The angular resolution of Lamb mode detection

It is shown experimentally that the angular resolution of Lamb mode detection can be strongly enhanced by properly positioning the detector in the ‘‘leaky’’ field. For this purpose we studied a 1‐mm‐thick aluminum plate (140 mm×200 mm) which has two pairs of closely spaced Lamb modes (s 1,a 1 and s...

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Bibliographic Details
Published in:Review of scientific instruments 1991-12, Vol.62 (12), p.3051-3055
Main Authors: Laperre, J., Thys, W., Notebaert, H.
Format: Article
Language:English
Subjects:
Acoustical measurements and instrumentation
Acoustics
Exact sciences and technology
Fundamental areas of phenomenology (including applications)
Physics
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Summary:It is shown experimentally that the angular resolution of Lamb mode detection can be strongly enhanced by properly positioning the detector in the ‘‘leaky’’ field. For this purpose we studied a 1‐mm‐thick aluminum plate (140 mm×200 mm) which has two pairs of closely spaced Lamb modes (s 1,a 1 and s 0,a 0) in the frequency region between 3 and 4 MHz. In order to obtain the necessary spatial resolution, the Lamb spectrum is measured by means of an acousto‐optical technique with a small aperture photodiode as detector. It turns out that for each pair of closely spaced modes, there is a detector position in the leaky field where the angular resolution is optimal. These results are explained by analyzing the acoustic profiles transmitted by the plate at different angles of incidence.
ISSN:0034-6748
1089-7623
DOI:10.1063/1.1142152