Wave Attenuation Coefficient Research Articles

Bulk and Rayleigh Waves Propagation in Three-Phase Soil with Flow-Independent Viscosity

The flow-independent viscosity of the soil skeleton has significant influence on the elastic wave propagation in soils. This work studied the bulk and Rayleigh waves propagation in three-phase viscoelastic soil by considering the contribution of the flow-independent viscosity from the soil skeleton. Firstly, the viscoelastic dynamic equations of three-phase unsaturated soil are developed with theoretical derivation. Secondly, the explicit characteristic equations of bulk and Rayleigh waves in three-phase viscoelastic soil are yielded theoretically by implementing Helmholtz resolution for the displacement vectors. Finally, the variations of the motion behavior for bulk and Rayleigh waves with physical parameters such as relaxation time, saturation, frequency, and intrinsic permeability are discussed by utilizing calculation examples and parametric analysis. The results reveal that the influence of soil flow-independent viscosity on the wave speed and attenuation coefficient of bulk and Rayleigh waves is significantly related to physical parameters such as saturation, intrinsic permeability, and frequency.

On the Scattering of Love Waves in a Layered Transversely Isotropic Irregular Poro-viscoelastic Composite Rock Structure

ABSTRACT In the present investigation, the scattering characteristics of Love waves due to the surface irregularity in a transversely isotropic layered poro-viscoelastic rock structure have been studied. The effects of the anisotropy parameter and porosity parameter of the upper layer on the phase and attenuation coefficient of Love waves have been analyzed. The expressions for the induced reflected displacement have also been obtained for different types of surface irregularity, viz. parabolic type, rectangular type, and triangular notch type in the considered layered rock structure. The behavior of reflected displacement under the efficacy of several physical parameters has also been examined.

The Propagation of Thermoelastic Waves in Different Anisotropic Media Using Matricant Method

Thermoelasticity is a generalization of classical theories of elasticity and thermal conductivity and describes a wide range of phenomenon. The theory can precisely predict the propagation of thermoelastics waves in case of an isotropic medium. However, the propagation of thermoelastic waves in the anisotropic medium is not fully understood. In this case, the theory of elasticity employs an approximate theory of temperature stress which does not take into consideration the interactions of temperature and deformations. In this paper, an analytical study has been carried out by using method of matricant to investigate the propagation of longitudinal elastic and heat waves in the anisotropic medium of a monoclinic, trigonal, hexagonal, and cubical crystal systems. In this article, a solution to the problem of the propagation of thermal waves and the propagation of a thermal wave along z -axis has been obtained. The attenuation coefficient and phase velocity of thermal waves for various materials are determined. Specifically, the problem of propagation of heat waves in one dimension has been solved.

Plane wave and fundamental solution in steady oscillation in swelling porous thermoelastic medium

The present paper is concerned with the fundamental solution and propagation of plane waves in swelling porous thermoelastic medium (SPTH) consisting of mixtures of solid, fluid, and gas. Fundamental solution in the form of elementary functions is obtained. It is observed that there exist four longitudinal waves and two transversal waves prssaopagating with different velocities. Numerical computations are performed to compute phase velocities and attenuation coefficients of the plane waves propagating in the medium. The results so obtained are presented graphically and compared to cases of swelling porous medium (SP) and without swelling porous thermoelastic medium (ELTH). The significant effect of swelling porosity is studied on the phase velocity and attenuation coefficient due to propagation of plane waves. Some basic properties of the fundamental solution are also deduced in the assumed model. These results are quite useful in the field of oil exploration industries and structure-related problems.

Nondestructive assessment of local microcracking degree in orthoclase and plagioclase feldspars using spectral analysis of backscattered laser-induced ultrasonic pulses

The laser-ultrasonic method for nondestructive assessment of a microcracking degree in laboratory specimens of orthoclase and plagioclase feldspars is proposed. The influence of the local concentration of microcracks on the spectral efficiency of backscattering of pulses of longitudinal ultrasonic waves in the studied specimens (the so-called “structural noise power”) is studied. A specially designed laser-ultrasonic transducer used in experiments combines laser excitation of probe broadband ultrasonic pulses in a black polyethylene film and piezoelectric detection of both probe pulses and that scattered in the specimen. We study specimens of a potash feldspar and soda-calcium plagioclase with nonuniformly distributed local microcracks. The cracking domains were identified by optical microscopy as well as using the attenuation coefficient of longitudinal ultrasonic waves measured in these domains. The increase in the ultrasonic attenuation coefficient was associated with a higher concentration of microcracks, which efficiently scatter acoustic waves. At the same time, the domains with a higher ultrasonic attenuation exhibited an increased structural noise power. The direct correlation between the growth of the structural noise power and a higher local concentration of microcracks can be used as a basis of a system of nondestructive ultrasonic monitoring of occurrence and evolution of local microcracks in rocks and geomaterials under external loads of different nature.

