Effects of pipe steel heterogeneity on the tensile strain capacity of a flawed pipeline girth weld

An accurate estimate of the tensile strain capacity of flawed girth welds is essential for the safe use of pipelines in harsh environments. Current strain-based flaw assessments neglect the unavoidable presence of strength heterogeneity between two connected pipes. This paper describes and quantifies the resulting effects on strain capacity. A theoretical framework predicts a remarkable sensitivity, which depends on the failure location (whether in the weld or base metal). A finite element study critically validates the predicted results. Probabilistic analysis reveals that pipe steel heterogeneity should be taken into account to allow for accurate evaluations of tensile strain capacity.