Experimental Investigation on Nonlinear Dynamic Characteristics of Bolt Preload Degradation

During long-term vibration service, the degradation of the bolt preload significantly affects the dynamic transmission characteristics of engineering assembled structures. In this study, an experimental apparatus based on resonance principles was developed to investigate nonlinear dynamic characteristics of the bolt preload degradation. A thin-walled bending spring design was incorporated to amplify the tangential contact forces at the bolted joint interface, thereby accelerating the degradation of the bolt preload. Real-time online measurements of the bolt preload and concerned acceleration responses were synchronously conducted to reveal the correlation between the preload degradation and the hysteresis loops, and the effects of initial preload and excitation amplitude were investigated separately. Additionally, the parameters of a time-varying Iwan model were identified to reproduce the hysteretic behavior and predict the evolution rules. The comparison results of experimental and numerical simulations showed good agreement and revealed the influence patterns of the bolt preload degradation on the hysteretic behavior.