Dependence Of Ultrasonic Velocity Research Articles

The Dependence of Ultrasonic Velocity in Ultra-Low Expansion Glass on Temperature

The coefficient of thermal expansion (CTE) is an important property of ultra-low expansion (ULE) glass, and the ultrasonic velocity method has shown excellent performance for the nondestructive measurement of CTE in large ULE glass. In this method, the accurate acquisition of the ultrasonic velocity in ULE glass is necessary. Herein, we present a correlation method to determine the ultrasonic TOF in ULE glass and to further obtain the ultrasonic longitudinal wave velocity (cL) indirectly. The performance of this method was verified by simulations. Considering the dependence of cL on temperature (T), we carried out the derivation of the analytical model between cL and T. Based on reasonable constant assumptions in the physical sense, a cL–T exponential model was produced, and some experimental results support this model. Additional experiments were carried out to validate the accuracy of the cL–T exponential model. The studies we conducted indicate that the cL–T exponential model can reliably predict the ultrasonic velocity in ULE glass at different temperatures, providing a means for the nondestructive CTE measurement of large ULE glass at a specified temperature.

Ultrasonic and Dielectric Studies of Polyurea Elastomer Composites with Inorganic Nanoparticles

The temperature dependence of ultrasonic velocity and ultrasonic attenuation were measured in polyurea elastomer composites with inorganic nanoparticles. The decrease in the ultrasonic velocity along with an attenuation maximum was observed above the glass transition temperature, Tg. The shape and position of this peak are directly proportional to the amount of embedded nanoparticles. In addition, the sharp anomalies in the ultrasonic velocity and ultrasonic attenuation were observed above the glass transition temperature in semicrystalline polyurea elastomers. These anomalies are related to the corresponding first order phase transition of these crystalline domain-containing networks. The ultrasonic attenuation peak related to glass transition is considerably smaller in these polyurea networks showing a small influence of the soft domains below the melting temperature, Tm. The first order phase transition in the semicrystalline polyurea elastomers shows a large temperature hysteresis of more than 10 K, which was confirmed by dielectric investigations. The addition of small amounts of inorganic nanoparticles resulted in a shift of the first order phase transition temperature in semicrystalline nanocomposites.

Non‐invasive characterisation method of carotid plaque composition using ultrasonic velocity‐change imaging

The instability of vessel plaque is thought to be associated with the size and distribution of the lipid core. Ultrasonic B-mode imaging (ultrasonic amplitude imaging) can visualise plaques, but it is unable to provide information about their composition. Based on the fact that the temperature dependence of ultrasonic velocity differs considerably between water and fat, the motivation for this reported work was that it was thought that ultrasonic velocity-change imaging could help characterise biological tissues. This method should be able to detect unstable plaque because it is lipid-rich. A blood vessel phantom of agar base material having similar ultrasonic properties to human soft tissue was made. A small piece of fat was inserted into the blood vessel phantom. Water (instead of blood) was passed through the model vessel using a tube pump. Ultrasonic velocity-change images were constructed from echo pulse waveforms obtained before and after warming using an ultrasonic transducer. Lipid-rich areas in the blood vessel phantom were obvious in the ultrasonic velocity-change image, but not in ultrasonic B-mode images. These results indicate that ultrasonic velocity-change imaging is able to characterise carotid artery plaque.

Evaluation of Residual Stresses in Carbon Steel Weld Joints by Ultrasonic L $$_\mathrm{{cr}}$$ cr Wave Technique

Ultrasonic based residual stress measurements are nondestructive and offer quantitative estimation of surface/sub-surface and bulk residual stresses. The underlying principle of the ultrasonic techniques is the ‘acoustoelasticity’ i.e. the stress dependence of ultrasonic velocity. Three pairs of 20 mm thick low carbon steel weld joints were fabricated using manual metal arc welding process with three marginally different heat inputs (optimum, marginally below optimum and above optimum) and used in the study. Critically refracted longitudinal (L $$_\mathrm{{cr}}$$ ) ultrasonic wave technique was employed for this study. This paper gives the details of development of ultrasonic L $$_\mathrm{{cr}}$$ wave based technique for residual stress measurements and the quantitative estimation of surface/sub-surface residual stresses in carbon steel weld joints. The study indicates lower value of tensile residual stress in weld joints made using marginally below optimum heat input when compared to the residual stress values in weld joints made using optimum and marginally above optimum heat inputs. The developed ultrasonic L $$_\mathrm{{cr}}$$ wave technique is found to be very sensitive even to the small variations in the residual stress profiles across the weld joints induced by marginally different heat inputs employed during welding.

