An assessment of stress intensity factors for surface flaws in a tubular member

In the safety assessment of pressure vessels and pipes with circumferential surface cracks, it is often necessary to consider fatigue crack propagation and fracture among the possible modes of failure. The stress intensity factors at crack tips are important parameters for estimating residual life and criticality. The purpose of this paper is to present a method to calculate the mode I stress intensities for semi-elliptical cracks in pipes. This method uses the finite element technique to analyse a crack but does not require the crack to be modelled explicitly. This method is ideal for use with either fatigue life calculations or use with structural optimisation processes. Accurate results are obtained using only a relatively small number of degrees of freedom without the need to explicitly mesh cracks. In this paper a range of examples are presented to demonstrate the accuracy of this method.