Continuum damage mechanics

Summary

Continuum damage mechanics describes the gradual loss of stiffness and strength of a material caused by the growth of microcracks and voids. Instead of tracking each defect, it adds an internal variable, the damage, to the constitutive equations. In the simplest models the damage is a scalar $D$ between $0$ for the intact material and $1$ for complete failure. The damage reduces the effective load-carrying area, and its evolution is governed by a law that respects the second law of thermodynamics. The theory, started by Kachanov and Rabotnov for creep rupture, is used to predict the onset of macroscopic cracks in creep, fatigue and brittle failure.