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RESEARCH PAPERS

Ultrasonic Control of Fastener Tightening Using Varying Wave Speed

[+] Author and Article Information
Sayed A. Nassar

Fastening and Joining Research Institute, Department of Mechanical Engineering, Oakland University, Rochester, MI 48309nassar@oakland.edu

Aditya B. Veeram

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

J. Pressure Vessel Technol 128(3), 427-432 (Aug 04, 2005) (6 pages) doi:10.1115/1.2218347 History: Received January 14, 2005; Revised August 04, 2005

A high precision ultrasonic technique and a test apparatus are developed for the real time control of the fastener elongation during the tightening process of bolted joints. This is accomplished by monitoring the propagation of longitudinal ultrasonic waves through the fastener material and the reflection of these waves at the end of the fastener. The round trip time of the longitudinal waves is continuously measured and monitored in real time. Using the wave speed in the fastener material, the change in the round trip time determines the fastener elongation, which creates fastener tension and joint clamp load. The wave speed through the bolt material is stress dependent; hence, it continuously changes as the fastener is being elongated during the tightening process. A varying wave speed algorithm is developed and utilized in order to compensate for wave speed variations. Because the torque-tension relationship in threaded fasteners is highly sensitive to friction variations, the scatter in such relationship is often unacceptable, especially in critical applications. By contrast, the automatic control of the fastener elongation during the tightening process would eliminate the dependence on the torque value as a predictor for the bolt tension. Hence, the new ultrasonic technique for the real-control of the fastener tension, by monitoring its elongation, would significantly enhance the reliability of bolted assemblies.

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Copyright © 2006 by American Society of Mechanical Engineers
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Figures

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Figure 1

Tension-elongation relationship

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Figure 2

Wave propagation in a stressed bolt

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Figure 3

Effect of bolt strain on material density

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Figure 4

Fastening test system apparatus

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Figure 5

Number of updates for M12 class 8.8 fastener at proof strength for different specifications

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Figure 6

Number of updates for M10 class 8.8 fastener at proof strength for different specifications

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Figure 7

Number of updates for M8 class 8.8 fastener at proof strength for different specifications

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Figure 8

Measurement error analysis on M12 bolt for different bolt grip lengths

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Figure 9

Measurement error analysis on M10 bolt for different bolt grip lengths

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Figure 10

Measurement error analysis on M8 bolt for different bolt grip lengths

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Figure 11

Graphical results for M12 fastener rundown (90mm bolt length)

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Figure 12

Graphical results for M10 fastener rundown (70mm bolt length)

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Graphical results for M8 fastener rundown (50mm bolt length)

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Figure 14

Verification graph of new technology with old technology and tensile test

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