Prefracture zone for longitudinal shear cracks in structured materials

Abstract

We obtain simple relations for the following critical fracture parameters of elastoplastic materials: the shear stresses, the prefracture zone length, and the stress intensity factor for mode III of fracture. There is a passage to the limit from a sufficient fracture criterion to a necessary fracture criterion as the prefracture zone length tends to zero. The critical stresses obtained from the necessary and sufficient criteria are substantially different. In the framework of the proposed model, the critical stress intensity factor obtained from the sufficient criterion depends on the grain diameter and the parameters of the τ-γ diagram of the material.