Theoretical Analysis of Preloaded Bolted Joints Subjected to Cyclic Loading

In this paper the performance of preloaded bolted joints is analysed. The prior torque tightening creates compression in the clamped members and tension in the bolt. So, when an external tensile load is applied to the joint a large amount of it is taken up by the members, thereby relaxing their compression, at the expense of only a slight increase in bolt tension. In this way preloading the joint has the effect of changing the bolt fatigue regime from a low mean load with high alternating load to a high mean load with a low alternating load. This is beneficial for its fatigue life.