Wrinkling of Lined Pipes Under Bending

The present study is motivated by the use of lined pipes in energy pipeline applications (oil, gas, etc.) where a corrosion-resistant thin-walled liner is fitted inside a carbon-steel outer pipe. The paper focuses on wrinkling of lined pipes (sometimes referred to as clad pipes), which are candidates for offshore pipeline applications. The pipe is composed by two pipes that are in contact; a thick-walled carbon-steel "outer pipe", and a thin-walled corrosion-resistant inner pipe, referred to as "liner pipe" fitted inside the carbon steel outer pipe. 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 lined pipe. 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. The values of curvature at which liner wrinkling occurs are determined. Copyright © 2012 by the International Society of Offshore and Polar Engineers (ISOPE).