Effect of Wall Thinning on the Failure of Pipes Subjected to Bending Load

Effects of circumferentially local wall thinning on the fracture behavior of pipes were investigated by monotonic four-point bending. Local wall thinning was machined on the pipes in order to simulate erosion/corrosion metal loss. The configurations of the eroded area included an eroded ratio of d/t = 0.2, 0.5, 0.6, and 0.8, and an eroded length of l = 10mm, 25mm, and 120mm. Fracture type could be classified into ovalization, local buckling, and crack initiation depending on the eroded length and eroded ratio. Three-dimensional elasto-plastic analyses were also carried out using the finite element method, which is able to accurately simulate fracture behaviors excepting failure due to cracking. It was possible to predict the crack initiation point by stress conditions at the center of the thinned area.