3 results
Search Results
Now showing 1 - 3 of 3
- ItemHigh strength nanocrystalline Cu–Co alloys with high tensile ductility(Cambridge : Cambridge University Press, 2018) Bachmaier, Andrea; Rathmayr, Georg Benedikt; Schmauch, Jörg; Schell, Norbert; Stark, Andreas; de Jonge, Niels; Pippan, ReinhardA supersaturated single-phase Cu–26 at.% Co alloy was produced by high-pressure torsion deformation, leading to a nanocrystalline microstructure with a grain size smaller than 100 nm. The nonequilibrium solid solution decomposed during subsequent isothermal annealing. In situ high-energy X-ray diffraction was used to map changes linked to the separating phases, and the development of a nanoscale Cu–Co composite structure was observed. To gain further information about the relationship of the microstructure and the mechanical properties after phase separation, uniaxial tensile tests were conducted on as-deformed and isothermally annealed samples. Based on the in situ diffraction data, different isothermal annealing temperatures were chosen. Miniaturized tensile specimens with a round cross section were tested, and an image-based data evaluation method enabled the evaluation of true stress–strain curves and strain hardening behavior. The main results are as follows: all microstructural states showed high strength and ductility, which was achieved by a combination of strain-hardening and strain-rate hardening.
- ItemPerspective on statistical effects in the adhesion of micropatterned surfaces(Melville, NY : American Inst. of Physics, 2021) Booth, Jamie A.; Hensel, RenéBioinspired micropatterned adhesives have attracted extensive research interest in the past two decades. In modeling the performance of these adhesives, the common assumption has been that the adhesive strength of each sub-contact is identical. Recent experiments, however, have shown that interfacial defects of different characters lead to a distribution of the adhesive strength within a fibrillar array. Based on experimental observations of detachment events, a statistical model for the distribution of the local adhesive strength and the resulting performance of a micropatterned adhesive are presented. This approach constitutes a paradigm shift, providing better understanding of micropatterned adhesives under real conditions. Examples presented include the prediction of unstable detachments in compliant systems. Future directions are discussed, including the extension of the statistical approach to non-uniform loading and rate-dependent effects, the contribution of suction to adhesion and aging of contacts over specific time periods, as well as the necessity for a more in-depth understanding of defect formation considering surface roughness and other imperfections in the system.
- ItemPlastic Deformation Modes of CuZr/Cu Multilayers([London] : Macmillan Publishers Limited, part of Springer Nature, 2016) Cui, Yan; Abad, Oscar Torrents; Wang, Fei; Huang, Ping; Lu, Tian-Jian; Xu, Ke-Wei; Wang, JianWe synthesized CuZr/Cu multilayers and performed nanoindentation testing to explore the dependence of plastic deformation modes on the thickness of CuZr layers. The Cu layers were 18 nm thick and the CuZr layers varied in thickness from 4 nm to 100 nm. We observed continuous plastic co-deformation in the 4 nm and 10 nm CuZr − 18 nm Cu multilayers and plastic-induced shear instability in thick CuZr layers (>20 nm). The plastic co-deformation is ascribed to the nucleation and interaction of shear transformation zones in CuZr layers at the adjacent interfaces, while the shear instability is associated with the nucleation and propagation of shear bands in CuZr layers. Shear bands are initialized in the CuZr layers due to the accumulated glide dislocations along CuZr-Cu interfaces and propagate into adjacent Cu layers via slips on {111} plane non-parallel to the interface. Due to crystallographic constraint of the Cu layers, shear bands are approximately parallel to {111} plane in the Cu layer.