Simultaneous measurement of thickness and sound velocity of porous coatings based on the ultrasonic complex reflection coefficient

The ultrasonic pulse-echo method is widely adopted in measuring coating thickness via parameter inversion of the reflection coefficient. However, the ultrasonic application to thermal barrier coatings (TBCs, as typically applied on aero-engine blades) remains a challenge, as the porous structure significantly attenuates sonic propagation, which is also difficult to characterize. In this article, a method that effectively addresses this issue without the need of the wave attenuation coefficient is presented. Specifically, the complex ultrasonic reflection coefficient can help calculate the coating-induced phase shift, which is found to linearly vary against the ultrasonic wave frequency. The slope of this linear function, depending on the structural porosity, enables simultaneous measurements of both the sound velocity and the thickness of the coating. Moreover, the effectiveness of the proposed method is verified by acoustic finite element simulations and experimental measurements of 8YSZ thermal barrier coatings.

Investigation of acoustic characterization of ultrasonic air coupling testing of NEPE propellant under strain control

To explore the acoustic characterization of composite solid propellant materials, the wave equation of the viscoelastic body was derived based on the linear viscoelastic constitutive model, and the theoretical relationship between ultrasonic sound velocity and attenuation coefficient, which are closely related to mechanical properties, such as elastic modulus, viscosity coefficient, and complex modulus, was obtained. Ultrasonic air-coupled testing experiments of the NEPE (Nitrate Ester Plasticized Polyether) propellant under different tensile strain states were carried out to obtain the variation law of ultrasonic transmission wave peak amplitude, sound velocity, and attenuation coefficient with strain variables in combination with the variation in propellant porosity under tensile strain. Furthermore, the acoustic parameters with strain and porosity were fitted by the regression equation, and the effect of mesoscopic damage on macroscopic mechanical properties was analyzed. The results show that with the increase in NEPE propellant tensile strain, the porosity increases exponentially. With the increase in porosity, the sound velocity decreases by first polynomials, the wave amplitude decreases by second polynomials, and the attenuation coefficient increases by third polynomials.

Experimental Study on Shear Wave Transmission in Fractured Media.

Unconventional oil and gas reservoirs have broad exploration and development prospects. Fracture parameters and effectiveness evaluation are two of the key tasks for the evaluation of these types of reservoirs. Array acoustic logging can be used for fracture evaluation to compensate for the deficiencies of the image logging fracture evaluation method. Therefore, to develop acoustic logging evaluation methods as well as nondestructive testing methods for fractures, experiments were conducted to study the shear wave transmission in fractured media. Experiment data demonstrate a good correlation between the shear wave attenuation coefficient and fracture width, and the shear wave attenuation coefficients rise logarithmically with the increase in the fracture width for all models with different porosities and distinct dip angles of fractures. The shear wave attenuation coefficient changes relatively faster with the fracture width when the fracture width is within 250 μm. In addition, the shear wave attenuation is affected by the core porosity and fracture dip angle. When the fracture width is constant, the shear wave attenuation caused by the 0° fracture is relatively larger and is obviously greater than that of the fractures at other angles, which is consistent with the existing experimental results. The results of this study can be used to guide further research on amplitude compensation methods for sonic signal transmission in fractured media and fracture evaluation methods.

Investigation of Ultrasonic Attenuation and Hardness Relationship in Ceramic-Metal Composites

