Acoustic response and fracture mechanics of granite subjected to thermal and stress cycling experiments

Abstract

Westerly granite displays a thermal analogue to the stress memory (Kaiser) effect when heated in slow cycles to consecutively higher temperatures in the range from 20/sup 0/ to 500/sup 0/C. The stress intensity factor (K/sub I/) dependence of crack velocity and acoustic emission rates for single tensile cracks measured under room conditions are not much influenced by heat-treatment. The critical stress intensity factor is reduced by heat-treatment in response to increases in the bulk micro-crack density. Amplitude distributions vary with K/sub I/ in a similar manner to that noted in non-heat-treated specimens, except after heating to 500/sup 0/C. Single tensile macrocracks generally show a stress intensity factor memory effect but that memory is lost at the onset of significant macrocrack extension.