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利用二阶摄动方法分析研究了轻微弯曲疲劳裂纹尖端应力强度因子的变化幅度,进一步得到了在循环载荷下直线裂纹微弯延伸尖端应力强度因子变化幅值的近似表达式。以匹配渐进扩张的形式考虑了远区域边界条件的效果,研究了裂尖附近的渐进应力场。利用Irwin公式计算出了由于裂纹发展而引起的应变能释放率变化幅值。预测了在具有非均匀断裂韧度的物质中裂纹的延伸。考虑了循环载荷、残余应力,以及由于焊接而引起的物质衰变等因素,利用了二阶摄动方法预测了沿着焊接点传播的弹脆性裂纹路径。
The second-order perturbation method is used to analyze and study the change range of the stress intensity factor of slight bending fatigue crack tip, and the approximate expression of the change amplitude of the stress intensity factor of the linear micro-bending extension tip under cyclic loading is obtained. The effect of the boundary conditions in the far area was considered in the form of gradual expansion and the asymptotic stress field near the crack tip was studied. Irwin formula was used to calculate the magnitude of the change of strain energy release rate due to the development of cracks. Prediction of crack propagation in materials with non-uniform fracture toughness. Considering cyclic loading, residual stress and material decay caused by welding, the second order perturbation method is used to predict the brittle crack propagation along the weld.