Three-dimensional elastic-plastic j-integral calculations for semielliptical surface cracks in a tensile plate

Using a finite element method, in conjunction with an equivalent domain integral approach, the elastic-plastic crack-tip J-integral is computed for semielliptical surface flaws in a plate under a remote tensile load. The computed elastic-plastic values of the J-integral are compared to the elastic ones. It is concluded that a linear elastic fracture mechanics approach can be used for semielliptical cracks of relative depth of a/t = 0.25 and aspect ratio of c/a ≦ 3, up to load levels of 0.9δ_y with an error of no more than 10% in the (equivalent) elastic-plastic stress intensity factor. A simple empirical equation for evaluating the elastic-plastic J-integral for surface flaws is proposed.