ON GRAIN SIZE DISPERSION EFFECTS IM METALLIC POLYCRYSTALS AND INTERNAL LENGTHS ASSOCIATED WITH DISCRETE PLASTIC SLIP HETEROGENEITIES

摘要

Scale transition theories were developed to model the inelastic behaviour of metals in order to account for plastic heterogeneities associated with anisotropy due to crystallographic texture. This "textural" heterogeneity hides another one linked to grain size. First, we show the impact of grain size dispersion on the macroscopic yield stress and on the evolution of the internal fields within the material. Concurrently, in order to improve the local behaviour representation, a model based on "discrete" plastic slip heterogeneities is developed. In a spherical grain, the plastic field is then characterized by at least two internal parameters: grain radius and characteristic distance between slip heterogeneities considered to be dislocation glide loops. The results point out a natural grain size effect in contrast to classic Eshelby's solutions.