FURTHER CONSTITUTIVE RESULTS IN FINITE PLASTICITY

Within the framework of a purely mechanical theory for finitely deforming elastic-plastic materials, it has been shown previously (1, 2) that strain-hardening behaviour may be characterized by a scalar function which involves all the constitu-tive response functions of the theory. In the present paper, it is demonstrated that this function is actually a scalar invariant of a certain fourth-order tensor which plays a fundamental role in the theory of plasticity. Also discussed are the matter of invertibility of the stress rate versus strain rate relation, certain consequences of a physically plausible work assumption (6) and some results which hold during per-fectly plastic behaviour. 1