Interface crack extension at any constant speed in orthotropic or transversely isotropic bimaterials - II. Two important examples

Part I [Int. J. Solids Struct., 39, 1165-1182] gives exact general solutions for steady dynamic extension by a semi-infinite crack along the interface of dissimilar orthotropic/transversely isotropic half-spaces under in-plane loading. Crack speed is any constant value, and results are valid for all six possible relations between the four body wave speeds. These results are applied here to sub-critical interface crack extension, and to debonding from a rigid half-space at any constant speed. The former case demonstrates well-known phenomena-the minimum Rayleigh speed is critical, and complex conjugate eigenvalues cause the crack edge oscillatory/square-root singular behavior that implies interpenetration. Calculations for representative materials show that eigenvalue and stress intensity factor amplitude variation with crack speed is small except near the critical value. Results for the latter case complement those of other recent studies: Singular behavior vanishes for super-critical/subsonic crack speeds, although oscillations remain. For trans-sonic crack speeds, eigenvalues are real, singular behavior is no longer square-root, and interpenetration can still occur below a critical speed. Lines of displacement gradient discontinuity radiate from the crack edge, but can vanish at a critical speed. Calculations show that eigenvalue variation with crack speed is more pronounced than in the first case.