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RESEARCH PAPERS

An Experimental Investigation of the Effects of Clamped Length and Loading Direction on Self-Loosening of Bolted Joints

[+] Author and Article Information
Ming Zhang

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

Yanyao Jiang1

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

Chu-Hwa Lee

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

1

To whom correspondence should be addressed.

J. Pressure Vessel Technol 128(3), 388-393 (Jul 21, 2005) (6 pages) doi:10.1115/1.2217972 History: Received May 24, 2004; Revised July 21, 2005

An experimental investigation was conducted to study the effects of clamped length and loading direction on the self-loosening behavior of bolted joints by using specially designed fixtures. The experiments mimicked two plates jointed by an M12×1.75 class 10.9 bolt and a nut. The joints were subjected to cyclic external loading. A constant preload of 25kN was used for all the experiments conducted. During an experiment, the relative displacement between the two clamped plates, δ, was a controlling parameter. The reduction in clamping force, the applied transverse load, and the nut rotation were measured cycle by cycle. The relationship between, Δδ2, the amplitude of the relative displacement between the two clamped plates, and, NL, the number of loading cycles to loosening is referred to as self-loosening curve and was obtained for different clamped lengths and applied load directions. Similar to a fatigue curve, an endurance limit can be identified from the self-loosening curve. It was found that increasing the clamped length can enhance the self-loosening endurance limits in terms of the controlled relative displacement of the two clamped plates. However, the load carrying capability was not influenced significantly due to the thickness of the clamped plates. For a given bolted jointed structure, an angle of the external load from the pure shearing direction resulted in an increase in self-loosening resistance.

Copyright © 2006 by American Society of Mechanical Engineers
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References

Figures

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Figure 19

Applied load versus δ at the endurance limits for different applied load directions

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Figure 20

Influence of load direction on self-loosening endurance limit in terms of the amplitude of the applied load

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Figure 1

Experimental setup for self-loosening experiment

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Figure 2

Apparatus for the effect of loading direction

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Figure 3

Illustration of self-loosening process

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Figure 4

Self-loosening curve (L=48mm, ϕ=0deg)

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Figure 5

Self-loosening curve (L=58mm, ϕ=0deg)

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Figure 6

Self-loosening curve (L=68mm, ϕ=0deg)

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Figure 7

Self-loosening curve (L=54mm, ϕ=0deg)

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Figure 8

Self-loosening curve (L=54mm, ϕ=15deg)

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Figure 9

Self-loosening curve (L=54mm, ϕ=30deg)

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Figure 10

Influence of clamped thickness on self-loosening endurance limit

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Figure 11

Influence of applied load direction on self-loosening endurance limit

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Figure 12

An example of combined self-loosening and fatigue

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Figure 13

Variations of dP∕dN and dθ∕dN with clamping force

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Figure 14

Variation of thread friction coefficient with clamping force

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Figure 15

Variation of nut-bearing friction coefficient with clamping force

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Figure 16

An example with no nut rotation in previous study (see Refs. 4-5)

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Figure 17

Transverse load versus δ at the endurance limits for different clamped lengths

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Figure 18

Self-loosening endurance limit in terms of the applied load for different clamped

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