with elasticity, viscous flows, etc. (Straughan in Heat waves. Applied mathematical sciences, vol. 177. Springer, Berlin, 2011). However, their derivation is not exempt from criticisms, that we here detail, in hopes of opening the way to reconsideration of old applications and proposition of new ones.},
note = {Online available at: \url{http://dx.doi.org/10.1007/s10659-013-9431-8} (DOI). Bargmann, S.; Favata, A.; Podio-Guidugli, P.: A Revised Exposition of the GreenNaghdi Theory of Heat Propagation. In: Journal of Elasticity. Vol. 114 (2014) 2, 143 - 154. (DOI:  10.1007/s10659-013-9431-8)}}
@article{suhuddin_microstructure_and_2014, 
author={Suhuddin, U. and Fischer, V. and Kroeff, F. and dos Santos, J.F.},
title={Microstructure and mechanical properties of friction spot welds of dissimilar AA5754 Al and AZ31 Mg alloys},
year={2014},
journal = {Materials Science and Engineering  A},
volume = {590},
pages = {384 - 389},
doi = {http://dx.doi.org/10.1016/j.msea.2013.10.057},
abstract = {In the present study, friction spot welding or refill friction stir spot welding was performed to consolidate dissimilar AA5754 Al and AZ31 Mg alloys. The intermetallic compounds of Al12Mg17 and Al3Mg2 were primarily found in the weld, distributed at the interface between the base materials and in the Al top sheet. The distribution of the intermetallic compounds and the interfacial area between the base materials affect the lap shear strength of the weld. It is concluded that the material flow induced by tool movement plays an important role in both the distribution of the intermetallic compounds and the interfacial area between the base materials.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.msea.2013.10.057} (DOI). Suhuddin, U.; Fischer, V.; Kroeff, F.; dos Santos, J.F.: Microstructure and mechanical properties of friction spot welds of dissimilar AA5754 Al and AZ31 Mg alloys. In: Materials Science and Engineering  A. Vol. 590 (2014) 384 - 389. (DOI:  10.1016/j.msea.2013.10.057)}}
@article{liu_effect_of_2014, 
author={Liu, J. and Ventzke, V. and Staron, P. and Schell, N. and Kashaev, N. and Huber, N.},
title={Effect of Post-weld Heat Treatment on Microstructure and Mechanical Properties of Laser Beam Welded TiAl-based Alloy},
year={2014},
journal = {Metallurgical and Materials Transactions  A},
volume = {45},
number = {1},
pages = {16 - 28},
doi = {http://dx.doi.org/10.1007/s11661-013-1886-5},
abstract = {Post-weld heat treatment is carried out on the laser beam welded γ-TiAl-based alloy Ti-48Al-1Cr-1.5Nb-1Mn-0.2Si-0.5B (at. pct). The macro/microstructure and mechanical properties of both as-welded and heat-treated specimens are investigated by radiography, SEM, and tensile tests. Moreover, high energy synchrotron X-ray diffraction is performed to measure the residual stresses and evaluate the microstructure evolution. It is found that the residual stresses are distributed in a three-peak shape in the region of the weld zone and heat-affected zone of the as-welded specimen due to the microstructural transformation and heat softening. The residual stresses are largely relieved after the heat treatment. The heat-treated specimens have a near fully lamellar microstructure and show balanced mechanical properties of strength and ductility. The diffraction shows that the phase transformation from α2 to γ takes place under tensile load at 1023 K (750 °C), and the grain size and lamellar spacing are refined in the weld zone. Finally, the fracture mechanisms are found to be controlled by the local stress concentration-induced strain misfit between α2 and γ phases in the near γ grains and delamination and debonding in the lamellae. Boride ribbons of 5 μm in the near fully lamellar microstructure are found not to be detrimental to the tensile properties.},
note = {Online available at: \url{http://dx.doi.org/10.1007/s11661-013-1886-5} (DOI). Liu, J.; Ventzke, V.; Staron, P.; Schell, N.; Kashaev, N.; Huber, N.: Effect of Post-weld Heat Treatment on Microstructure and Mechanical Properties of Laser Beam Welded TiAl-based Alloy. In: Metallurgical and Materials Transactions  A. Vol. 45 (2014) 1, 16 - 28. (DOI:  10.1007/s11661-013-1886-5)}}
@article{bargmann_computational_modelling_2014, 
author={Bargmann, S. and Xiao, T. and Klusemann, B.},
title={Computational modelling of submicron-sized metallic glasses},
year={2014},
journal = {Philosophical Magazine},
volume = {94},
number = {1},
pages = {1 - 19},
doi = {http://dx.doi.org/10.1080/14786435.2013.838326},
abstract = {The present contribution is concerned with the modelling and computation of stable shear localization process in submicron-sized metallic glasses. To this end, a non-local thermodynamically consistent, continuum mechanical, constitutive model is developed. In our previous work, we formulated the model in the small strain framework. In current work, this model is extended to finite strains. The numerical implementation is carried out with the help of the finite element method. Numerical examples are presented – illustrating the general model behaviour which is correlated to experimental observations. It is shown that the proposed finite deformation model is well suitable to predict the stable shear localization process in submicron-sized metallic glasses and its size effect. The model confirms that with decreasing sample size the shear localization process starts at a later deformation state. Additionally, the finite deformation model is able to predict the failure process in submicron-sized metallic glasses as well as the delay of it with decreasing sample size qualitatively correct.},
note = {Online available at: \url{http://dx.doi.org/10.1080/14786435.2013.838326} (DOI). Bargmann, S.; Xiao, T.; Klusemann, B.: Computational modelling of submicron-sized metallic glasses. In: Philosophical Magazine. Vol. 94 (2014) 1, 1 - 19. (DOI:  10.1080/14786435.2013.838326)}}
@article{ventzke_einseitiges_ndyaglaserstrahlschweissen_2014, 
author={Ventzke, V. and Riekehr, S. and Horstmann, M. and Haack, P. and Kashaev, N.},
title={Einseitiges Nd:YAG-Laserstrahlschweissen zum Herstellen von T-Stossverbindungen aus Aluminiumlegierungen fuer den Flugzeugbau},
year={2014},
journal = {Schweissen und Schneiden},
volume = {66},
number = {1-2},
pages = {22 - 26},
abstract = {Im Flugzeugbau werden T-Stoßverbindungen aus Aluminiumlegierungen entweder durch Nieten oder zweiseitiges Laserstrahlschweißen hergestellt. Der Beitrag beschreibt das einseitige Nd:YAG-Laserstrahlschweißen als Methode zur Herstellung von Haut-Clip-Verbindungen aus AA6156-T4/AA6013- T6 und AA2139-T3/AA6013-T6 in T-Stoßausführung. Ein grundlegendes Problem bei dieser Vorgehensweise ist das hohe Porositätsniveau in einseitig lasersrahlgeschweißten T-Stoßverbindungen. Es wird gezeigt, dass die Porenbildung nicht durch die Art der Aluminiumlegierungen, die Schweißrichtungsvariationen und die Fügeflächenvorbereitung bestimmt wird, sondern durch einen zu hohen Einstrahlwinkel zwischen Laserstrahl und Hautfeld. Erforderlich ist eine Einstrahlung des Laserstrahls im Bindebereich zwischen Clip und Hautfeld, um durch Verringerung des Einstrahlwinkels eine Reduzierung des Porositätsniveaus erzielen zu können. 

In aircraft construction, T-joints between aluminium alloys are manufactured either by riveting or by two-sided laser beam welding. The article describes one-sided Nd:YAG laser beam welding as a method of manufacturing skin/clip joints between the AA6156-T4/AA6013-T6 and AA2139-T3/AA6013-T6 aluminium material combinations in T-joint designs. One fundamental problem associated with this procedure is the high porosity level in T-joints executed by means of one-sided laser beam welding. It is shown that the formation of pores is determined not only by the types of the aluminium alloys, the variations in the welding directions and the preparation of the joining faces but also by an excessive angle of incidence between the laser beam and the skin field. The laser beam must be transmitted in the bonding region between the clip and the skin field in order to reduce the porosity level by decreasing the angle of incidence.},
note = {Ventzke, V.; Riekehr, S.; Horstmann, M.; Haack, P.; Kashaev, N.: Einseitiges Nd:YAG-Laserstrahlschweissen zum Herstellen von T-Stossverbindungen aus Aluminiumlegierungen fuer den Flugzeugbau. In: Schweissen und Schneiden. Vol. 66 (2014) 1-2, 22 - 26.}}
@article{sarac_materials_by_2014, 
author={Sarac, B. and Klusemann, B. and Xiao, T. and Bargmann, S.},
title={Materials by design: An experimental and computational investigation on the microanatomy arrangement of porous metallic glasses},
year={2014},
journal = {Acta Materialia},
volume = {77},
pages = {411 - 422},
doi = {http://dx.doi.org/10.1016/j.actamat.2014.05.053},
abstract = {The correlation of a material’s structure with its properties is one of the important unresolved issues in materials science research. This paper discusses a novel experimental and computational approach by which the influence of the pores on the mechanical properties of bulk metallic glasses (BMGs) can be systematically and quantitatively analyzed. The experimental stage involves the fabrication of a template whose pore configurations are pre-determined by computer-aided design tools, and replication of the designed patterns with BMGs. Quasi-static mechanical characterization of these complex microstructures is conducted under uniaxial tension and in-plane compression. For the numerical simulations, a non-local gradient-enhanced continuum mechanical model is established, using thermodynamic principles and periodic boundary conditions. The combination of the experimental and numerical results has identified the importance of the pore configuration, overall porosity and diameter to the spacing ratio of the pores to attain optimized material properties.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.actamat.2014.05.053} (DOI). Sarac, B.; Klusemann, B.; Xiao, T.; Bargmann, S.: Materials by design: An experimental and computational investigation on the microanatomy arrangement of porous metallic glasses. In: Acta Materialia. Vol. 77 (2014) 411 - 422. (DOI:  10.1016/j.actamat.2014.05.053)}}
@article{bargmann_a_computational_2014, 
author={Bargmann, S. and Reddy, B.D. and Klusemann, B.},
title={A computational study of a model of single-crystal strain-gradient viscoplasticity with an interactive hardening relation},
year={2014},
journal = {International Journal of Solids and Structures},
volume = {51},
number = {15-16},
pages = {2754 - 2764},
doi = {http://dx.doi.org/10.1016/j.ijsolstr.2014.03.010},
abstract = {The behavior of a model of single-crystal strain-gradient viscoplasticity is investigated. The model is an extension of a rate-independent version, and includes a new hardening relation that has recently been proposed in the small-deformation context (Gurtin and Reddy, 2014), and which accounts for slip-system interactions due to self and latent hardening. Energetic and dissipative effects, each with its corresponding length scale, are included. Numerical results are presented for a single crystal with single and multiple slip systems, as well as an ensemble of grains. These results provide a clear illustration of the effects of accounting for slip-system interactions.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.ijsolstr.2014.03.010} (DOI). Bargmann, S.; Reddy, B.D.; Klusemann, B.: A computational study of a model of single-crystal strain-gradient viscoplasticity with an interactive hardening relation. In: International Journal of Solids and Structures. Vol. 51 (2014) 15-16, 2754 - 2764. (DOI:  10.1016/j.ijsolstr.2014.03.010)}}
@article{campo_microstructure_and_2014, 
author={Campo, K.N. and Campanelli, L.C. and Bergmann, L. and dos Santos, J.F. and Bolfarini, C.},
title={Microstructure and interface characterization of dissimilar friction stir welded lap joints between Ti–6Al–4V and AISI 304},
year={2014},
journal = {Materials and Design},
volume = {56},
pages = {139 - 145},
doi = {http://dx.doi.org/10.1016/j.matdes.2013.11.002},
