Fracture path emanating from a rapidly moving heat source—the effect of thermal shock waves under high rate response

Abstract

Instantaneous fracture paths emanating from a moving heat source on the surface of an infinite solid medium are investigated. As a first order treatment, the fracture path is approximated by the spatial loci of the material continua subjected to a maximum tensile stress (stress criterion) or a minimum strain energy density (energy criterion). The crack initiation at these locations is assumed to occur simultaneously and no evolution in crack growth is accounted for. By characterizing the thermomechanical field in terms of a thermal Mach number M which weighs the relative speed of the moving heat source with respect to the heat propagation speed in the solid, the fracture paths are obtained in the full range of M. In the subsonic range with M < 1, the emphasis is placed on the fracture paths in the transition of the thermal Mach number. The results predicted by the thermal wave and the classical diffusion models are compared. At the transonic and in the supersonic ranges with M ⩾ 1, the formation of thermal shock waves in the physical domain is focused and the fracture paths as well as the damage pattern in the neighborhood of the rapidly moving heat source are obtained. It is found that the thermal shock effects cannot be neglected when the material continua experience high rate changes of temperature and the failure patterns predicted by the stress and the energy criteria present much larger deviations than those in the problems with crack singularities.