Ultrasonic Properties of Plutonium Monochalcogenides

A computer program in MATLAB is developed for the numerical computation of ultrasonic properties in Pu- monochalcogenides in present investigation in the temperature range 100-300K along , and 111> directions. The program calculates the second and third order elastic constants, relaxation time, ultrasonic coupling constants and ultrasonic attenuation by considering the interaction of sound wave with complete spectrum of thermal phonon modes and by taking two basic parameters i.e., nearest neighbour distance and hardness parameters. The program has been successful for the study of (i) temperature dependence of the second and third order elastic constants, (ii) temperature and crystallographic dependence of ultrasonic velocities for longitudinal and shear waves with thermal relaxation time, ultrasonic coupling constants and ultrasonic attenuation for PuS, PuSe and PuTe. The behaviour of acoustic parameters as a function of higher temperature has been discussed in correlation with other thermophysical parameters.

Mean grain size evaluation of tungsten- and boron-carbide composites sintered at various temperatures by ultrasonic methods

In this study, the mean grain size of different ceramic-metal composites made from tungsten carbide and boron carbide have been determined with the ultrasonic velocity technique. In addition, the electroless coating method was used to coat the tungsten carbide samples. The prepared samples were sintered at different temperatures ranging from 1200°C to 1400°C in an argon atmosphere. Powders were placed in a 30 mm diameter mold and pressed using a hydraulic press at a pressure of 200 bar. The results were compared to the mean grain size obtained from Scanning Electron Microscopy (SEM). This study shows a clear dependence of ultrasonic velocity on grain size in composites of boron carbide and tungsten carbide. Especially the temperature dependence of mean grain size for tungsten carbide composites can be seen very clearly.

Acoustic studies of melting and crystallization of sodium nitrite nanocrystals in the pores of mesoporous silicate matrices

A conventional phase-pulse acoustic method was used to study melting and crystallization of sodium nitrite embedded in the pores of mesoporous silicate matrices. The pore diameter was 20, 37, and 52 A. The measurements were performed at a frequency of 3–8 MHz in the temperature interval 290–560 K. The temperature dependence of ultrasonic velocity was found to exhibit anomalies corresponding to phase transitions of sodium nitrite. The transitions were smeared in temperature and shifted to lower temperatures from the melting point T b of bulk sodium nitrite; the shift in crystallization temperature was greater than that of the melting temperature. The irreversible character of melting was revealed. The size dependence of the melting temperature of sodium nitrite was obtained. Phenomena observed in the experiments were discussed with the use of different size effect models.

Pressure dependence of elastic properties of low-silica calcium alumino-silicate glasses

The hydrostatic and uni-axial pressure dependence of elastic properties of a low-silica calcium alumino-silicate glass (LSCAS) is determined by ultrasonic pulse-echo techniques at room temperature. The experimental results are used to obtain the third-order elastic constants (TOECs) of these glasses. The pressure dependence of fractal bond connectivity of these glasses is discussed. The normal behavior of positive pressure dependence of ultrasonic velocities was observed for the glass. The pressure dependence of both shear modulus and bulk modulus are positive for these glasses.

Ultrasonic evaluation of hydride concentration in zirconium-niobium alloys

An ultrasonic method has been developed to observe the solid solubility phase transition of metallic hydride in zirconium-niobium alloy. This measured the change in ultrasonic velocity with temperature as the sample was cooled through the expected solid solubility temperature (SST). At the SST, free hydrogen forms a hydride precipitate within the metallic structure on cooling, and the temperature dependence of ultrasonic velocity was seen to change at this temperature, for both longitudinal and shear waves. These results were compared to those of thermal expansion, using a dilatometer, where again the SST could be estimated. Analysis of the data indicates that both measurements could be used as the basis for a possible nondestructive estimation of hydrogen content in these alloys.

