Pipe Girth Weld Residual Stress Intensity Factor Profiles for Structural Integrity Assessment

Abstract

The influence of the residual stress field in a welded structure on crack growth and fracture is commonly assessed through its contribution to the stress intensity factor (SIF) for the crack of interest. This contribution is most often calculated by assuming a bounding through-thickness residual stress profile for the specific type of weldment with an appropriate SIF solution for the crack location, shape and structure of concern. Although more realistic residual stress profiles for stainless steel pipe girth welds have been developed recently their use, in some cases, leads to an underestimate of the SIF. A new approach is developed for determining bounding SIF values for cracks in residual stress fields of stainless steel pipe girth welds. The forms of the proposed SIF profiles are based on recently published SIF solutions for cracks in periodic residual stress fields [1]. It is shown that the SIF profiles bound those based on a large database of residual stress measurements without being excessively conservative. The outcome is a simple new method for defining more realistic SIF profiles for use in structural integrity assessments of stainless steel pipe girth welds.