Our previous report suggests that the loosening rotation can occur when slip on bearing surfaces of bolt-nut joints, even if its magnitude is minute. It is the purpose of this report to continue considerations about this subject through loosening experiments which are carried out by adding transverse repeat loads. In the experiments, test joints with bolt-nut samples having duTerences of shape, pitch and surface treatment are employed. Experimental results shows that the loosening(loss of axial tension) exists in all test samples as far as the bearing-surface-slip occurs(even when its amplitude is 1〜2μm), and that the loosening rotation progresses in such conditions. The duTerences mentioned above only influences on speed of the loosening.
