Variation of mixed modes stress intensity factors of an inclined semi-elliptical surface crack

In this paper, a singular integral equation method is applied to calculate the stress intensity factor along crack front of a 3D inclined semi-ellipti cal surface crack in a semi-infinite body under tension. The stress field i nduced by displacement discontinuities in a semi-infinite body is used as t he fundamental solution. Then, the problem is formulated as a system of int egral equations with singularities of the form r(-3). In the numerical calc ulation, the unknown body force doublets are approximated by the product of fundamental density functions and polynomials. The results show that the p resent method yields smooth variations of mixed modes stress intensity fact ors along the crack front accurately for various geometrical conditions. Th e effects of inclination angle, elliptical shape, and Poisson's ratio are c onsidered in the analysis. Crack mouth opening displacements are shown in f igures to predict the crack depth and inclination angle. When the inclinati on angle is 60 degree, the mode I stress intensity factor F-I has negative value in the limited region near free surface. Therefore, the actual crack surface seems to contact each other near the surface.