Abstract
Explanation of loosening phenomena of screw fastener subjected to cyclical transverse load has still remained obscure. The present authors carried out experimental studies in the case of the screw fastener subjected to a rotating radial load, and obtained the following facts. Loosening is slightly dependent on the rotating speed. When the radial load rotates anticlockwise, increase in its magnitude beyond some level yields complete loosening. This level is given by the critical force for the nut bearing surface to slip. When the radial load rotates clockwise, loosening is stooped to remain some bolt stress, and this bolt stress is proportional to the load level.
