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

The Instability of Plastic Flow of Metals at Very Low Temperatures. II.

Evidence is presented to show that the load drops observed in most metals at very low temperatures arise from thermal instability rather than mechanical instability of the lattice. Measurements of the temperature rise are described.</jats:p

The Influence of Temperature and Strain Rate on the Flow Stress of Magnesium Single Crystals

The temperature and strain rate-dependence of the flow stress of magnesium single crystals was measured in the temperature range 1� 45-248 oK. Some incidental observations were also made on the form of the stress-strain curves and the appearance of Blip lines. The deformation characteristics show close similarity with those of the face-centred cubic metals.</jats:p

The Influence of Temperature and Strain Rate on the Flow Stress of Annealed and Decarburized Iron at Subatmospheric Temperatures

The influence of temperature and strain rate on the flow stress of annealed and decarburized iron in the stages of uniform deformation has been studied at temperatures down to 78 oK. The Cottrell� Stokes law is not obeyed in iron, and the results are explainable in terms of the strong Peierls-Nabarro force in this metal.</jats:p

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