Reliability of Welded Joints With Short Fatigue Cracks

Abstract

This study investigates the reliability of a cracked welded T-joint typically found in offshore structures. In the initial stages of crack propagation, when the crack is very small, propagation rates have been found to vary from those determined using traditional linear elastic fracture mechanics, possibly resulting in significant differences in the predicted lifetime of a structure. This effect is shown in a reliability analysis that uses measurements of crack closure tests performed by other workers to predict the lifetime of a welded T-joint with a surface crack located at the toe of the weld. The reliability in terms of fatigue lifetime is calculated using Paris’ crack propagation equation based upon an effective stress intensity factor calculated with Newman and Raju’s formulation for a cracked flat plate and modified with a weld magnification factor. The obtained reliabilities are then compared to those found without short crack considerations.