破壊評価線図を用いた高圧自緊容器の構造健全性保証

抄録

The failure assessment diagram was constructed to assess the structural integrity of high-pressure autofrettaged vessels with a semi-elliptical axial defect, and a systematic sensitivity analysis of factors influencing unstable fracture under the residual stress field was performed. Under the maximum service pressure, increase in the autofrettage radius has a beneficial effect on critical flaw size ac, although it has little effect on the yielding scale at unstable fracture. Increase in the fracture toughness has a beneficial effect on both factors. When the inner-to-outer radius ratio is constant, increase in the vessel dimensions has a similar effect as decreasing the fracture toughness. When the inner radius and the safety factor of the pressure concerning plastic collapse failure are constant, the relative size of and the yielding scale at unstable fracture decrease with increasing wall thickness. In every case analyzed, the concept of leak before break (LBB) does not hold. However, the structural integrity is assured because the critical defect size is large enough to be easily detected during in service inspection.