Two ultrasonic techniques employing electromagnetic-acoustic transduction are presented for performing measurements of the resonant torsional frequencies and Q of solid cylindrical metallic rods. One of these techniques uses long radio-frequency pulses to drive the sample into resonance and the other uses continuous-wave excitation. Measurements are performed on an aluminum alloy. Since the transduction involves no mechanical coupling, the background damping is low; the Q is 1.2×105 at 755 kHz with the sample simply supported on its side. The shear velocity is determined with an accuracy of better than 2 parts in 104 (limited by the uncertainty in the measurement of the sample radius).
Tópico:
Ultrasonics and Acoustic Wave Propagation
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31
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Información de la Fuente:
FuenteThe Journal of the Acoustical Society of America