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

In the manufacturing of flexible pipes, the pressure armor wires are submitted to successive folding and unfolding processes to achieve its final form. This process results in residual stresses that must be taken into account when calculating the total stresses, they are subjected to in operational situations and in fatigue life calculations. After the manufacturing, the flexible pipe is submitted to the so-called Factory Acceptance Test (FAT), in which a huge internal pressure is applied and then removed. In this latter process, a part of the residual stresses is alleviated, resulting in the residual stress field that must be considered in subsequent mechanical analysis. This paper presents finite element models developed to simulate all the folding and unfolding operations, besides the internal pressure application and removal during the Factory Acceptance Test for Z-shaped pressure armor profiles. This modelling contributes to a more representative manufacturing process, leading to a more assertive stress evaluation.