Values Of Sound Velocity Research Articles

Scatter of Young's Modulus E and of sound velocity values of pure metals

Abstract There exists a large scatter of Young's moduli handbook values. The most important reason for this is the diversity of measurement methods used in various laboratories. The average E-value of these measurements is not the best one. A more accurate value may be obtained by verification of handbook data for four elastic coefficients E, G, B and PR, using two known relations for isotropic materials. In some cases discussed by the author, a correlation exists between the E-moduli and the latent fusion heat magnitude sequences for a certain group of metals, which may be used for verification of some E-values. The E-values obtained in a previous MP-paper by the author published in Materials Testing 11–12/2004, using the relative method of calculation based on a correct E-value for pure aluminum, seem to be superior to those obtained directly by the formula E = V2d.

RECONSTRUCTION OF SOUND SOURCES BY MEANS OF AN INVERSE BOUNDARY ELEMENT FORMULATION

The self-developed Boundary Element code BEMCUP-3D solves structural-dynamic and acoustic problems as well as fluid-structure-interaction-phenomena in the frequency domain. Attainable outputs of this program are e.g. the system matrices. The inverse acoustic problem (sound source identification) is considered without inversion of matrices. The envelope surface (measurement surface), which encloses the entire arbitrarily shaped sound source, is treated as an exterior problem. The Dirichlet data on this surface or boundary are given from the proper sound pressure distribution of the sound source, which is also an exterior problem. This ensures that the corresponding velocity values on the measurement surface are exactly the same for both problems. Next the region between the sound source (an arbitrarily vibrating structure) and the envelope surface (a measurement surface in experimental investigations) is treated as an interior problem. The boundary conditions on the outer surface (measurement surface) for this problem are of Dirichlet type and the already available Neumann data, the sound pressure and the velocity distributions. An algorithm makes sure that after solving the unknown sound pressure and velocity values of the sound source are situated in the solving vector. Simple sound sources enable to investigate the stability, an optimal shape and an optimal position of the measurement surface.

Propagation of disturbances of pressure in a porous medium under conditions of filtration of a two-phase flow

The paper deals with the results of experimental investigation of unsteady-state processes in a channel with a porous medium under conditions of filtration of liquid-vapor flow and pressure disturbances initiated by injection of steam or noncondensing gases from an outside source. Singular features are studied of the propagation of pressure waves in a porous medium compared to dynamic processes occurring in an unfilled round pipe. The experimentally measured values of the propagation velocity of low-amplitude pressure waves in a channel with a pebble bed correspond to the calculated values of the equilibrium sound velocity of a liquid-vapor medium. It is for the first time that this result is obtained.

The use of acoustic microscopy to study the mechanical properties of glass-ionomer cement

Objectives. The aim of the study was to investigate the relationship between microstructure, acoustic and mechanical properties of hardened dental cement samples, prepared with different powder/water ratios. Methods. Glass-ionomer dental cement samples, prepared with a standard amount of cement powder and different amounts of water have been examined after being hardened. Surface microstructure and ultrasound, longitudinal and shear velocities were obtained with a scanning acoustic microscope. Conditional effective elastic modulus and Poisson's ratio have been calculated using longitudinal and shear sound velocity values. Then on the same samples elastic modulus and microhardness have been determined by standard tests. Additional samples have been used to determine compressive strength. Results. Density; conditionally instantaneous elastic modulus; high-elasticity modulus and compression strength of the samples decrease when large amounts of water were used for their preparation. At the same time porosity and microhardness of the cement matrix increase. Acoustic parameters and parameters of elasticity, calculated on the basis of sound velocity, demonstrated changes, similar to those obtained in standard mechanical tests. Significance. The established relation between microstructure, acoustic and mechanical parameters demonstrated a high capacity of acoustic microscopy application for non-destructive characterization of dental materials. A particular advantage of the acoustic microscopy is the opportunity to evaluate microstructure and mechanical properties on the same sample.

連続波超音波を用いた固体試料の音速測定とその補正法

In a sound velocity measurement in solid, the properties of electrical source and ultrasonic transducer bonded to a solid material become the error sources. In this paper, the error sources are estimated from the simulation using transmission line model of a measurement system and their experiments. A novel method for correcting the measured values of sound velocity by a numerical fitting is suggested. The usefulness of our method is demonstrated by comparing with other methods. Sound velocity measurement with the accuracy better than 1% without regard to the electrical and mechanical effects or bonding layers effects have been successfully accomplished.

