Experimental and numerical study on the indentation response of mechanically lined pipe

Mechanically lined pipe (MLP) has become a low-cost and reliable solution for transporting corrosive hydrocarbons and has been used in many onshore and offshore projects. During the long-term service period, MLP is susceptible to impacts from third-party foreign objects, which can lead to severe local denting and potential failure. The indentation response of MLP to these events is still not fully understood. This paper conducted an experimental and numerical study based on lined pipe specimens fabricated using a custom hydraulic expansion facility. The lined pipes, which have finished diameters of 50 mm, are composed of a carrier made of carbon steel Grade GB45 (AISI 1045) and a liner made of copper Grade T2. Four types of indenters, including spherical, cylindrical, wedge, and square shapes, are adopted to introduce dents into the specimens. The indentation experiment was also performed on single-wall counterpart pipes. The results show that different indenters lead to distinct liner separation profiles along the specimen's length. The axial strain distribution near the dent exhibits opposite behavior between the carrier and liner tubes. In addition, the mechanical contribution of the liner and the influence of carrier pipe thickness are also discussed.