abstract = {The feasibility of dissimilar friction stir welding (FSW) in overlap configuration between Ti–6Al–4V alloy (Ti64) and AISI 304 austenitic stainless steels (304SS) was investigated. Sound joints were achieved when placing titanium as the upper workpiece. Joints were successfully produced by employing a welding speed of 1 mm/s and rotational speeds of 300 and 500 rpm. A lamellar microstructure was formed in the stir zone of Ti64, where grain size was found to increase with increasing rotational speed, and austenitic equiaxed grains were obtained near the interface of 304SS coupon. Energy dispersive X-ray spectroscopy (SEM-EDS) of the interface revealed a thin intermixed region and suggested intermetallic compound formation. Microhardness data in the titanium weld zone for both rotational speeds exhibited slightly lower values than the base material, with the lowest values in the heat affected zone, whereas the microhardness values in the stainless steel side around the weld center were found to be higher than those obtained for the base material.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.matdes.2013.11.002} (DOI). Campo, K.N.; Campanelli, L.C.; Bergmann, L.; dos Santos, J.F.; Bolfarini, C.: Microstructure and interface characterization of dissimilar friction stir welded lap joints between Ti–6Al–4V and AISI 304. In: Materials and Design. Vol. 56 (2014) 139 - 145. (DOI:  10.1016/j.matdes.2013.11.002)}}
@article{konchakova_application_of_2014, 
author={Konchakova, N. and Bargmann, S.},
title={Application of a Gradient Crystal Plasticity Model to Numerical Analysis of Metal Part of Nanoporous Metal – Polymer Composites},
year={2014},
journal = {Procedia Engineering},
volume = {81},
pages = {1348 - 1353},
doi = {http://dx.doi.org/10.1016/j.proeng.2014.10.155},
abstract = {The application of a gradient extended theory to the computation of the mechanical response of a single crystalline sub-micron gold, which is the part of nano-composites, is in the focus of the contribution. The research takes into account the dependence of the macroscopic behavior of a crystalline material on the size and morphology of the grains, the volume fraction of different phases, and the subgrain material modeling. A gradient hardening contribution is included into the crystal plasticity model in order to study the influence of the grain size on the response of single crystalline. It is assumed that the grain boundaries act as barriers to plastic deformation. The highly coupled system of equations is solved by applying a dual mixed finite element algorithm. Numerical results of the sub-micron gold crystal deformation under cyclic shear loading are presented. The gradient effect in the deformation field is discussed.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.proeng.2014.10.155} (DOI). Konchakova, N.; Bargmann, S.: Application of a Gradient Crystal Plasticity Model to Numerical Analysis of Metal Part of Nanoporous Metal – Polymer Composites. In: Procedia Engineering. Vol. 81 (2014) 1348 - 1353. (DOI:  10.1016/j.proeng.2014.10.155)}}
@article{mosler_a_novel_2014, 
author={Mosler, J. and Shchyglo, O. and Montazer Hojjat, H.},
title={A novel homogenization method for phase field approaches based on partial rank-one relaxation},
year={2014},
journal = {Journal of the Mechanics and Physics of Solids},
volume = {68},
pages = {251 - 266},
doi = {http://dx.doi.org/10.1016/j.jmps.2014.04.002},
abstract = {This paper deals with the analysis of homogenization assumptions within phase field theories in a finite strain setting. Such homogenization assumptions define the average bulk׳s energy within the diffusive interface region where more than one phase co-exist. From a physical point of view, a correct computation of these energies is essential, since they define the driving force of material interfaces between different phases. The three homogenization assumptions considered in this paper are: (a) Voigt/Taylor model, (b) Reuss/Sachs model, and (c) Khachaturyan model. It is shown that these assumptions indeed share some similarities and sometimes lead to the same results. However, they are not equivalent. Only two of them allow the computation of the individual energies of the co-existing phases even within the aforementioned diffusive interface region: the Voigt/Taylor and the Reuss/Sachs model. Such a localization of the averaged energy is important in order to determine and to subsequently interpret the driving force at the interface. Since the Voigt/Taylor and the Reuss/Sachs model are known to be relatively restrictive in terms of kinematics (Voigt/Taylor) and linear momentum (Reuss/Sachs), a novel homogenization approach is advocated. Within a variational setting based on (incremental) energy minimization, the results predicted by the novel approach are bounded by those corresponding to the Voigt/Taylor and the Reuss/Sachs model. The new approach fulfills equilibrium at material interfaces (continuity of the stress vector) and it is kinematically compatible. In sharp contrast to existing approaches, it naturally defines the mismatch energy at incoherent material interfaces. From a mathematical point of view, it can be interpreted as a partial rank-one convexification.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.jmps.2014.04.002} (DOI). Mosler, J.; Shchyglo, O.; Montazer Hojjat, H.: A novel homogenization method for phase field approaches based on partial rank-one relaxation. In: Journal of the Mechanics and Physics of Solids. Vol. 68 (2014) 251 - 266. (DOI:  10.1016/j.jmps.2014.04.002)}}
@article{shi_on_the_2014, 
author={Shi, B. and Bartels, A. and Mosler, J.},
title={On the thermodynamically consistent modeling of distortional hardening: A novel generalized framework},
year={2014},
journal = {International Journal of Plasticity},
volume = {63},
pages = {170 - 182},
doi = {http://dx.doi.org/10.1016/j.ijplas.2014.05.008},
abstract = {Many important physical effects of materials undergoing plasticity at the macroscale cannot be captured realistically by isotropic and kinematic hardening only. For instance, the evolution of the texture in polycrystals results macroscopically in a distorted yield surface. This paper deals with adequate hardening models for such a distortion. To be more precise, a novel general frame for finite strain plasticity models is elaborated. To the best knowledge of the authors, it is the first one combining the following features: (1) proof of thermodynamical consistency; (2) decomposition of distortional hardening into dynamic hardening (due to currently active dislocations) and latent hardening (due to currently inactive dislocations); (3) difference of the yield surface’s curvature in loading direction and in the opposite direction. The cornerstone of this model is a new plastic potential for the evolution equations governing distortional hardening. Although this type of hardening is characterized through a fourth-order tensor as internal variable, the structure of the aforementioned potential is surprisingly simple. Even though the final model is rather complex, it requires only few model parameters. For these parameters, in turn, physically sound bounds based on the convexity condition of the yield surface can be derived. Three different examples demonstrate the predictive capabilities of the novel framework.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.ijplas.2014.05.008} (DOI). Shi, B.; Bartels, A.; Mosler, J.: On the thermodynamically consistent modeling of distortional hardening: A novel generalized framework. In: International Journal of Plasticity. Vol. 63 (2014) 170 - 182. (DOI:  10.1016/j.ijplas.2014.05.008)}}
@article{deng_electrocapillary_coupling_2014, 
author={Deng, Q. and Weissmueller, J.},
title={Electrocapillary Coupling during Electrosorption},
year={2014},
journal = {Langmuir},
volume = {30},
number = {34},
pages = {10522 - 10530},
doi = {http://dx.doi.org/10.1021/la501353g},
abstract = {The electrocapillary coupling coefficient, ς, measures the response of the electrode potential, E, to tangential elastic strain at the surface of an electrode. Using dynamic electro-chemo-mechanical analysis, we study ς(E) simultaneously with cyclic voltammetry. The study covers extended potential intervals on Au, Pt, and Pd, including the electrosorption of oxygen species and of hydrogen. The magnitude and sign of ς vary during the scans, and quite generally the graphs of ς(E) emphasize details which are less obvious or missing in the cyclic voltammograms (CVs). Capacitive processes on the clean electrode surfaces exhibit ς < 0, whereas capacitive processes on oxygen-covered surfaces are characterized by ς < 0 on Au but ς > 0 on Pt and Pd. The findings of ς < 0 during the initial stages of oxygen species adsorption and ς > 0 for hydrogen electrosorption agree with the trend that tensile strain makes surfaces more binding for adsorbates. However, the large hysteresis of oxygen electrosorption on all electrodes raises the question: is the exchange current associated with that process sufficient for its measurement by potential response during small cyclic strain?},
note = {Online available at: \url{http://dx.doi.org/10.1021/la501353g} (DOI). Deng, Q.; Weissmueller, J.: Electrocapillary Coupling during Electrosorption. In: Langmuir. Vol. 30 (2014) 34, 10522 - 10530. (DOI:  10.1021/la501353g)}}
@article{goushegir_friction_spot_2014, 
author={Goushegir, S.M. and dos Santos, J.F. and Amancio-Filho, S.T.},
title={Friction Spot Joining of aluminum AA2024/carbon-fiber reinforced poly(phenylene sulfide) composite single lap joints: Microstructure and mechanical performance},
year={2014},
journal = {Materials and Design},
volume = {54},
pages = {196 - 206},
doi = {http://dx.doi.org/10.1016/j.matdes.2013.08.034},
abstract = {Friction Spot Joining is a promising alternative joining technology for polymer–metal hybrid structures. In this work, the feasibility of Friction Spot Joining of aluminum AA2024-T3 (bare and alclad)/carbon-fiber reinforced poly(phenylene sulfide) is reported. The process temperature and the microstructure of the joints were investigated. Lap shear tensile strength as high as 27 MPa was achieved by using aluminum bare specimens. Sand blasting was also performed as an effective mechanical surface pre-treatment on aluminum surfaces, which resulted in higher surface roughness and accordingly improved mechanical performance for the selected conditions. In addition, the alclad specimens exhibited promising mechanical performance (lap shear strength of up to 43 MPa) that justifies further investigations. Finally, the bonding and failure mechanisms of the joints are briefly discussed.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.matdes.2013.08.034} (DOI). Goushegir, S.M.; dos Santos, J.F.; Amancio-Filho, S.T.: Friction Spot Joining of aluminum AA2024/carbon-fiber reinforced poly(phenylene sulfide) composite single lap joints: Microstructure and mechanical performance. In: Materials and Design. Vol. 54 (2014) 196 - 206. (DOI:  10.1016/j.matdes.2013.08.034)}}
@article{roy_wrinkling_of_2014, 
author={Roy, A. and Kundu, S. and Mueller, K. and Rosenauer, A. and Singh, S. and Pant, P. and Gururajan, M.P. and Kumar, P. and Weissmueller, J. and Singh, A.K. and Ravishankar, N.},
title={Wrinkling of Atomic Planes in Ultrathin Au Nanowires},
year={2014},
journal = {Nano Letters},
volume = {14},
number = {8},
pages = {4859 - 4866},
doi = {http://dx.doi.org/10.1021/nl502259w},
abstract = {A detailed understanding of structure and stability of nanowires is critical for applications. Atomic resolution imaging of ultrathin single crystalline Au nanowires using aberration-corrected microscopy reveals an intriguing relaxation whereby the atoms in the close-packed atomic planes normal to the growth direction are displaced in the axial direction leading to wrinkling of the (111) atomic plane normal to the wire axis. First-principles calculations of the structure of such nanowires confirm this wrinkling phenomenon, whereby the close-packed planes relax to form saddle-like surfaces. Molecular dynamics studies of wires with varying diameters and different bounding surfaces point to the key role of surface stress on the relaxation process. Using continuum mechanics arguments, we show that the wrinkling arises due to anisotropy in the surface stresses and in the elastic response, along with the divergence of surface-induced bulk stress near the edges of a faceted structure. The observations provide new understanding on the equilibrium structure of nanoscale systems and could have important implications for applications in sensing and actuation.},
