Strain-space plasticity formulation for hardening-softening materials with elastoplastic coupling

Abstract

Engineering materials such as concretes, rocks and soils exhibit a strong strain-softening behavior in the post-failure range, showing a significant elastoplastic coupling for the degradation of elastic modulus with increasing plastic deformation. Stress-space formulation of plasticity based on Drucker’s stability postulate for these materials encounters difficulties in modeling the softening/elastoplastic coupling behavior; strain-space formulation is therefore necessary for further progress. In this article we first introduce a general form of strain-space plasticity formulation which is somewhat similar to that developed previously by Yoder and Iwan. To account for the elastoplastic coupling effect, the conventional plasticity theory is combined with the fracturing theory of Dougill to give a more general form of strain-space formulation. Attempt is then made to apply the general theory to model the softening behavior of a concrete element failed in a mixed crushing/cracking mode.