Experimental and numerical studies of bolted joints subjected to axial excitation

The dynamic behaviour of bolted joints subjected to axial excitation is investigated using experimental and numerical methods. Firstly, the amount of reduction in clamp force is found by experiments. In addition, the damage of threads is analysed using scanning electron microscope (SEM) and Energy Dispersive X-ray (EDX). Secondly, by changing the tightening torque, the amplitude of the axial excitation, and coating lubricant (MoS2) on the threads, their effects on both the clamp load loss and the damage of threads are determined in experiments. It is found that the clamp force decreases rapidly in the early stage because of the cyclic plastic deformation, and then slowly because of fretting wear in the later stage. With the increase of the tightening torque and the decrease of the amplitude of the axial excitation, the clamp load loss decreases and the damage of threads becomes slight. The lubrication (MoS2) of bolt threads is useful to reduce bolt loosening and damage of threads.A three-dimensional finite element model used to simulate the bolted joint under axial excitation is created using ABAQUS, through which the frictional stress, slip amplitude and frictional work per unit area along two specified paths on the first thread are studied. It is found that the FE results agree with the experimental observations very well