Fracture and general yield for carbon steel pipes with local wall thinning

Monotonic bending tests without internal pressure are conducted on 4 and 3.5 in. diameter full-scale carbon steel pipe specimens with local wall thinning in order to evaluate the structural integrity of power plant piping. The local wall thinning is simulated as erosion/corrosion metal loss. The eroded area of the wall thinning is subjected to tensile or compressive stress by applied bending moment. The maximum moments obtained from the tests are compared with the plastic collapse moments based on the net-section stress approach. The net-section stress approach based on flow stress σf gives a conservative estimation, sometimes overly conservative. Although the net-section approach based on ultimate tensile strength σu gives a slightly non-conservative estimation for some cases, the calculated values are close to the experimental data. Using the net-section stress approach based on σu, the eroded depth and the angle at which a pipe undergoes general yielding were obtained.