On the superplastic flow under non-uniform stress–strain state

A procedure to identify the Region II of superplastic flow under non-uniform stress–strain state is suggested in this report. The plastic behaviour is described in terms of stress and strain rate tensors. The scalar invariants of these tensors are assumed to be related by a unique function describing structural superplasticity for the case of multiaxial loading. Stress and strain rate deviators are assumed to be proportional while the von Mises yield condition is used.