Effects of local damage on asymptotic stress field of a growing creep crack

A parametric study on the effects of local damage field on the crack-tip stress field of a growing Mode I creep crack is performed in the framework of Continuum Damage Mechanics (CDM). According to the results of creep crack growth analysis based on CDM and Finite Element Method, the damage distribution1-(D/D cr)=h(θ)rm represented by a power law function of the radiusr from the crack tip is postulated for the damage variableD. The damage effects are incorporated into the Norton creep law by means of the hypothesis of strain equivalence of CDM. The resulting two-point boundary value problems of differential equations for the growing creep cracks in the states of plane strain and plane stress are solved by means of a shooting method. For a given creep exponentn of the Norton law, the exponentp of the asymptotic stress field σ ij ∞r p is found to be governed by the exponentm of the power law damage distributionr m.