Surface cracks in shells under different hoop stress distributions

An external surface flaw in a thin-walled shell subjected to various types of elementary hoop stress distributions is considered. The surface defect is assumed to lie on one of the principal curvature planes of the shell, and to present an elliptical-arc shape. The stress-intensity factors (SIFs) along the crack front for the above loadings on the crack faces are derived by applying the finite element method. Then approximate values of SIF in the case of a cracked pressure vessel are computed by employing the results for elementary stress distributions together with the superposition principle and the power series expansion of the actual hoop stress.