Effect of kinematic hardening on the yield surface evolution after strain-path change

Abrupt strain path changes without elastic unloading have been used to investigate the yield surface of sheet metals, both experimentally and theoretically. These investigations emphasized an apparent non-normality phenomenon, following such a strain-path change. Subsequently, these results inspired the development of plasticity models including non-associated flow rules and non-normality theories. In this study, this type of abrupt strain-path changes is investigated using kinematic hardening models in the context of associated plasticity. The aim is to emphasize the contribution of kinematic hardening ingredient to the apparent violation of the normality condition. The results show that kinematic hardening slope and curvature of the material have a strong influence to contribute to this apparent non-normality.