note = {Online available at: \url{http://dx.doi.org/10.1021/nl502259w} (DOI). Roy, A.; Kundu, S.; Mueller, K.; Rosenauer, A.; Singh, S.; Pant, P.; Gururajan, M.P.; Kumar, P.; Weissmueller, J.; Singh, A.K.; Ravishankar, N.: Wrinkling of Atomic Planes in Ultrathin Au Nanowires. In: Nano Letters. Vol. 14 (2014) 8, 4859 - 4866. (DOI:  10.1021/nl502259w)}}
@article{nazarenko_effective_bulk_2014, 
author={Nazarenko, L. and Bargmann, S.},
title={Effective bulk moduli of materials containing stochastically distributed nano-inhomogeneities with surface stresses},
year={2014},
journal = {PAMM: Proceedings in Applied Mathematics and Mechanics},
volume = {14},
number = {1},
pages = {537 - 538},
doi = {http://dx.doi.org/10.1002/pamm.201410256},
abstract = {In the present contribution, a mathematical model for the investigation of the effective properties of a material with randomly distributed nano-particles is proposed. The surface effect is introduced via Gurtin-Murdoch equations describing properties of the matrix/nano-particle interface. They are added to the system of stochastic differential equations formulated within the framework of linear elasticity. The homogenization problem is reduced to finding a statistically averaged solution of the system of stochastic differential equations. These equations are based on the fundamental equations of linear elasticity, which are coupled with surface/interface elasticity accounting for the presence of surface tension. Using Green's function this system is transformed to a system of statistically non-linear integral equations. It is solved by the method of conditional moments. Closed-form expressions are derived for the effective moduli of a composite consisting of a matrix with randomly distributed spherical inhomogeneities. The radius of the nano-particles is included in the expression for the bulk moduli. As numerical examples, nano-porous aluminum and nano-porous gold are investigated assuming that only the influence of the interface effects on the effective bulk modulus is of interest. The dependence of the normalized bulk moduli of nano-porous aluminum on the pore volume fraction (for certain radii of nano-pores) are compared to and discussed in the context of other theoretical predictions. The effective Young's modulus of nano-porous gold as a function of pore radius (for fixed void volume fraction) and the normalized Young's modulus vs. the pore volume fraction for different pore radii are analyzed.},
note = {Online available at: \url{http://dx.doi.org/10.1002/pamm.201410256} (DOI). Nazarenko, L.; Bargmann, S.: Effective bulk moduli of materials containing stochastically distributed nano-inhomogeneities with surface stresses. In: PAMM: Proceedings in Applied Mathematics and Mechanics. Vol. 14 (2014) 1, 537 - 538. (DOI:  10.1002/pamm.201410256)}}
@article{konchakova_dualmixed_finite_2014, 
author={Konchakova, N. and Husser, E. and Bargmann, S.},
title={Dual-mixed finite element analysis of crystalline sub-micron gold},
year={2014},
journal = {PAMM: Proceedings in Applied Mathematics and Mechanics},
volume = {14},
number = {1},
pages = {329 - 330},
doi = {http://dx.doi.org/10.1002/pamm.201410152},
abstract = {An extended crystal plasticity model is applied to crystalline sub-micron gold in order to study the mechanical response. Numerical results for different crystal sizes are presented and discussed. The governing equations are discretized and, subsequently, solved via a dual-mixed finite element formulation [1, 2]. The evolution equation of the dislocation density is taken as a global field relation additionally to the balance of linear momentum, whereas the flow rule is solved locally at the Gauß point level [3,4].},
note = {Online available at: \url{http://dx.doi.org/10.1002/pamm.201410152} (DOI). Konchakova, N.; Husser, E.; Bargmann, S.: Dual-mixed finite element analysis of crystalline sub-micron gold. In: PAMM: Proceedings in Applied Mathematics and Mechanics. Vol. 14 (2014) 1, 329 - 330. (DOI:  10.1002/pamm.201410152)}}
@article{klusemann_nonlocal_modeling_2014, 
author={Klusemann, B. and Xiao, T. and Bargmann, S.},
title={Non-local modeling of size effects in amorphous metals},
year={2014},
journal = {PAMM: Proceedings in Applied Mathematics and Mechanics},
volume = {14},
number = {1},
pages = {529 - 530},
doi = {http://dx.doi.org/10.1002/pamm.201410252},
abstract = {The present contribution is concerned with the modeling of lengthscale-dependent behavior of submicron sized amorphous metal. As these samples reach the size of a few hundred nanometers, the main deformation mechanism changes from catastrophic to a stable shear localization. For the underlying model description, we resort to a thermodynamically consistent approach. Klusemann & Bargmann [1] presented results for a small strain formulation which was extended recently to finite strains by Bargmann et al. [2]. The non-local material model is formulated with a dual mixed finite element approach. It is shown that the proposed finite deformation model is well suited to predict the stable shear localization process in submicron-sized metallic glasses and its size effect. The model confirms the experimental observation that with decreasing sample size the shear localization process becomes stable and delayed. The finite deformation model is able to predict the failure process in submicron-sized metallic glasses as well as the delay of it with decreasing sample size.},
note = {Online available at: \url{http://dx.doi.org/10.1002/pamm.201410252} (DOI). Klusemann, B.; Xiao, T.; Bargmann, S.: Non-local modeling of size effects in amorphous metals. In: PAMM: Proceedings in Applied Mathematics and Mechanics. Vol. 14 (2014) 1, 529 - 530. (DOI:  10.1002/pamm.201410252)}}
@article{diaz_modeling_of_2014, 
author={Diaz, G. and Mosler, J.},
title={Modeling of fiber-reinforced PMMA at different scales},
year={2014},
journal = {PAMM: Proceedings in Applied Mathematics and Mechanics},
volume = {14},
number = {1},
pages = {159 - 160},
doi = {http://dx.doi.org/10.1002/pamm.201410067},
abstract = {This paper deals with the modeling of fiber-reinforced PMMA. Focus is on the macroscopic mechanical response with emphasis on the fracture properties such as the ultimate strength and the fracture energy. In order to capture the macroscopic mechanical response of PMMA, a finite element formulation is presented. While the elastic response of the fibres and that of the surrounding matrix are modelled in standard manner, i.e., by standard bulk material models, the relevant failure modes such as cracking of the fibres are accounted for by means of the so-called Strong Discontinuity Approach (SDA). Since the fibres are relatively small, their fracture mechanical properties crucially depend on their geometry, i.e., they show a pronounced size effect. Based on numerical analyses of fibres with different geometries, the aforementioned size effect is naturally incorporated into the formulation.},
note = {Online available at: \url{http://dx.doi.org/10.1002/pamm.201410067} (DOI). Diaz, G.; Mosler, J.: Modeling of fiber-reinforced PMMA at different scales. In: PAMM: Proceedings in Applied Mathematics and Mechanics. Vol. 14 (2014) 1, 159 - 160. (DOI:  10.1002/pamm.201410067)}}
@article{stutz_material_saving_2014, 
author={Stutz, L. and Beck, W. and Arends, S. and Horstmann, M. and Ventzke, V. and Kashaev, N.},
title={Material saving and cost reduction with hot forming of U-shaped titanium part - Materialeinsparung und Kostenreduzierung durch Heissumformung von U-foermigen Titanbauteilen},
year={2014},
journal = {Materialwissenschaft und Werkstofftechnik},
volume = {45},
number = {9},
pages = {841 - 846},
doi = {http://dx.doi.org/10.1002/mawe.201400292},
abstract = {Titanium alloy sheets are widely used for highly loaded components in the aerospace industry as well as spacecrafts. The unique combination of high strength, outstanding corrosion resistance and thermal endurance makes titanium alloys the preferred material for applications with severe requirements.

Due to the limited formability at room temperature, forming processes have to be conducted in a multitude of steps what is costly and labour intensive. Additionally, typical titanium alloy sheets show a significant anisotropy of mechanical properties and material flow. Undesired earing, wall thickness variation and residual stresses are the result.

Complex shaped parts can be produced at elevated temperatures to avoid named drawbacks. The present work introduces a newly developed hot deep drawing process, applied to titanium sheets at FormTech. In comparison with conventional superplastic forming processes via gas pressure, hot deep drawing comes with a significantly reduced process time and hence, increased output over time.

Titanium sheets of the work horse alloy Ti–6Al–4V were formed in a single stroke to a U-shaped component at process temperatures ranging from 750 to 890 °C. Specimens were extracted to validate the neglectable influence of the hot forming process on mechanical properties and fatigue behaviour. In conclusion, hot deep drawing of titanium sheets offers a cost efficient alternative to a gas pressure superplastic forming process, while maintaining its main benefits such as significantly improved formability, low residual stresses and tight tolerances.},
note = {Online available at: \url{http://dx.doi.org/10.1002/mawe.201400292} (DOI). Stutz, L.; Beck, W.; Arends, S.; Horstmann, M.; Ventzke, V.; Kashaev, N.: Material saving and cost reduction with hot forming of U-shaped titanium part - Materialeinsparung und Kostenreduzierung durch Heissumformung von U-foermigen Titanbauteilen. In: Materialwissenschaft und Werkstofftechnik. Vol. 45 (2014) 9, 841 - 846. (DOI:  10.1002/mawe.201400292)}}
@article{rodrigues_fricriveting_of_2014, 
author={Rodrigues, C.F. and Blaga, L.A. and dos Santos, J.F. and Canto, L.B. and Hage, E. Jr. and Amancio-Filho, S.T.},
title={FricRiveting of aluminum 2024-T351 and polycarbonate: Temperature evolution, microstructure and mechanical performance},
year={2014},
journal = {Journal of Materials Processing Technology},
volume = {214},
number = {10},
pages = {2029 - 2039},
doi = {http://dx.doi.org/10.1016/j.jmatprotec.2013.12.018},
abstract = {Friction Riveting (FricRiveting) is an innovative, fast and energy-efficient spot joining process used to join lightweight hybrid metal–polymer and metal–composite structures. In this process, a cylindrical metallic rivet is used to join one or more thermoplastic components by means of plasticizing and deforming the tip of a metallic rivet through frictional heating and pressure inside the polymeric parts. This work studies the feasibility of the FricRiveting technique for polycarbonate/aluminum 2024-T351 alloy spot joints by investigating the temperature development (measured by infrared thermography), microstructure (evaluated by optical microscopy) and mechanical properties (investigated by tensile testing) of the joints. The thermographic temperature investigation indicated that the average peak process temperatures were from 280 to 360 °C, from 56% to 72% of the AA 2024 eutectic point and below the temperature range of extensive thermal degradation of polycarbonate (480–550 °C). Furthermore, the typical deformed tip of the rivet – the anchoring zone – was attained for all joints investigated in this study, as induced by thermo-mechanical processing. The anchoring efficiency represented by the aspect ratio of the deformed rivet was evaluated by optical microscopy. Aspect ratio values were compared with the process temperatures and the tensile strengths of the joints. Increases in process heat input resulted in larger aspect ratios. High average values of ultimate tensile forces varying from 6659 ± 62 N to 8540 ± 182 N (68.4–87.8% of the ultimate tensile strength of the metallic rivet) were achieved, with final ductile fracture occurring in the metallic rivet for joints with aspect ratios of 0.88 ± 0.02 and in the polymeric base plate for joints with aspect ratios of 0.61 ± 0.03 and 0.68 ± 0.04. The volumetric ratio – a recent, more complex three dimensional approach for evaluating the mechanical performance of the joints – was also investigated, revealing similar interactions with process temperatures and tensile strengths as the aspect ratio. The results of this work proved that FricRiveting is a feasible method for use on the PC-AA 2024-T351 material combination, as it yields strong joints.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.jmatprotec.2013.12.018} (DOI). Rodrigues, C.F.; Blaga, L.A.; dos Santos, J.F.; Canto, L.B.; Hage, E. Jr.; Amancio-Filho, S.T.: FricRiveting of aluminum 2024-T351 and polycarbonate: Temperature evolution, microstructure and mechanical performance. In: Journal of Materials Processing Technology. Vol. 214 (2014) 10, 2029 - 2039. (DOI:  10.1016/j.jmatprotec.2013.12.018)}}
