Dynamic loosening and tightening of a single-bolt assembly

Previous analyses of threaded fasteners under vibration are based on static equilibrium conditions with supporting data limited to low frequency lending. Such analyses predict only a net loosening action. This paper presents a dynamic model of a single-bolt assembly with moderate pre-load subjected to axial harmonic vibration. Simulations with this model predict that threaded fasteners can, on the average, loosen or tighten in the presence of vibration; and that the applied vibration, as well as other system parameters, can be tuned so that either action occurs. Measurements from a single-bolt assembly apparatus are presented and compared with the simulations.