Finite Element Modelling of Residual Stresses in Flexible Pipe Pressure Armor C Profiles

Abstract The pressure armor is one of the structural metallic layers of a flexible pipe for offshore application. Its primary function is to resist radial loads, internal to prevent burst, and external to avoid crushing. It is made by a metallic wire wound around the pipe nucleus in a helical shape. That wire can have several shapes, like Z-profiles and C-profiles. During the manufacturing process of flexible pipes, the pressure armor wires are subjected to successive steps of folding and unfolding to achieve the desired final form, which results in residual stresses in the wire. The pipe is submitted to the so-called Factory Acceptance Test (FAT) to alleviate the residual stress, where a substantial internal pressure is applied and removed. The final stress field then must be considered in further mechanical analysis. This paper is a sequence of previously published work on the conforming process for Z-shaped pressure armors and presents the conforming process of C-shaped profile armors. Some differences in the process are highlighted throughout the text. The paper focuses on a developed finite element model to simulate all the necessary conforming process, besides the internal pressure application and removal during the FAT, for a C-shaped pressure armor profile. Throughout the article, details of the modeling, the applied boundary conditions, and loads are shown, as well as the achieved results.