@article{behrouzi_inherent_and_2014, 
author={Behrouzi, A. and Soyarslan, C. and Klusemann, B. and Bargmann, S.},
title={Inherent and induced anisotropic finite visco-plasticity with applications to the forming of DC06 sheets},
year={2014},
journal = {International Journal of Mechanical Sciences},
volume = {89},
pages = {101 - 111},
doi = {http://dx.doi.org/10.1016/j.ijmecsci.2014.08.025},
abstract = {In the current work we present a finite visco-plasticity model accounting for inherent and induced plastic anisotropy as well as Bauschinger effect for the interstitial free (IF) steels and its application to a forming process simulation of DC06 sheets. The inherent plastic anisotropy uses a Hill-48 type structural tensor whereas the induced anisotropy is modeled via its evolution accounting for dynamic (active) and latent (inactive) parts. The latter appears to be an eminent requirement for predicting the qualitative effect of the evolving dislocation microstructures under orthogonal loading path changes, i.e., the cross hardening. A nonlinear isotropic and Armstrong–Frederick type kinematic hardening is also involved. Finally, the rate dependence of the plastic response is incorporated using Johnson–Cook type formulation. The model is implemented as VUMAT user defined material subroutine for ABAQUS and used in a set of sensitivity analyses to present mentioned model features. The model parameters are identified based on a set of experiments involving monotonic shear, uniaxial tension, forward to reverse shear and plane strain tension followed by shear tests. Finally, the channel forming process of a DC06 sheet is simulated. A good agreement with the experimental findings is observed, in both the tool response history curves and the extent of spring-back which is conclusive on the final product geometry.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.ijmecsci.2014.08.025} (DOI). Behrouzi, A.; Soyarslan, C.; Klusemann, B.; Bargmann, S.: Inherent and induced anisotropic finite visco-plasticity with applications to the forming of DC06 sheets. In: International Journal of Mechanical Sciences. Vol. 89 (2014) 101 - 111. (DOI:  10.1016/j.ijmecsci.2014.08.025)}}
@article{butzke_stress_concentration_2014, 
author={Butzke, J.E. and Mittelstedt, C.},
title={Stress concentration phenomena in the vicinity of composite plate-doubler junctions by a layerwise analysis approach},
year={2014},
journal = {Composite Structures},
volume = {118},
pages = {351 - 366},
doi = {http://dx.doi.org/10.1016/j.compstruct.2014.07.041},
abstract = {This paper presents an analysis method for the determination of displacements, strains and stresses in a laminated composite plate subjected to tensile load that is reinforced by a doubler. The analysis approach consists of two parts. Firstly, a ’global’ solution that is based on Classical Laminated Plate Theory (CLPT) is introduced. Secondly, a ’local’ model is derived that enables the assessment of the three-dimensional stress state near the plate-doubler junction. The local solution employs a discretization of the physical layers into a number of mathematical layers which necessitates the numerical treatment of a quadratic eigenvalue problem. Consequently, the current approach can be classified as being a semi-analytical layerwise analysis method. Results are generated for several different plate-doubler configurations, and it is found that the current analysis model delivers excellent results when compared to finite element simulations, however with only a fraction of the computational time and effort that are needed for the FEM analyses.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.compstruct.2014.07.041} (DOI). Butzke, J.E.; Mittelstedt, C.: Stress concentration phenomena in the vicinity of composite plate-doubler junctions by a layerwise analysis approach. In: Composite Structures. Vol. 118 (2014) 351 - 366. (DOI:  10.1016/j.compstruct.2014.07.041)}}
@article{goncalves_improvement_of_2014, 
author={Goncalves, J. and dos Santos, J.F. and Canto, L.B. and Amancio Filho, S.T.},
title={Improvement of the Friction Spot Welding (FSpW) to join Polyamide 6 and Polyamide 66/Carbon Fiber Laminate - Aperfeicoamento da Tecnica de Soldagem Pontual por Friccao (FSpW) para Uniao de Poliamida 6 e Laminado de Poliamida 66 com Fibra de Carbono},
year={2014},
journal = {Soldagem & Inspecao},
volume = {19},
number = {1},
pages = {19 - 27},
doi = {http://dx.doi.org/10.1590/S0104-92242014000100004},
abstract = {Friction Spot Welding is an innovative technique developed and patented in 2005 by the research center Helmholtz Zentrum
Geesthacht (HZG). Advantages of the process include fast joining cycles, low operational costs and good mechanical performance.
It was originally developed to weld lightweight metals and has been continuously improved to weld polymers. There are only few
studies on friction spot welding of thermoplastics and the welding of polymeric composites by FSpW is still unpublished. This study
demonstrated the technical feasibility of welding a polyamide 6 (PA6) plate over a carbon fiber polyamide 66 laminate (CF-PA66) by
FSpW. The thermal history, the surface finish, the microstructure of the weld region and the mechanical shear strength of PA6/CF-PA66
lap joints were investigated. The increase of the diameter of the clamping ring - originally designed for welding lightweight metals - led
to the selection of welding parameters that result in high heat input, resulting in an increased welded area, and lower notch left by the
tool in the sample that improved the surface finish of the weld. This optimization resulted in a PA6/CF-PA66 joint with lap shear strength
of 35 MPa (2196 N), with fracture occurring mainly in the top plate of PA6.

A Soldagem Pontual por Fricção (‘Friction Spot Welding – FSpW’) é uma técnica inovadora que foi desenvolvida e patenteada em 2005
pelo centro de pesquisa alemão Helmholtz Zentrum Geesthacht (HZG). A técnica apresenta ciclos rápidos, baixo custo operacional
e gera soldas com alto desempenho mecânico. Foi inicialmente projetada para a soldagem de ligas metálicas leves. A soldagem de
polímeros é alvo de pesquisas recentes e a soldagem de compósitos poliméricos por FSpW ainda é inédita. Este estudo demonstrou
a viabilidade técnica da soldagem de chapa de poliamida 6 (PA6) e laminado de poliamida 66 e fibra de carbono (CF-PA66) por
FSpW. O histórico térmico, o acabamento superficial, a microestrutura da região da solda e a resistência mecânica ao cisalhamento
de juntas sobrepostas PA6/CF-PA66 foram investigados. O aumento do tamanho do anel de fixação da ferramenta original, projetada
para a soldagem de metais, possibilitou a seleção de parâmetros de soldagem que resultaram em grande aporte térmico, resultando no
aumento da área soldada, num menor entalhe (inscrição) deixado pela ferramenta na amostra, produzindo melhoria no acabamento
superficial da solda. Essa otimização resultou em uma junta PA6/CF-PA66 com resistência ao cisalhamento de 35 MPa (2196 N), com
fratura predominante na placa superior de PA6.},
note = {Online available at: \url{http://dx.doi.org/10.1590/S0104-92242014000100004} (DOI). Goncalves, J.; dos Santos, J.F.; Canto, L.B.; Amancio Filho, S.T.: Improvement of the Friction Spot Welding (FSpW) to join Polyamide 6 and Polyamide 66/Carbon Fiber Laminate - Aperfeicoamento da Tecnica de Soldagem Pontual por Friccao (FSpW) para Uniao de Poliamida 6 e Laminado de Poliamida 66 com Fibra de Carbono. In: Soldagem & Inspecao. Vol. 19 (2014) 1, 19 - 27. (DOI:  10.1590/S0104-92242014000100004)}}
@article{junior_feasibility_study_2014, 
author={Junior, W.S. and Handge, U.A. and dos Santos, J.F. and Abetz, V. and Amancio-Filho, S.T.},
title={Feasibility study of friction spot welding of dissimilar single-lap joint between poly(methyl methacrylate) and poly(methyl methacrylate)-SiO2 nanocomposite},
year={2014},
journal = {Materials and Design},
volume = {64},
pages = {246 - 250},
doi = {http://dx.doi.org/10.1016/j.matdes.2014.07.050},
abstract = {In this work, the feasibility of friction spot welding (FSpW) of a commercial poly(methyl methacrylate) (PMMA) GS grade and a PMMA 6 N/2 wt% silica (SiO2) nanocomposite was investigated. Single-lap joints welded at rotational speeds of 1000, 2000 and 3000 rpm were produced. The analysis of the joint microstructure and material flow pattern indicated that joints could be produced using all of the tested welding conditions. However, the joint produced at 1000 rpm displayed sharp weld lines (weak links), indicating insufficient heat input, while the welds produced at 3000 rpm displayed excessive plastic deformation (bulging of the bottom plate), volumetric defects and a lack of material mixing in the welded area, associated with higher heat input. The weld produced at a rotational speed of 2000 rpm resulted in improved material mixing, which was indicated by the absence of weld lines and volumetric defects due to the more correct heat input. This welding condition was selected for further mechanical testing. Lap shear testing of PMMA GS/PMMA 6 N/2 wt% SiO2 nanocomposite single lap joints welded at 2000 rpm resulted in an average ultimate lap shear strength of 3.9 ± 0.05 MPa. These weld strength values are equal to or better than those obtained using state-of-the-art welding techniques for PMMA materials, thereby demonstrating the potential of friction spot welding for thermoplastic nanocomposites.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.matdes.2014.07.050} (DOI). Junior, W.S.; Handge, U.A.; dos Santos, J.F.; Abetz, V.; Amancio-Filho, S.T.: Feasibility study of friction spot welding of dissimilar single-lap joint between poly(methyl methacrylate) and poly(methyl methacrylate)-SiO2 nanocomposite. In: Materials and Design. Vol. 64 (2014) 246 - 250. (DOI:  10.1016/j.matdes.2014.07.050)}}
@article{qi_effect_of_2014, 
author={Qi, F. and Staron, P. and Ventzke, V.},
title={Effect of Local Laser Surfacing on the Fatigue Crack Propagation Rate of Al-alloy 6056 and its Laser beam Weld},
year={2014},
journal = {Procedia Materials Science},
volume = {3},
pages = {1834 - 1840},
doi = {http://dx.doi.org/10.1016/j.mspro.2014.06.296},
abstract = {A new surfacing method based on the laser melting was investigated in this study in order to improve the fatigue crack propagation performance of high strength al-alloy and its laser beam weld. The main objective was to reduce the Fatigue Crack Propagation (FCP) rate and increase the fatigue life of Al-alloy welded structure. The fatigue crack propagation rate of Al-alloy 6056 was assessed using CT-100 specimen including base material, base material with Local Laser Surfacing (LLS), laser beam weld and laser beam weld with LLS respectively. The results show a significant reduction in fatigue crack propagation rate with LLS treatment because the fatigue crack retardation phenomenon is obvious when the fatigue crack close to or meet the laser surfacing lane. The fatigue life of BM with LLS specimen is higher than that of BM specimen. For the LBW, there shows same results. That is FCP rate of the specimen of laser beam weld with LLS treatment shows significant reduction compared with the specimen of laser beam weld without LLS treatment. The facture surface and microstructure of LLS and LBM were observed also in order to explain the basic mechanism of LLS improving the fatigue life.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.mspro.2014.06.296} (DOI). Qi, F.; Staron, P.; Ventzke, V.: Effect of Local Laser Surfacing on the Fatigue Crack Propagation Rate of Al-alloy 6056 and its Laser beam Weld. In: Procedia Materials Science. Vol. 3 (2014) 1834 - 1840. (DOI:  10.1016/j.mspro.2014.06.296)}}
@article{ventzke_onesided_ndyag_2014, 
author={Ventzke, V. and Riekehr, S. and Horstmann, M. and Haack, P. and Kashaev, N.},
title={One-sided Nd:YAG laser beam welding for the manufacture of T-joints made of aluminium alloys for aircraft construction},
year={2014},
journal = {Welding and Cutting},
volume = {13},
number = {4},
pages = {245 - 249},
