A Comparative Buckling Study for the Carcass Layer of Flexible Pipes

Abstract

When there are some failures on the external plastic layer of a flexible pipe, a high value of hydrostatic pressure can be transferred to its interlocked carcass layer, maybe causing a collapse. So it is necessary to predict on the design of a flexible pipe the maximum value of pressure that would be acceptable to avoid collapse of the carcass layer. That value depends on the imperfections on the internal diameter due to fabrication uncertainties. To study that problem, two numerical finite element models were created and used to simulate external pressure loading condition. The first model is a full 3D approximation, composed by solid elements. The second one is a 3D ring approximation, still made by solids. An analytical model using an equivalent thickness approach for carcass was done. A good correlation between analytical and numerical models was achieved for pre-buckling behavior, but analytical buckling behavior was not the same as numerical values predictions. Discussions about these differences are done.