Full Size Fatigue Crack-Growth Testing for Girth Welds
Fatigue crack-growth modeling has a significant impact in establishing defect acceptance criteria for the inspection of fracture-critical, girth-welded components, such as risers and tendons. ExxonMobil has developed an experimental technique to generate crack-growth data, in actual welded tubulars, that account for the particular material properties, geometry, and residual stresses. The technique is fully compatible with conventional fracture mechanics models. It uses a series of pre-designed notches made around the welds on a production quality, full-scale specimen that is tested efficiently in a resonant fatigue setup. The crack development from notches is monitored during testing and evaluated post-mortem. Given its simplicity and high loading frequency, the technique provides growth data germane to the component at hand at a lower cost and faster than standard, small-scale tests.