Modeling mixed hardening of alkali halides with a modified version of an internal state variables model

In the ductile regime of inelastic flow, alkali halides behave similarly to various metals. Their behavior is fully plastic, shows strong rate and history dependencies, and exhibits anisotropic hardening. In this paper, the authors present the most recent version of SUVIC, a viscoplastic model with internal state variables (ISV). After recalling the main features of alkali halides inelastic response, the modified equations of the model are presented. They are then used to represent the behavior of polycrystalline sodium chloride submitted to conventional triaxial compression (CTC) and reduced triaxial extension (RTE) tests, using results that highlight mixed (kinematic and isotropic) hardening of the material, hence showing a type of Bauschinger effect. A discussion follows.