If a subsurface flaw is located near a component surface, the subsurface flaw is transformed to a surface flaw in accordance with a subsurface-to-surface flaw proximity rule. The re-characterization process from subsurface to surface flaw is adopted in all fitness-for-service (FFS) codes. However, the specific criteria of the re-characterizations are different among the FFS codes. Recently, the authors have proposed a new subsurface-to-surface flaw proximity rule based on experimental data and equivalent fatigue crack growth rates. In this study, fatigue crack growth calculations were carried out for pipes with subsurface flaws, using the proposed subsurface-to-surface flaw proximity rule and the current proximity rule provided in the current JSME and ASME Section XI. Different pipe sizes, flaw aspect ratios and ligament distances from subsurface flaws to inner surface of pipes were taken into account. As the results, the current proximity rule gives less conservative fatigue lives, when the aspect ratios of the subsurface flaws are small.
Fatigue Crack Growth Calculations for Pipes Considering Subsurface to Surface Flaw Proximity Rules
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Katsumata, G, Li, Y, Hasegawa, K, & Lacroix, V. "Fatigue Crack Growth Calculations for Pipes Considering Subsurface to Surface Flaw Proximity Rules." Proceedings of the ASME 2015 Pressure Vessels and Piping Conference. Volume 1A: Codes and Standards. Boston, Massachusetts, USA. July 19–23, 2015. V01AT01A009. ASME. https://doi.org/10.1115/PVP2015-45880
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