汽车车架焊接支座的疲劳分析

Fatigue analysis for welded bracket of car frame

汽车车架承载焊接接头对保证汽车安全有重要意义。为预测越野车车架焊接支座的疲劳寿命,采用三维弹塑性有限元方法对车架支座进行了应力分析,确定车架支座的受力薄弱环节。根据越野车在不同路面行驶时的载荷谱及支座材料的疲劳性能数据,利用MSC.Fatigue商用软件对车架支座的疲劳寿命进行了预测。计算车架支座在不同存活率下的概率疲劳寿命。分析表明,在焊接质量完好时,越野车支架在三种路面行驶均有较高的疲劳寿命。当车身支架与纵梁连接的上部焊接接头存在咬边焊接缺陷时,将严重降低车架支座的疲劳寿命,必须对有缺陷的焊接接头进行焊补。

The welded joints of a car frame subjected to loads are essential to ensure the car safety.In the present work,the fatigue life for the welded bracket of a go-anywhere car frame is predicted.First,the stress analysis of the welded bracket was carried out using the three-dimensional elastic plastic finite element method.Then, the weak link of the welded bracket was found.Thereafter, based on the various loading spectrums obtained from car running on different load surfaces and the fatigue performance data of the bracket material,the fatigue life for the bracket of car frame was predicted by using the MSC.Fatigue commercial software.The fatigue life for the bracket of the car frame was calculated with various livability.The analysis indicated that the fatigue life of the bracket was high enough ,when the welded joints are well-qualified.However,when there was welding undercut defects in the upper welds between the bracket and the car frame, the fatigue life of the bracket will decrease severely.In this case,repair welding is necessary for the welded joint with defects.