考虑焊接螺母的排气管支架疲劳优化研究

Fatigue Life Optimization of the Exhaust Pipe Support Bracket Based on Projection Weld Nuts

针对在四通道液压振动台及试车场路试过程中,某样车排气管支架出现的焊接螺母疲劳开裂问题,在考虑焊接螺母焊点和螺栓预紧力的前提下,建立开裂支架的局部非线性有限元模型,根据Miner线性疲劳累计损伤理论和材料S-N曲线,对正弦信号激励下的排气管支架进行疲劳分析。在此基础上,提出优化方案,进行仿真疲劳寿命预测,并对简化后的局部排气管支架模型进行疲劳验证,优化前后的仿真模型寿命曲线趋势与试验结果基本吻合,危险区域分布与试验一致。针对焊接螺母或者螺栓连接的支架疲劳开裂问题,在考虑螺栓预紧力的基础上,建立局部模型疲劳分析并结合试验验证,提出优化方案解决问题。试验结果表明,该流程方法对解决实际问题具有一定的借鉴意义。

Aiming at the fatigue crack problem of the weld nut in an exhaust pipe support bracket of a prototype vehicle during the road test on the hydraulic shaker and on the proving ground,a simplified nonlinear finite element model was established considering the projection weld nuts and bolt pretension.The Miner’s linear fatigue damage accumulation rule and the S-N curve of the materials were used to predict the fatigue life of the bracket under the sinusoidal excitation.Based on the fatigue simulation results,an optimized structure was presented and then the fatigue life was predicted.The lab fatigue tests were carried out to verify the simplified finite-element-model and the fatigue life and dangerous areas obtained from the FEA agree with the test results.Finally,the optimization measures were presented to solve the fatigue crack problem of the weld nut.The proposed method has some certain significance to serve as a reference.