Direct simulation of fatigue crack growth for arbitrary-shaped defects in pressure vessels

Abstract

An advanced technique has been developed by the authors to predict fatigue crack growth for longitudinal and circumferential planar defects with arbitrary shape in pressure vessels. This is based on the step-by-step integration of an experimental fatigue crack growth law at a set of points along the crack front, enabling the crack shape developed during the fatigue process to be predicted. The stress intensity factors along the crack front are calculated by a three-dimensional finite element method. Automatic regeneration of finite element models for propagating cracks designed for this technique makes the simulation technique highly efficient. In this paper, following a description of the principle of the technique, some typical crack geometries are investigated. These include external and internal surface longitudinal cracks, an embedded longitudinal crack, a twin crack configuration and two circumferential surface cracks. The results obtained are compared with both the widely used ASME XI and BSI PD6493 guidelines, and some discussion on the safe use of the two guidelines is made.