ABSTRACT
In the chapters devoted to elastoplasticity theory (presented here by B.Loret) we have seen that a basic assumption of this theory is the decomposition of incremental strain into a reversible (elastic) part and an irreversible (plastic) part. This decomposition is not at all an obvious fact, and some micromechanical considerations (Krawietz23) for assemblies of grains seem to indicate that it is not generally possible to separate these two parts of an incremental strain. Anyway the existence of plastic irreversibilities implies nonlinearity of the dε versus dσ relationship. This non-linearity is described in elastoplastic theories with a unique potential by two different constitutive tensors linking dε to dσ, one being related to loading and the other to unloading.
