Plane stress elastic-plastic fracture criteria and constraint intensity in crack tip regions

Both experimental and finite element methods have been used to study thin plate elastic-plastic fracture criteria for different specimen geometries with various crack depths. It was found that the critical values of J-integral at initiation were independent of specimen geometries and crack depths and can be considered as the material constants, while the stress-strain fields in the crack tips of various specimen geometries with different crack depths were in better agreement with the HRR solution in the plane stress case because the constraint intensity in crack tip regions required by the HRR solution, which is very low in the plane stress case, had been met by those in thin plates of various specimens.