Features of crack propagation in the elastic field of wedge disclination combined with edge superdislocation

The parameters of a crack formed in the field of elastic stresses from a Somigliana dislocation, which is a superposition of a negative wedge disclination and an edge superdislocation, are analyzed. Analytical expressions are found out for the stress intensity factors at crack tips, describing their dependencies on the disclination strength, screening radius of its elastic field, Burgers vector of the superdislocation and crack parameters. Equilibrium crack configurations are calculated. It is shown that an increase in the disclination strength to a certain critical value leads to an abrupt increase in the crack size. In this case, a one-direction propagated crack located in the tensile stress zone of the superdislocation is transformed into a two-direction propagated crack located on both sides of the superdislocation, and the crack reaches sizes comparable with the screening radius of the elastic field of the disclination. At the initial stage, the crack is formed due to the field of elastic stresses from the superdislocation, and its further growth is carried out mainly due to the tensile elastic fields from the disclination. The dependence of the critical disclination strength on the Burgers vector of the superdislocation is obtained. It is concluded that the localization of dislocation and disclination charges in the same area of the structure leads to a synergistic effect in the formation of the microcrack.