Rotating Loosening Mechanism of a Nut Connecting a Rotary Disk Under Rotating-Bending Force

[+] Author and Article Information
Yasuo Fujioka

Material Engineering Division 3, Toyota Motor Corporation, 1200, Misyuku, Susono, Shizuoka, 410-1193, Japanfujioka@y.tec.toyota.co.jp

Tomotsugu Sakai

Training & Training Development Division, Toyota Techno Service Corporation, 5-5, Nishimachi, Toyota, Aichi, 470-0025, Japantomsakai@nano.tec.toyota.co.jp

J. Mech. Des 127(6), 1191-1197 (Feb 27, 2005) (7 pages) doi:10.1115/1.2049087 History: Received July 18, 2004; Revised February 27, 2005

Structures composed of a rotary disk and a shaft, which are fastened with bolts and nuts having tapered bearing surfaces, are loaded with a rotating-bending force. Upon investigation, two rotating mechanisms of the nut were derived. In one mechanism a high-pressure contact area is formed at the nearest loading point on threads and bearing surfaces. This leads to a difference in the curvature radii between the bearing surface of the disk and that of the nut. During the revolution of the disk, two friction torques occur in opposite directions on the bearing surface and the threads, respectively. The relative rotating direction of the nut is dominated by the greater torque. The other mechanism is due to the eccentricities caused by dimensional errors of the bolt, nut, and disk. By combining the two mechanisms, the rotations of the nuts either cause a loosening or tightening after many revolutions of the disk.

Copyright © 2005 by American Society of Mechanical Engineers
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Figure 1

Schematic diagram of the specimen

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Figure 2

Radii around a tapered bearing surface (a cross section perpendicular to the bolt axis)

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Figure 3

Deformation image of the bearing surface around a bolt and nut

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Figure 4

Direction of a nut rotation (the disk rotates clockwise and the bolt is fixed to the disk)

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Figure 5

Dimensions of the nut and rotary disk

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Figure 6

Experimental results of relative rotation of the nuts under rotating-bending cyclic loading

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Figure 7

Dimensions of radii

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Figure 8

Calculation results of the relative rotation of nuts under a rotating-bending force

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Figure 9

Phenomenon of the relative rotation of the nut during a single complete rotation of the rotary disk

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Figure 10

Relation among the load direction, high-pressure contact area position, and the rotating direction of the nut

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Figure 11

Experimental results of the relative rotation of the nut during a single complete rotation of the rotary disk

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Figure 12

Deformations by the external load on the bearing surfaces

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Figure 13

Slip direction due to the external load

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Figure 14

Direction of correction factors and modified values




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