Numerical investigation of buckling behavior of dented lined pipe under bending

The mechanically lined pipe, which consists of a carbon steel carrier and a thin-walled corrosion-resistant alloy liner, has proved to be a practical way to prevent the pipeline from internal corrosion. However, the local dent caused by third-party falling objects severely threatens the integrity of the lined pipe, especially the more fragile liner. This work investigates the influence of a local dent on the plastic responses and stability of a lined pipe system during bending. After validation of the numerical framework with the experimental results of a 12-inch lined pipe, the indentation and bending responses of two typical scenarios, namely, TDI and LDI, are examined. It is found that the liner could maintain a certain moment level after reaching the maximum instead of collapsing promptly. Furthermore, classic diamond buckling mode is observed in the TDI case, while the LDI case exhibits a twin triangular-shaped buckling mode. In addition, extensive parametric studies regarding important variables of the full-scale problem are performed. Amongst other findings, the buckling and collapse of the dented lined pipe are found to be affected by the orientation of the dent, which should be taken into account for practical dent evaluation.