轻型货车前桥焊缝失效载荷分析与厚度匹配优化

Failure Load Analysis and Thickness Matching Optimization of Weld Seam on Front Axle of a Light Truck

针对某轻型货车前桥焊缝疲劳失效问题,在试验场采集车辆耐久试验载荷谱,通过虚拟迭代的方法得到前桥各连接点的载荷时间历程,建立前桥有限元模型,并采用惯性释放方法对前桥焊缝进行疲劳寿命仿真,分析结果与试车试验场道路试验失效特征一致,验证了模型的准确性;进一步通过虚拟应变片获得焊缝处局部应力状态,通过损伤方向分布、单轴损伤对比和主应力方向分布,确定试验场随机道路载荷下前桥焊缝处失效主导载荷;分析失效焊缝区域中3处焊缝厚度对疲劳寿命的影响趋势。最后运用自适应响应面法对三者进行匹配优化,对优化后前桥进行疲劳寿命仿真分析,结果表明焊缝区疲劳寿命提升近8倍,试验场道路试验也满足10000 km不失效的耐久性要求。

In view of the weld seam failure in the front axle of a light truck,the load spectra of vehicle durability test are collected in proving ground,and the virtual iteration method is used to get the load time history of each connecting point of front axle.The finite element model of front axle is built and a fatigue life simulation on front axle’s weld seam is carried out using inertia relief method.The analysis results are consistent with the failure features of road test in proving ground,verifying the accuracy of the model.Furthermore,the local stress state at the weld seam is obtained by means of virtual strain gauge,the failure dominant load of the weld seam under the random load of proving ground is determined by studying the damage direction distribution,uniaxial damage comparison and principal stress direction distribution,and the effects of the weld seam thickness at three localities in failed zone on fatigue life are analyzed.Finally,a matching optimization is conducted on the three thickness parameters by applying adaptive response surface technique and the results show that the fatigue life of the weld seam zone is increased by nearly 8 times,and the road test in proving ground also meets the durability requirement of 10000 km driving without failure.