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RESEARCH PAPERS

Finite Element Modeling of Self-Loosening of Bolted Joints

[+] Author and Article Information
Ming Zhang

Department of Mechanical Engineering (312), University of Nevada, Reno, NV 89557

Yanyao Jiang1

Department of Mechanical Engineering (312), University of Nevada, Reno, NV 89557yjiang@unr.edu

Chu-Hwa Lee

Advanced Engineering Center, Ford Motor Company, 20000 Rotunda Drive, Dearborn, MI 48121

1

Corresponding author.

J. Mech. Des 129(2), 218-226 (Jan 25, 2006) (9 pages) doi:10.1115/1.2406092 History: Received March 21, 2005; Revised January 25, 2006

A three-dimensional finite element (FE) model with the consideration of the helix angle of the threads was developed to simulate the second stage self-loosening of a bolted joint. The second stage self-loosening refers to the gradual reduction in clamping force due to the back-off of the nut. The simulations were conducted for two plates jointed by a bolt and a nut and the joint was subjected to transverse or shear loading. An M12×1.75 bolt was used. The application of the preload was simulated by using an orthogonal temperature expansion method. FE simulations were conducted for several loading conditions with different preloads and relative displacements between the two clamped plates. It was found that due to the application of the cyclic transverse load, microslip occurred between the contacting surfaces of the engaged threads of the bolt and the nut. In addition, a cyclic bending moment was introduced on the bolted joint. The cyclic bending moment resulted in an oscillation of the contact pressure on the contacting surfaces of the engaged threads. The microslip between the engaged threads and the variation of the contact pressure were identified to be the major mechanisms responsible for the self-loosening of a bolted joint. Simplified finite element models were developed that confirmed the mechanisms discovered. The major self-loosening behavior of a bolted joint can be properly reproduced with the FE model developed. The results obtained agree quantitatively with the experimental observations.

Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

Three-dimensional finite element mesh model

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Figure 2

Finite element results and experimental observations

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Figure 3

Clamping force reduction with the influence of Δδ∕2(P0=25kN)

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Figure 4

Nut rotation with the influence of Δδ∕2(P0=25kN)

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Figure 5

Influence of preload (Δδ∕2=0.45mm)

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Figure 6

Influence of friction coefficient between the clamped plates on the FE results

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Figure 7

First engaged nut thread

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Figure 8

Variations of contact pressure of three nodes with loading cycles

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Figure 9

Variations of contact pressure distribution with loading along the arc ABCED

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Figure 10

Amplitude and mean value of the contact pressure distribution

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Figure 11

Microslip amplitude along the contact surface of the first engaged thread

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Figure 12

Distribution of microslip amplitude in the bolt axial direction

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Figure 13

Equivalent loading scheme to the surface contact of the engaged threads

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Figure 14

Microslip model

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Figure 15

Simulation result from the microslip model (Fig. 1)

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Figure 16

Analytical model for microslip mechanism

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Figure 17

Slip–stick model

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Figure 18

Simulation result from the slip–stick model (Fig. 1)

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Figure 19

Evolution of the slip–stick conditions in the contact area with the variation of the bending moment (refer to Fig. 1 for B, C, D in the bending history): (a) slip–stick condition when the bending moment reached 10Nm; (b) slip–stick condition after the bending moment returned zero from 10Nm; and (c) slip–stick condition after the bending moment reached −10Nm.

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