Simplified Three-Dimensional Finite Element Models of a Flexible Pipe Interlocked Carcass Under Bending

A flexible pipe interlocked carcass is characterized by having both high flexibility and radial stiffness, being, therefore, a layer of relevant structural function. When designing a carcass, these two properties must be met at the same time, which is only possible thanks to its helical and interlocked geometry. On the other hand, the geometric complexity makes its modeling process equally complex, whether numerical or analytical. In this context, over the last years, the authors published some papers with the objective of better understanding the mechanical behavior of the carcass under tension and bending loads, as it is important for the development of more efficient modeling techniques. Regarding bending, two fully three-dimensional finite element models of the interlocked carcass were recently presented, which considered the exact helical shape of the carcass and all contacts involved in the interlocking. Despite being very complete, these models were quite computationally expensive models. To simplify the carcass modeling process, the ring hypothesis is commonly adopted, which consists of disregarding its lay angle. This approach has already been widely used and studied for collapse problems, but, to the authors’ knowledge, its impact has not yet been evaluated for the bending case. Therefore, the present work proposes a series of simplified finite element models of the interlocked carcass under bending loads and that are computationally efficient, in addition to a detailed evaluation of the impacts of all adopted simplifications, always having as paradigm for comparison the costly, most complete, fully helical interlocked versions.