Coupled fracture mode associated with anti-plane loading of cracks and notches

Abstract

The purpose of this paper is to investigate by means of the 3D Finite Element method a coupled fracture mode generated by anti-plane loading of a straight through-the-thickness crack in a linear elastic plate. This coupled fracture mode represents one of three-dimensional phenomena, which are currently largely ignored in numerical simulations and failure assessment of structural components weakened by cracks. It arises due to the boundary conditions on the plate free surfaces, which negate the transverse shear stress components corresponding to classical mode III. Instead, a new singular stress state in addition to the well-known 3D corner singularity is generated. This singular stress state (or coupled fracture mode) can affect or contribute significantly to the fracture initiation conditions. The coupled singular mode exists even if the applied anti-plane loading produces no singularities (K III = 0). In this case there is a strong thickness effect on the intensity of the coupled fracture mode.