Fatigue failure is a time-delayed failure that is one of the major threats to the pipeline integrity. For crack-like gouges in dents, the crack grows due to pressure cycling and eventually fails by fatigue. This work, which was funded by PRCI via Project MD-4-16, developed a viable engineering approach and a pragmatic fatigue model for predicting fatigue life of dents and gouges in pipelines. In particular, an equivalent stress method was developed with use of finite element analysis (FEA), and the crack driving force was determined based on the FEA results and the stress intensity factors...
Fatigue failure is a time-delayed failure that is one of the major threats to the pipeline integrity. For crack-like gouges in dents, the crack grows due to pressure cycling and eventually fails by fatigue. This work, which was funded by PRCI via Project MD-4-16, developed a viable engineering approach and a pragmatic fatigue model for predicting fatigue life of dents and gouges in pipelines. In particular, an equivalent stress method was developed with use of finite element analysis (FEA), and the crack driving force was determined based on the FEA results and the stress intensity factors (SIF) from API 579. The proposed fatigue model was evaluated with full-scale fatigue test data for line pipes containing dents and gouges, and then refined. The results showed that the refined fatigue model can predict adequate fatigue lives of dents and gouges in pipelines due to cyclic pressure.
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