Fatigue crack paths in notched shells

An external surface flaw is assumed to be located at the root of a notch in a metallic double-curvature thin-walled shell subjected to an internal pressure. This defect presents an elliptical-arc shape with the ellipse aspect ratio changing during the whole crack propagation, as has experimentally been observed. An approximate expression of the stress-intensity factor along the crack front is deduced by applying the finite element method and the superposition principle. Then a numerical procedure is carried out to predict the crack growth for cylindrical and spherical shells under cyclic internal pressure. Some results are compared with those determined by other Authors for unnotched shells.