疲劳载荷作用下焊接点三维线弹性弯曲裂纹路径预测

利用二阶摄动方法研究了疲劳载荷作用下结构线弹性裂纹的弯曲扩展问题并求解了三维动态应力强度因子.利用二阶摄动方法研究了疲劳载荷作用下裂纹路径预测时的应力准则与能量准则之间的关系.就均匀物质而言,在二阶摄动分析理论的框架内,两种准则指明了相同的三维疲劳弯曲裂纹扩展路径.但在具有非均匀断裂韧度的物质中,能量准则优越于应力准则.作为二阶摄动方法的实际运用,研究了焊接结构中疲劳线弹性裂纹的形态特征和弯曲扩展路径问题,综合考虑了诸如远场动态作用应力、焊接残余应力、局部物质衰变以及不同尺寸的缺陷的存在等因素,绘制出疲劳载荷作用下退化区域中裂纹弯曲扩展的临界轨迹曲线.

Three Dimensional Crack Path Prediction of Brittle Fracture in Weldment Under Fatigue Load

Based on a second order perturbation method, three dimensional fatigue stress intensity factors are analyzed for a curved crack. The method is extended to obtain an approximate represen-tation of a three dimensional fatigue stress intensity factors at the tip of a curved crack. A fatigue en-ergy release rate due to three dimensional curved crack growth can be calculated by using Irwin's formula. Considerations are made for a three dimensional fatigue curved crack in materials with in-homogeneous fracture toughness. Paths of a brittle three dimensional fatigue curved crack propagat-ing along a welded joint are predicted as a practical application of the present method, where the ef-fects of fatigue applied stresses, residual stresses, and material deterioration due to welding are tak-en into considerations.