Simulation and experimental study on liner collapse of lined composite pipe

With the application of lined composite pipe in the offshore oil and gas transportation system, the instability and collapse problems of its liner has been paid more and more attention. In this paper, A nonlinear finite element model of elastic-plastic instability of the confined liner of lined composite pipe is established. Considering the initial out-of-roundness (delta 0/R) defect, the instability configuration and displacement equilibrium path of the liner before and after critical buckling are considered, the delta 0/R defect sensitivity and the relationship between D/ t ratio of the liner are analyzed. Finally, the finite element solution and analytical solution are verified by experimental data in this paper and experimental data reported elsewhere. It is concluded that delta 0/R defect relative to 1 % will reduce the critical instability load value by about 65 %. The relative error between finite element calculation results of instability critical load and experiment test measured load is 1.82 %. The experimental results are in good agreement with the finite element calculation results. Thus it can be seen that by using the nonlinear finite element model of elastic-plastic instability of the confined liner model established in this paper, not only the critical unstable load of the confined steel liner can be accurately solved, but also the cost of experiment test can be greatly saved. It provides a theoretical basis for the buckling-restrained design of lined composite pipe.