Prediction of the yield surface evolution and some apparent non-normality effects after abrupt strain-path change using classical plasticity

The two-stage abrupt strain path change method is used to investigate the subsequent yield surface evolution, as predicted by associated J(2) plasticity models. Experimental results from the literature have revealed several specificities of the yield surface evolution following such a strain path change, including formation of a vertex and apparent non-normality. The current study showed that some features of this behavior can be simulated using models based on associated plasticity. Kinematic hardening had the most important effect, together with rate sensitivity and elasticity. The results suggest that some apparent violation of the normality condition can result from the combined effects of kinematic hardening, rate sensitivity and elasticity, even when the normality rule is built into the model.