Damage Localization--A Precursor to Failure

This paper reviews the concept of damage localization and its application to time-independent (quasi-static) and time-dependent processes in heterogeneous materials. For quasi-static process in a heterogeneous material with Weibull distribution, damage can be expressed by a function of state variable. Accordingly, the criterion for damage localization depends on Weibull modulus m. In particular, damage localization can appear even though stress gradient remains fixed and it is closely related to strain localization. For time-dependent process, damage evolution law can be expressed by a function of stress and damage f(sigma,D). Accordingly, the criterion for damage localization can be expressed by f(D)gf/D. Provided damage evolution law can be expressed by kinetics of microdamage, it is found that intrinsic Deborah number D* plays a key role in damage localization. The criterion for damage localization has been applied to two extremes of time-dependent processes: spallation under wave loading and creep.