AN IRREVERSIBLE THERMODYNAMICS THEORY FOR ELASTIC-PLASTIC-DAMAGE MATERIALS

Constitutive and damage evolution equations for elastic-plastic-damage materials are developed based on the irreversible thermodynamics theo ry. The internal state of materials is described first by an isotropic hardening variable r, a second rank symmetric damage tensor D and a s calar damage variable beta related to the further development of the d amage. The effect of crack closure under compression is expressed by i ntroducing a modified elastic strain tenser. The Helmholtz free energy rho psi is decomposed into the terms related to global elastic deform ation of the damaged materials, local elastic distortion due to plasti c deformation and that of the surface energy generated by the material damage. A dissipation potential function in the space of the conjugat e forces of the internal state variables is expressed as the sum of th e plastic and the damage pan. The constitutive and the damage evolutio n equations resulting from these potentials are applied to elucidate t he damage process of tubular specimens of spheroidized graphite cast i ron under tension and torsion. (C) Elsevier, Paris.