Effects of upset timing on heat input and joint strength in friction welding of a 6061 aluminum alloy

In this paper, the effect of the upset timing on joint strength of the friction welded joints of 6061 aluminum alloy was discussed by using the evaluation factors of the deformation heat input in the upset stage and the upset burn-off length. The results showed the followings. When the upset pressure was applied before the braking, the deformation heat input in the upset stage and the upset burn-off length were so large more that sound weld joints could be obtained easily, than that of the synchronized timing at the same welding parameters. In the synchronized timing, when the upset pressure was large, the actual pressure could not attain to a set up pressure. Meanwhile, when the upset pressure was applied after the braking, the deformation heat input in the upset stage and upset burn-off length were so small that sound weld joints could not obtained. Therefore, it was made clear by using effect of the upset timing in joint performance was much related with the deformation heat input and upset burn-off length. And the sound welded joints were obtained with 200 J/s or more deformation heat input and 2.5 mm or more upset burn-off length.