Effect of isotropic damage evolution on (visco)plasticity

Abstract

Two main approaches are used to model the effect of damage evolution on the behavior of structural materials in the frame of CDM theory. In case of a weak coupling between damage and deformation processes, the effect of material damage on the elastic properties is disregarded. In this sense a coupling is established by introducing the damage variables (scalar or tensor) into the constitutive equation of the continuum solid when the effective state variables concept is used (cf. Kachanov, 1958, 1986; Rabotnov, 1968, 1969; Leckie and Hayhurst, 1973, 1974; Hayhurst, 1972, 1983, etc.). In case of a fully (strong) coupled approach, damage evolution affects both elastic properties of the material (stiffness and compliance) and inelastic response (cf. Chaboche, 1977, 1978, 1993; Cordebois and Sidoroff, 1979, 1982; Lemaitre, 1984, 1992; Litewka, 1985, 1986; Murakami and Kamiya, 1987 to mention only some of them). In this chapter the first approach is discussed when the classical strain equivalence principle is used to define the effective stress in Lemaitre’s sense (Lemaitre, 1971) and the isotropic (scalar) damage variables are selected to legislate an experimentally fitted damage evolution law.