P. Kiełczyński

New ultrasonic Bleustein-Gulyaev wave method for measuring the viscosity of liquids at high pressure

In this paper, a new method for measuring the viscosity of liquids at high pressure is presented. To this end the authors have applied an ultrasonic method using the Bleustein-Gulyaev (BG) surface acoustic wave. By applying the perturbation method, we can prove that the change in the complex propagation constant of the BG wave produced by the layer of liquid loading the waveguide surface is proportional to the shear mechanical impedance of the liquid. In the article, a measuring setup employing the BG wave for the purpose of measuring the viscosity of liquids at high pressure (up to 1 GPa) is presented. The results of high-pressure viscosity measurements of triolein and castor oil are also presented. In this paper the model of a Newtonian liquid was applied. Using this new method it is also possible to measure the viscosity of liquids during the phase transition and during the decompression process (hysteresis of the dependence of viscosity on pressure).

Measurement of the shear storage modulus and viscosity of liquids using the Bleustein–Gulyaev wave

In the article, a method for measuring the rheological properties of viscoelastic liquids using the (surface shear) Bleustein–Gulyaev (B–G) wave is presented. By applying the perturbation method, one can prove that the change in the complex propagation constant of the B–G wave produced by the layer of viscoelastic liquid loading the waveguide surface is proportional to the shear acoustic impedance of the liquid. From the analysis performed by the authors, it results that the sensitivity of the B–G wave method used to determine the rheological parameters of the liquid is even higher than the sensitivity of the Love wave method. In this article, a practical measuring setup employing the B–G wave for the purpose of measuring the rheological properties of the liquid is presented. Subsequently, by measuring the change in the velocity and attenuation of the B–G wave, the shear impedance of the liquid was evaluated. Knowledge of the shear impedance of the investigated liquid then made it possible to calculate, f...

Application of SH surface acoustic waves for measuring the viscosity of liquids in function of pressure and temperature

Viscosity measurements were carried out on triolein at pressures from atmospheric up to 650 MPa and in the temperature range from 10°C to 40°C using ultrasonic measuring setup. Bleustein-Gulyaev SH surface acoustic waves waveguides were used as viscosity sensors. Additionally, pressure changes occurring during phase transition have been measured over the same temperature range. Application of ultrasonic SH surface acoustic waves in the liquid viscosity measurements at high pressure has many advantages. It enables viscosity measurement during phase transitions and in the high-pressure range where the classical viscosity measurement methods cannot operate. Measurements of phase transition kinetics and viscosity of liquids at high pressures and various temperatures (isotherms) is a novelty. The knowledge of changes in viscosity in function of pressure and temperature can help to obtain a deeper insight into thermodynamic properties of liquids.

Employment of a novel ultrasonic method to investigate high pressure phase transitions in oleic acid

In this work, the variation of sound velocity with hydrostatic pressure for oleic acid is evaluated up to 350 MPa. During the measurement, we identified the phase transformation of oleic acid and the presence of the hysteresis of the dependence of sound velocity on pressure. From the performed measurements, it can be seen that the dependence of sound velocity on pressure can be used to investigate phase transformations in natural oils. Ultrasonic waves were excited and detected using piezoelectric LiNbO3(Y-36 cut) 5 MHz transducers. The phase velocity of the longitudinal ultrasonic waves was measured using a cross-correlation method to evaluate the time of flight.

An application of Love SH waves for the viscosity measurement of triglycerides at high pressures

A new ultrasonic method of viscosity measurements at a high-pressure conditions has been presented. The method is based on the Love wave amplitude measurement. The same electronic setup as in the Bleustein–Gulyaev (B–G) wave method applied by the authors recently for a high-pressure measurement was adopted. The new sensors were made of metallic materials, which make them more reliable at high-pressure conditions. The method has been successfully applied for the viscosity measurement of some triglycerides at high-pressure conditions up to 1 GPa. The results have been compared with the earlier results obtained using B–G waves. This comparison has shown that Love wave method sensors are more reliable than B–G wave sensors and are also cheaper in fabrication, although the sensitivity of Love wave sensors is lower. During the measurement, the phase transitions in the investigated liquids were observed.

