Abstract
When the external force acts repeatedly, the bolted joint will sometimes loosen. So the accident is caused. For this reason, many researches of loosening of the thread joint have been done for many years. However, it seems that it still is not fully clear about the mechanism loosening of the thread joint by bending repeatedly. In the present study, the rotary bending loosening examination machine is made, it experiments using nominal bolt and nut diameter, M8. The results are that the bolted joint loosens by bending repeatedly and is influencing by rotary direction. However, when the clamp force is large, loosening is small, and the influence of bending moment and rotary direction become small, too.
