Abstract: Bolted joint loosening is one of the important modes of bolted joint failure. In the project, the bolted joints are often subjected to alternating lateral dynamic loads, and the bolts tend to loosening very easily as the bolt axis is perpendicular to the direction of the pretension forces. The reductions of the preload will change the inherent mechanical properties of the bolted joints and even cause the failure of entire structure. In order to study the critical loosening load of the bolted joint under the lateral load, the mechanical model of the bolted joint is established, and the forces of thread are analyzed. A new computing method of the bolted critical loosening load with flexible thread is derived. A set of experimental device for lateral vibration is designed and assembled, which is used to test the mechanical behavior of bolted joint under lateral vibration. The presented calculation method of bolted critical loosening load is verified by comparing the theoretical calculation and experimental results. The distribution law of thread stress under lateral load is given based on the new theoretical calculation method, and the stress distribution characteristics of rigid thread model and flexible thread model are compared. The results show that the thread stress given by flexible thread model can reflect the overall variation of thread stress.

Key words: bolted joint, transverse load, flexible thread, critical loosening load, computing method