Volumetric Properties of Surfactant in Water and in Mixed Solvent from Sound Velocity and Density Measurements

Abstract A simple, automatic and economic apparatus was constructed for a precise measurement of sound velocity using a resonance method. It gives the sound velocity value with an accuracy of less than 3×10-3% (±2 cm s-1). Sound velocity and density measurements were carried out in aqueous solutions of several compounds of alkyltrimethylammonium bromide (C1TAB, C8TAB, C10TAB, C12TAB, C14TAB, and C16TAB, where Ci is the number of carbons in straight-chain hydrocarbon groups) at 25 °C. Also, the measurements for C12TAB in a mixed solvent with water and 2-propanol were performed. The critical micelle concentrations (CMC) were determined from the inflection point of the compressibility and electric conductivity. The partial molar adiabatic compressibility (κm* ) and the partial molar volume (Vm*) for the surfactant were determined below and above CMC in water and in the mixed solvent from the apparent molar quantities. The partial molar quantities were also found to be dependent on the concentrations of the added alcohol. These results were interpreted from the points of view of the surfactant conditions and solvent structures.

STRUCTURE, VIBRATIONAL, AND CALORICAL PROPERTIES OF FULLERENE C60IN TOLUENE SOLUTION

The structure, vibrational and calorical properties of fullerene C60 in toluene solution were investigated both experimentally and theoretically in detail. The aggregation kinetics results indicated that the structure of C60 aggregates in toluene could be described as a fractal system. The electronic absorption spectra of C60 toluene solution with different concentration testify to the molecular character of absorption. The vibrational spectrum of smallest stable spherical cluster formed from the 13 single fullerene C60 molecules in toluene solution was calculated using the molecular dynamics approach and compared with Raman spectroscopy data. The numerical values of thermodynamical coefficients αP, βT,βS, cP, cV and sound velocity were determined from the (P-ρ-T) data measured for C60 toluene solution.

Structure and thermophysical properties of fullerene C60 aqueous solutions

The structure and thermophysical properties of fullerene C60aqueous solutions were investigated both experimentally and theoretically. The aggregation kinetics results indicated that the structure of fullerene C60aggregates in water could be described as a fractal system. The IR and electronic absorption spectra obtained confirm the presence of the crystalline phase in aqueous solution. The numerical values of thermodynamic coefficientsαP,βT,βS,cP, andcV, and sound velocity were determined from the measured (P–V–T) data. The vibrational spectrum of the crystalline structure (Thsymmetry group) formed from the hydrated single fullerene C60molecules in aqueous solutions was calculated using the molecular dynamics approach.

Sound velocity in the head of the dwarf sperm whale, Kogia sima, with anatomical and functional discussion

The velocity of sound through spermaceti oil from the melon of two Kogia sima specimens, stranded in Florida in 1995, was determined across a range of temperatures between 7 and 38°C and at pressures between 0 and 90 atm. Sound velocity values ranged between 1395-1669 m s−1, increasing linearly with increasing pressure but decreasing non-linearly with increasing temperature. Polynomials were generated to describe sound velocity as a function of temperature and pressure for the core and peripheral lipids of the melon. The results suggest that, at normal body temperature, sound travelling from the back to the front of the melon would have a tendency to focus during dives to any depth, largely due to heat exchange across the periphery of the melon. Effects of changes in ambient temperature and pressure are described and discussed in relation to anatomy.

Elastic modules of solid C60: measurement and relationship with nanostructure

Elastic moduli of solid C60 have been measured in single crystal of primary fullerite and diverse metastable phases of polymerized and amorphous C60 synthesized under high-pressure high-temperature (HPHT) conditions within the wide range of pressure p=5–13GPa and temperature T=500–1870K. Small sizes and heterogeneity of HPHT samples admit application of the specific microacoustic technique. A focused ultrasonic beam and ultra-short probing pulses have been employed to measure sonic velocities and study elastic module within an area of 100–300μm in diameter. Ultrasonic measurements have revealed permanent increase of elastic module of HPHT phases when there is rise in pressure and temperature. The bulk elastic module K and shear module G are compared with those in diamond for three-dimensional (3D) polymerized C60. Amorphous C60 produced at the highest pressure p=13GPa and temperature T=1600–1900K possesses unique mechanical properties which includes the highest value of the longitudinal sound velocity (cL=26km/s) among substances now known and values of the bulk module (K≈700–800GPa) substantially greater than the bulk elastic module in diamond (K≈440∼490GPa). Essential elastic heterogeneity of the most HPHT states has been shown including smooth distribution of elastic properties over a specimen for crystalline polymerized phases.Experimental results as well as model calculations developed on the base of the finding evidence that elastic properties correlate with state of fullerene molecules, character and number of covalent bonds and nanostructure of the matter. Measuring elastic properties is one of the effective ways to get information on nanostructure of solid C60, to classify and identify its diverse phases.