abstract = {In aircraft construction, T-joints between aluminium alloys are manufactured either by riveting or by two-sided laser beam welding. This article describes one-sided Nd:YAG laser beam welding as a method of manufacturing skin/clip joints between the AA6156-T4/AA6013-T6 and AA2139-T3/ AA6013-T6 aluminium material combinations in T-joint designs. One fundamental problem associated with this procedure is the high porosity level in T-joints executed by means of one-sided laser beam welding. It is shown that the formation of pores is determined not only by the types of the aluminium alloys, the variations in the welding directions and the preparation of the joining faces but also by an excessive angle of incidence between the laser beam and the skin field. The laser beam must be transmitted in the bonding region between the clip and the skin field in order to reduce the porosity level by decreasing the angle of incidence.},
note = {Ventzke, V.; Riekehr, S.; Horstmann, M.; Haack, P.; Kashaev, N. : One-sided Nd:YAG laser beam welding for the manufacture of T-joints made of aluminium alloys for aircraft construction. In: Welding and Cutting. Vol. 13 (2014) 4, 245 - 249.}}
@article{enz_fracture_behavior_2014, 
author={Enz, J. and Iwan, H. and Riekehr, S. and Ventzke, V. and Kashaev, N.},
title={Fracture Behavior of a Laser Beam Welded High-strength Al-Zn Alloy},
year={2014},
journal = {Procedia Materials Science},
volume = {3},
pages = {1828 - 1833},
doi = {http://dx.doi.org/10.1016/j.mspro.2014.06.295},
abstract = {Laser beam welding of butt joints made of the newly developed high-strength Al-Zn alloy PA734 is conducted. A new approach of the Helmholtz-Zentrum Geesthacht is used to solve the problems of weldability and softening. The results of the fatigue, fatigue crack propagation and fracture toughness tests are discussed relating to the microstructural characteristics and the mechanical properties of the laser welded joints and compared to the base material. The obtained data can be used for the assessment of the damage tolerance behaviour of the laser welded integral aircraft structures made of Al-Zn alloys.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.mspro.2014.06.295} (DOI). Enz, J.; Iwan, H.; Riekehr, S.; Ventzke, V.; Kashaev, N.: Fracture Behavior of a Laser Beam Welded High-strength Al-Zn Alloy. In: Procedia Materials Science. Vol. 3 (2014) 1828 - 1833. (DOI:  10.1016/j.mspro.2014.06.295)}}
@article{scheider_a_damage_2014, 
author={Scheider, I. and Nonn, A. and Voelling, A. and Mondry, A. and Kalwa, C.},
title={A Damage Mechanics based Evaluation of Dynamic Fracture Resistance in Gas Pipelines},
year={2014},
journal = {Procedia Materials Science},
volume = {3},
pages = {1956 - 1964},
doi = {http://dx.doi.org/10.1016/j.mspro.2014.06.315},
abstract = {Investigation of running ductile fracture in gas transmission pipelines and the derivation of reliable crack arrest prediction methods belong to major topics in pipeline research. The yet available crack arrest criterion, known as the Battelle Two-Curve Method (BTCM), leads to reliable predictions up to grade X70 line pipe steels for which it has been validated. This includes specific limits in terms of mechanical properties, pressure and geometry. The application of this criterion to modern pipeline steels, i.e. especially grades X80 and beyond in combination with larger diameters and high pressure, has led to mispredictions of the BTCM. Hence, in order to ensure safe design of pipelines, new methods are required based on in depth knowledge and appropriate characterization of material resistance. This paper presents a procedure for the assessment of dynamic ductile fracture resistance based on combined experimental and numerical investigations. The procedure involves quasi-static and dynamic drop- weight tear testing (DWTT) on modified specimens with pre-fatigued crack for grades X65, X80 and X100 materials, and the application of cohesive zone (CZ) and Gurson-Tveergard-Needleman (GTN) models to describe ductile material damage. The damage model parameters are calibrated on basis of DWTT results and subsequently used to simulate dynamic crack propagation in a pipeline. The influence of material properties (strain hardening, toughness), pipe geometry, usage factor and decompression behaviour on ductile fracture propagation behaviour is studied and evaluated. The results will contribute to an enhanced understanding of major parameters controlling ductile fracture propagation and will help to establish a reliable procedure for safe design of new high-capacity pipelines with regard to crack arrest.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.mspro.2014.06.315} (DOI). Scheider, I.; Nonn, A.; Voelling, A.; Mondry, A.; Kalwa, C.: A Damage Mechanics based Evaluation of Dynamic Fracture Resistance in Gas Pipelines. In: Procedia Materials Science. Vol. 3 (2014) 1956 - 1964. (DOI:  10.1016/j.mspro.2014.06.315)}}
@article{junior_friction_spot_2014, 
author={Junior, W.S. and Emmler, T. and Abetz, C. and Handge, U.A. and dos Santos, J.F. and Amancio-Filho, S.T. and Abetz, V.},
title={Friction spot welding of PMMA with PMMA/silica and PMMA/silica-g-PMMA nanocomposites functionalized via ATRP},
year={2014},
journal = {Polymer},
volume = {55},
number = {20},
pages = {5146 - 5159},
doi = {http://dx.doi.org/10.1016/j.polymer.2014.08.022},
abstract = {In the present study, the feasibility of Friction Spot Welding (FSpW) of a commercial-grade poly(methyl methacrylate) (PMMA) (PMMA GS) and PMMA 6N/functionalized silica (SiO2) nanocomposites was investigated. The silica nanoparticles were functionalized via atom transfer radical polymerization (ATRP) with PMMA chains to achieve a uniform dispersion in the polymer matrix. The successful functionalization of silica nanoparticles with PMMA chains via ATRP was evaluated by ATR-FT-IR and TGA measurements. Rheological investigations of the silica nanocomposites showed a plateau of the storage modulus G′ at low frequencies (0.01–0.03 rad/s) as a result of elastic particle–particle interactions. Overlap friction spot welds consisting of PMMA GS and a 2 wt% SiO2-g-PMMA nanocomposite were successfully prepared and compared to spot joints of PMMA GS welded with PMMA 6N and PMMA 6N/silica nanocomposite with 2 wt% unfunctionalized silica nanoparticles. Raman mappings of selected areas of cross-sectional plastographic specimens revealed an increased mixing behavior between the two polymer plates in the case of PMMA GS/2 wt% SiO2-g-PMMA joints. Although the joints welded with PMMA 6N/silica nanocomposites showed a reduction of 22% in lap shear strength and 21% displacement at peak load compared with the neat PMMA spot welds, they can compete with other state-of-the-art PMMA welding techniques such as thermal bonding and ultrasonic welding, which indicates the potential of friction spot welding as an alternative fabrication technology for joining future nanocomposite engineering parts.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.polymer.2014.08.022} (DOI). Junior, W.S.; Emmler, T.; Abetz, C.; Handge, U.A.; dos Santos, J.F.; Amancio-Filho, S.T.; Abetz, V.: Friction spot welding of PMMA with PMMA/silica and PMMA/silica-g-PMMA nanocomposites functionalized via ATRP. In: Polymer. Vol. 55 (2014) 20, 5146 - 5159. (DOI:  10.1016/j.polymer.2014.08.022)}}
@article{hoppe_abinitio_modeling_2014, 
author={Hoppe, S. and Michl, A. and Weissmueller, J. and Mueller, S.},
title={Ab-initio modeling of electromechanical coupling at Si surfaces},
year={2014},
journal = {Journal of Applied Physics},
volume = {116},
number = {7},
pages = {073507},
doi = {http://dx.doi.org/10.1063/1.4893375},
abstract = {The electromechanical coupling at the silicon (100) and (111) surfaces was studied via density functional theory by calculating the response of the ionization potential and the electron affinity to different types of strain. We find a branched strain response of those two quantities with different coupling coefficients for negative and positive strain values. This can be attributed to the reduced crystal symmetry due to anisotropic strain, which partially lifts the degeneracy of the valence and conduction bands. Only the Si(111) electron affinity exhibits a monotonously linear strain response, as the conduction band valleys remain degenerate under strain. The strain response of the surface dipole is linear and seems to be dominated by volume changes. Our results may help to understand the mechanisms behind electromechanical coupling at an atomic level in greater detail and for different electronic and atomic structures.},
note = {Online available at: \url{http://dx.doi.org/10.1063/1.4893375} (DOI). Hoppe, S.; Michl, A.; Weissmueller, J.; Mueller, S.: Ab-initio modeling of electromechanical coupling at Si surfaces. In: Journal of Applied Physics. Vol. 116 (2014) 7, 073507. (DOI:  10.1063/1.4893375)}}
@article{li_effects_of_2014, 
author={Li, W.Y. and Fu, T. and Huetsch, L. and Hilgert, J. and Wang, F.F. and dos Santos, J.F. and Huber, N.},
title={Effects of tool rotational and welding speed on microstructure and mechanical properties of bobbin-tool friction-stir welded Mg AZ31},
year={2014},
journal = {Materials and Design},
volume = {64},
pages = {714 - 720},
doi = {http://dx.doi.org/10.1016/j.matdes.2014.07.023},
abstract = {The effects of rotational and welding speeds on the microstructure and mechanical properties of bobbin-tool friction stir welded (BT-FSW) Mg AZ31 were investigated. The results indicated that the thermo-mechanically affected zone (TMAZ) consisted of equiaxed grains, which were inconsistent with the deformed, rotated and elongated grains found in the TMAZs of bobbin-tool friction stir welded Al alloys and friction stir welded Al and Mg alloys. The average grain size increased as the ratio of the rotational speed to welding speed increased. Excellent welds with no degradation in hardness were produced using a low heat input. Mechanical tests revealed that the ultimate tensile strengths gradually increased with increasing welding speed while keeping the rotational speed constant. The rotational and welding speeds had only slight influences on the yield stress and fracture elongation.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.matdes.2014.07.023} (DOI). Li, W.Y.; Fu, T.; Huetsch, L.; Hilgert, J.; Wang, F.F.; dos Santos, J.F.; Huber, N.: Effects of tool rotational and welding speed on microstructure and mechanical properties of bobbin-tool friction-stir welded Mg AZ31. In: Materials and Design. Vol. 64 (2014) 714 - 720. (DOI:  10.1016/j.matdes.2014.07.023)}}
@article{vainio_orientation_distribution_2014, 
author={Vainio, U. and Schnoor, T.I.W. and Koyiloth Vayalil, S. and Schulte, K. and Mueller, M. and Lilleodden, E.T.},
title={Orientation Distribution of Vertically Aligned Multiwalled Carbon Nanotubes},
year={2014},
journal = {The Journal of Physical Chemistry  C},
volume = {118},
number = {18},
pages = {9507 - 9513},
doi = {http://dx.doi.org/10.1021/jp501060s},
abstract = {Carbon nanotube “forests” show great promise in a variety of applications, from supercapacitors to fuel cells, but the realization of such materials for functional devices relies on a better control over processing routes such that targeted structures and associated properties can be reproducibly obtained. The orientation distribution of the nanotubes is a critical structural property affecting both electrical and mechanical response, yet it remains a challenging characteristic to quantify. Small-angle X-ray scattering (SAXS) is a technique well suited to investigate the vertical alignment of nanotubes. Here we show that the orientation distribution obtained from SAXS is not satisfactorily represented by the normal distribution or the Lorentzian, which have been used until now. Instead, an excellent agreement between model and data is found with the generalized normal distribution (GND). Such quantification of the carbon nanotube alignment can be used as direct input in simulations for optimizing structure–property relations.},
note = {Online available at: \url{http://dx.doi.org/10.1021/jp501060s} (DOI). Vainio, U.; Schnoor, T.I.W.; Koyiloth Vayalil, S.; Schulte, K.; Mueller, M.; Lilleodden, E.T.: Orientation Distribution of Vertically Aligned Multiwalled Carbon Nanotubes. In: The Journal of Physical Chemistry  C. Vol. 118 (2014) 18, 9507 - 9513. (DOI:  10.1021/jp501060s)}}
@article{sarac_property_optimization_2014, 
