Fatigue investigations on steel pipeline containing 3D coplanar and non-coplanar cracks

Abstract

Fluctuated loadings from currents, waves and sea ground motions are observed on offshore steel pipelines, and they will result in small cracks to propagate continuously and cause unexpected damage to offshore/geotechnical infrastructures. In spite of the availability of efficient techniques and high-power computers for solving crack problems, investigations on the fatigue life of offshore pipelines with 3D interacting cracks are still rarely found in open literature. In the current study, systematic numerical investigations are performed on fatigue crack growth behaviours of offshore pipelines containing coplanar and non-coplanar cracks. Extended finite element method (XFEM) is adopted to simulate the fatigue crack growth. The qualitative validations of numerical results are made for certain cases with available experimental results. Parametric studies are conducted to investigate the influences of various important parameters on fatigue crack growth. The results will be helpful to assess the fatigue behaviours of steel pipeline with 3D interacting cracks.