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  • 1
    Electronic Resource
    Electronic Resource
    Absolute measurements of elastic-wave phase and group velocities in lossy materials (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 3477-3486 
    Details
    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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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Resonance techniques and apparatus for elastic-wave velocity determination in thin metal plates (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 192-198 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The principles of operation of a new pulsed ultrasonic resonance spectrometer are presented. The system incorporates: (1) the use of electromagnetic-acoustic transducers (EMATs), (2) a method of obtaining acoustic signals similar to the sampled continuous-wave scheme described by Bolef and Miller, (3) the Clark method of recording line shapes, and (4) a high power gated rf amplifier and a unique implementation of superheterodyne and quadrature phase sensitive detection circuitry. The result is a spectrometer capable of measuring both shear and longitudinal ultrasonic velocities in very thin samples with much greater reproducibility than other pulse methods. It also has applicability in measuring attenuation and other physical properties such as composite material bonding that can be accessed using ultrasound. Experimental results of tests using EMATs in the 0.1–20 MHz range on thin (1.27 and 2.49 mm thick) aluminum sheets are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144776
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Evaluation of pipeline girth welds using low-frequency horizontally polarized waves (1982)
    Springer
    Journal of nondestructive evaluation 3 (1982), S. 155-173 
    Details
    ISSN: 1573-4862
    Keywords: elastic waves ; electromagnetic transducers ; nondestructive evaluation ; ultrasonic transducers ; ultrasonic scattering ; ultrasonic waves ; wave phenomena
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The practical implementation of alternative acceptance criteria for pipeline girth welds requires the use of inspection tools capable of determining the principal dimensions and positions of planar flaws. A new ultrasonic inspection method is described that permits complete volumetric inspection of the girth welds. The new system uses noncontacting electromagnetic-acoustic transducers (EMATs) that operate at low ultrasonic frequencies (454 kHz). Theoretical models of the measurements are developed and verified experimentally. In addition, practical performance limits of the new system are established in terms of minimum flaw sizes that can be detected. The results are related to accept-reject curves based on a model of the failure processes. An inspection protocol for field applications is also described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00566557
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Determination of sheet steel formability using wide band electromagnetic-acoustic transducers (1992)
    Springer
    Research in nondestructive evaluation 4 (1992), S. 165-182 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01617526
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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