Experimental Identification of Kinematic and Isotropic Hardening in Rocksalt

ABSTRACT: In recent years, internal state variable models have gained popularity for describing the behavior of rocksalt. Among the various advantages of such models, the possibility to distinguish between kinematic and isotropic hardening phenomena is of the outmost importance, as physical (microscopic) evidences clearly show that both aspects must be considered in properly formulated constitutive equations. However, if the mixed nature of hardening is fairly well established from the micromechanical point of view, it is usually not clear how one should proceed to separate the components of hardening from macroscopic test results. In this paper, the authors present a general approach aimed at obtaining experimentally these informations from laboratory tests on rocksalt samples. The proposed procedure is based on the use of triaxial compression tests. Using schematic and experimental results on rocksalt, it is shown how such tests can be used to isolated the kinematic and isotropic components. A previously developed model is used to illustrate the procedure.