A MECHANISM FOR PLASTICITY-INDUCED CRACK CLOSURE UNDER PLANE-STRAIN CONDITIONS

Plasticity-induced crack closure is associated with a wedge of materia l in the wake of a fatigue crack. A model is proposed to explain the d evelopment of this wedge under plane strain conditions. This model is based on the non-linearity of the crack path. If the plastic zone size is an order of magnitude or larger than the characteristic length of a crack deflection, then the plastic deformation changes the shape of both crack flanks in different ways. This causes a residual displaceme nt on the crack flanks. Different examples for the development of such plasticity induced wedges are shown.