ELASTOPLASTIC CONSTITUTIVE-EQUATIONS WITH EXTENDED FLOW RULES

The traditional elastoplastic constitutive equation with a single smoo th yield surface is extended so as to describe the dependency of the d irection of a plastic stretching on a stress rate or a stretching. Bes ides, the loading criterion for the extended constitutive equation is formulated. Further, it is shown that a direction of plastic stretchin g cannot be arbitrary but has to fulfill an inequality under the loadi ng criterion.