The Evaluation of Loosening of Small Bolts Under Transverse Vibration

Abstract

Self-loosening of threaded fasteners sometimes occurs under dynamic loads such as vibration and shock. For mechanical structures, the self-loosening with rotation of threaded fasteners under transversely repeated load is particularly important. Although bolts of M8 and above have been studied by experimental methods and numerical analyses, there are few studies about small bolts of less than or equal to M5. In this paper, we have examined the loosening behavior of bolts of M3 and M5 by comparing with M10 bolts. As a result, we showed that small bolts easily cause slips on bolt bearing surfaces by very small amplitudes because of small initial bolt tension and small grip length, and when slips on bolt bearing surfaces occur, small bolts loose by the same behavior of M10 bolts. In addition, the loosening of threaded fasteners of M5 using plain washers, spring washers, conical spring washers or toothed washers are also the same as that of M10 bolts.