author={Sarac, B. and Wilmers, J. and Bargmann, S.},
title={Property optimization of porous metallic glasses via structural design},
year={2014},
journal = {Materials Letters},
volume = {134},
pages = {306 - 310},
doi = {http://dx.doi.org/10.1016/j.matlet.2014.07.064},
abstract = {Systematization of material parameters is essential for property optimization. In this work, a gradient-extended continuum mechanical model implemented into a finite element code is utilized to analyze the influence of pore hierarchy on the overall mechanical response of porous metallic glasses. A spectrum of samples with randomized (stochastic) pore designs is comparatively studied with their periodic counterparts. It is shown that the pore design as well as the volume fraction has a strong effect on the mechanical response of the porous metallic glass structures. The results underline design aspects for certain applications.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.matlet.2014.07.064} (DOI). Sarac, B.; Wilmers, J.; Bargmann, S.: Property optimization of porous metallic glasses via structural design. In: Materials Letters. Vol. 134 (2014) 306 - 310. (DOI:  10.1016/j.matlet.2014.07.064)}}
@article{huetsch_a_study_2013, 
author={Huetsch, L.L. and Herzberg, K. and dos SantosJ.F. and Huber, N.},
title={A study on local thermal and strain phenomena of high-speed friction stir-processed Mg AZ31},
year={2013},
journal = {Welding in the world},
volume = {57},
number = {4},
pages = {515 - 521},
doi = {http://dx.doi.org/10.1007/s40194-013-0047-1},
abstract = {The increasing demand for low-weight structural materials yields a growing interest in Mg alloys. The aim of this work is to investigate the microstructural, thermal, and mechanical development of high-speed friction stir-processed Mg AZ31. The process parameters were developed with underlying preset to develop a fine-grained microstructure. Microstructural as well as hardness investigations were conducted. The energy input per unit length as well as the temperature evolution around the tool was predicted using finite element methods calibrated and backed up by temperature measurements. Local strain evolution analysis was conducted using digital image correlation (DIC) on tensile test. Process zone investigations have been conducted using microtensile tests. This study has shown that while maintaining constant weld quality, the energy input per unit length continuously decreased with increasing processing speed between 1 and 5 m/min, reached a threshold at higher speeds. Thermal analysis revealed temperatures between 470 and 300 °C directly under the tool depending on processing speed accompanied by a strong asymmetry between the advancing side (AS) and the retreating side. Hardness measurements showed an increase with increasing processing speed as well as a hardness peak development on the AS. DIC on tensile test confirmed the asymmetric strength distribution within the process zone. Microtensile test display a ductility increase of up to 85 % compared to the base material within the process zone.},
note = {Online available at: \url{http://dx.doi.org/10.1007/s40194-013-0047-1} (DOI). Huetsch, L.L.; Herzberg, K.; dos SantosJ.F.; Huber, N.: A study on local thermal and strain phenomena of high-speed friction stir-processed Mg AZ31. In: Welding in the world. Vol. 57 (2013) 4, 515 - 521. (DOI:  10.1007/s40194-013-0047-1)}}
@article{husser_determination_of_2013, 
author={Husser, E. and Clausmeyer, T. and Gersteyn, G. and Bargmann, S.},
title={Determination of average dislocation densities in metals by analysis of digitally processed TEM images- Bestimmung von durchschnittlichen Versetzungsdichten in Metallen durch Analyse digital bearbeiteter Transmissionselektronenmikroskopie-Aufnahmen},
year={2013},
journal = {Materialwissenschaft und Werkstofftechnik},
volume = {44},
number = {6},
pages = {541 - 546},
doi = {http://dx.doi.org/10.1002/mawe.201300027},
abstract = {This paper describes an effective and simple procedure to derive information about the dislocation density distribution in metals by applying standard techniques of digital image processing on gray scaled microstructure images obtained from transmission-electron microscopy. In a representative transmission-electron microscopy image, two local dislocation density values were investigated by classical methods and were used as input parameter for further processing. A correlation between dislocations and image intensities is assumed such that dark areas in microstructural images are seen as a dense concentration of dislocations. Then, the contrast is increased for each transmission-electron microscopy photography. In the next step, posterization, a gradation of tone, is applied to these images. From this, a pixel weighted average distribution of gray level correlated dislocation densities is obtained as well as an average value for a given set of images. The implementation of the several processing steps is done in Matlab employing graphical user interfaces.

Dieser Artikel zeigt eine effektive und einfache Methode auf, um Informationen über die Verteilung der Versetzungsdichte in Metallen durch Anwendung von Standardtechniken der digitalen Bildverarbeitung auf Grauwertbilder der Mikrostruktur zu gewinnen. Die Mikrostrukturbilder wurden mit Hilfe der Transmissionselektronenmikroskopie aufgenommen. Zwei lokale Werte für die Versetzungsdichte wurden durch Auszählung an einer repräsentativen Transmissionselektronenmikroskopie-Aufnahme des hier betrachteten Tiefziehstahls DC06 ermittelt und als Eingabewerte für die weitere Analyse verwendet. Basierend auf der Annahme, dass eine Korrelation zwischen der Anzahl an Versetzungen und der Intensität der Aufnahmen in der Hinsicht besteht, dass dunkle Zonen der Mikrostrukturbilder eine dichte Versetzungskonzentration darstellen, wurde zunächst der Kontrast einer jeden Transmissionselektronenmikroskopie-Aufnahme eines gegebenen Bildsatzes erhöht. Anschließend wurde eine Farbabstufung vorgenommen, für die dann jeweils die Bestimmung der Versetzungsdichten durch lineare Interpolation und Extrapolation unter Verwendung der lokal ermittelten Werte erfolgte. Hieraus ergeben sich Pixel-gewichtete Durchschnittswerte für die zu den Grauwerten korrelierenden Versetzungsdichten sowie ein Durchschnittswert für die gesamte Bildermenge. Die Implementierung der einzelnen Verarbeitungsschritte erfolgte in Matlab unter Verwendung einer grafischen Benutzeroberfläche.},
note = {Online available at: \url{http://dx.doi.org/10.1002/mawe.201300027} (DOI). Husser, E.; Clausmeyer, T.; Gersteyn, G.; Bargmann, S.: Determination of average dislocation densities in metals by analysis of digitally processed TEM images- Bestimmung von durchschnittlichen Versetzungsdichten in Metallen durch Analyse digital bearbeiteter Transmissionselektronenmikroskopie-Aufnahmen. In: Materialwissenschaft und Werkstofftechnik. Vol. 44 (2013) 6, 541 - 546. (DOI:  10.1002/mawe.201300027)}}
@article{kashaev_comparative_study_2013, 
author={Kashaev, N. and Horstmann, M. and Ventzke, V. and Riekehr, S. and Huber, N.},
title={Comparative study of mechanical properties using standard and micro-specimens of base materials Inconel 625, Inconel 718 and Ti-6Al-4V},
year={2013},
journal = {Journal of Materials Research and Technology : JMRT},
volume = {2},
number = {1},
pages = {43 - 47},
doi = {http://dx.doi.org/10.1016/j.jmrt.2013.03.003},
abstract = {To improve innovative joining and deposition technologies for the construction of dissimilar joints, precise knowledge of the local mechanical properties of materials must be obtained. In the present article a comparative study of the tensile properties and fatigue behaviour in case of flat standard and micro-specimens of base materials Inconel 625, Inconel 718 and Ti-6Al-4V was accomplished. The aim of the study was to develop an efficient method for the investigation of the local mechanical properties by the use of micro-specimens subjected to electro discharge machining treatment and to obtain reliable tensile and fatigue test results. By the miniaturization of specimens a significant effect of roughness on mechanical properties was obtained. By considering a correction for the effective load-bearing cross-section the data obtained from micro-specimens are within 3% error with respect to standard specimen results. The results showed that the proposed technique can be successfully used to determine the tensile and fatigue properties of a small material volume.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.jmrt.2013.03.003} (DOI). Kashaev, N.; Horstmann, M.; Ventzke, V.; Riekehr, S.; Huber, N.: Comparative study of mechanical properties using standard and micro-specimens of base materials Inconel 625, Inconel 718 and Ti-6Al-4V. In: Journal of Materials Research and Technology : JMRT. Vol. 2 (2013) 1, 43 - 47. (DOI:  10.1016/j.jmrt.2013.03.003)}}
@article{steglich_crashworthiness_of_2013, 
author={Steglich, D. and Bohlen, J. and Tian, X. and Riekehr, S. and Kashaev, N. and Bargmann, S. and Letzig, D. and Kainer, K.U. and Huber, N.},
title={Crashworthiness of Magnesium Sheet Structures},
year={2013},
journal = {Materials Science Forum, Light Metals Technology Conference, LMT 2013},
volume = {765},
pages = {590 - 594},
doi = {http://dx.doi.org/10.4028/www.scientific.net/MSF.765.590},
abstract = {A hollow rectangular profile, as an example of a typical structural component made of
magnesium alloy sheets has been built, tested and evaluated in order to assess its behaviour during
axial crushing. The profiles were joined from plane sheets of AZ31 and ZE10, respectively, by laser
beam welding and were then tested in compression. Numerical simulations have been conducted to
understand the complex interplay between hardening characteristics of the materials under
investigation, profile cross-section variation and energy absorption. The results from the compression
testing of the profiles show that the welds are not the source of damage initiation and failure. The
performance of the magnesium profiles in terms of dissipated specific energy is confirmed for small
and intermediate displacements to be comparable to that of aluminium profiles. For large
displacements, however, the shear-type failure mode of magnesium causes a sharp drop of the
crushing force and thus limits the energy absorption. These findings demonstrate the requirement for
an alloy and wrought magnesium process development specifically for crash applications which aims
at progressive hardening along with high ductility for improving the bending and shear behaviour.},
note = {Online available at: \url{http://dx.doi.org/10.4028/www.scientific.net/MSF.765.590} (DOI). Steglich, D.; Bohlen, J.; Tian, X.; Riekehr, S.; Kashaev, N.; Bargmann, S.; Letzig, D.; Kainer, K.U.; Huber, N.: Crashworthiness of Magnesium Sheet Structures. In: Materials Science Forum, Light Metals Technology Conference, LMT 2013. Vol. 765 (2013) 590 - 594. (DOI:  10.4028/www.scientific.net/MSF.765.590)}}
@article{ziehmer_examination_of_2013, 
author={Ziehmer, M. and Tschoepe, A. and Birringer, R. and Markmann, J.},
title={Examination of the Energy Phase Space of Mixed Copper Grain Boundaries by Orientation Imaging Microscopy (OIM) and Sphere-on-a-Plate Method},
year={2013},
journal = {Acta Materialia},
volume = {61},
number = {15},
pages = {5586 - 5594},
doi = {http://dx.doi.org/10.1016/j.actamat.2013.05.042},
abstract = {This article reports on an experimental study of the energy phase space of mixed copper grain boundaries by a combination of electron backscatter diffraction (EBSD) and the so-called sphere-on-a-plate method. Single crystal copper spheres with diameters of a few microns were sintered onto flat single crystal {1 1 1} copper plates, resulting in random initial grain boundary configurations. EBSD measurements together with an assumption about the grain boundary plane orientation were used for the determination of the five macroscopic degrees of freedom of the grain boundaries. The tilt and twist components of the grain boundaries were calculated making use of the interface plane scheme representation of grain boundaries. Upon annealing, the spheres rotated along gradients in the grain boundary energy phase space. Thus, points of the trajectories of single spheres could be recorded between the single annealing steps, allowing for tracing the path of single spheres towards and into energy minima regions. The results gathered from 13 spheres underline a strong complexity of the grain boundary energy phase space.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.actamat.2013.05.042} (DOI). Ziehmer, M.; Tschoepe, A.; Birringer, R.; Markmann, J.: Examination of the Energy Phase Space of Mixed Copper Grain Boundaries by Orientation Imaging Microscopy (OIM) and Sphere-on-a-Plate Method. In: Acta Materialia. Vol. 61 (2013) 15, 5586 - 5594. (DOI:  10.1016/j.actamat.2013.05.042)}}
