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  • 1
    Electronic Resource
    Electronic Resource
    Effect of precipitate coherency strains on acoustic harmonic generation (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 2957-2962 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A model is presented of the dependence of acoustic harmonic generation in polycrystalline solids on the coherency strains resulting from the lattice mismatch at the interface between the matrix material and a precipitated second phase in the matrix material. The acoustic nonlinearity parameter (a quantitative measure of acoustic nonlinearity) is shown to depend on the second, third, and fourth order elastic constants of the material, the precipitate-matrix lattice misfit parameter, and the volume fraction of precipitates. The model is applied to the artificial aging of aluminum alloy 2024 from the T4 to the T6 temper. Experimental measurements on samples of Al 2024 taken at various heat treatment times not only confirm the predictions of the model but together with the model provide a basis for assessing the influence of precipitate phase transformations on the aging process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364327
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Crystalline structure and symmetry dependence of acoustic nonlinearity parameters (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 3372-3380 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A quantitative measure of elastic wave nonlinearity in crystals is provided by the acoustic nonlinearity parameters. The nonlinearity parameters are defined for arbitrary propagation modes for solids of arbitrary crystalline symmetry and are determined along the pure mode propagation directions for 33 crystals of cubic symmetry from data reported in the literature. The magnitudes of the nonlinearity parameters are found to exhibit a strong dependence on the crystalline structure and symmetries associated with the modal direction in the solid. Calculations based on the Born–Mayer potential for crystals having a dominant repulsive contribution to the elastic constants from the interatomic pair potential suggest that the origin of the structure dependence is associated with the shape rather than the strength of the potential. Considerations based on variations in crystal symmetry during loading along pure mode propagation directions of face-centered-cubic solids provide a qualitative explanation for the dependence of the acoustic nonlinearity parameters on modal direction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357463
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Absolute ultrasonic displacement amplitude measurements with a submersible electrostatic acoustic transducer (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4182-4188 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An experimental technique for absolute measurement of ultrasonic wave particle displacement amplitudes in liquids is reported. The technique is capable of measurements over a frequency range of two decades with a sensitivity less than one angstrom. The technique utilizes a previously reported submersible electrostatic acoustic transducer (ESAT) [Rev. Sci. Instrum. 50, 31 (1979)] featuring a conductive membrane stretched over a recessed electrode. An uncertainty analysis shows that the displacement amplitude of an ultrasonic plane wave incident on the ESAT can be experimentally determined to better than 2.3%–4%, depending on frequency, in the frequency range of 0.5–15 MHz. Membranes with lower and more uniform areal densities can improve the accuracy and extend the operation to higher frequencies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143231
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Constant frequency pulsed phase-locked-loop instrument for measurement of ultrasonic velocity (1991)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 2451-2456 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new instrument based on a constant frequency pulsed phase-locked-loop (CFPPLL) concept has been developed to accurately measure the ultrasonic wave velocity in liquids and changes in ultrasonic wave velocity in solids and liquids. An analysis of the system shows that it is immune to many of the frequency-dependent effects that plague other techniques including the constant phase shifts of reflectors placed in the path of the ultrasonic wave. Measurements of the sound velocity in ultrapure water are used to confirm the analysis. The results are in excellent agreement with values from the literature, and establish that the CFPPLL provides a reliable, accurate way to measure velocities, as well as for monitoring small changes in velocity without the sensitivity to frequency-dependent phase shifts common to other measurement systems. The estimated sensitivity to phase changes is better than a few parts in 107.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1142262
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  • 5
    Electronic Resource
    Electronic Resource
    Liquid-membrane coupling response of submersible electrostatic acoustic transducer (1989)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 60 (1989), S. 487-488 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A mathematical model of the liquid-membrane coupling response of the submersible electrostatic acoustic transducer (ESAT) [Rev. Sci. Instrum. 50, 31 (1979)] is presented. The model predicts that the ESAT responds to an incident ultrasonic wave of frequency ω and a constant displacement amplitude ξ0 with an output that is proportional to 2ξ0[1+(σω/Z)2]−1/2, where σ is the membrane areal density and Z is the acoustic impedance of the immersion fluid. Measurements taken over the frequency range from 1 to 11 MHz are in good agreement with the model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140404
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  • 6
    Electronic Resource
    Electronic Resource
    Scanning electron acoustic microscopy of indentation-induced cracks and residual stresses in ceramics (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 1870-1872 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The ability of scanning electron acoustic microscopy (SEAM) to characterize ceramic materials is assessed. SEAM images of Vickers indentations in SiC whisker-reinforced alumina clearly reveal not only the radial cracks, the length of which can be used to estimate the fracture toughness of the material, but also reveal strong contrast, interpreted as arising from the combined effects of lateral cracks and the residual stress field left in the SiC whisker-reinforced alumina by the indenter. The strong contrast is removed after the material is heat treated at 1000 °C to relieve the residual stresses around the indentations. A comparison of these observations with SEAM and reflected polarized light observations of Vickers indentations in soda-lime glass both before and after heat treatment confirms our interpretation of the strong contrast.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104019
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Nonlinear acoustic response from precipitate-matrix misfit in a dislocation network (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 5469-5472 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An analytical model is presented for the effects on the acoustic nonlinearity of the interaction of matrix dislocations with precipitate coherency strains in metallic alloys. The acoustic nonlinearity parameters are shown to depend linearly on the dislocation density, volume fraction of precipitates and precipitate-matrix misfit parameters, and on the fourth power of the dislocation loop length. The model predicts changes in the acoustic nonlinearity parameter associated with the growth of precipitates during the artificial aging of aluminum alloy 2024 that are in good agreement with experimental measurements reported in the literature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368309
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  • 8
    Electronic Resource
    Electronic Resource
    Determination of precipitate nucleation and growth rates from ultrasonic harmonic generation (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 1952-1954 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An analytical model based on precipitate-dislocation interactions is presented that predicts a decrease in ultrasonic harmonic generation during the nucleation of precipitates and an increase during precipitate growth up to the point of precipitate-matrix coherency loss. The opposing effects allow independent, indirect assessments of nucleation and growth rates from a curve fit of the model equation to experimental data. Application to the assessment of S′ precipitation during the artificial aging of AA2024 yields a constant nucleation rate of 5.4×1015 m−3 s−1 and a growth rate increasing as the 1.2 power of time in the range 72–432 min during heat treatment at 463 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1311951
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