Effects of grain size distribution and stress heterogeneity on yield stress of polycrystals: A numerical approach

This paper addresses the relation between the grain size distribution, the elastic stress field fluctuations and the description of incipient plasticity in polycrystals with local elastic anisotropy. We propose a numerical approach based on full-field computations on polycrystalline microstructures. The generation of microstructures with prescribed grain size distribution and grain shape is made by combining dense-sphere packing with Power diagrams. By using a local plastic criterion based on the stress field statistics, it is shown that the macroscopic Hall-Petch relation significantly depends on the grain size distribution and the stress heterogeneity. Previous results of the literature obtained with mean-field approaches are confirmed by our study.