Impact and indenting damage of CVD-produced ZnS and ZnSe ceramics

Abstract

Time series of acoustic emission pulses were excited in ductile ZnS and ZnSe ceramics either by a falling weight or by indenting the Vickers pyramid. Energy distributions in emitted acoustical emission pulses were found to be random (Poisson-like) in the events of short (0.3-0.5 ms) impact forcing. In the case of the gradual (∼1 s) indenting, the energy distributions followed a power law typical for the self-similar structures appearing through long-range interactions between nucleating microcracks (scaling). In ductile materials, the rate of straining governs the dislocation motion. Provided enough loading time, such as in indenting experiments, the sliding dislocations form bunches, which serve as weak points for the crack nucleation. Given a tend to self-organizing in the ensemble of dislocations, the energy release in impeded cracking process (i. e. indenting) exhibits statistically ordered behavior.