@article{bargmann_on_energy_2013, 
author={Bargmann, S. and Favata, A. and Podio-Guidugli, P.},
title={On Energy and Entropy Influxes in the Green-Naghdi Type III Theory of Heat Conduction},
year={2013},
journal = {Proceedings of the Royal Society  A},
volume = {469},
number = {2152},
pages = {20120705},
doi = {http://dx.doi.org/10.1098/rspa.2012.0705},
abstract = {The energy-influx/entropy-influx relation in the Green–Naghdi Type III theory of heat conduction is examined within a thermodynamical framework à la Müller–Liu, where that relation is not specified a priori irrespectively of the constitutive class under attention. It is shown that the classical assumption, i.e. that the entropy influx and the energy influx are proportional via the absolute temperature, holds true if heat conduction is, in a sense that is made precise, isotropic. In addition, it is proved that influx proportionality cannot be postulated in general, because a counterexample can be given in the case of transversely isotropic conduction.},
note = {Online available at: \url{http://dx.doi.org/10.1098/rspa.2012.0705} (DOI). Bargmann, S.; Favata, A.; Podio-Guidugli, P.: On Energy and Entropy Influxes in the Green-Naghdi Type III Theory of Heat Conduction. In: Proceedings of the Royal Society  A. Vol. 469 (2013) 2152, 20120705. (DOI:  10.1098/rspa.2012.0705)}}
@article{klusemann_modeling_and_2013, 
author={Klusemann, B. and Bargmann, S.},
title={Modeling and simulation of size effects in metallic glasses with a non-local continuum mechanics theory},
year={2013},
journal = {Journal of the Mechanical Behavior of Materials},
volume = {22},
number = {1-2},
pages = {51 - 66},
doi = {http://dx.doi.org/10.1515/jmbm-2013-0009},
abstract = {The present contribution is concerned with the modeling and computation of size effects in metallic glasses. For the underlying model description, we resort to a thermodynamically consistent, gradient-extended continuum mechanics approach. The numerical implementation is carried out with the help of the finite element method. Numerical examples are presented and compared with existing experimental findings to illustrate the performance of the constitutive model. In this regard, the influence of the material length scale is investigated. It is shown that with decreasing sample size or decreasing material length scale, a delay of the shear localization is obtained. In addition, the tension-compression asymmetry observed in experiments is captured by the proposed model. Further, the rate-dependent behavior as well as the influence of the results to initial local defects are investigated.},
note = {Online available at: \url{http://dx.doi.org/10.1515/jmbm-2013-0009} (DOI). Klusemann, B.; Bargmann, S.: Modeling and simulation of size effects in metallic glasses with a non-local continuum mechanics theory. In: Journal of the Mechanical Behavior of Materials. Vol. 22 (2013) 1-2, 51 - 66. (DOI:  10.1515/jmbm-2013-0009)}}
@article{suhuddin_formation_of_2013, 
author={Suhuddin, U. and Fischer, V. and dos Santos, J.F.},
title={Formation of Intermetallic Compounds in Dissimilar Friction Spot Weld of Al to Mg Alloys},
year={2013},
journal = {Materials Science Forum, Light Metals Technology Conference, LMT 2013},
volume = {765},
pages = {731 - 735},
doi = {http://dx.doi.org/10.4028/www.scientific.net/MSF.765.731},
abstract = {In the present study, friction spot welding has been used for joining dissimilar AA5754 aluminum to AZ31 magnesium alloys. To get more insight into the microstructure, stop-action experimentation was employed. The welding cycle was forced to stop during the dwell time, and subsequently, the weld was quenched by pouring a mixed solution of ice and water to freeze the microstructure. Formation of the liquid phase leading to a formation of brittle intermetallic compound has been studied. Microstructural analyses reveal that formation of intercalated layers and a high density of grain boundaries induced by plastic deformation enhance the formation of eutectic structure during the welding process.},
note = {Online available at: \url{http://dx.doi.org/10.4028/www.scientific.net/MSF.765.731} (DOI). Suhuddin, U.; Fischer, V.; dos Santos, J.F.: Formation of Intermetallic Compounds in Dissimilar Friction Spot Weld of Al to Mg Alloys. In: Materials Science Forum, Light Metals Technology Conference, LMT 2013. Vol. 765 (2013) 731 - 735. (DOI:  10.4028/www.scientific.net/MSF.765.731)}}
@article{wang_catalytic_activity_2013, 
author={Wang, L.-C. and Zhong, Y. and Jin, H. and Widmann, D. and Weissmueller, J. and Behm, R.J.},
title={Catalytic activity of nanostructured Au: Scale effects versus bimetallic/bifunctional effects in low-temperature CO oxidation on nanoporous Au},
year={2013},
journal = {Beilstein Journal of Nanotechnology},
volume = {4},
pages = {111 - 128},
doi = {http://dx.doi.org/10.3762/bjnano.4.13},
abstract = {The catalytic properties of nanostructured Au and their physical origin were investigated by using the low-temperature CO oxidation as a test reaction. In order to distinguish between structural effects (structure–activity correlations) and bimetallic/bifunctional effects, unsupported nanoporous gold (NPG) samples prepared from different Au alloys (AuAg, AuCu) by selective leaching of a less noble metal (Ag, Cu) were employed, whose structure (surface area, ligament size) as well as their residual amount of the second metal were systematically varied by applying different potentials for dealloying. The structural and chemical properties before and after 1000 min reaction were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The catalytic behavior was evaluated by kinetic measurements in a conventional microreactor and by dynamic measurements in a temporal analysis of products (TAP) reactor. The data reveal a clear influence of the surface contents of residual Ag and Cu species on both O2 activation and catalytic activity, while correlations between activity and structural parameters such as surface area or ligament/crystallite size are less evident. Consequences for the mechanistic understanding and the role of the nanostructure in these NPG catalysts are discussed.},
note = {Online available at: \url{http://dx.doi.org/10.3762/bjnano.4.13} (DOI). Wang, L.-C.; Zhong, Y.; Jin, H.; Widmann, D.; Weissmueller, J.; Behm, R.J.: Catalytic activity of nanostructured Au: Scale effects versus bimetallic/bifunctional effects in low-temperature CO oxidation on nanoporous Au. In: Beilstein Journal of Nanotechnology. Vol. 4 (2013) 111 - 128. (DOI:  10.3762/bjnano.4.13)}}
@article{klusemann_analysis_and_2013, 
author={Klusemann, B. and Svendsen, B. and Bargmann, S.},
title={Analysis and comparison of two finite element algorithms for dislocation density based crystal plasticity},
year={2013},
journal = {GAMM-Mitteilungen},
volume = {36},
number = {2},
pages = {219 - 238},
doi = {http://dx.doi.org/10.1002/gamm.201310013},
abstract = {The purpose of the current work is the formulation and comparison of two finite element algorithms for a dislocation density based crystal plasticity model. We study multiscale inelastic materials whose behavior is influenced by the evolution of inelastic microstructure and the corresponding material or internal lengthscales. The work is an extension of the first investigation in Klusemann et al. [1] which was limited to a one-dimensional bar. In the γ -algorithm, the displacement u and glide system slips γα are global unknowns and determined via weak field relations. The non-dimensional densities of geometrically necessary dislocations ∼α are local quantities and solved for via a strong field relation. In the Q -algorithm, both the displacement uand dislocation densities ∼α are modeled as global, and the glide system slips γα as local. As it turns out, both algorithms generally predict the same microstructural behavior on a single crystal level. However, for a polycrystal the two solution strategies predict different material behaviors due to the formulation-dependent representation of the boundary conditions. The introduction of a boundary layer in the model leads to good agreement between both algorithms for single and polycrystal simulations.},
note = {Online available at: \url{http://dx.doi.org/10.1002/gamm.201310013} (DOI). Klusemann, B.; Svendsen, B.; Bargmann, S.: Analysis and comparison of two finite element algorithms for dislocation density based crystal plasticity. In: GAMM-Mitteilungen. Vol. 36 (2013) 2, 219 - 238. (DOI:  10.1002/gamm.201310013)}}
@article{wang_composites_of_2013, 
author={Wang, K. and Weissmueller, J.},
title={Composites of Nanoporous Gold and Polymer},
year={2013},
journal = {Advanced Materials},
volume = {25},
number = {9},
pages = {1280 - 1284},
doi = {http://dx.doi.org/10.1002/adma.201203740},
abstract = {Nanoporous gold made by alloy corrosion can be vacuum-impregnated with epoxy resin to produce a polymer-based nanocomposite that is reinforced by an interconnected network of metal nanostructures. The composite
is ductile in tension and compression, its strength considerably exceeds that of each of the constituent phases, and its electric conductivity reaches 1% of that of high-purity massive copper. The finding validates a
novel materials design strategy that exploits the trend of “smaller is stronger” in metal nanostructures by incorporating them into a bulk composite material.},
note = {Online available at: \url{http://dx.doi.org/10.1002/adma.201203740} (DOI). Wang, K.; Weissmueller, J.: Composites of Nanoporous Gold and Polymer. In: Advanced Materials. Vol. 25 (2013) 9, 1280 - 1284. (DOI:  10.1002/adma.201203740)}}
@article{rao_asymmetric_mechanical_2013, 
author={Rao, D. and Huber, K. and Heerens, J. and dos Santos, J.F. and Huber, N.},
title={Asymmetric mechanical properties and tensile behaviour prediction of aluminium alloy 5083 friction stir welding joints},
year={2013},
journal = {Materials Science and Engineering  A},
volume = {565},
pages = {44 - 50},
doi = {http://dx.doi.org/10.1016/j.msea.2012.12.014},
abstract = {The asymmetric material flow, severe plastic deformation and thermal cycle imposed on the base material during friction stir welding (FSW) result in unique microstructural development, which causes a gradient in local mechanical properties in the weld region. Micro-tensile and indentation testing were applied to determine the local mechanical properties in a friction stir welded joint. The local stress–strain curves exhibited a drastic change at the advancing side (AS) due to a steep gradient of mechanical properties. Finite Element Model (FEM) predictions of the tensile performance of the welded joints, based on the local mechanical properties measured by micro-tensile testing, were in very good agreement with the macro-tensile test data.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.msea.2012.12.014} (DOI). Rao, D.; Huber, K.; Heerens, J.; dos Santos, J.F.; Huber, N.: Asymmetric mechanical properties and tensile behaviour prediction of aluminium alloy 5083 friction stir welding joints. In: Materials Science and Engineering  A. Vol. 565 (2013) 44 - 50. (DOI:  10.1016/j.msea.2012.12.014)}}
@article{willumeit_magnesium_degradation_2013, 
author={Willumeit, R. and Feyerabend, F. and Huber, N.},
title={Magnesium degradation as determined by artificial neural networks},
year={2013},
journal = {Acta Biomaterialia},
volume = {9},
number = {10},
pages = {8722 - 8729},
doi = {http://dx.doi.org/10.1016/j.actbio.2013.02.042},
abstract = {Magnesium degradation under physiological conditions is a highly complex process where temperature, the use of cell culture growth medium and the presence of CO2, O2 and proteins can influence the corrosion rate and the composition of the resulting corrosion layer. Due to the complexity of this process, it is almost impossible to predict the parameters that are most important and whether some parameters have a synergistic effect on the corrosion rate.

