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RESEARCH PAPERS

Study of the Effect of Hole Clearance and Thread Fit on the Self-Loosening of Threaded Fasteners

[+] Author and Article Information
Sayed A. Nassar, Basil A. Housari

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

J. Mech. Des 129(6), 586-594 (Sep 06, 2006) (9 pages) doi:10.1115/1.2717227 History: Received January 13, 2006; Revised September 06, 2006

This study provides an experimental and theoretical investigation of the effect of hole clearance and thread fit on the self-loosening of tightened threaded fasteners that are subjected to a cyclic transverse service load. An experimental procedure and test setup are developed in order to collect real-time data on the rate of clamp load loss per cycle as well as the loosening rotation of the bolt head. Three levels of hole clearance are investigated; namely, 3%, 6%, and 10% of the bolt nominal diameter. For the commonly used 2A thread fit for a selected bolt size, three classes of the nut thread fit are considered; namely, 1B, 2B, and 3B. A simplified mathematical model is used for the analytical investigation of the effect of the hole clearance and thread fit on threaded fasteners self-loosening. The experimental and theoretical results are presented and discussed.

Copyright © 2007 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Schematic of the self-loosening machine

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Figure 2

The fixture used in the experimental setup

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Figure 3

Bolt free-body diagram

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Figure 4

Schematic of bolted joint

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Figure 5

Forces on the bearing surface

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Figure 6

Thread sector force components

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Figure 7

The force-angle curve

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Figure 8

Average loosening data for different hole clearance levels for the 1B-2A thread fit combination

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Figure 9

Effect of hole clearance on the number of cycles to complete loosening for the 1B-2A thread fit combination

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Figure 10

Average loosening data for different hole clearance levels for the 2B-2A thread fit combination

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Figure 11

Effect of hole clearance on the number of cycles to complete loosening for the 2B-2A thread fit combination

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Figure 12

Average loosening data for different hole clearance levels for the 3B-2A thread fit combination

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Figure 13

Effect of hole clearance on the number of cycles to complete loosening for the 3B-2A thread fit combination

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Figure 14

Effect of thread fit combinations on self-loosening for 3% hole clearance

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Figure 15

Effect of thread fit combinations on self-loosening for 6% hole clearance

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Figure 16

Effect of thread fit combinations on self-loosening for 10% hole clearance

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Figure 17

Schematic of the clearance between the bolt thread and the nut thread

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Figure 18

Clearance between threads for the 1B-2A, 2B-2A, and 3B-2A thread fit combination

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Figure 19

Simulation results for the minimum, average, and maximum thread clearance for the 1B-2A bolts

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Figure 20

Simulation results for the minimum, average, and maximum thread clearance for the 2B-2A bolts

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Figure 21

Simulation results for the minimum, average, and maximum thread clearance for the 3B-2A bolts

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Figure 22

Effect of thread fit on the number of cycles until complete self-loosening from 6000lb preload

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