Dependence of Ultrasonic Velocity on Porosity and Pore Shape in Sintered Materials

A new approach to predict the longitudinal and transverse ultrasonic velocities in porous materials is presented. The model is based on a previously derived Young's modulus-porosity correlation assuming spheroidal geometry of the pores. It is also assumed that the Poisson's ratio of porous materials does not change significantly with porosity. The longitudinal and transverse ultrasonic velocities are given as functions of the Young's modulus, Poisson's ratio, density of the pore-free material and of the porosity and axial ratio (z/x) of the spheroidal pores. Experimental data drawn from the literature on different porous sintered materials including SiC, Al2O3, YBa2Cu3O7−x , porcelain, sintered iron, Si3N4, and sintered tungsten, were used to verify the model. A strong relationship between pore shape and the slope of the ultrasonic velocity–porosity curve was confirmed. In general, the calculated values are in fairly good agreement with the experimental data. When the actual shape (axial ratio) of the pores was known, the approach was shown to predict the experimental data better than a similar model derived by Phani. It is suggested that the present approach, coupled with the measurement of the ultrasonic velocity, may constitute a simple nondestructive technique to gain knowledge of the morphology of the porosity in sintered materials.

Ultrasonic investigations of CuOP2O5 glass

The ultrasonic velocity and attenuation in four different samples of the (CuO)x(P2O5)1 − x glass system (x = 0.1500, 0.3030, 0.3768, 0.5106) have been measured at temperatures between 80 and 300 K using the ultrasonic pulse echo overlap technique at 10 MHz. The samples were prepared by the melt-quench method. The velocity data have been used to find the elastic moduli and Debye temperature for each composition. The results indicate that, for each composition, the velocities decrease slowly and steadily with increasing temperature and there is no indication of a minimum in the variation of velocity with temperature unlike many other glasses. The dependence of ultrasonic velocity and attenuation with temperature has been interpreted in terms of a thermally activated relaxation process. The model is based on an asymmetric double-well potential having distribution of both the barrier height and the asymmetry between the two wells. Attempts have been made to explain the apparent discrepancy found in the velocity variation between the theory and experiment.

Ultrasonic study of ferroelectric phase transition in DDSP

Abstract The paper presents the results of the temperature dependence of ultrasonic velocity and attenuation of longitudinal waves in the vicinity of ferroelectric phase transition temperature of Ca2 Sr(C2D2 CO2)6 single crystals. The dispersion of ultrasonic velocity, caused by a polarization relaxation, have been observed in the [100] direction. The polarization relaxation time, obtained from ultrasonic attenuation measurements, follows the Curie-Weiss law and is similar to one obtained from the dielectric measurements.

Acoustic investigations of the pressure-temperature phase diagram of Rb2ZnCl4 crystals

The influence of hydrostatic pressure on the temperature dependence of ultrasonic velocities, attenuation coefficients, and electroacoustic coefficient f is studied at the phase transition temperatures of Rb2ZnCl4 crystals. The pressure-temperature phase diagram is obtained. The results are considered within the frame of phenomenological theory.

Relaxation behavior of ultrasonic attenuation in YBa/sub 2/Cu/sub 3/O/sub 7/

It is shown that temperature-dependence ultrasonic attenuation data of YBa/sub 2/Cu/sub 3/O/sub 7/ at various frequencies exhibit anomalies at temperatures close to T/sub c/. These attenuation maxima are found to be the result of a relaxation mechanism added on top of an unusual attenuation background. It is proposed that the grain boundary motions induced by the structural distortion and the propagation of sound waves enhances the energy dissipation around T/sub c/. Whether this structural distortion is the consequence of the onset of a superconducting state remains undetermined. It is also possible that either a tunneling effect of the acoustoelectric effect contributes to sound energy dissipation. The temperature dependence of ultrasonic velocity shows a softening around T/sub c/ which may be an intrinsic property of high-temperature superconductors. >

