Enhanced Surface Defect Detection Using Focused Electromagnetic Acoustic Transducers (EMATs)

Thring, C.B. , Somerset, W.E. and Edwards, R.S. (2017) Enhanced Surface Defect Detection Using Focused Electromagnetic Acoustic Transducers (EMATs). In: 2017 ICU Honolulu: Sixth International Congress on Ultrasonics, Honolulu, HI, USA, 18-20 Dec 2017, 045001. (doi: 10.1121/2.0000683)

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Abstract

Electromagnetic Acoustic Transducers (EMATs) are non-contact ultrasound transducers which function primarily via Lorentz force induction. Their non-contact nature allows for fast scanning, inspection of challenging surfaces, and performance in harsh environments. To meet industry demand, non-destructive evaluation (NDE) techniques need increasingly high resolution for the detection of smaller defects. For surface acoustic wave inspection of surface-breaking defects, using a higher frequency wave gives better depth resolution. However, the EMAT coil width has to decrease to increase the frequency, leading to a trade off with the signal strength. The use of geometric focusing is showing promise for increasing ultrasound strength and defect imaging precision, overcoming some of the issues associated with the use of higher frequency surface acoustic waves. Understanding and optimising transducer design is essential to obtain optimal signal strength, high frequency operation, and the ability to operate at stand-off from the sample. In this work multiple focused and unfocused EMAT coil configurations are presented. Focusing is seen to give significantly enhanced resolution for defects, with accurate detection of thin cracks, 0.2 wide, 2 mm length, 1.5 mm depth. The relationship between coil design and stand-off is investigated. Multiple phased coils are proposed to increase signal strength without lowering the frequency.

Item Type:Conference Proceedings
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Thring, Dr Claire
Authors: Thring, C.B., Somerset, W.E., and Edwards, R.S.
College/School:College of Science and Engineering > School of Engineering > Systems Power and Energy
ISSN:1939-800X
Published Online:08 March 2018
Copyright Holders:Copyright © 2018 Acoustical Society of America
First Published:First published in Proceedings of Meetings on Acoustics 32(1): 045001
Publisher Policy:Reproduced in accordance with the publisher copyright policy

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