Thermal fracture studies in ceramic systems using an acoustic emission technique

An acoustic emission technique for measuring the failure time in thermal shock experiments is described. The technique offers a unique opportunity to measure the heat-transfer coefficient of the test system and hence, to obtain a fully quantitative measure of the peak surface stress generated during the test. Measurements on soda-lime glass have demonstrated that rapid thermal fracture in the material occurs when the surface stress attains a critical value equal to the propagation stress for the most deleterious surface flaw. The effects of slow crack growth on the failure time are also investigated and correlated with recently developed theory.