Finite element multi-impact simulations using a crystal plasticity law based on dislocation dynamics

The currently used finite element models utilize the crystal plasticity laws based on the dislocation dynamics to analyze possible microstructural surface changes (including crystal rotations and variations of the dislocation density) under multiple normal and oblique impacts. First, the evolution of a local misorientation field under a single normal impact, quantified by the kernel average misorientation, was studied both experimentally and theoretically. After that, the proposed crystal plasticity formulation was used to quantify the effect of the material microstructure on the residual compressive stress induced by multiple impacts. As expected, the value of the maximum compressive stress was not changed after few impacts. In addition, particular attention was paid to the evolution of the dislocation density and disorientations inside the grains. The obtained results indicate that in contrast to the normal impacts, the oblique impacts did not significantly modify the compressive residual stress, but strongly affected the metal microstructure near the surface in terms of its disorientation and dislocation density.