A Physically Motivated Modification of the Strain Equivalence Approach

A phenomenological thermodynamic approach used for describing elasto-plasticity coupled with isotropic damage is considered. Using this approach it was recently shown by the authors that certain unwanted features exist in the plasticity-induced damage theories. This paper gives a suggestion on how to solve these issues. Based on physical arguments a simple modification of the postulate of strain equivalence is suggested. To show the effects of the modification, the von Mises plasticity model coupled with isotropic damage is used as a prototype model in the derivations. Both analytical considerations and simulations of a strain-controlled uniaxial model are performed. The results reveal that the modification of the postulate of strain equivalence gives promising results. In contrast to the postulates of strain equivalence and (complementary) energy equivalence, the present formulation predicts the elastic strain to vanish when failure takes place.