Tensile stress dependence of the sound velocity in Fe-rich amorphous wires

Experimental results concerning the dependence of the longitudinal sound velocity in Fe 77.5Si 7.5B 15 amorphous wires on the tensile stress applied along the length of the wire are reported. We tested Fe 77.5Si 7.5B 15 amorphous wires, 125 μm in diameter, in the as-cast state and after stress–relief process. The measurements were made using the magnetostrictive delay line principle. The obtained results show a strong dependence of the longitudinal sound velocity in the amorphous wire on the applied tensile stress. For a given value of the bias magnetic field, the longitudinal sound velocity increases with increasing the tensile stress value. For about 16 MPa tensile stress and 700 A/m bias magnetic field values, the saturation value of the longitudinal sound velocity is reached.

Stress dependence of sound velocity in Fe-based amorphous wires

The dependence of the longitudinal sound velocity on the bias magnetic field and tensile stress in Fe/sub 77.5/Si/sub 7.5/B/sub 15/ amorphous wires are presented, The measurements were made using the magnetostrictive delay line principle. The results show that changes in longitudinal sound velocity with bias magnetic field and tensile stress applied along the length of amorphous wires are strongly dependent on the thermal treatment. In the as-cast state, the change of the longitudinal sound velocity is negligible. There is a monotonic dependence of the sound velocity value on the tensile stress up to about 12 MPa. For about 16 MPa and 600 A/m tensile stress and bias magnetic field magnitude, respectively the saturation value of the longitudinal sound velocity is reached.

Theoretical and experimental studies of surface waves on solid–fluid interfaces when the value of the fluid sound velocity is located between the shear and the longitudinal ones in the solid

The existence of two surface waves propagating on a plane solid–fluid interface is demonstrated when the value of the fluid sound velocity is located between the shear and the longitudinal ones in the solid. First, the Scholte–Stoneley dispersion equation is studied analytically and numerically to find the roots corresponding to the Stoneley and the Rayleigh waves. The anatomy of each one is then described with the formalism of the evanescent plane waves: both waves are unleaky. Finally, the results are confirmed experimentally by measuring the times of flight on a Plexiglas–water interface and on a PVC–water interface.

Ultrasonic Wave Propagation in Particle Compounded Gels

Attenuation and sound velocity in particle compounded agar were measured by an ultrasonic wave transmission technique at frequencies ranging from 1 MHz to 8 MHz. The observed values were discussed using Urick's theory for viscous suspensions. The measured values of attenuation and sound velocity were in good agreement with the calculated values using Urick's theory up to a particle concentration of 10%. This means that Urick's theory can be applied not only to suspensions, but also to particle compounded gels. Furthermore, from the investigation of the experimental results obtained using this theory, it was clarified that the attenuation depends on the particle density. In particular, it should be noted that n depends on the particle diameter (the attenuation α can be expressed with the equation α= α0fn, where α0 and n are constants and f is frequency). All measured and calculated results suggested that the acoustic properties in these kinds of particle compounded gels could be estimated theoretically.

Solution properties and sweetness response of selected bulk and intense sweeteners.

Two bulk sweeteners (sucrose and maltitol) and four intense sweeteners (acesulfame K, aspartame, sodium cyclamate, and sodium saccharin) are used in this study. Densities and sound velocity values of the sweeteners in solution are measured at 20 degrees C, and their apparent molar and specific volumes, their isentropic apparent molar and specific compressibilities, as well as their compressibility hydration numbers are calculated and reported. The introduction of solute molecules in water results in a volume change of the solvent as a result of attractive forces exerted by the solute molecules; such forces are in the form of electrostrictive or hydrogen-bonding forces, or charge-dipole attraction. Changes of molar volumes with increasing concentration give an indication of the extent of solute-solute interaction, whereas isentropic compressibilities give a direct measurement of the state of hydration of the solute molecules. The compressibility hydration numbers reported give an indication of the number of water molecules disturbed by the presence of each solute molecule in solution. Isentropic compressibilities seem to be a more sensitive parameter for distinguishing the bulk sweeteners from the artificial sweeteners. The sweetness response of the sweeteners is then explained in terms of their solution behaviors.

Phonon scattering in diamond films

Abstract We have studied the thermal conductivity κ of free standing diamond films with different quality and sizes of the crystallines in bulk. The measurements were performed in the temperature range 10–350 K by steady-state heat flux technique. We have estimated the value and temperature dependence of the phonon mean free path lp using the simple gas kinetic equation for thermal conductivity: κ≈1/3 l p C p v. The values of heat capacity Cp and mean sound velocity v are known from literature for massive crystals. At high (room) temperatures the mean free path of phonons is limited by the phonon–phonon Umklapp interaction and phonon scattering on point defect in bulk. Both these processes lead to increasing of lp(T) with cooling the sample but they have different temperature dependencies. So from lp(T) dependence one can judge the quality (purity) of the sample. At low temperatures the phonon-boundary scattering dominates and lp is limited by the crystalline sizes. The mean free path of phonons in the best of samples has reached the value of a few microns at temperatures 20–70 K, which agrees with the middle sizes of crystallites estimated from X-ray measurements and from microphotos. At lower temperatures the value of lp is increasing again. It can be attributed to the phonon penetration through the boundaries between crystallines. The temperature dependence of λ in this process follows l(T)∼T−(1−2).

