Effect of Pitch Difference on Anti-loosening Performance and Fatigue Strength for High Strength Bolts and Nuts

A slight pitch difference is considered between the bolt and nut in this study. Here, the pitch ofnut is α μm larger than the pitch of bolt. In the first place, the distance δ, of nut screwed onto bolt withoutany prevailing torque, is experimentally and analytically obtained for each level of α. Then, the relationshipbetween axial force and prevailing torque during tightening process is tested. According to the obtainedtorque-axial force relationship, for four different levels of α, the loosening experiment based on NAS3350(National Aerospace Standard) is performed, and the loosening and dropping status of the nuts areinvestigated. Considering both the anti-loosening ability and the clamping ability of the nut, the desirablerange of α is discussed. After that, according to the loosening experiment results, three levels of α areselected to make a further study about the effect of the pitch difference on the fatigue life of bolt. The fatigueexperiment is performed and the S-N curves are obtained. Finally, the finite element method is used to makea simulation of the fatigue experiment and the mean stress and stress amplitude at each thread bottom of boltare analyzed.13th International Conference on Fracture, June 16–21, 2013, Beijing, Chin

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-nutconnection of α=0 μm, the bolt fracture does not happen at the No. 1 thread by introducing a slight pitch difference of α=5 μm and α=15 μm, 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

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

Effect of Pitch Difference on Anti-loosening Performance and Fatigue Strength for High Strength Bolts and Nuts

A slight pitch difference is considered between the bolt and nut in this study. Here, the pitch ofnut is α μm larger than the pitch of bolt. In the first place, the distance δ, of nut screwed onto bolt withoutany prevailing torque, is experimentally and analytically obtained for each level of α. Then, the relationshipbetween axial force and prevailing torque during tightening process is tested. According to the obtainedtorque-axial force relationship, for four different levels of α, the loosening experiment based on NAS3350(National Aerospace Standard) is performed, and the loosening and dropping status of the nuts areinvestigated. Considering both the anti-loosening ability and the clamping ability of the nut, the desirablerange of α is discussed. After that, according to the loosening experiment results, three levels of α areselected to make a further study about the effect of the pitch difference on the fatigue life of bolt. The fatigueexperiment is performed and the S-N curves are obtained. Finally, the finite element method is used to makea simulation of the fatigue experiment and the mean stress and stress amplitude at each thread bottom of boltare analyzed.13th International Conference on Fracture, June 16–21, 2013, Beijing, Chin