Crack Extension Induced by Thermal Stresses Associated with Uniform Heating in a Circle

Abstract

The time-dependent stress intensity factor of a semi-infinite crack has been obtained when an infinite plate is heated uniformly in a circle near the crack tip. The intensity depends on the heating location D and the radius R. But the radius dependence is small and the total amount of heat gives almost the same intensity as point heat as long as R/D remains small. This is preferable for cleavage cutting in which surface melting should be avoided. Glass plates were heated by an exposure of the CO₂ laser beam and crack opening displacements were measured by an interference method. The measured crack deformation corresponds well with the thermal stress analysis. At the onset of the crack extension, similar stress intensity was attained for the same plate thickness irrespective of the heating intensity and location.