Principles of local sound velocity and attenuation measurements using transmission acoustic microscope

Fundamentals of transmission acoustic microscopy as applied to measurements of sound velocities and attenuation in thin specimens and films are discussed. The method is based on measuring the output signal A as a function of a distance z between the radiating and the receiving lenses in the two-lens focusing system of the transmission microscope. It is proposed to measure the A(z) dependence twice: initially without a specimen, and then in the presence of it. When a specimen is absent, maximum of the A(z)-curve arises in the confocal position of the lenses. In the presence of an object, the main peak of the curve is shifted, and its magnitude diminishes. Measuring the changes makes it possible to determine local values of sound velocities and attenuation. For data interpretation a theory of formation of the output signal in the two-lens focusing system was developed. The relationship between the peak shift and the ratio of sound velocities in a specimen and a couplant contains a correction depending on beam angle aperture.

The case for a body-centered cubic phase (α′) for iron at inner core conditions

The molecular dynamics (MD) method is used to simulate the structures and elastic constants of liquid and solid iron at Earth's core conditions. The configurational energy of the iron system is approximated as a sum of Morse-type pair interactions between Fe ions. The contribution to pressure from the electronic thermal energy is taken from band structure calculations reported for solid iron. The three energy parameters for the Morse potential are determined empirically to reproduce (1) the volume compression data of hexagonal close-packed (hcp) iron up to 304 GPa at 300 K, (2) the density ϱ, bulk modulus K T , and volume thermal expansivities α of liquid iron at 1900 K, (3) the three elastic constants of face-centered cubic (fcc) iron at 1428 K, and (4) the α values of both fcc and hep iron at high pressures. Then we apply the MD method with the optimized potential to simulate ϱ, K S , μ (rigidity), and α of liquid, fcc, hcp, and bcc (body-centered cubic) iron at pressures up to 400 GPa, and temperatures up to 8000 K. At these P-T conditions, the fcc, hcp and bcc iron phases have very similar simulated values for both ϱ and K S , and the fcc and hcp phases also have essentially the same μ values. However, the predicted μ values are found to be much smaller for the bcc phase than for the fcc or hcp phase. We further apply the MD technique to simulate the 200 and 240 GPa phase transitions at high temperatures previously found from shock compression experiments by Brown and McQueen [Brown J.M., McQueen, R.G., 1986. Phase transitions, Grüneisen parameter, and elasticity for shocked iron between 77 GPa and 400 GPa. J. Geophys. Res. 91, 7485–7494]. When we interpret the 200 GPa and the subsequent 240 GPa transitions as the changes from hcp to bcc, and from bcc to liquid, in which the bcc phase and the other phases are considered to be nonmagnetic at these very high-pressure and high-temperature conditions, the MD simulated values of the longitudinal sound velocity drops at the two transitions compare well with the corresponding shock compression data. This prompts us to suggest that the bcc phase, unlike the hcp and fcc phases, duplicates the longitudinal sound velocity in the 200 to 240 GPa region as found by Brown and McQueen. This, in a consequence, suggests possible existence of bcc iron in the inner core conditions.

Relation for calculating the heat capacity at constant volume for multicomponent systems by using the values of sound velocity for the pure components and binary systems

It is known that heat capacities at constant volume CV can be calculated by using the relation connecting CV with values of sound velocity for these substances [A. J. Matheson, Molecular Acoustics (Wiley, London, 1971)]. The relation for calculating CV for mixtures following the lattice model of regular mixtures in the zero quasichemical approximation [I. Prigogine, The Molecular Theoryof Solutions (North Holland, Amsterdam, Interscience, New York, 1957)] on the basis of some data including sound velocity referring to the pure components has been derived. The analogous problem for mixed solutions, namely for the solutions containing several solutes, has been solved. The relation for calculating CV for a mixed solution consisting of the solvent and one of the solutes and having the same solvent chemical potential value (which the considered mixed solution has), follows the same conditions.

Ideal-gas specific heat and second virial coefficient of HFC-125 based on sound-velocity measurements

The sound velocity in gaseous pentafluoroethane (HFC-125, CF3CHF2) has been measured by means of a spherical acoustic resonator, Seventy-two sound-velocity values were measured with an uncertainty of ±0.01% at temperatures from 273 to 343 K and pressures from 101 to 250 kPa. The ideal-gas specific heats and the second acoustic-virial coefficients have been determined on the basis of the Sound-velocity measurements. The second virial coefficients calculated from the present sound-velocity measurements agree with literature values which were determined fromPVT measurements by means of a Burnett method.