A generalized thermodynamically consistent distortional hardening model for Mg alloys

Abstract

In the current work, a generalized distortional hardening model is developed by assuming each part of dissipation non-negative. More precisely, quadratic forms are assumed for dissipation and thermodynamical consistency is fulfilled naturally. In order to balance the contributions of isotropic and distortional hardening into dissipation, a weighting coefficient w is introduced in contrast to the work in Feigenbaum and Dafalias (2007). It is found that the saturation directions of distortional hardening are governed by this coefficient w, which is related with deformation modes. In particular, by setting the coefficient w = 2, the current generalized model recover to the one based on convex plastic potential, cf. Shi and Mosler (2013), and thus Armstrong–Frederick type distortional hardening law is obtained. The predictive ability of the current distortional hardening model is verified by comparison with experimental observations in three cases: stress-strain behaviours along different directions, biaxial tensile test and biaxial compression test. The evolution of normalized yield surfaces for the three cases is briefly discussed.