Development and Evaluation of Improved Model for Engineering Critical Assessment of Pipelines

In past work, the authors developed a very useful model for engineering critical assessment (ECA) of pipelines with stress corrosion cracking (SCC). That model uses the effective area method to characterize the crack-depth profile along with flow strength and fracture toughness failure criteria. In the current work, the model was improved in four areas. Tearing instability was added to the fracture toughness failure criteria, formulations for computing values of the J integral for surface cracks were improved, interaction criteria were developed for co-planar flaws, and relationships for estimating values of the strain-hardening exponent were developed. To help validate the improved model, J fracture toughness tests were conducted using compact-tension (CT) specimens, and burst tests were conducted on pipe samples with large flaw length-to-depth ratios.