Crack propagation under constant deformation and thermal stress fracture

Abstract

An analogy is drawn for crack propagation in brittle solids under constant deformation (strain) and under thermal shock. Following the original approach by Berry it is shown theoretically that under constant deformation an initially short crack, unstable at a critical strain, propagates to a new length which requires a finite increase in strain before it will become unstable again. Similar behavior is expected under conditions of thermal shock where an initially short crack, unstable at a critical temperature difference, propagates to a new length such that a finite increase in temperature difference is required before the crack will again continue to propagate. Relative changes in strength as a result of this type of crack behavior are predicted and verified by experimental results for two industrial polycrystalline aluminum oxides subjected to thermal shock by means of a water quench.