Underlying fracture trends and triggering on Mode-II crack branching and kinking for quasi-brittle solids

A geometrical model on multiple cracks initiation from boundary with singular stress fields has been proposed for the fracture analysis of Mode-II crack. The conservation law has been explored utilizing a partial integral path, from which an analytical solution of the energy release rate for multiple cracks initiation from a crack tip has been established. Some underlying fracture trends of cracks initiation from a crack tip, including crack side-branching and crack kinking, for quasi-static Mode-II deformation have been theoretically investigated, which implies actually some degree of instability for Mode-II fracture. The K-based criterions and fracture toughness for Mode-II crack side-branching and kinking have been defined. The fracture configurations of crack side-branching and kinking under Mode-II loading and corresponding fracture toughness predicted by the present modelling agree well with the experimental observations on the rock fracture reported in the literatures.