Admittance of axially polarized lossy piezoceramic cylinders loaded with a viscoelastic liquid

Analytical formulas for the electrical admittance of a viscoelastically loaded cylindrical piezoceramic resonator vibrating in a shear mode are established. In the analysis, mechanical losses in a piezoelectric ceramic and in a liquid were taken into account. The admittance was calculated based on the solutions of the equations of motion of the piezoelectric ceramics and viscoelastic liquid. These solutions fulfilled the appropriate boundary conditions on the cylindrical surfaces of the resonator. In this way, analytical formulas for admittance dependent on the material parameters of ceramics and viscoelastic liquid were established. Analyzing the obtained admittance diagrams, the changes in resonant frequencies Δfs and Δfm as a function of the liquid viscosity η were evaluated. From the numerical calculations of the authors it follows that the Kanazawa–Gordon formula, which is derived for planar resonators and relates the shift in resonant frequency to the viscosity of the Newtonian liquid, can also be v...

Piezoelectric sensors for investigations of microstructures

In the paper the application of a piezoelectric bimorph as a sensor to investigate surfaces is considered. The voltage sensitivity and the stiffness of bimorphs with a central metal plate is analysed. This metal plate reinforces the bimorph structure. The derived formulae are used to calculate the parameters of the sensors, which consist of different combinations of metal and ceramic layers. The sensors have been calibrated using the quasistatic method. The experimental results are in good agreement with the calculations. Possible methods for increasing sensor sensitivity are also discussed.

Determination of physicochemical properties of diacylglycerol oil at high pressure by means of ultrasonic methods.

The purpose of the paper is to address, using ultrasonic methods, the impact of temperature and pressure on the physicochemical properties of liquids on the example of diacylglycerol (DAG) oil. The paper presents measurements of sound velocity, density and volume of DAG oil sample in the pressure range from atmospheric pressure up to 0.6GPa and at temperatures ranging from 20 to 50°C. Sound speed measurements were performed in an ultrasonic setup with a DAG oil sample located in the high-pressure chamber. An ultrasonic method that uses cross-correlation method to determine the time-of-flight of the ultrasonic pulses through the liquid was employed to measure the sound velocity in DAG oil. This method is fast and reliable tool for measuring sound velocity. The DAG oil density at high pressure was determined from the monitoring of sample volume change. The adiabatic compressibility and isothermal compressibility have been calculated on the basis of experimental data. Discontinuities in isotherms of the sound speed versus pressure point to the existence of phase transitions in DAG oil. The ultrasonic method presented in this study can be applied to investigate the physicochemical parameters of other liquids not only edible oils.

Resonant piezoelectric ring transformer

We have investigated experimentally the factors which influence electrical and mechanical losses as well as harmonic generation in a piezoelectric ceramic. To this end, we have used a piezoelectric ring transformer. The experiments were done for rings with different dimensions of electrodes. The secondary circuit was open, short circuited or loaded by a small resistance. The results obtained can be used as a basis for the theoretical analysis of physical phenomena in piezoelectric ceramics under high power excitation. They can also be used to differentiate mechanical and electrical losses during transformer operation. This can have large practical importance when elaborating new ceramic compositions for various applications (actuators, sensors, etc.).

An inverse method for determining the elastic properties of thin layers using Love surface waves

Estimation of the mechanical and geometrical parameters of thin coatings and surface layers in materials is of great practical importance in engineering and technology. Indeed, surface properties of many vital engineering components, such as turbine blades, pistons, or bearings, directly affect the longevity and safety of modern machinery. In this article, the authors present a novel inversion procedure for simultaneous determination of thickness, shear elastic constant, and density of thin coating layers in materials. The inversion procedure is based on measurements of the dispersion curve for surface acoustic waves of the Love type. The inverse problem is formulated as an optimization problem with the appropriately designed objective function, depending on the material parameters of the coating layer, ultrasonic frequency, and the experimental data, i.e. measured phase velocity of the surface Love wave. The minimization of the objective function provides three parameters of a thin layer, i.e. its thickness, shear elastic constant, and density. The proposed inverse method was checked experimentally for different layered structures, such as copper layer on steel substrate or ceramics-on-ceramics. The agreement between the results of calculations with the proposed inversion method and the experimental data was good.