Effects of crystal plasticity on materials loaded at high pressures and strain rates

A crystal plasticity model is used to examine the effects of grain microstructure on the local deformation of metals subjected to high pressure and high strain rate loading characteristic of ballistic impact, explosive loading and laser ablation. The crystal elastic moduli are pressure dependent to capture the large volume strains properly and to enable evolution of shocks from steep pressure gradients. Results are obtained for a normal incidence pressure wave and a pressure wave traveling parallel to the metal surface. The results show that regions of nonuniform strain, characterized by patchy bands, can develop in the wake of the pressure wave. The magnitude and extent of the bands depends on the grain structure and the width of the zone over which the pressure rises. A steep pressure gradient produces a small process zone and leaves little chance for strain redistribution.