计及成形因素影响的车身结构疲劳分析

基于随机振动理论,推导了车身结构随机振动响应谱的计算公式;采用Goodman曲线进行交变载荷的等损伤转换,建立了应力幅和平均应力之间的关系式;以材料的疲劳极限作为疲劳抗力指标,将残余应力等效为平均应力,以研究成形因素对疲劳性能的影响;以某汽车尾端横梁为例,采用基于有限元分析结果的疲劳分析法,考虑冲压成形因素的影响,进行了车身结构的动态应力计算、疲劳寿命预测和改进设计.结果表明,所预测的疲劳性能与整车道路试验结果吻合.

A Fatigue Analysis on Auto-body Structure with the Consideration of Forming Effects

Based on random vibration theory, the formulas for the random vibration response spectra of au-to-body structure are deduced. The alternative loading is converted to the loading with equivalent damage by using Goodman curve, and a relationship between stress amplitude and mean stress is established. Taking the fatigue limit of materials as the indicator of fatigue resistance, the residual stress is equivalent to mean stress for studying the effects of forming factors on fatigue performance. With the cross member at tail end of vehicle taken as an example, the dynamic stress calculation, fatigue life prediction and modification design of auto-body structure are performed by adopting fatigue analysis method based on the results of FEA for considering the effects of forming factors. The results show that the fatigue performance predicted well agrees with the results of vehicle road test.