In material characterization, they contain a large amount of information at the frequency obtained about the mechanical and physical properties of the material under investigation, thanks to shear waves during the longitudinal passage of ultrasonic waves from materials.In this study, an experimental study was carried out on metal matrix composite samples to examine the variation of some ultrasonic parameters such as wave attenuation coefficients. Ultrasonic longitudinal and shear attenuation values obtained in copper-silicon carbide composites were measured at 4 MHz using the pulse-echo technique. All of the produced samples were sintered at 1050 ºC using microwave sintering technique. The variation of the shear attenuation values with the longitudinal wave in the material with the % SiC volumetric percentages of the hardness in the samples were measured. The experimental results obtained are discussed and analyzed to develop a technique in ultrasonic nondestructive testing for microstructure determination. It contains a large amount of information in the frequency obtained about the mechanical and physical properties of the material examined by the passage of ultrasonic waves through the materials. In this study, an experimental study was carried out to examine the variation of some ultrasonic parameters such as wave attenuation coefficients on metal matrix SiC doped composite samples. Ultrasonic longitudinal and shear attenuation values of produced copper-silicon carbide composite samples were measured at 4 MHz frequency by pulse-echo technique. Variations of longitudinal and shear attenuation values and hardness with % SiC volume percentages were determined. The experimental results obtained are discussed and analyzed to improve the ultrasonic nondestructive testing method for microstructure determination.

Attenuation of acoustic waves and Grüneisen tensor in lithium fluoride crystals

The anisotropy of acoustic attenuation in lithium fluoride crystals in the range of 0.4–1.6 GHz was studied by the method of Bragg light diffraction on acoustic waves. The obtained values of the velocity and attenuation coefficient of acoustic waves were used to determine all independent real and imaginary elastic constants. Based on the Akhiezer attenuation mechanism, the anisotropy of acoustic attenuation was determined for the propagation of longitudinal and transverse waves in the (001) and (110) planes. All directions along which pure longitudinal and transverse acoustic waves propagate are found. To describe the anisotropy of acoustic attenuation, the Grüneisen acoustic tensor is used for the first time, the components of which have been determined from the values of the attenuation coefficient of acoustic waves along the crystallographic axes [100], [110], and [111]. It is shown that the orientational dependence of the effective Grüneisen constant, defined in terms of the components of this tensor, describes well the anisotropy of the attenuation of acoustic waves in the studied frequency range. The proposed approach can be used to all cubic crystals in which the main attenuation mechanism is the phonon–phonon Akhiezer mechanism.

Anisotropy of elastic and photoelastic properties of lithium niobate crystals

The elastic and photoelastic constants of lithium niobate crystals and the attenuation coefficients of acoustic waves at room temperature have been determined by the Bragg diffraction of light by sound. The components of the photoelasticity tensor were determined by the modified Dixon method. The obtained values of the constants were used to determine the anisotropy of the effective elastic and photoelastic constants with a change in the direction of propagation of acoustic waves in the (100) symmetry plane, for different directions of the wave vector and polarization of light relative to the sound wave vector. It is shown that, for certain geometries of the Bragg light diffraction, there is a correlation between the orientation dependences of the effective elastic and photoelastic constants in the investigated plane. The results of the study can be used to analyze the anisotropy of the photoelastic properties of lithium niobate crystals and determine the diffraction geometry with the highest efficiency of Bragg light diffraction.

Propagation Prediction of Body Waves in Fluid-Saturated Soils with Flow-Independent Viscosity

A systematic study of wave theory in thermoviscoelastic soil is essential for engineering applications such as geophysical exploration. In the present work, the influences of flow-independent viscosity of the soil skeleton and the thermal effect on elastic waves are considered, and the propagation behaviors of body waves in thermoviscoelastic saturated soil are investigated. Firstly, the thermoviscoelastic dynamic coupling model of saturated soil were established by employing the Biot model, the generalized thermoelastic theory, and the Kelvin–Voigt linear viscoelastic model. Secondly, the dispersion equations of body waves in thermoviscoelastic saturated soil were theoretically derived with structural symmetry considered. Finally, the variations of wave velocity and the attenuation coefficient of the body waves with the thermophysical parameters are discussed. The results revealed that the enhancement of the relaxation time of soil caused an increase of wave velocity and the attenuation coefficient of P1, P2, and S waves, and a decrease of the wave velocity and attenuation coefficient of the thermal wave. Different ranges of the permeability coefficient and frequency have different effects on the P1, P2, and S waves. The variation of thermal conductivity and the phase-lags of heat flux and temperature gradient only affect the thermal wave.

Justification of the parameters of a microwave installation with a metal-dielectric resonator for defrosting of colostrum of animals

The article is devoted to the substantiation of the structural performance of an ultra-high-frequency (UHF) installation of continuous flow action for defrosting and warming up animal colostrum. The dielectric parameters of colostrum in the frozen and liquid state were analyzed to determine the generated power and the depth of penetration of electromagnetic waves. For a given generator power, a threshold power that depends on the electric field strength (EF), and taking into account the change in the attenuation coefficient of electromagnetic waves during heating, a theoretical assessment of the optimal volume of raw materials in which animal colostrum is disinfected was carried out. These indicators are consistent with the design parameters of unconventional cavity resonators.

