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Abstracts
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Authors
Ogi, H; Hirao, M; Honda, T; Fukuoka, H
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Title
Ultrasonic diffraction from a transducer with arbitrary geometry and strength distribution
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Journal
J Acoust Soc Am 98 (2) Pt 1 Aug 1995 pp 1191-1198
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Abstract:The exact solution to the Hemholtz equation with a Dirichlet boundary condition is obtained to study three-dimensional ultrasonic diffraction phenomena and derive the numerical data of amplitude loss and the phase shift for correcting induced errors. Calculation is made for near field diffraction, for the rectangular transducers, and for the transducers with strength distribution on the radiating area. In the near field, where the wavelength and the propagation distance are comparable with each other, the longitudinal and shear waves undergo different diffraction. For transducers having a noncircular shape and a strength distribution on the area, both the amplitude loss and the phase shift experience different tendencies from the classical work on the circular piston source. Use of diffraction data specific to each measurement condition is then necessary to correct the errors. The calculated results are verified for pulse-echo measurements using a shear wave electromagnetic acoustic transducer.
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