The Slippage Analysis at Bearing Surface of Bolted Joints due to Cyclic Transverse Loads

Bolted joints are widely used in mechanical structures due to their easy installation and maintenance. However, self-loosening of bolted joints caused by cyclic transverse loads has remained unsolved. In this study, the parametric finite element (FE) model is established to simulate the self-loosening. The slippage state at bearing surface and thread surface is investigated based on the FE model. Moreover, the influences of transverse frequency, amplitude, friction coefficient and initial preload on residual preload are discussed under a certain amount of time; the variations in back-off angle of nut and residual preload with time are analyzed under multi transverse loops. The results show that thread surface undergoes complete slip prior to the bearing surface, which provides theoretical guidance for looseness-proof design of bolted joints to some degree. The FE model can also be used to design the initial preload and predict the connections life under given vibration environment.