The influence of a prolonged rest at room temperature on the activity of acoustic emission upon micro-indentation of preliminarily deformed MgO single crystals was investigated. It was found that the number of acoustic emission signals after the specimens have rested increased at low loads P (∼50g) applied to an indenter and decreased at high loads P (∼200g). The change observed in the activity of acoustic emission depends on the degree of preliminary deformation. It was assumed that the observed effects were associated with the difference between the sources of acoustic pulses: the main contribution to the activity of acoustic emission comes from the breakaway of dislocation pile-ups at low loads P and from the formation of microcracks and macrocracks at high loads.

The Influence of Rest on the Micromechanical Properties of Preliminarily Deformed MgO Single Crystals. R.P.Zhitaru, V.A.Rahvalov: Physics of the Solid State, 2007, 49[5], 883-6