Finite Element Approach for Fatigue Life Prediction of Threaded Bolts with Experimental Validation

Predicting the fatigue life of threaded bolts is crucial in aerospace and mechanical assemblies where cyclic loading can cause early joint failure. Previous research conducted experiments to develop S-N curves for high-strength bolts under different pretension and temperature conditions (Zhang et al. 2024). However, there are a very few numerical methods that can replicate these results, especially for bolts with screw threads. In this work a finite element analysis (FEA) methodology is developed to predict the fatigue performance of threaded bolts under axial loading and validated using the experimentally derived Series-1 S-N data for M20 high-strength bolts. The approach includes detailed FEA modelling (3D solid) with explicit thread geometry to capture local stress distributions under cyclic tensile loading. Peak stress amplitudes are employed to estimate fatigue life by applying the Basquin relation and the Series-1 S-N curve. The results are compared with the calculated fatigue life to the published experimental dataset to check the accuracy of the correlation. Preliminary results show that the proposed FEA method aligns with the observed fatigue life within the experimental variability, confirming its effectiveness for directly assessing the fatigue of threaded bolts without pretension. This method provides an experimental based simulation methodology for aerospace bolt design, enabling engineers to incorporate validated fatigue predictions into digital engineering processes for ensuring structural integrity.