It is common knowledge that a bolt is apt to loosen due to slippage between the contact surfaces of joined parts. Loosening tests using real parts enable precise scrutiny of real phenomena under the influence of multiple factors such as slip distance, surface roughness, and coefficient friction. However, estimating the influence of the individual factors is very difficult because the friction forces of real contact surfaces are compiled based on variations in friction coefficients, meaning friction is not stable. Therefore, the effects of factors were investigated using Finite Element Analysis (FEA) to control friction coefficients. The procedures were as follows. Assuming a joined structure consisting of a bolt, nut, and washer, bolt axial tension was generated through constant movement of a washer in the bolt’s axial direction, following which the washer was constantly vibrated in one direction transverse to the bolt axis. This vibration generated displacements equivalent to the degree of slippage between the two clamped parts. During vibration, the rotating angles of the bolt and the contact pressure of the threads and bearing surfaces were calculated. The results were as follows. The vibrating displacements of a washer have considerable influence on the rotational loosening of a bolt. In cases where there was only minor displacement of the washer vibrations, the rotational loosening angle rapidly decreased, although the loosening did not cease completely. Therefore, the magnitude of what is called “critical slip” was not confirmed under the conditions of this study. In addition, the friction coefficient has a significant influence on the rotational loosening of a bolt. When the respective friction coefficient values of the threads and bearing surfaces are not balanced, rotational loosening cannot continue. Surface roughness readily affects contact pressure, so it tends to make the contact pressure localized. In particular, high-pressure areas were affected by several projections set on the threads. However, under those conditions the rotational loosening did not differ greatly from the results of the fine surface models subject to the same vibrating amplitude and friction coefficient. Consequently, the localized contact pressure had little evident effect on loosening. Above all, FEA reproduced the loosening of the bolt, and the reference made in this analysis is useful.

1.
Sakai
T.
,
1978
, “
Investigations of Bolt Loosening Mechanisms (1st Report, On the Bolts of Transversely Loaded Joints)
,”
Bulletin of the JSME
,
21
, No.
159
, pp.
1385
1390
2.
Yamamoto
A.
, and
Kasei
S.
,
1984
, “
A Solution for Self-Loosening Mechanism of Threaded Fasteners under Transverse Vibration
,”
Bulletin of the JSPE
,
18
, No.
3
, pp.
261
266
3.
Zadoks
R. I.
, and
Kokatam
D. P. R.
,
2001
,
Investigation of the Axial Stiffness of a Bolt Using a Three-Dimensional Finite Element Model
,
Journal of Sound and Vibration
,
246
, No.
2
, pp.
349
373
4.
Pai
N. G.
, and
Hess
D. P.
,
2002
,
Experimental Study of Loosening of Threaded Fasteners due to Dynamic Shear Loads
,
Journal of Sound and Vibration
,
253
, No.
3
, pp.
585
602
5.
Pai
N. G.
, and
Hess
D. P.
,
2002
,
Three-Dimensional Finite Element Analysis of Threaded Fastener Loosening due to Dynamic Shear Load
,
Engineering Failure Analysis
,
9
, pp.
383
402
6.
Pai
N. G.
, and
Hess
D. P.
,
2003
,
Influence of fastener placement on vibration-induced loosening
,
Journal of Sound and Vibration
,
268
, No.
3
, pp.
617
626
7.
Hobbs
J. W.
,
Burguete
R. L.
, and
Patterson
E. A.
,
2003
,
Investigation into the Effect of the Nut Thread Run-Out on the Stress Distribution in a Bolt Using the Finite Element Method
,
Journal of Mechanical Design
,
125
, No.
3
, pp.
527
532
8.
Fukuoka
T.
, and
Takaki
T.
,
2003
,
Elastic Plastic Finite Element Analysis of Bolted Joint During Tightening Process
,
Journal of Mechanical Design
,
125
, No.
4
, pp.
823
830
9.
Yamamoto, A., 1995, Bolt Joints Engineering-Theory and Design (In Japanese), Yokendo, pp. 133–135
This content is only available via PDF.
You do not currently have access to this content.