Abstract
The Ono's rotary bending fatigue testing and the cantilever rotary bending fatigue testing were carried out on friction-welded 6061 aluminum alloy joints, and the relationship between the deformation heat input in the upset stage or the upset burn-off length and fatigue strength was examined. In the Ono's type testing, sound joints, which fractured in the heat affected zone in the tensile testing, fractured in the heat affected zone also and the fatigue limit of these joints is slightly lower than that of 6061 aluminum alloy base metal. This is because joints fractured in the softened area in both tensile testing and Ono's type testing using smoothed test specimens. While, in the cantilever type testing, the fatigue limit of sound joints was a little more than or a little less than that of 6061 aluminum alloy base metal. It seems that a weld condition and a structure at the weld interface affected fatigue strength in the cantilever type testing using notched test specimens. Judging from the fatigue limit obtained, sound joints can be produced when either the deformation heat input in the upset stage or the upset burn-off length exceeds a certain value.
