HARDNESS LAW FOR INELASTIC DEFORMATION

Certain formulations of elastic-viscoplastic constitutive equations lead to inelastic deformations being governed by a functional relation between the plastic deformation rate and the stress. A parameter that appears in certain forms of this equation can be interpreted as an internal variable measure of the overall resistance of the material to plastic flow. In this paper, it is taken to be a second order tensor and designated the hardness stress." A procedure for calculating changes in the hardness stress parameter for general multiaxial loading histories is proposed in this paper. These evolutionary equations lead to induced plastic anisotropy. Stress-strain relations that would be predicted by this procedure appear to be consistent with experimental results for various multiaxial loading histories including proportional and non-proportional cyclic loading. © 1978."