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Proceedings Paper

Noncontact ultrasonic thickness gauging of aluminum sheet with submicron accuracy using Electromagnetic Acoustic Transducers (EMATs)
Author(s): Stuart B. Palmer; Stephen Dixon; Christopher Edwards
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Paper Abstract

We have developed a non-contact ultrasonic system capable of measuring the thickness of aluminium sheet with sub-micron accuracy. The thickness of sheet has been calculated from ultrasonic data obtained using a send-receive, radially polarized shear wave Electromagnetic Acoustic Transducer (EMAT). Sheets in the thickness range between 0.1mm to 0.5mm have been measured using this non-contact approach at a stand-off of up to 1.5mm. The ultrasonic echo trains have been processed using Fourier analysis to extract transit time measurements for the two possible shear wave polarizations within the sheet. Two broadband EMAT systems have been used to perform the measurements with center frequency of approximately 5 MHz and frequency content up to 10 MHz and 20 MHz respectively. The most accurate measurements of thickness on thin sheets have been made using Fourier analysis rather than direct temporal measurements and have yielded thicknesses accurate to within 0.2%. This accuracy is potentially of significant commercial benefit to sheet manufacturers. There are also other potential applications of this approach, particularly for the measurement of very thin layers on aluminium substrates and these will be discussed in the presentation.

Paper Details

Date Published: 18 June 2002
PDF: 9 pages
Proc. SPIE 4704, Nondestructive Evaluation and Health Monitoring of Aerospace Materials and Civil Infrastructures, (18 June 2002); doi: 10.1117/12.470724
Show Author Affiliations
Stuart B. Palmer, Univ. of Warwick (United Kingdom)
Stephen Dixon, Univ. of Warwick (United Kingdom)
Christopher Edwards, Univ. of Warwick (United Kingdom)

Published in SPIE Proceedings Vol. 4704:
Nondestructive Evaluation and Health Monitoring of Aerospace Materials and Civil Infrastructures
Andrew L. Gyekenyesi; Steven M. Shepard; Dryver R. Huston; A. Emin Aktan; Peter J. Shull, Editor(s)

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