Experimental, Numerical, and Analytical Studies on the Bending of Mechanically Lined Pipe

Mechanically lined pipe (MLP) is often used for offshore oil and gas transport because of its low cost and corrosion resistance. During installation and operation, the pipe may undergo severe bending deformation, which causes the liner to separate from the outer pipe and buckles, affecting the stability of the whole line. In this paper, the buckling response of MLP subjected to bending is investigated to clarify its bending characteristics by employing both experiments, numerical simulation, as theoretical methods. Two types of MLPs were manufactured with GB 45 carbon steel (SLP) and Al 6061 (ALP) used as the outer pipe material, respectively. The hydraulic expansion and bending experiments of small-scale MLPs are conducted. In addition to the ovalized shape of the cross-section for the SLP specimens, the copper liner was found to wrinkle on the compressive side. In contrast, the liner of ALP remains intact without developing any wrinkling and collapse mode. In addition, a dedicated numerical framework and theoretical models were also established. It was found both the manufacturing and bending responses of the MLP can be well reproduced, and the predicted maximum moment and critical curvatures are in good agreement with the experimental results.