Effect of Thread and Bearing Friction Coefficients on the Vibration-Induced Loosening of Threaded Fasteners

Abstract

This study provides a theoretical and experimental investigation of the effect of the thread and bearing friction coefficients on the self-loosening of threaded fasteners that are subjected to cyclic transverse loads. The friction coefficients are varied by using different types of coating and lubrication. A phosphate and oil coating and an olefin and molydisulfide solid film lubricant are used on the bolts tested. A mathematical model is developed to evaluate the self-loosening behavior in threaded fasteners when subjected to cyclic transverse loads. An experimental procedure and test setup are proposed in order to collect real-time data on the loosening rate (rate of clamp load loss per cycle) as well as the rotational angle of the bolt head during its gradual loosening. The experimental values of the friction coefficients are used in the mathematical model to monitor their effect on the theoretical results for the loosening rate. Experimentally, the friction coefficients are modified by changing the coating or the lubrication applied to the fasteners. The theoretical and experimental results are presented and discussed.

Screw-Bone Implant Loosening: Complication, Cause and Assessment

“…The main failure mode for bolted joint when exposed to vibrational environment is self-loosening Housari et al [32] Effect of thread and bearing friction coefficients on the vibration-induced loosening of threaded fasteners…”

“…The varying axial load can cause micro slippage between the contact thread [31]. Housari et al [32] concluded that the friction coefficient that plays a role in the loosening rate is affected by the fastener coating and lubricant.…”

Anti-loosening performance of coatings on fasteners subjected to dynamic shear load

“…They found that the increase of the friction coefficient decreased the preload loss. Houari [18] and Karamis [27] showed that the increase of the bearing friction reduced the loosening rate. Furthermore, Zaki et al [19] found that the increase of the coating thickness decreased the friction coefficients of the thread and head bearing, therefore thick coated fasteners would loosen at a faster rate than thin coated fasteners [28].…”

“…There has been much research on this topic. Self-loosening mechanisms [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] and their various influencing factors [17][18][19][20][21] were studied through experiments, theoretical analyses and numerical simulation. A variety of measures were proposed to prevent self-loosening, such as chemical locking [21], step lock bolt (SLB) [22], and double-nut [8,23].…”

“…Coating and lubrication are often used for reducing the friction coefficients of threaded fasteners [24,25].…”