Failure Behavior of Pipe Having Local Wall Thinning in Downstream Region of Orifice

Monotonic four-point bending tests were conducted using pipe specimens having orifice undergoing local wall thinning. The effects of local wall thinning on the fracture behaviors of pipe were investigated. Local wall thinning was machined on the inside of pipes in order to simulate erosion/corrosion metal loss. The configurations of the eroded area were l = 100 mm in eroded axial length, d/t = 0.5 and 0.8 in eroded ratio, and 2θ = 180° in eroded angle. The area undergoing local wall thinning was subjected to either tensile or compressive stress. Failure type could be classified into ovalization, local buckling, and crack initiation, depending on eroded ratio, and stress at the eroded area. Three-dimensional elasto-plastic analyses were also carried out using the finite element method, which is able to accurately simulate fracture behaviors. The crack initiation point could be successfully predicted by the criterion proposed by Miyazaki et al..