Formulation of damage evolution equation for elastic-plastic-damage materials in stress space
Kamiya Kunio; Murakami Sumio
Abstract:An irreversible thermodynamic theory for elastic-plastic-damage materials by use of damage potential expressed in stress space is formulated and its validity is discussed. By expressing Gibbs thermodynamic potential and the dissipation potential in terms of a second rank damage tensor D, a scalar damage variable b, Cauchy stress s and isotropic hardening parameter of plasticity r, constitutive and evolution equations for elastic-plastic-damage materials are first derived according to the constitutive theory of irreversible thermodynamics. Then, after discussing the essential features of the resulting equations, they are applied to the cases of uniaxial and torsional loadings. Finally, the changes in Young's modulus, Poisson's ratio and shear modulus due to damage development and the initial and the subsequent damage surface expressed in stress space are compared with the corresponding experimental results on the tubular specimen of spheroidized graphite cast iron. Key Words:elastic-plastic-damage, irreversible thermodynamics, Gibbs thermodynamics potential, constitutive equation, damage evolution equation, damage surface, spheroidized graphite cast iron