Wrinkling of Lined Steel Pipes Under Bending

Lined pipes are used in energy pipeline applications (oil, gas, etc.); a corrosion-resistant thin-walled liner is fitted inside a carbon-steel outer pipe. The paper focuses on wrinkling of lined pipes (sometimes also referred to as “mechanical clad” pipes), which are candidates for offshore pipeline applications. The lateral confinement of the liner pipe due to the deformable outer pipe and its interaction with the outer pipe has a decisive influence on the wrinkling behaviour of the thin-walled liner. The problem is solved numerically, using nonlinear finite elements to simulate the lined pipe and its interaction with the outer pipe. Nonlinear geometry with large strains is taken into account, and the material of both pipes is elastic-plastic. Stresses and strains are monitored throughout the deformation stage with emphasis on possible detachment of the liner from the outer pipe and the formation of wrinkles. It is shown that the behaviour is characterized by a first bifurcation in a uniform wrinkling pattern, followed by a secondary bifurcation and finally a localization of the buckled pattern. The values of curvature at which liner wrinkling occurs are determined. The numerical results are compared with available experimental results.