On Crack Initiation Near Stress Sources with Weak Divergences

Analytical expressions are obtained for the configurational force and the value of the relaxation of the elastic energy during the initiation of a microcrack in a small neighborhood of an arbitrary singular stress source. When analyzing the conditions for crack initiation at sources with weak divergences, the concepts of instantaneous initiation of a finite-length crack were used. As a criterion for the initiation of such a crack, the simultaneous fulfillment of the force and energy conditions is considered. Within these concepts, in the configuration space of the system parameters (geometrical characteristics and strength of mesodefects and the value of external stress), the regions are determined where cracks can nucleate in the case of a combined mesodefect, which is a superposition of junction disclination dipole and a planar shear mesodefect. It is shown that the crack initiation is greatly facilitated by the loss of stability of a shear mesodefect.