耐压船体结构典型接点疲劳寿命评估

潜艇在潜浮过程中,由于静水外压引起的工作应力与焊接残余应力叠加,形成拉压循环应力,导致耐压船体的局部结构可能出现低周疲劳裂纹.一般情况下,高强度钢在抗拉强度提高的同时往往伴随着材料塑性储备和断裂韧性的下降,因此分析高强度钢潜艇结构的低周疲劳寿命非常重要.本文基于断裂力学和Paris公式建立了潜艇耐压结构低周疲劳寿命的工程估算方法,根据裂纹无损检测的概率统计和含裂纹圆柱壳极限应力分析,给出了初始裂纹和裂纹临界状态的建议值.应用本文的简化方法分析了某潜艇结构和锥柱结合壳模型的低周疲劳寿命,锥柱结合壳模型的数值算例表明本文的计算结果与试验测试结果相吻合.

Fatigue Life Prediction of Structural Details of Submarine Pressure Hull

The low-cycle fatigue induced crack propagation occurs in the structural details of submarine pressure hull when the applied stresses are superimposed on the residual welding stresses during its ascending and/or descending.It is important to assess the fatigue life for submarine pressure hull made of the high strength steel because the high strength steel presents a decrease in the material plasticity and fracture toughness with an increase of the tensile strength. In the present paper, a simplified approach is presented for low-cycle fatigue life prediction of submarine pressure hull based on the fracture mechanics and Paris law.The initial and critical sizes of cracks are proposed based on the statistics of the crack detection probability by non-destructive inspections and analysis results of the limit stress level of cracked cylindrical shell. The present method is employed to predict the fatigue life of a submarine pressure hull and experimental model of pressure cone-cylinder shell.The examples show that the results by the present method are in agreement with the experimental data of cone-cylinder model under cyclic external pressure.