不锈钢车体侧墙电阻点焊接头疲劳寿命预测

Fatigue Life Prediction of Spot Welded Joints of Stainless Steel Body Side Wall

通过测量SUS301L不锈钢点焊接头整体结构在服役过程中自然频率的改变情况,来分析点焊接头服役过程中损伤问题,并推导出点焊接头的寿命预测数学方程。通过疲劳试验和自然频率动态测试,实现对电阻点焊试件疲劳各个阶段的损伤情况的监测,结果表明:点焊试件在寿命达到20%时裂纹萌生;在60%时,微裂纹扩展为宏观裂纹,损伤达到50%;达到80%寿命左右时,裂纹迅速扩展,直至完全破坏。以自然频率下降幅度变化率和疲劳损伤度推导出数学方程进行寿命预算,该数学方程的计算结果与试验数据基本相同。

In this paper, fatigue damage problem of the spot welding joint of stainless steel body were researched based on the characteristics of the natural frequency, and its fatigue life were predicted. At each fatigue stage, damage degree of spot welded specimen was monitored by the fatigue test and dynamic response tests. The results showed that when fatigue life reached to 20%, crack began to initiation, when fatigue life reached to 60%, spot welded joint specimens appeared a macroscopic crack and the damage degree reached to 50%. When the fatigue life reach to 80%, the crack of expanded rapidly until the spot welded joint was completely destroyed. Based on the relation between the change rate of the natural frequency and the fatigue damage, a new fatigue life prediction model was established. The result from experimental tests were consistent with the fatigue life prediction model.