学術雑誌論文

学術雑誌論文

text

Journal of the Acoustical Society of America. 1995, 98(1), p. 458-464

Ultrasonic attenuation and grain-size evaluation using electromagnetic acoustic resonance

Acoustical Society of America

英語

text

1995-07

https://doi.org/10.1121/1.413703

Hirotsugu Ogi, Masahiko Hirao, and Takashi Honda. Ultrasonic attenuation and grain-size evaluation using electromagnetic acoustic resonance. Journal of the Acoustical Society of America, 1995, 98(1), 458. https://doi.org/10.1121/1.413703.

Electromagnetic acoustic resonance is applied for determining the frequency dependence of the ultrasonic attenuation and the average grain size of low-carbon steels. Use of a noncontacting electromagnetic acoustic transducer (EMAT) makes it possible to isolate the attenuation within the plate specimens. The method relies on the Lorentz force mechanism to couple the EMAT to the specimen surfaces and then eliminates the other losses, which may otherwise occur with the contacting piezoelectric transducers. The measurement is independent of the EMAT used, the specimen thickness, the surface condition, the lift-off, etc., and is stable because of the noncontacting nature. First, the resonant frequencies are measured, to the accuracy of 10 Hz, by sweeping the operating frequency and obtaining the amplitude spectrum over a band in the 0.520-MHz range. The ringing signals are excited and received by a shear wave EMAT and then processed with a superheterodyne receiver. Second, the attenuation coefficient as a function of the resonant frequency is determined. At each resonant frequency, the output signal rings down exponentially with time and the attenuation coefficient is obtained from the time constant by fitting an exponential decay to them. After correcting for the diffraction effect, the average grain size is obtained from the fourth-power term in the frequency dependence. The final results are favorably compared with the average of the three-dimensional grain-size distribution of steels.

Copyright 1995 Acoustical Society of America. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the Acoustical Society of America.

84150

Ultrasonic attenuation and grain-size evaluation using electromagnetic acoustic resonance

Acoustical Society of America

英語

1995-07

Journal of the Acoustical Society of America

98

1

458

464

https://doi.org/10.1121/1.413703

https://hdl.handle.net/11094/84150