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Title: Considerations for Measuring Acoustic Birefringence in Thin Sheets Using Electromagnetic Acoustic Transducers

Abstract

In aluminium or steel sheets it is generally accepted that the energy of through thickness shear waves is steered into two orthogonal polarisations, parallel and perpendicular to the rolling direction of the sheet. Ultrasonic velocity measurements used to determine the orientation distribution coefficients (ODCs) in thin sheets can be obtained from the fast Fourier Transform of the time domain signal. In the case of thin birefringent samples, data from radially polarised shear waves can be analysed in the frequency domain allowing peaks to be resolved that correspond to the slightly different velocities associated with each shear wave polarisation. By rotating a linearly polarised electromagnetic acoustic transducer through 360 deg. in small increments it is observed that the calculated velocities are not constant and are dependent on the signal processing used with the fast Fourier Transform. Further investigation using simulated waveforms show that this inconsistency in calculated velocity was not due to any physical effect of the ultrasound in the test sample but rather an artefact of the data analysis itself.

Authors:
;  [1]
  1. Ultrasound Group, Dept. of Physics, University of Warwick, CV4 7AL (United Kingdom)
Publication Date:
OSTI Identifier:
21054938
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 894; Journal Issue: 1; Conference: Conference on review of progress in quantitative nondestructive evaluation, Portland, OR (United States), 30 Jul - 4 Aug 2006; Other Information: DOI: 10.1063/1.2718108; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ALUMINIUM; ALUMINIUM ALLOYS; BIREFRINGENCE; COMPUTERIZED SIMULATION; DATA ANALYSIS; FOURIER TRANSFORMATION; ROLLING; SHEAR; STEELS; TRANSDUCERS; WAVE FORMS

Citation Formats

Fletcher, M. P., and Dixon, S. Considerations for Measuring Acoustic Birefringence in Thin Sheets Using Electromagnetic Acoustic Transducers. United States: N. p., 2007. Web. doi:10.1063/1.2718108.
Fletcher, M. P., & Dixon, S. Considerations for Measuring Acoustic Birefringence in Thin Sheets Using Electromagnetic Acoustic Transducers. United States. doi:10.1063/1.2718108.
Fletcher, M. P., and Dixon, S. Wed . "Considerations for Measuring Acoustic Birefringence in Thin Sheets Using Electromagnetic Acoustic Transducers". United States. doi:10.1063/1.2718108.
@article{osti_21054938,
title = {Considerations for Measuring Acoustic Birefringence in Thin Sheets Using Electromagnetic Acoustic Transducers},
author = {Fletcher, M. P. and Dixon, S.},
abstractNote = {In aluminium or steel sheets it is generally accepted that the energy of through thickness shear waves is steered into two orthogonal polarisations, parallel and perpendicular to the rolling direction of the sheet. Ultrasonic velocity measurements used to determine the orientation distribution coefficients (ODCs) in thin sheets can be obtained from the fast Fourier Transform of the time domain signal. In the case of thin birefringent samples, data from radially polarised shear waves can be analysed in the frequency domain allowing peaks to be resolved that correspond to the slightly different velocities associated with each shear wave polarisation. By rotating a linearly polarised electromagnetic acoustic transducer through 360 deg. in small increments it is observed that the calculated velocities are not constant and are dependent on the signal processing used with the fast Fourier Transform. Further investigation using simulated waveforms show that this inconsistency in calculated velocity was not due to any physical effect of the ultrasound in the test sample but rather an artefact of the data analysis itself.},
doi = {10.1063/1.2718108},
journal = {AIP Conference Proceedings},
number = 1,
volume = 894,
place = {United States},
year = {Wed Mar 21 00:00:00 EDT 2007},
month = {Wed Mar 21 00:00:00 EDT 2007}
}
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