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Absolute measurements of elastic-wave phase and group velocities in lossy materials (1992)

Fortunko, C. M. ; Peterson, G. L. ; Chick, B. B. ; [et al.]

[S.l.] : American Institute of Physics (AIP)

Review of Scientific Instruments 63 (1992), S. 3477-3486

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ISSN: 1089-7623

Source: AIP Digital Archive

Topics: Physics , Electrical Engineering, Measurement and Control Technology

Notes: 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 this 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 improvements, which increase the signal-to-noise ratio and linearity, and signal-processing 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 the phase velocities in a very lossy, 50-mm-thick, glass/epoxy specimen in the 0.3–1.2-MHz region.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.1143752

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Determination of sheet steel formability using wide band electromagnetic-acoustic transducers (1992)

Clark, A. V. ; Fortunko, C. M. ; Lozev, M. G. ; [et al.]

Springer

Research in nondestructive evaluation 4 (1992), S. 165-182

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ISSN: 1432-2110

Source: Springer Online Journal Archives 1860-2000

Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: Abstract An electromagnetic-acoustic transducer (EMAT) system was used in conjunction with a “sampled” CW signal-processing method to generate, receive, and process longitudinal and shear waves in thin steel sheets. Using the system, swept-frequency measurements were made up to 7.5 MHz. To relate the measurements to sheet steel formability, a dimensionless frequency ratio,K, was computed from the resonant frequencies. From theoretical considerations,K should be related to a measure of steel sheet formability, $$\bar r$$ . This parameter is traditionally measured by plastically deforming uniaxial tension specimens. Good correlation was found betweenK and $$\bar r$$ for a set of steel sheet representative of those typically used to produce automobile body parts.