LBB characteristic on pipe subjected to cyclic load

LBB condition for pipe with a circumferential crack under cyclic axial load and bending moment was proposed in this study. An evaluation model was considered for the fatigue LBB condition in consideration of geometrical compatibility at crack penetration. Based on the evaluation model and the characteristic of fatigue crack penetration behaviors, the fatigue LBB condition was investigated. The main results obtained in this study were as follows: 1) The main parameters to control the static LBB condition were initial crack angle, initial crack depth and mechanical properties. But, it was concluded that the main ones to control the fatigue LBB condition were initial crack angle and mechanical properties. 2) In pipes with an elliptical crack, the influence of initial crack angle, crack location and pipe thickness on the fatigue LBB condition was evaluated quantitatively, compared with pipes with a simple through cracks. (author)