A criterion for crack propagation from crack-tip

A new concept of strain energy along radius from crack tip within plastic zone is presented based on the analysis of deformations behavior of crack tip in terms of fracture mechanics and plastic mechanics,and a criterion of crack propagation is proposed.In order to avoid the singularities in strain energy integral in the criterion of crack propagation,a concept of critical intrinsic zone of crack propagation is introduced in this study.Through a comparison among the results with that of other theory,it is found that the criterion of crack propagation proposed is reasonable.