Predicting Fatigue Growth of Pipeline Cracks With Non-Ideal Depth Profiles

Abstract The MAT-8 fracture model has been widely applied in the pipeline industry since it was first introduced in 2016. It was recently modified to handle burst pressure predictions in pipe joints with axial surface flaws with complex depth profiles. However, this recent innovation did not address the fatigue growth of a complex crack-like feature. The present article fills this knowledge gap. Fatigue crack growth was analyzed in finite element simulations of 50 complex crack features that have been reported by ILI vendors. Based on the finite element results, an analytical methodology for modeling fatigue growth of complex crack-like features has been developed, which can be directly utilized in a probabilistic framework. Further work is required to experimentally validate the Modified MAT-8 model, including the burst pressure predictions and the fatigue crack growth estimates for cracking features with non-ideal depth profiles. Nevertheless, the approach presented herein represents a material improvement in handing fatigue propagation in crack-like flaws, compared with current models that assume an elliptical crack that encompasses a complex flaw.