An investigation on the cumulative law of damage

The damage of material is essentially manifested as microcracks and microcavities. The irreversible process of damage cumulation is the process of nucleation and propagation of microcracks and microcavities, which are plastic deformation. The optical correlativity of the material surface steadily decreases with the development of the microplastic deformation. This is the basis on which the method of laser speckle spectrum correlation is built. The method is applied to an analysis of the process of damage growth and we have come to the conclusion that the cumulation law of damage for steel and aluminium alloys cannot be expressed linearly. In fact, there are different damage rates in the whole process, which consists of three stages. (orig./RW)