Half-space radiation by EMATs

A Green's function calculation of the far field radiation patterns of three types of electromagnetic acoustic transducers (EMAT's), radiating into a half-space, is presented as a demonstration of a computational technique. Two of the EMAT's consist of periodically polarized magnets su...

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Bibliographic Details
Published in:Journal of nondestructive evaluation 1980-09, Vol.1 (3), p.157-181
Main Authors: PARDEE, W.J, THOMPSON, R.B
Format: Article
Language:English
Subjects:
Analysing. Testing. Standards
Applied sciences
Exact sciences and technology
Metals. Metallurgy
Nondestructive testing
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Summary:A Green's function calculation of the far field radiation patterns of three types of electromagnetic acoustic transducers (EMAT's), radiating into a half-space, is presented as a demonstration of a computational technique. Two of the EMAT's consist of periodically polarized magnets surrounded by solenoidal coils to produce, respectively, shear-horizontal (SH) and shear vertical (SV) bulk waves. The third consists of a uniformly polarized magnet and periodic meander coil, which produces SV bulk waves. The three components of the surface traction are calculated from Maxwell's equations, based on the assumption that the magnets are uniformly magnetized and the current flows uniformly through the coil. The eddy currents and static fields for the three EMAT's are included in the solutions to Maxwell's equations. The far-field response to an arbitrary (three-dimensional) point force (Green's function) on the surface of a half-space is calculated. The combination of these results is used to evaluate numerically the (nonpoint force) elastic wave radiation from the three EMAT's.
ISSN:0195-9298
1573-4862
DOI:10.1007/BF00567089