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Abstracts
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Authors
Fortunko, CM; Petersen, GL; Chick, BB; Renken; Preis
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Title
Absolute Measurements of Elastic-Wave Phase and Group Velocities in Lossy Materials
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Journal
Rev Sci Instr 63 (6) June 1992 pp 3477-3486
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Abstract: Traditional methods of determining phase and group velocities are often inadequate for many thick-section materials that exhibit greater than 30 dB, frequency-dependent propagation losses across the passband of the transducer. This article describes a measurement method that addresses the problem. Our method is mechanized as a pulsed, swept-frequency interferometer. The method's accuracy and reliability are enhanced by a combination of circuit-design methods which remove circuit related measurement errors and compensate for diffraction. First we describe the foundations of our measurement method and its mechanization. Then we describe the signal-processing procedures, used to calibrate the instrumentation and to determine the absolute phase and group velocities. To illustrate the method, we determine phase velocities in a very lossy, 50 mm thick, glass/epoxy specimen in the 0.3-1.3 MHz region.
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