Numerical simulation of surface crack propagation considering the crack closure effects and the three-dimensional stress constraints

It is assumed that the shape of the surface crack keeps semi-ellipse during propagation under mode-I loading. Then the stress intensity factor along the semi-elliptical crack front can be evaluated by use of the Newman and Raju's formula. An equivalent thickness conception is proposed to consider the crack closure effects and the three-dimensional stress constraints along the crack front by use of the theory obtained for the straight through thickness crack. Based on the Elber's fatigue-crack-closure theory, a surface-crack-propagation model is developed to simulate crack propagation numerically, investigate the evolution of the shape-ratios and calculate the fatigue life. It shows good agreements to compare the numerical predictions with the available experimental results.