New Bending Algorithm for Field-Driven Molecular Dynamics

A field-driven bending method is introduced in this paper according to the coordinate transformation between straight and curved coordinates. This novel method can incorporate with the periodic boundary conditions in analysis along axial, bending, and transverse directions. For the case of small bending, the bending strain can be compatible with the beam theory. Consequently, it can be regarded as a generalized SLLOD algorithm. In this work, the bulk copper beam under bending is analyzed first by the novel bending method. The bending stress estimated here is well consistent to the results predicted by the beam theory. Moreover, a hollow nanowire is also analyzed. The zigzag traces of atomic stress and the corresponding 422 common neighbor type can be observed near the inner surface of the hollow nanowire, which values are increased with an increase of time. It can be seen that the novel bending method with periodic boundary condition along axial direction can provide a more physical significance than the traditional method with fixed boundary condition

Grain orientation and dislocation patterns

International audienceDislocation patterns have been characterized by transmission electron microscopy and Kikuchi line analysis in pure, polycrystalline aluminium deformed in tension at room temperature in the strain range 0.05-0.34. The angular strain relationship of the dislocation boundaries, their scaling behaviour and the occurrence of similitude shows that two dislocation patterns coexist in all grains, however, with very different characteristics dependent on the grain orientation. An analysis of the hardening behaviour of the grains in the polycrystal and a comparison with single crystal behaviour show a similar strong correlation pointing to the slip pattern as a dominating factor both behind the microstructural evolution and the hardening. An analysis of operating slip systems has underpinned the division of the stereographic triangle based on the microstructural characterization and the hardening behaviour

Strain hardening behaviour and the Taylor factor of pure magnesium

Taylor orientation factors for strain hardening in textured and random polycrystals of magnesium were derived from the ratio of the strain hardening rates of polycrystals to that of single crystals deforming by equivalent polyslip. For polycrystals with textures that inhibit basal and prismatic slip while favouring pyramidal polyslip, the Taylor factor is estimated to be between 2.1 and 2.5, increasing to about 4.5 for randomly textured polycrystals. The micromechanics of strain hardening in polycrystals are discussed