Volume 104, Issue 5, November 1998
Index of content:
- ULTRASONICS, QUANTUM ACOUSTICS, AND PHYSICAL EFFECTS OF SOUND 
104(1998); http://dx.doi.org/10.1121/1.423856View Description Hide Description
It is well known that the circumferential waves supported by thin cylindrical, water-loaded shells correspond closely to those on a water-loaded plate, i.e., to the Scholte–Stoneley waveA and to the Lamb waves and Until now, however, it had not been possible to definitely observe the acoustic excitation of the wave on a shell using steady-state or long-pulse incident sound waves (while excitation of the A and waves was clearly evident). The reason for this is the rapid decay of the propagating waves, whose high attenuation also rendered their multicircuit resonances too broad to be individually observable. In the present experiment, carried out with ultrashort, spark-generated acoustic pulses whose diffraction by a steel shell is visualized by the shadowgraph method, the (“pseudo-Rayleigh”) wave could be observed immediately after its excitation, before it had any time to decay. Spectral analysis of its observed re-radiation permitted the extraction of its phase-velocity dispersion curve, which by comparison with previously calculated dispersion curves uniquely characterized it as being the wave.
Direct and continuous measurement of depth-dependent reflection coefficients of Rayleigh waves for surface discontinuity: Normal slot104(1998); http://dx.doi.org/10.1121/1.423857View Description Hide Description
A new method and principle were presented for the continuous measurement of the depth-dependent reflection coefficient of Rayleigh waves or their pulse interacting with various surface discontinuities. The method was to record the reflection echo amplitudes for varying depth during scanning the Rayleigh wave pulse with a small lateral beam width along a surface discontinuity with a small slope in depth. In the experiments using a declined slot and intensively focused Rayleigh waves, the coefficients were continuously measured with quite good reproducibility in the range of (slot-depth/Rayleigh wave wavelength) In the results showed good agreement with other experimental results that had been determined by conventional method [L. J. Bond, Ultrasonics71, 71–77 (1979); M. Hirao et al., J. Acoust. Soc. Am. 72, 602–606 (1982); H. M. Frost et al., Proc. Ultrason. Symp. IEEE (1975), 604–607] as intermittent point-to-point data and several numerical results [L. J. Bond, Ultrasonics71, 71–77 (1979); R. J. Blake and L. J. Bond, ibid. 28, 214–228 (1990); M. Munasinhe, Ph.D. thesis, McGill University, Canada 1973; A. K. Mal and L. Knopoff, Bull. Seismol. Soc. Am. 55, 319–334 (1965)]. Especially, in the extremely shallow range of the reflection coefficients, showing quite good agreement with the numerical estimation, were measured while any other experimental data for slots or down steps have not been reported in It was shown that the new method could be used to evaluate more conveniently and quantitatively the depth or depth profile of various surface features in the long-wavelength or shallow-depth region of about
104(1998); http://dx.doi.org/10.1121/1.423858View Description Hide Description
The Hill relaxation spectral function, originally designed for the description of dielectric relaxation spectra, has been applied to a variety of sonic attenuation spectra. Both theoretical models and measured broadband spectra have been considered. It was found that the Hill function can be favorably used to represent the acoustic relaxationproperties of critically demixing liquids but also of such liquidsystems that show precritical behavior. The Hill spectral function also complies with the thermal and viscoelastic boundary effects in suspensions and emulsions, with the special absorption characteristics of surfactant solutions with high critical micelle concentration, and with effects of cluster formation in solutions of transition metal halides. Empirical relations between the relaxation time distribution parameters of the Hill function and characteristics of theoretical models are displayed.
104(1998); http://dx.doi.org/10.1121/1.423859View Description Hide Description
This paper discusses the theoretical aspects of the scanning acoustic microscopy response when used to inspect layered solids with bond defects. By using the transfer matrix method and spring boundary conditions, the solution of elastic wave scattering by an interface weakness in a layered solid has been presented in the wave number domain. The microscopy response has been calculated by combining this scattering solution with the scanning acoustic microscopy model. The results show that the acoustic microscopy response is sensitive to normal bond compliance in all defocus range. However, the shear bond compliance has influence on the response only at large defocus. The relations between the microscopy response and bond compliances significantly depend on the defect width, shape, and the material properties of the layer and substrate.
104(1998); http://dx.doi.org/10.1121/1.423860View Description Hide Description
A technique for investigating magnetoacoustic phenomena such as the ultrasonic analogs of the Faraday, Cotton–Mouton, and Kerr effects is reported. This technique makes it possible to measure the ellipticity and the angle of rotation of the polarization plane of ultrasound.Measurements were made using data on amplitude and phase variations of the voltage on a receiving piezoelectric transducer as a function of the magnetic induction.