Free-Decay Measurement for Attenuation and Internal Friction
Ultrasonic attenuation has a great utility in the wide variety of materials characterization (Mason, 1958; Truell et al., 1969; Beyer and Letcher, 1969; Goebbels, 1980; Ritchie and Fantozzi, 1992). It is capable of sensing the dislocation mobility associated with deformation and heat treatment, and of determining the grain size of polycrystalline metals. The importance of attenuation for materials characterization is well recognized. Measurement difficulties are also well known and have prevented actual applications. This Chapter discusses a principle for the attenuation measurement with plane-bulk waves, relying on electromagnetic acoustic resonance (EMAR). Use of a noncontacting and weakly coupling EMAT has a distinctive advantage of eliminating the extra energy losses, which otherwise occur in case of using a conventional contacting transducer.
KeywordsInternal Friction Attenuation Coefficient Diffraction Effect Ultrasonic Attenuation Attenuation Measurement
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