FEM fatigue simulation for an offshore pipeline containing interacting cracks

Abstract

Large plastic strain commonly exists in offshore pipelines due to reeling installation procedures. When two steel pipes are joined together through welding, small cracks are usually existing in the welding zone. The pipelines can withstand the crack extension or facture during installation when the crack size is small. Every single moment, there will be cyclic load acting on offshore pipelines. Existing multiple cracks at the offshore pipelines will grow and merge into big ones. It will lead to fatigue failure. A lot of research work has been done carried out on stress analysis of multiple cracks in offshore pipelines. The current study presents the investigation on the fatigue behavior of two 3D interacting cracks in an offshore pipeline. Finite element method is used to model the fatigue behavior of the interacting cracks under cyclic loading. The parameters affecting the fatigue behavior of the pipelines have been studied thoroughly.