Experimental Ultrasonic Data Research Articles

Ultrasonic absorption of aniline/cyclohexane mixtures of critical and non‐critical composition

AbstractResults of measurements of the temperature and frequency dependence of ultrasonic absorption (a/f2) of aniline/cyclohexane mixtures of critical and non‐critical composition are reported. The data obtained with the mixture of critical composition are analysed in terms of the Ferrell‐Bhattacharjee theory (Phys. Rev. A31, 1788 (1985)). The value of the critical amplitude ω0 of the relaxation rate used for calculation of the scaling variable Ω is obtained from static and dynamic light scattering data taken from the literature (ω0 = (42±3)GHz). This value of ω0 agrees with that obtained from a fit of the dynamic scaling function F(Ω) to the experimental ultrasonic absorption data (ω0 = (42±5) GHz).

Power-law relationships between the dependence of ultrasonic attenuation on wavelength and the grain size distribution

Grain size is one of the factors that influence mechanical properties of metals like strength and fracture toughness. Ultrasonic waves propagating in polycrystalline materials are subject to attenuation dominated by grain boundary scattering. The importance of grain size estimation for industrial applications warrants the investigation of alternative methods of nondestructive grain size determination. Analysis of the power-law behavior of ultrasonic attenuation experimental data is used to link the wavelength dependence of the attenuation coefficient directly to the grain size distribution. The outcome is a simple relationship between the power law that describes the grain size distribution and the power-law dependence of attenuation on wavelength. Careful attention is given to the limitations in terms of a practical grain size distribution with finite limits. Two types of measurements are presented to verify the theoretical development: grain size distribution and ultrasonic attenuation. Nickel samples were prepared using three different annealing durations. The attenuation exponent is experimentally shown to be an appropriate nondestructive measurement of the grain size distribution exponent.

A new wideband spread target maximum likelihood estimator for blood velocity estimation. II. Evaluation of estimator with experimental data

For pt.I see ibid., vol.38, p.1-16, Jan. 1991. The signal models and performance of the estimation strategies described in pt.I are tested with experimental ultrasonic data. The ultrasonic data analyzed verify the theoretical model and predicted performance. The averaged correlation, verified experimentally, confirms that the correlation envelope can be used to estimate the velocity of scatterers and that the shape of the correlation function conveys information regarding the velocity profile within the sample volume. For both the wideband point and range spread estimators, the predicted improvement in velocity resolution and the reduction in height of subsidiary velocity peaks are demonstrated. Through the use of these estimation strategies, information regarding the mean velocity and velocity variation are available for each spatial location within the vessel. This information is presented using a three-dimensional spatial velocity profile display, which appears to offer a number of advantages in the rapid identification of pathology.

Theoretical Evaluation of Sound Velocity and Other Acoustic Parameters for Aqueous Solutions of Sodium Dodecyl Sulphate (NaDS) at 298.15 K

Abstract The intermolecular free length Lf has been evaluated employing thermodynamic approach of Eyring and Hirschfelder while free length theory (FLT) of Jacobson has been used to compute the theoretical values of ultrasonic velocity. Subsequently, the theoretical values of other acoustic parameters were calculated. The results of theoretically calculated parameters have been compared with those derived from experimental ultrasonic velocity data. Both, v theo and v exp differ by 0.20% and v theo > v exp. The results for ⊘K theo and ⊘K exp show the maximum variation (62%) while data for R theo and R exp change by minimum (0.07%) and R theo > R exp.

On the feasibility of ultrasonic NDE to estimate the bond quality of diffusion-welded joints

A set of 14 diffusion-bonded test specimens with different bond qualities has been investigated by ultrasound using compressional and shear waves at normal incidence with frequencies from 2–15 MHz. The ultrasonic test results, double way transmission-to-reflection ratio and signal-to-noise ratio, have been correlated to the results of tensile tests and notched-bar toughness tests. Defects observed in metallographic and SEM images from the diffusion bonds are narrow long strips (unbonded valleys originating from the surface roughness and from coarse grains in the grinding wheel), flat areas in the bond line without enough recrystallization (areas in which the diffusion process was inhibited), and contamination with alumina powder in the bond plane. In order to gain a deeper understanding of the ultrasonic interaction with these defects and to predict optimal inspection parameters, the ultrasonic scattered amplitude has been calculated using a quasi-static model and has been compared to the experimental results. Except for the bond contaminated by alumina powder, the ultrasonic experimental data, the model calculations, and the mechanical test results are well correlated.

