Multiple Focused EMAT Designs for Improved Surface Breaking Defect Characterization

Thring, C.B. , Fan, Y. and Edwards, R.S. (2017) Multiple Focused EMAT Designs for Improved Surface Breaking Defect Characterization. In: 43rd Annual Review of Progress in Quantitative Nondestructive Evaluation, Atlanta, GA, USA, 17-22 Jul 2016, 020019. ISBN 9780735414747 (doi: 10.1063/1.4974560)

Abstract

Ultrasonic Rayleigh waves can be employed for the detection of surface breaking defects such as rolling contact fatigue and stress corrosion cracking. Electromagnetic Acoustic Transducers (EMATs) are well suited to this technique as they can directly generate Rayleigh waves within the sample without the requirement for wedges, and they are robust and inexpensive compared to laser ultrasonics. Three different EMAT coil types have been developed, and these are compared to assess their ability to detect and characterize small (down to 0.5 mm depth, 1 mm diameter) surface breaking defects in aluminium. These designs are: a pair of linear meander coils used in a pseudo-pulse-echo mode, a pair of focused meander coils also used in pseudo-pulse-echo mode, and a pair of focused racetrack coils used in pitch-catch mode. The linear meander coils are able to detect most of the defects tested, but have a much lower signal to noise ratio and give limited sizing information. The focused meander coils and the focused racetrack coils can detect all defects tested, but have the advantage that they can also characterize the defect sizes on the sample surface, and have a stronger sensitivity at their focal point. Measurements using all three EMAT designs are presented and compared for high resolution imaging of surface-breaking defects.

• Item Type: Conference Proceedings
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Thring, Dr Claire
• Authors: Thring, C.B., Fan, Y., and Edwards, R.S.
• College/School: College of Science and Engineering > School of Engineering > Systems Power and Energy
• ISSN: 0094-243X
• ISBN: 9780735414747
• Copyright Holders: Copyright © 2017 AIP Publishing
• First Published: First published in AIP Conference Proceedings 1806(1): 020019
• Publisher Policy: Reproduced in accordance with the publisher copyright policy