考虑塑性损伤的船体裂纹板低周疲劳裂纹扩展行为研究

船舶结构的扩展断裂失效往往是低周疲劳破坏和累积递增塑性破坏耦合作用的结果,疲劳裂纹的扩展就是裂纹尖端前缘材料刚度不断降低延展性不断耗失而逐渐分离的结果.基于弹塑性断裂力学理论,文章提出了考虑累积塑性损伤的低周疲劳裂纹扩展速率预测模型.通过低周疲劳裂纹扩展试验拟合出模型相关材料参数并验证预测模型的合理性.通过系列有限元计算对平均应力及应力幅值的影响因素进行了数值分析.该模型的计算结果与已有实验结果基本吻合;对合理预估船体裂纹板的常幅低周疲劳裂纹扩展寿命有重要意义.

Low-Cycle Fatigue Crack-Propagation Behavior for Ship Cracked Plate Considering Accumulative Plastic Damage

The fracture failure of ship structure is often the coupling result of low-cycle fatigue dam-age and accumulative incremental plastic damage. Low-cycle fatigue crack propagation process is gradual separation results in front of crack tip material with the decreases of the stiffness and the continuous loss of the ductility of the crack tip. A prediction model of low-cycle fatigue crack growth rate based on accumulative incremental plastic damage at crack tip is presented in this study. In or-der to validate the model and to calibrate the model parameters, the low-cycle fatigue crack propa-gation experiment was carried out for notch cracked plate specimen made of Q235 steel. The effects of stress ratio and crack closure on low-cycle fatigue crack propagation were investigated by elas-tic-plastic finite element stress-strain analysis of a cracked component. A good comparison was found between predictions and experimental results, which show that it is important for considering the ac-cumulative incremental plastic damage at crack tip to predict the low-cycle fatigue crack propaga-tion life of hull cracked plate.