预拉伸对不锈钢电阻点焊接头疲劳寿命的影响  

Effect of pretension on fatigue life of stainless steel resistance spot welded joint

作　　者：朱国仁[1] 庞立林 朱慨迅 杨明[1] 王洪潇 Zhu Guoren;Pang Lilin;Zhu Kaixun;Yang Ming;Wang Hongxiao(Jilin University,Changchun 130022,China;CRRC Changchun Railway Vehicles Co.,Ltd.,Changchun 130062,China)

机构地区：[1]吉林大学,长春130022 [2]中车长春轨道客车股份有限公司,长春130062

出　　处：《焊接》2020年第11期1-4,61,共5页Welding & Joining

基　　金：吉林省重点科技攻关项目(20170204071GX)。

摘　　要：不锈钢电阻点焊接头疲劳测试中,断裂处多数在焊点附近。其原因归结为焊接接头处存在残余应力。文中对SUS301不锈钢3.5 mm和4.5 mm两组不同板厚组合的点焊试件进行疲劳测试,得出给定应力下的中值疲劳寿命,随后通过预拉伸削弱点焊接头内部残余应力后重新进行疲劳测试,进行最优载荷区间分析;同时测试焊态及拉伸试件残余应力,对疲劳寿命改善机理进行分析。结果表明,加载预拉载荷T后,不锈钢点焊接头的疲劳寿命得到显著提升;随着T的增大接头疲劳寿命的提升程度也将增大,但当T达到55%以上时接头将会发生形变,影响性能;T最优的选取区间为50%F,在此区间内能够将接头疲劳寿命从中短寿命区提升至无限寿命区;在选取最优区间的预拉载荷后,焊点内部残余拉应力在受力方向减小较多,能够低于100 MPa,垂直受力方向也能够降至1/3。In the fatigue test of stainless steel resistance spot welded joints,most of the cracks occurred near the spot welded joints.The reason was ascribed to the residual stress that existed in resistance spot welded joints.In this paper,fatigue tests were carried out on the spot welded specimens with different thickness of 3.5 mm and 4.5 mm of SUS301 stainless steel,and the median fatigue life under given stress was obtained.Then the fatigue test was carried out again after the residual stress of the spot welded joint was weakened by pretension,and the optimal load interval was analyzed.At the same time,the residual stress of welded and tensile specimens was tested,and the improvement mechanism of fatigue life was analyzed.The results showed that the fatigue life of stainless steel spot welded joints was significantly improved after the pretension load T was loaded.With the increase of T,the improvement degree of fatigue life of the joint also increased,but when T reached more than 55%,the joint would be deformed to affect performance.The optimal selection interval of T was 50%F-,in which the fatigue life of the joint could be improved from the short and medium life zone to the infinite life zone.After selecting the optimal pretension load,the residual tensile stress in the spot welded joint decreased greatly in the stress direction and could be less than 100 MPa,while the stress in the vertical direction could also be reduced to 1/3.

关 键 词：电阻点焊接头 残余应力 预拉载荷 疲劳寿命 

分 类 号：TG405[金属学及工艺—焊接]