Study on the characteristic parameters of the loosening of bolt-fastened structures under transverse load
To establish a criterion for assessing the looseness of bolt-fastened structures subjected to transverse vibration loads,a bolt loosening experiment was conducted based on the staircase tests. Finite element simulation calculations were also employed to quantitatively characterize the parameters indicative of bolt loosening. Initially,a bolt loosening test was conducted using an improved testing apparatus. Under three different preload conditions,three minimum lateral loosening load amplitudes corresponding to each condition were determined through staircase tests. Subsequently,a finite element model of the bolt-fastened structure with threaded contact surfaces was created under the specified experimental conditions. Finally,lateral loads were incrementally imposed until the preload of the finite element model decreased significantly. After completing the simulation,an analysis of various parameters on the contact surface of the bolt-fastened structure splint was performed,and variations in different parameters during the loosening of the bolt-fastening structure were discussed. Both experimental and simulation results demonstrated that the loosening of bolt-fastened structures was primarily influenced by the frictional forces acting at the contact surfaces between the upper and lower splints. Under different preload conditions,the minimum lateral loosening load that loosens the bolt fastening structure was also different. A higher preload corresponded to a greater minimum lateral loosening load. Simultaneously,it turned out that three maximum displacement of the bolt-fastened structure on the center line of the splint almost remained constant when subjected to three minimum transverse loosening loads. This displacement value was independent of bolt preloads,serving as a fundamental property of the bolt-fastened structure. Therefore,this paper employed this displacement value is a distinctive parameter for bolt-fastened structures to characterize the loosening of bolt-fastened structures under lateral vibration loads. The minimum lateral load amplitude can be calculated based on this parameter when the size and preload of the bolt-fastened structure are known. The investigation results can serve as a foundation for the anti-loosening design of bolt-fastened structures in high-speed trains.
bolt-fastened structurepreloadbolt loosethe amount of displacementanti-loosening design
万方数据
维普
