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RESEARCH PAPERS

Application of an Ultrasonic Technique to Assess Contact Performance of Bolted Joints

[+] Author and Article Information
Massimiliano Pau1

Department of Mechanical Engineering,  University of Cagliari, Piazza d’Armi, 09123 Cagliari, Italypau@dimeca.unica.it

Antonio Baldi

Department of Mechanical Engineering,  University of Cagliari, Piazza d’Armi, 09123 Cagliari, Italy

1

Corresponding author.

J. Pressure Vessel Technol 129(1), 175-185 (Jul 13, 2006) (11 pages) doi:10.1115/1.2435719 History: Received July 28, 2005; Revised July 13, 2006

Bolted joints are a widespread type of connection used in mechanical engineering, but their performance, in terms of contact area size and shape and pressure distribution, is not easy to verify due to the nature of closed contact, which makes it difficult to investigate them with most experimental techniques. This study proposes the application of an ultrasonic method (through immersion scans of the potential contact region between the members of a bolted joint) aimed at obtaining both graphical maps of contact conditions and, after a calibration process, actual contact pressure distributions. The analysis is carried out on a number of joints characterized by different values of plate thickness and applied load. Moreover, to evaluate the quantitative accuracy of the ultrasonic technique, the results have been compared to those of another experimental technique (pressure-sensitive film) and numerical findings obtained by a finite element model of the experimental setup.

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Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

Bolted joint used for the experimental tests

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Figure 2

Schematic representation of the experimental setup for the ultrasonic tests

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Figure 3

Typical contact map obtained from ultrasonic reflection data: 1, no contact region; 2, bolt location; and 3, contact area

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Figure 4

Profile of ultrasonic reflection along a radius of the contact region for three levels of load (12-12 joint)

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Figure 5

Calibration curve (15MHz frequency, 0.2μm rms roughness)

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Figure 6

Result of a pressure-sensitive film analysis (8-8-600MPa)

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Figure 7

FE model of the bolted joints

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Figure 8

Typical contact pressure trend as obtained from the FE analysis (12-12-600MPa)

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Figure 9

Ultrasonic reflection maps for some of the bolted joints tested

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Figure 10

Procedure for calculation of contact pressure distribution starting from the ultrasonic reflection data

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Figure 11

Pressure trend along the contact radius: comparison between FE and ultrasonic results (error bars indicate ±2 standard deviation)

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Figure 12

Length of the contact radius: comparison between ultrasonic and pressure-sensitive film results (error bars indicate ±2 standard deviation)

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Figure 13

Contact map and cross profile for a bolted joint in which the surfaces of the plates are not planar. In this case, the contact area is no longer joined at the holes in the plates.

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