Artificial Neural Networks are a mathematical tool that can be used to approximate and analyse non-linear problems with multiple inputs. In this work, we present the first analysis of corrosion data obtained using this method, which reveals that CO2 and the composition of the buffer system play a crucial role in the corrosion of magnesium, whereas O2, proteins and temperature play a less prominent role.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.actbio.2013.02.042} (DOI). Willumeit, R.; Feyerabend, F.; Huber, N.: Magnesium degradation as determined by artificial neural networks. In: Acta Biomaterialia. Vol. 9 (2013) 10, 8722 - 8729. (DOI:  10.1016/j.actbio.2013.02.042)}}
@article{szabo_friction_stir_2013, 
author={Szabo, R. and Bergmann, L. and dos Santos, J.F.},
title={Friction stir welding of structural steel S235 and S355},
year={2013},
journal = {Welding and Material Testing},
volume = {22},
number = {4},
pages = {3 - 7},
abstract = {High-quality, defect-free welds were successfully produced in S235 and S355 structural steels by friction stir welding. To explore the potential advantages injoining structural steels by FSW, the present study focuses on basic characterization of friction stir welded S235JR and S235JR plates. A remarkably fine-grained microstructure was observed in the stir zone for both materials by optical microscopy. Hardness measurements across the specific zones of the cross-section of the welds indicated higher values compared with base materials ones. The objective of this work was to demonstrate the feasibility of friction stir welding (FSW) for joining of structural steel.},
note = {Szabo, R.; Bergmann, L.; dos Santos, J.F.: Friction stir welding of structural steel S235 and S355. In: Welding and Material Testing. Vol. 22 (2013) 4, 3 - 7.}}
@article{qi_hierarchical_nestednetwork_2013, 
author={Qi, Z. and Weissmueller, J.},
title={Hierarchical Nested-Network Nanostructure by Dealloying},
year={2013},
journal = {ACS Nano},
volume = {7},
number = {7},
pages = {5948 - 5954},
doi = {http://dx.doi.org/10.1021/nn4021345},
abstract = {Applications of porous microstructures in functional materials often impose conflicting requirements on the pore size, which may be met by hierarchical structures that combine porosity on distinctly different length scales. Here we report an electrochemical dealloying strategy that yields bulk samples of porous gold with a hierarchical microstructure. A nanoscale network of solid ligaments forms the lower hierarchy level, which is nested within the geometrically similar, but much larger, network of the upper hierarchy level. Starting from a dilute solid solution of Au in Ag, controlled electrochemical corrosion yields nanoporous Ag–Au alloy as an intermediate product. Coarsening of the porous alloy creates the large ligaments of the upper hierarchy level. Those are then again dealloyed, which creates the fine ligaments of the lower hierarchy level. We show that the material exhibits enhanced charge transport kinetics while maintaining a large specific surface area.},
note = {Online available at: \url{http://dx.doi.org/10.1021/nn4021345} (DOI). Qi, Z.; Weissmueller, J.: Hierarchical Nested-Network Nanostructure by Dealloying. In: ACS Nano. Vol. 7 (2013) 7, 5948 - 5954. (DOI:  10.1021/nn4021345)}}
@article{bargmann_microscopic_temperature_2013, 
author={Bargmann, S. and Ekh, M.},
title={Microscopic temperature field prediction during adiabatic loading using gradient extended crystal plasticity},
year={2013},
journal = {International Journal of Solids and Structures},
volume = {50},
number = {6},
pages = {899 - 906},
doi = {http://dx.doi.org/10.1016/j.ijsolstr.2012.11.010},
abstract = {The problem of interest is grain-size-dependent hardening in polycrystalline metals. We study the multiphysics problem of heat conduction coupled to gradient crystal plasticity and investigate the temperature field on the grain level for adiabatic loading. The underlying equations for the thermomechanical coupling are derived for a crystal plasticity model with gradient hardening. The influence of the temperature field on misorientation of the slip directions between adjacent grains is investigated. Additionally, the influence of the loading velocity and the size of the grain structure are examined. Numerical simulations are presented and analyzed.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.ijsolstr.2012.11.010} (DOI). Bargmann, S.; Ekh, M.: Microscopic temperature field prediction during adiabatic loading using gradient extended crystal plasticity. In: International Journal of Solids and Structures. Vol. 50 (2013) 6, 899 - 906. (DOI:  10.1016/j.ijsolstr.2012.11.010)}}
@article{bargmann_remarks_on_2013, 
author={Bargmann, S.},
title={Remarks on the Green–Naghdi theory of heat conduction},
year={2013},
journal = {Journal of Non-Equilibrium Thermodynamics},
volume = {38},
number = {2},
pages = {101 - 118},
doi = {http://dx.doi.org/10.1515/jnetdy-2012-0015},
abstract = {The Green–Naghdi theory of heat conduction enjoys great research interest because it is developed in a very general way and because it is capable of accounting for thermal pulse transmission in a very general manner. In this paper, that theory is revisited, and some questions it leaves open are pointed out.},
note = {Online available at: \url{http://dx.doi.org/10.1515/jnetdy-2012-0015} (DOI). Bargmann, S.: Remarks on the Green–Naghdi theory of heat conduction. In: Journal of Non-Equilibrium Thermodynamics. Vol. 38 (2013) 2, 101 - 118. (DOI:  10.1515/jnetdy-2012-0015)}}
@article{abibe_mechanical_and_2013, 
author={Abibe, A.B. and Amancio-Filho, S.T. and dos Santos, J.F. and Hage, E.jr.},
title={Mechanical and failure behaviour of hybrid polymer–metal staked joints},
year={2013},
journal = {Materials and Design},
volume = {46},
pages = {338 - 347},
doi = {http://dx.doi.org/10.1016/j.matdes.2012.10.043},
abstract = {Structural applications that use multi-material structures in the transportation industry have increased in recent years. Weight reduction in order to avoid excessive emissions is the driving force of this trend. The current joining technologies for such complex structures have potential for engineering and performance improvement. This preliminary study shows an alternative joining method for hybrid structures, the so-called Injection Clinching Joining (ICJ) [Abibe et al., J Thermoplast Compos 2011;24(2): 233–49], based on the principles of staking, injection moulding, and mechanical fastening. The main objectives of the paper are to exploit the mechanical behaviour of overlap joints produced by this proposed method and assess its potential as an applicable technology. The measurements used in this research are optical and scanning electron microscopy, X-ray computer microtomography, lap-shear strength testing and in situ strain distribution. Different failure modes were found, depending on the joining conditions. Net tension failure had a brittle and catastrophic nature, while rivet pull-out presented a more desirable slow ductile failure mode. The joint strengths were good, ranging from 35.9% to 88.5% of the base material’s experimental ultimate tensile stress. Although there is a lack of studies on structural staking applications, this paper shows potential for these joining techniques and introduces ICJ as a potential focus of future research.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.matdes.2012.10.043} (DOI). Abibe, A.B.; Amancio-Filho, S.T.; dos Santos, J.F.; Hage, E.jr.: Mechanical and failure behaviour of hybrid polymer–metal staked joints. In: Materials and Design. Vol. 46 (2013) 338 - 347. (DOI:  10.1016/j.matdes.2012.10.043)}}
@article{shi_on_the_2013, 
author={Shi, B. and Mosler, J.},
title={On the macroscopic description of yield surface evolution by means of distortional hardening models: Application to magnesium},
year={2013},
journal = {International Journal of Plasticity},
volume = {44},
pages = {1 - 22},
doi = {http://dx.doi.org/10.1016/j.ijplas.2012.11.007},
abstract = {Texture evolution in polycrystals due to rotation of the atomic lattice in single grains results in a complex macroscopic mechanical behavior which cannot be reasonably captured only by classical isotropic or kinematic hardening in general. More precisely and focusing on standard rate-independent plasticity theory, the complex interplay at the microscale of a polycrystal leads to an evolving macroscopic anisotropy of the yield surface, also known as distortional or differential hardening. This effect is of utmost importance, if non-radial loading paths such as those associated with forming processes are to be numerically analyzed. In the present paper, different existing distortional hardening models are critically reviewed. For a better comparison, they are reformulated into the modern framework of hyperelastoplasticity, and the same objective time derivative is applied to all evolution equations. Furthermore, since the original models are based on a Hill-type yield function not accounting for the strength differential effect as observed in hcp metals such as magnesium, respective generalizations are also discussed. It is shown that only one of the resulting models can fulfill the second law of thermodynamics. That model predicts a high curvature of the yield function in loading direction, while the opposite region of the yield function is rather flat. Indeed, such a response can be observed for some materials such as aluminum alloys. In the case of magnesium, however, that does not seem to be true. Therefore, a novel constitutive model is presented. Its underlying structure is comparably simple and the model is thermodynamically consistent. Conceptually, distortional hardening is described by an Armstrong–Frederick-type evolution equation. The predictive capabilities of the final model are demonstrated by comparisons to experimentally measured data.},
note = {Online available at: \url{http://dx.doi.org/10.1016/j.ijplas.2012.11.007} (DOI). Shi, B.; Mosler, J.: On the macroscopic description of yield surface evolution by means of distortional hardening models: Application to magnesium. In: International Journal of Plasticity. Vol. 44 (2013) 1 - 22. (DOI:  10.1016/j.ijplas.2012.11.007)}}
@article{schnubel_retardation_of_2013, 
author={Schnubel, D. and Horstmann, M. and Huber, N.},
title={Retardation of fatigue crack growth in aircraft aluminium alloys via laser heating – Simulation based design optimisation},
year={2013},
journal = {International Journal of Structural Integrity},
volume = {4},
number = {4},
pages = {429 - 445},
doi = {http://dx.doi.org/10.1108/IJSI-08-2012-0020},
abstract = {Purpose – While normally the formation of thermally induced residual stresses is seen mainly as detrimental side effect from production processes like welding or casting, the well-directed introduction of thermal residual stresses can also be used as tool to retard fatigue crack growth (FCG). In the presented paper, the use of a defocused laser to modify the residual stress state, and by that to retard the FCG, is examined. The focus lies on the simulation-based optimisation of the heating line position for achieving a maximum fatigue life. The paper aims to discuss these issues.

Design/methodology/approach – In the presented work, the developed prediction methodology for the FCG coupling process simulation and subsequent fracture mechanics analysis is used to identify the optimum positioning of either one or two heating lines on a C(T)100 specimen that leads to a maximised total lifetime. Afterwards, the prediction results are validated experimentally for selected cases.

Findings – The predictions match the experiments within the experimental scatter indicating the correct identification of the optimum heating line positions. This demonstrates the large potential for reducing the experimental effort needed for design optimisation using the proposed strategy.

Originality/value – The used methodology of coupling of welding simulation with subsequent fracture mechanics analysis in order to optimise the FCG behaviour of structures is innovative and only very few published studies addressed parts of similar approaches.},
note = {Online available at: \url{http://dx.doi.org/10.1108/IJSI-08-2012-0020} (DOI). Schnubel, D.; Horstmann, M.; Huber, N.: Retardation of fatigue crack growth in aircraft aluminium alloys via laser heating – Simulation based design optimisation. In: International Journal of Structural Integrity. Vol. 4 (2013) 4, 429 - 445. (DOI:  10.1108/IJSI-08-2012-0020)}}
@article{campanelli_metallurgy_and_2013, 
author={Campanelli, L.C. and Suhuddin, U.F.H. and Antonialli, A.I.S. and dos Santos, J.F. and Alcantara, N.G. and Bolfarini, C.},
title={Metallurgy and Mechanical Performance of AZ31 Magnesium Alloy Friction Spot Welds},
year={2013},
journal = {Journal of Materials Processing Technology},
volume = {213},
number = {4},
pages = {515 - 521},
doi = {http://dx.doi.org/10.1016/j.jmatprotec.2012.11.002},
abstract = {Microstructural features were studied along the cross-section of AZ31 magnesium alloy friction spot welded joints made using different combinations of welding parameters. Static lap shear testing was performed to eva