Diffraction of a plane SH-wave causes semi-infinite mode III crack extension in an unbounded linear elastic solid. The solid is nonorthotropic, with a single plane of material symmetry that is perpendicular to the crack edge. The crack plane itself lies at an arbitrary angle to the axes of material symmetry, the SH-wave direction is largely arbitrary, and extension is not necessarily instantaneous or at a constant speed. An exact transient study produces the fracture energy release rate, and uses a full-field analytical solution to derive the dynamic stress intensity factor on any plane radiating from the moving crack edge. A crack path stability analysis of the factor indicates that crack extension in the original plane can occur in directions associated with maximum and minimum values of the shear wave speed. The energy release rate for such extensions shows that, if an isotropic solid subjected to the same type of loading has the same specific fracture energy, then the nonorthotropic solid may fracture first.
Transient Response of an Inhomogeneous Elastic Solid to an Impulsive SH-source : Variable SH-wave Velocity