Evaluation of the surface damage of brittle materials based on the attenuation of laser-induced surface acoustic wave

In this paper, the surface damage of machined surface of brittle material is evaluated by using the attenuation of laser-induced surface acoustic wave (SAW) in propagation. Taking the typical brittle material single crystal silicon as an example, the feasibility of evaluating surface layer damage based on the attenuation of SAW is demonstrated theoretically and experimentally. Theoretical analysis shows that the micro-cracks produced in the processing of brittle materials can cause significant changes in the attenuation coefficient of SAW. After the lapped silicon wafer is etched, the surface roughness Ra is almost unchanged, while the attenuation coefficient of SAW decreases from 4.3 dB/cm to 2.0 dB/cm, which indicates that the surface layer damage of the silicon can still significantly change the attenuation coefficient after removing the influence of the surface roughness. After measuring the attenuation coefficients of SAW of silicon wafers in different processing steps, it is found that with the improvement of processing accuracy, the attenuation coefficient of SAW decreases, and the attenuation coefficient of SAW reflects the changes in surface damage. Experiments show that surface scratches can also significantly change the attenuation coefficient of SAW. Therefore, the wave attenuation coefficient of the laser-induced SAW can be used to evaluate the surface damage of the brittle material machined surface.

Influence of endotoxemy on development of non-alcoholic fatty liver disease

Objective — to investigate endotoxin levels and to assess the relationship between endotoxemia and metabolic parameters and the degree of steatosis and fibrosis in patients with non‑alcoholic fatty liver disease (NAFLD) against the background of metabolic syndrome (MS).
 Materials and methods. The study included 68 patients with NAFLD with metabolic disorders and 20 people of the control group. Women prevailed in both investigational groups, the mean age was 49.34 ± 10.8 years. All patients underwent evaluation of their anthropometric parameters, investigation of body composition with determination of the percentage of visceral adipose tissue (VAT). To reveal VAT dysfunction, visceral adiposity index (VAI) was calculated with M. C. Amato method. Steatometry was performed by determining the wave attenuation coefficient and carrying out shear wave elastography. Endotoxin levels in blood serum were determined using a set of reagents «LAL Chromogenic Endpoint Assay» manufactured by «Hycult Biotech» (Netherlands).
 Results. Bacterial endotoxin levels in peripheral blood in the examined patients were almost three times higher in comparison with the control group (p < 0.05). Patients with overweight and obesity had significantly higher endotoxin levels compared with the control group (p < 0.05). The significant increase in endotoxin levels has been defined in obese NAFLD patients compared to the NAFLD patients with normal weight (p < 0.05). The direct correlation was found between endotoxin parameters and parameters of abdominal and visceral obesity. In the group of patients with high VAT activity, the maximal values of this indicator were observed, which significantly differed from the corresponding indicator in patients with low and medium VAI (p < 0.05). There was a direct correlation between moderate endotoxin and insulin resistance, a direct weak relationship between endotoxin and lipid profile parameters. In patients with grade 2 and 3 steatosis, significant differences in the level of endotoxemia were observed compared with the control group (p < 0.05) and patients with grade 1 steatosis (p < 0.05). At high grades of liver fibrosis (F3F4) there was a tendency to reduce endotoxemia compared with the low‑grade fibrosis (p < 0.05).
 Conclusions. The revealed relationships between endotoxemia level and metabolic factors of NAFLD development indicate the pathogenetic role of bacterial endotoxemia in triggering a cascade of metabolic reactions with the subsequent accumulation of lipids in the liver tissue and the progression of steatosis and fibrosis.

A surface acoustic wave hydrogen sensor with tin doped indium oxide layers for intermediate temperatures

High temperature surface acoustic wave (SAW) gas sensors with conducting sensing layers require tuning of the sheet conductivity for optimal response. Conducting metal oxides are attractive sensing materials for their tunable electronic properties and high thermal stability, amongst others. Here, we have investigated the application of indium oxide (IO) and indium tin oxide (ITO) films on langasite (LGS)-based SAW reflective delay line sensor devices for monitoring hydrogen at 350 °C. Specifically, we modeled the effect of the IO and ITO sensing layer thickness on the wave velocity, attenuation, and effective electromechanical coefficient. This was followed by an experimental demonstration of tuning of the ITO film sheet conductivity by controlling the dopant concentration and yielding an improvement in the sensor sensitivity. The current study provides a pathway towards the development of conductivity-based sensing layers for high temperature SAW gas sensors with improved sensitivity.

