MECHANISMS AND MODELS FOR LARGE-STRAIN HETEROGENEOUS PLASTICITY

Two features are of predominant importance for the large-strain plastic deformation of heterogeneous materials: the connectivity of the phases, and the spread of their strengths. When the softer phase is continuous and the harder phase is not, the non-uniformity of deformation is the greater, the greater the spread of strengths. When there are many hard inclusions, the altered flow patterns are significant far away from the particles, and effective-medium models are inapplicable. In cases where ''self-consistent'' models should apply, the main problem is the derivation of the interaction stiffness for grossly non-linear materials: it controls the relative spread of stresses and strains or strain rates. Reasons are given why, for the actual form of the constitutive relations, a large spread of stresses is more tolerable in a model than a large spread of strain rates.