Investigation of phase transitions in glyceride/paraffin oil mixtures using ultrasonic velocity measurements

AbstractA pulse echo technique has been used to measure the ultrasonic velocity of a number of 15% w/w glyceride/paraffin oil mixtures with increasing temperature (0–70 C). At the lower temperatures the glycerides are completely solid and there is a fairly steady decrease in velocity with temperature (ca. −3.8 ms−1C−1). As the temperature rises the glycerides become increasingly soluble in the paraffin oil and the velocity decreases more rapidly. Once the glyceride is completely soluble in the paraffin oil, a fairly steady decrease in velocity with temperature (ca. −3.3 ms−1C−1) resumes. The dependence of ultrasonic velocity on the amount of solid glyceride present means the technique can be used to investigate phase transitions in binary glyceride/oil mixtures.

Intermolecular Interactions in 4,4′-di-n-propoxy-azoxybenzene. Part II—Experimental

Abstract Temperature dependence of Ultrasonic velocity and specific volume have been studied in the case of 4,4′-di-n-propoxy-azoxybenzene dissolved in a non-interacting and non-mesogenic solvent, benzene, at different concentrations. The concentration of the liquid crystal molecules was chosen such that the intermolecular separation lies in the range of 8.5 A to 13.5 A. It was observed that the solutions of liquid crystalline substances exhibit interesting variations in the physical parameters as a function of temperatures. Physical quantities like adiabatic compressibility, molar sound velocity, molar compressibility and intermolecular freelength have also been calculated. Present study offers an experimental support to the probability distribution picture obtained with the help of our theoretical investigations.

Ultrasonic investigations of incommensurate Rb2Zncl4

Abstract Elastic properties of Rb2Zncl4 were investigated by measuring the velocity and attenuation of both, transversal and longitudinal ultrasonic waves propagating along the crystallographic axes. At the lock-in phase transition temperature only v44 shows a remarkable anomaly. This anomaly has been found to be asymmetric with respect to the interchange of oscillation and propagation direction of the transverse ultrasonic wave. The anomaly of v44 at Tc is proportional to the contents of commensurate regions in the IC structure. From the temperature dependence of ultrasonic velocities at the phase transition from paraelectric to IC phase the critical behaviour of the order parameter should correspond rather to the (n = 2)-Heisenberg-model than to the Ising model.

Dependence of ultrasonic velocity on structure in a homologous series of nonelectrolytes in aqueous medium

Ultrasonic velocities (u) have been measured for various concentrations (x), and (du/dx)x=0 evaluated, in dilute aqueous solutions of nonelectrolytes which form solid clathrate structures of type II, or are members of a homologous series of alcohols, ketones or cyclic ethers. Changes in (du/dx)x=0 in these classes of compounds were found to be correlated with changes in structure. Elongation of the hydrocarbon chain by addition of a CH2 group is accompanied by an increase in (du/dx)x=0. Replacement of C−C by C=C, C−H by C−OH, CH2) by −O−, and CH−OH by C=O, lead to decreases in (du/dx)x=0. It is postulated that maximal values of (du/dx)x=0 should be observed for hydrocarbons with only single C−C bonds.

The Sound Velocity near the Pressure Induced Tricritical Point of TGSe

The temperature dependence of ultrasonic velocities of TGSe single crystal was studied at several hydrostatic pressures. Particularly, the sound velocities near tricritical point ( T tri =40.6°C, p tri =5 kbar) were measured minutely. At atmospheric pressure, there is a difference between the transition temperature and the temperature at which the anomalous part of the sound velocity takes maximum. On approaching tricritical point, this temperature difference becomes small and disappears ultimately in the first order phase transition region. The pressure dependence of the magnitude of anomalous part of the sound velocity along the a * axis is examined. It is found that these pressure dependences are due to tricritical nature if the polarization relaxation is taken into account.

Measurement of Residual Stress Using the Temperature Dependence of Ultrasonic Velocity

Measurement of Residual Stress Using the Temperature Dependence of Ultrasonic Velocity