L51842 Strain Criteria for the Assessment of Girth Weld Defects

This is the first project in a multi-year effort intended to develop alternative defect acceptance criteria for pipelines experience high longitudinal strains. The strain capacity of girth welds containing welding defects is investigated using numerical analysis with comparison to experimental data. The key deliverables of this project are (1) a three-region strain design diagram, and (2) a set of parametric equations allowing the computation of allowable strains with the input of defect depth, defect length, CTOD (Crack Tip Opening Displacement) toughness, and weld strength mismatch. The three-region strain design diagram provides a quick method to determine if a large strain design is possible. The parametric equations can be used to provide a rough estimate of strain limits for a given set of input parameters.