Fatigue analysis on offshore pipelines with embedded cracks

Fatigue-life prediction of offshore pipelines becomes a major issue to ensure the integrity and reliability of offshore pipelines since many catastrophic failures of piping components were caused by fatigue crack growth. Fatigue crack growth of pipelines has been studied extensively by experimental tests. It is well recognized that scale factors and the large amount of costs on the experimental set up are major challenges to conduct a full-scale fatigue test. The adequate confidence to design offshore oil and gas system productions should be built upon a series of preliminary fatigue tests using full-scale numerical simulations. In our current work, a systematic investigation has been carried out on the fracture resistance behavior of offshore pipelines containing an elliptical embedded crack under cyclic tension loadings. Extended finite element method (XFEM) is adopted for numerical simulations. The influences of different initial crack length and stress ratio on fatigue crack growth are investigated in details. Furthermore, the comparison between the values obtained from the theoretical analysis, BS7910 and current investigation is made on the fatigue crack growth rate, from which it is obvious that the results obtained by XFEM are reasonable and reliable. •Fatigue investigation is performed on offshore pipeline with embedded cracks.•Extended finite element method (XFEM) is adopted for numerical simulations.•The fatigue results are validated by the theoretical solutions.•Comparisons with BS7910 fatigue assessment are carried out.