Evaluation of the First‐ and Higher‐Order Volume and Pressure Derivatives of Dielectric Constants of Alkali Halide Crystals

AbstractAn analysis of first and higher order volume and pressure derivatives of low frequency or static dielectric constant is presented for sixteen alkali halide crystals with NaCl structure using seven different potential forms for the short range overlap repulsive energy. The potential parameters are calculated using recent values of van der Waals potentials and taking proper account of the thermal contribution derived from consistent experimental ultrasonic data. Calculated values of volume derivatives of dielectric constant and optic mode Grüneisen parameters are compared with available experimental data. The results obtained from some potential forms present distinctly better agreement with experiment in comparison of others. The usefulness of such potential forms is demonstrated in predicting the higher order pressure derivatives of dielectric constants of ionic crystals.

Temperature derivatives at constant volume of the elastic constants of alkali halide crystals

A new method has been developed for calculating the temperature derivatives at constant volume of the elastic constants of the alkali halides using the concept of phonon pressure. Calculated values of temperature derivatives of elastic constants are compared with the corresponding values recently derived from ultrasonic experimental data.

Ultrasonic attenuation and the phase diagram of antiferromagnetic chromium

The authors have used the thermal activation model for polarisation domains in antiferromagnetic chromium to predict the ultrasonic attenuation in the magnetic field-temperature plane, explaining some experimental ultrasonic data and making predictions of new phase boundaries.

Brillouin scattering from surface waves

Reflection experiment Brillouin scattering data yield information about all relevant features of the surface wave problem, i.e., distinct surface waves, resonances with the bulk continuum and distortions of the continuum at and near the bulk band thresholds. All these effects are here studied by means of a straightforward application of the surface Green function matching method to 001-Si, 110-GaAs and polycrystalline Al. This allows for the discussion of (i) anisotropy features and (ii) an analysis of possible effects of changes of the elastic constants at the surface. It is shown that these cannot explain some remaining discrepancies between Brillouin scattering data on one hand and ultrasonic experimental data as well as theoretical calculations on the other hand.

Acid dissociation constants and rates as studied by ultrasonic absorption

Experimental ultrasonic absorption data on solutions of H2SO4 and H3PO4 are interpreted in terms of proton transfer equilibria. The acid dissociation constants obtained are compared with those obtained using other methods and are shown to be consistently lower. A model is proposed to explain this in terms of ΔVθ and ΔHθ involved in the steps leading to recombination of the proton with the anion. This model is supported by the values of the reaction distance parameters calculated from the value of the rate constant obtained for the recombination rate. The accuracy of this rate constant is dependent on the accuracy of the ΔVθ value used for the equilibrium. Experimental density data are presented here as an aid in determining ΔVθ. Problems involving activity coefficients in such solutions are discussed in the course of checking the values used for species present in sulfuric acid solutions.

Volume viscosity and structure of n-propanol by ultrasonics

The adiabatic volume viscosities η v and η′ v have been evaluated in n-propanol along with X 2 (the molefraction of molecules arranged in pairs with antiparallel dipole moments), using experimental ultrasonic absorption data in the temperature range 10°C to 80°C. Both η v and η′ v decrease nonlinearly with temperature and the ratio η′ v/η v is found to be nearly unity at all temperatures.

The soft acoustic phonon mode and its relation to the martensitic transformation in In-Tl alloys

Phonon dispersion curves for indium and f.c.t. and f.c.c. indium-thallium alloys have been calculated using the optimised model potential theory. The presence of a soft acoustic mode along [110], polarised [1 1 0] has been established. The closer the alloy composition is to the phase boundary, the softer this mode becomes: 1 2 (C 11–C 12) tends towards zero, in agreement with experimental ultrasonic velocity data.

Ultrasonic study of volume viscosity and structure of ethanol as a function of pressure

Structural volume viscosities η v and η v' have been evaluated in ethanol along with Δ V, Δ F and x 2 (the mole fraction of molecules arranged in pairs with antiparallel dipole moments) using experimental ultrasonic absorption data in the pressure range 1–5000 kg/cm 2. Both η v and η v' increase with pressure and the ratio η v/gh v' is found to be nearly unity at all the pressures. x 2 shows an exponential fall with pressure and Δ V shows a minimum at p ≈1000 kg/cm 2.

Relation between Ultrasonically Measured Properties and the Coefficients in the Solid Equation of State

A relation is found by straight forward thermodynamic methods between the derivatives with respect to pressure of the isothermal and adiabatic bulk moduli which gives (∂BT/∂p)T at zero pressure from the experimental (∂Bs/∂p)T plus temperature-dependent-only thermodynamic properties. Although BT<Bs is required by thermodynamics, we find (∂BT/∂p)T>(∂Bs/∂p)T for Cu, Ag, Au, Al, NaCl, and Na. The coefficients a1 and a2 in the equation of state are evaluated from ultrasonic experimental data and compared with those obtained by experiments in high pressure physics. Agreement between the a1's is good but between the a2's it is poor.