基于模态应力恢复的轿车发动机舱盖焊点疲劳寿命分析

建立汽车发动机舱盖焊点有限元模型，并将分析结果与试验模态对比，验证该有限元模型的准确性.分别采用准静态法和模态应力恢复法得到焊点的应力-时间历程；基于Palmgren-Miner线性损伤累积准则和S-N曲线对比评估焊点疲劳寿命，并在模态应力恢复方法中考虑截止频率和结构阻尼对焊点疲劳寿命的影响.与虚拟台架试验的对比结果表明：准静态预测的焊点寿命大于试验寿命，截止频率为200 Hz且结构阻尼为0.06的模态应力恢复结果与试验结果较吻合.基于模态应力恢复法优化设计的发动机舱盖通过耐久路试.

Fatigue life analysis on spot welds in automotive hood based on modal stress recovery

The finite element model of spot welds on automotive hood is built and analyzed. The omparison of the analysis results with the test mode results indicates that the finite element model is valid. The quasi-static and modal stress recovery methods are used to obtain the time history of stress. The fatigue life estimation of spot welds is implemented based on Palmgren-Miner linear damage accumulation rule and S-N curve, and the effect of cut-off frequency and structural damping on the fatigue life of spot welds is considered in modal stress recovery method. The comparison with the virtual rig test results indicate that the fatigue life obtained by quasi-static method is larger than that of test, and the modal stress recovery result is consistent with the test result while the structural damping is 0.06 and the cut off frequency is 200 Hz. The optimized hood passed the durability road test.