Fatigue Failure Analysis for Bolt-Nut Connections having Slight Pitch Differences using Experimental and Finite Element Methods

In this paper, fatigue failure is considered, for bolt-nut connections, when a slight pitch difference is introduced between the bolt and the nut. To improve the fatigue life, three types of pitch difference are produced on the specimens and the experimental results are compared and discussed in terms of FEM analysis. Considering the standard bolt-nut connection of alpha=0 mu m, the bolt fracture does not happen at the No. 1 thread by introducing a slight pitch difference of alpha=5 mu m and alpha=15 mu m, as observed from the experiments. Furthermore, it is found that the fatigue life can be extended by introducing suitable pitch differences. The effect of bolt-nut fitted clearance, on the fatigue failure is also investigated.