Fundamental study on dislocation dynamics simulation of cyclic deformation

Fundamental aspects on the dislocation dynamics analysis of cyclic deformation of BCC iron single crystal were examined. To assume that the grain of the single crystal has a diameter of 10.0 μm, a grain boundary condition, which impedes the motion of dislocations, is applied. Then, the effects of the initial dislocation densities and the length of the dislocation sources, say Frank-Read source, on the mechanical response were examined. The difference of dislocation length with the same initial dislocation densities affects the magnitude of yield stress. The influence of the dislocation length on the yield stress is relatively small compared to the initial dislocation densities. The difference of the number of dislocations with the same initial dislocation length affects the slope of the stress-strain relationship in the elastic-plastic regime. Since the total displacement of dislocations contributing to the slip deformation varies with the number of dislocations, it could be found that the slope of the stress-strain relationship in the elastic-plastic regime is governed by the number of dislocations. The numerical result of the dislocation dynamics analysis of the cyclic deformation with a few numbers of cycles shows that the plastic strain can be generated by the evolution of dislocation structure, and the stress-strain relationship shows an elastic-perfectly plastic behavior.