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为研究超声冲击处理对传动轴总成球笼-法兰焊缝表面残余应力的影响,采用超声冲击强化对球笼-法兰激光焊接焊缝进行了焊趾冲击和全覆盖冲击试验。分析了超声冲击前后裂纹产生原因,测试了焊趾冲击和全覆盖冲击前后残余应力值。残余应力测量结果表明,采用冲击工艺,可以在焊缝表面一定深度下产生压应力,最高测得-237MPa。全覆盖冲击后焊缝整体处于压应力状态下,焊缝中心残余压应力进一步增大;焊趾冲击后,焊缝中心应力值没有较大变化,焊趾处压应力值增大。经超声冲击后,组织发生塑性变形形成了高位错密度的包状结构,这个高位错密度的表面层能够有效阻碍表面应变层底部的晶体在交变应力作用下向表层滑移,抑制表面裂纹产生。
In order to study the effect of ultrasonic impact treatment on the residual stress on the surface of the cage-flange weld of the drive shaft assembly, the weld-toe impact and full-coverage impact tests on the cage-flange laser welding weld were carried out by ultrasonic impact. The causes of cracks before and after ultrasonic impact were analyzed. The residual stress before and after the weld toe impact and the full covering impact were tested. Residual stress measurement results show that the impact process, the weld surface can produce a certain depth of compressive stress, the maximum measured -237MPa. After full coverage impact, the weld seam is in a state of compressive stress, and the residual compressive stress in the weld center increases further. After the weld toe impact, there is no significant change in the stress at the weld center and the compressive stress at the weld toe. After ultrasonic impact, the structure of plastic deformation occurs to form a high dislocation density of the package structure, the high dislocation density of the surface layer can effectively hinder the bottom of the surface strain of the crystal under the action of alternating stress to the surface slip, inhibit the generation of surface cracks .