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Research Papers

A Mathematical Model for Vibration-Induced Loosening of Preloaded Threaded Fasteners

[+] Author and Article Information
Sayed A. Nassar, Xianjie Yang

Fastening and Joining Research Institute, Department of Mechanical Engineering, Oakland University, Rochester, MI 48309

J. Vib. Acoust 131(2), 021009 (Feb 18, 2009) (13 pages) doi:10.1115/1.2981165 History: Received November 12, 2007; Revised July 01, 2008; Published February 18, 2009

A mathematical model is proposed for studying the vibration induced loosening of threaded fasteners that are subjected to harmonic transverse excitation, which often causes slippage between the contact surfaces between engaged threads and under the bolt head. Integral equations are derived for the cyclic shear forces as well as the bearing and thread friction torque components. They depend on the ratio of the relative rotational to translational velocities. The relationship between the dynamic thread shear force and bending moment is developed. When the external transverse excitation is large enough, it causes the threaded fasteners to loosen. Numerical results show that the dynamic transverse shear forces on the underhead contact surface, and between the engaged threads, decrease the bearing, and thread friction torque components. The effect of bolt preload, bearing and thread friction coefficients, the amplitude of the harmonic transverse excitation, and the bolt underhead bending on the bolt loosening are investigated. Experimental verification of the analytical model results of the bolt twisting torque is provided.

Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

The relative movement on the underhead bearing surface to the joint members

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Figure 2

The RTb−ηb and RFb−ηb relationships under the transverse shear force Fbs, where ηb=vb1∕ωb

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Figure 3

(Fbs∕Tb)−ηb and (Fts∕Tt)−ηt relationships under the transverse shear force Fts, where ηb=vb1∕ωb and ηt=vt1∕ωt

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Figure 4

Schematic relative movement on the thread surface

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Figure 5

RTt−ηt and RFt−ηt relationships under the transverse shear force Fts, where ηt=vtx∕ωt

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Figure 6

The force diagram of the bolt

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Figure 7

The schematic diagram for bolt joint under transverse cyclic loading

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Figure 8

Schematic diagram under scenarios III and IV: (a) The kinetic diagram (b) force diagram of the bolt

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Figure 9

The schematic for scenario V under transverse cyclic loading

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Figure 10

The variations of the critical bearing friction torque Tb resistant to slippage under different transverse cyclic displacement excitations

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Figure 11

The variations of the critical thread friction torque Tt under different transverse cyclic displacement excitations

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Figure 12

The effect of bearing friction coefficient μb on the variation of the critical bearing friction torque Tb under transverse cyclic excitation

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Figure 13

The effect of preload F on the variation of the critical bearing friction torque Tb under transverse cyclic excitation

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Figure 14

The bending effect on the variation of the critical thread friction torque Tt under transverse cyclic excitation

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Figure 15

The bending effect on the variation of the critical bearing torque Tb under transverse cyclic excitation

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Figure 16

A schematic for the vibration loosening test machine (modified junker machine)

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Figure 17

Experimental and analytical data on the twisting and thread friction torques variation under the preload of 13,928N

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Figure 18

Experimental and analytical data on the twisting torque for a bolt preload of 9780N

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