Investigations of Bolt Loosening Mechanisms : 2nd Report, On the Center Bolts of Twisted Joints

Abstract

A theoretical analysis was made on the loosening mechanisms of bolts that are at the center of rotation when joints are twisted alternately and the following were derived: (1) the condition necessary for the bolts to loosen by self rotation, (2) the physical meaning and the theoretical equation of the critical angle of relative rotation between the clamped parts (below that angle the bolts do not rotate), (3) the Q-N characteristics under non-rotating loosening caused by fretting wear (Q: clamping force, N: number of loading cycles). Some loosening tests were carried out and it was verified that the theoretical results (1) and (3) qualitatively coincide with the empirical results.