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Frequency dependent directivity of periodic permanent magnet electromagnetic acoustic transducers
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Hill, Samuel Joseph and Dixon, S. (2014) Frequency dependent directivity of periodic permanent magnet electromagnetic acoustic transducers. NDT & E International, Volume 62 . pp. 137-143. doi:10.1016/j.ndteint.2013.12.009 ISSN 0963-8695.
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Official URL: http://dx.doi.org/10.1016/j.ndteint.2013.12.009
Abstract
Beam steering has been achieved using shear horizontal waves generated using a periodic permanent magnet (PPM) electromagnetic transducer (EMAT). Unlike phased arrays, where steering is achieved by carefully controlling the firing of individual elements, the spatial periodicity of the PPM EMAT is ultilised to steer the beam whilst exciting all elements simultaneously. Due to the periodic nature of the array, the interference of individual waves from each of the elements creates a highly frequency dependent angle of propagation, allowing the directivity to be changed by simply varying the frequency of the input signal. Simultaneous excitation precludes the need for complicated and expensive phased array hardware. A frequency domain model is developed so that the beam characteristics, such as steering angle and beam width, can be calculated, allowing for investigation into the beam steering qualities of the PPM transducer. Broadband pulsed generation is also demonstrated, showing how a wave is generated over a large range of angles, meaning a large area can be covered with a single pulse. Interesting properties of this wave, such as a variation of frequency as a function of angle, and how this can be useful, are also discussed.
| Item Type: | Journal Article | ||||||||||
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| Divisions: | Faculty of Science, Engineering and Medicine > Engineering > Engineering Faculty of Science, Engineering and Medicine > Science > Physics |
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| Journal or Publication Title: | NDT & E International | ||||||||||
| Publisher: | Elsevier Sci Ltd. | ||||||||||
| ISSN: | 0963-8695 | ||||||||||
| Official Date: | March 2014 | ||||||||||
| Dates: |
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| Volume: | Volume 62 | ||||||||||
| Page Range: | pp. 137-143 | ||||||||||
| DOI: | 10.1016/j.ndteint.2013.12.009 | ||||||||||
| Status: | Peer Reviewed | ||||||||||
| Publication Status: | Published | ||||||||||
| Access rights to Published version: | Restricted or Subscription Access |
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