Material Instability due to Evolution of Microdamage

Abstract Concerning material instability due to evolution of microdamage, there are two significant problems: the evolution of damage and the behaviour at critical failure. For this sake, we performed a collaborative analytical, numerical and experimental study of the nucleation, growth and coalescence of microdamage and its relation to the fracture. In this paper, we provide a brief review of our recent results. We found that we can use a partial differential equation in phase space to describe the evolution of number density of ideal microdamage. For a viscous medium, continuum damage was found to have the forms similar to some empirical expressions. Strictly speaking, the above differential equation of damage evolution can not be extended to critical failure. Hence, we performed a series of numerical simulations. It was found that evolution induced catastrophe (EIC) plays a significant role in failure. The main features of EIC are as follows. This criticality is very sensitive to microscopic configuration of microdamage for a specified macroscopic fraction of damage and the failure should be described by means of probability function. This feature of the instability may explain unpredictable failure from sample to sample in a batch.