Experimental Evaluation of Screw Thread Loosening in Bolted Joints with Some Parts and Analytical Approach of Loosening Mechanism of the Joints under Repeated Transverse Loadings

The experiments to loosen bolted joints and joints with double nuts and eccentric nuts were carried out using Junker’s machine and NAS machine. As the results, no loosening was found in the bolted joints with the market-sold eccentric nuts and the conventional nuts in almost all joints were loosened. In addition, in order to know the loosening mechanism, several finite element analyses were performed and reproduced the phenomenon that the bolts were loosened, or the nut rotates, when the repeated transverse loads were applied. Based on this result, the mechanism of the bolt loosening (the nut rotation) is investigated.