ACM建模下焊点疲劳计算的网格敏感性分析

焊点通常是车身疲劳开裂的位置，用有限元方法准确计算焊点疲劳损伤在汽车设计阶段非常重要，本文研究网格前处理对焊点疲劳损伤计算精度的影响。焊点的建模采用主流的区域接触模型（Area Contact Model，ACM），网格敏感性分析主要考虑载荷类型、网格尺寸和偏心距3个因素。结果表明:在纯剪载荷下，网格尺寸对焊点损伤计算没有影响；在拉伸和弯矩载荷下，网格尺寸越大，焊点损伤越大；纯剪载荷时，偏心距越大，焊点损伤越大，而拉弯载荷下正好相反。最后统计了网格细化对229个车身结构焊点疲劳损伤的影响，并对焊点ACM建模提出指导性建议。

Mesh Sensitivity Analysis of Weld Spot Fatigue Damage Calculation Based on ACM Modeling

Fatigue crack in a vehicle generally initiates on the weld spot position. It is important to ensure that the fatigue damage of weld spot can be accurately estimated by CAE in the early stage of vehicle design. In this paper, the mesh effect on weld spot fatigue damage calculation was analyzed systematically. Area Contact Model (ACM) was used to build the weld spot model. For mesh sensitivity analysis, three factors were considered, including loading type, mesh size and spacing distance. The results show that under pure shearing loads, the fatigue damage of weld spot is not sensitive to the mesh size, but increases with the spacing distance. While under tensile peel loading, fatigue damage increases with mesh size, but decreases with the spacing distance increasing. In the last part, we analyzed the effect of mesh minimization on the calculation of spot weld fatigue damage in some components of a vehicle. The mesh sensitivity were then evaluated by comparing the fatigue damage of 229 welds spot under three element sizes. It can be concluded that a coarse element size can be used in a vehicle fatigue analysis. For most concerned elements, a mesh refining is needed, when one should consider the spacing size and loading type.