On the extensional-torsional response of a flexible pipe with damaged tensile armor wires

This work investigates the extensional-torsional response of a flexible pipe with one up to ten wires broken in its outer tensile armor. Experimental tests were conducted, and the results obtained are compared to those from a finite element (FE) and a simplified analytical model. In these tests, the pipe was firstly subjected to pure tension and, then, to clockwise and anticlockwise torsion. The experimental results indicate a decrease in the stiffness of the pipe with the increasing number of broken wires as well as a significant impact on its extensional-torsional balance. High stress concentrations in the wires close to those damaged were observed. Furthermore, local changes in the curvature of the pressure armor and the inner carcass induced bending strains not only in these layers, but also in the inner tensile armor wires. The FE model captured these effects and agreed well with the experimental measurements, while the analytical model predicted the overall response of the pipe, but local effects could not be evaluated.