Experimental investigation of wave attenuation and bulk drag coefficient in mangrove forest with complex root morphology

Mangrove forests play a crucial role in coastal protection. Numerous experimental studies have been performed to examine the interaction between wave flows and mangrove forests, while the mangrove forests are commonly modeled as cylinder arrays, and the effect of the complex root system on wave attenuation is still unclear. A series of physical experiments were conducted to study the hydrodynamic characteristics induced by a 10-m-long mangrove forest model, which was built to reproduce a mature Rhizophora forest. Wave-attenuation analysis was performed to highlight the importance of considering the wave damping produced by mangrove roots under different water depths. In addition, the wave-attenuation coefficient β increases linearly with an increase in the relative wave height and wave steepness to varying degrees. In addition, the bulk drag coefficient (CD), a key parameter for quantifying the mean vegetation resistance, was obtained based on the classical model proposed by Dalrymple et al. (1984). The influences of several dimensionless hydrodynamic parameters on the CD are discussed in detail. The results show that the Ursell number and Keulegan–Carpenter number (KCd) have stronger correlations with CD for vegetation models without roots. The KCLe number calculated using effective characteristic length Le is suitable for describing the CD of the mangrove model for given water depth. Then, a new parameter, KCrv, was defined using the average pore velocity and vegetation-related hydraulic radius by considering the bulk characteristics of the wave and vegetation. Finally, a generic empirical formula was proposed for the CD to reveal the drag coefficient characteristics of vegetation with a relatively high correlation.

Analytical study of electro-mechanical parameters on Love wave in an imperfectly bonded VPCM layered structure

This study is carried out to investigate the mechanical and electrical characteristics of Love waves in a visco-piezo-composite medium bounded between an orthotropic upper stratum and an elastic substrate of conducting type medium. The mechanically imperfect boundary conditions have been considered for both the interfaces of the sandwiched stratum. By solving coupled electromechanical field equations analytically, the electric potential, and mechanical displacement are obtained for the respective medium. After that, by using the relevant boundary conditions, the expression of dispersion has been established. The effect of various parameters such as viscosity, piezo-electric, dielectric, imperfection parameter, thickness ratio parameters on phase velocity, and attenuation coefficient of Love waves have been discussed. For the validation of our solution, the classical Love wave equation is obtained in the limiting sense (i.e. in the absence of piezoelectricity, upper surface, viscosity, imperfection parameters). To date, nobody has considered a Voigt-type viscous effect in composite piezo-structure to study Love wave propagation, even in the latest research works. Results indicate that the piezo-electric parameter possesses a great positive impact on phase velocity and attenuation coefficient. The attenuation co-efficient converges to some constant magnitude for different values of the thickness ratio parameter. The present investigation may find various applications in many problems of automatic remote control, space exploration, and piezoelectric ceramic devices. Moreover, it can be used in the investigation of the deformation and mechanical behavior of the sedimentary rock.

State space approach to characterize Rayleigh waves in a layer lying over a half-space with nonlocal thermoelasticity

The paper deals with a new model based on Eringen's nonlocal thermoelasticity. The propagation of Rayleigh waves in a nonlocal thermoelastic layer which is lying over a nonlocal thermoelastic half-space is considered in the context of energy dissipation theory. The normal mode analysis is employed to the considered equations to obtain vector matrix differential equation which is then solved by state space approach.The frequency equation of Rayleigh surface wave is derived. The effect of the nonlocal parameter on phase velocity, attenuation coefficient, specific loss and penetration depth of Rayleigh surface waves is presented graphically.

Propagation and reflection of plane waves in biological tissue based on nonlocal TPL thermoelasticity

The investigation for propagation and reflection of plane waves is carried out based on three-phase-lag (TPL) thermoelasticity with the aids of Eringen's nonlocal theory in a special medium - biological tissue. The scalar and vector potential functions of Helmhotz decomposition are adopted to obtain the propagation speeds, attenuation coefficients and reflection coefficients of plane waves analytically. There are two sets of dispersive attenuated longitudinal waves whose speeds of propagation are associated with angular frequency, and independent transverse elastic shear wave which exhibits no attenuation. It is found that the blood perfusion rate has few effects on wave propagation speed and attenuation coefficient and the phase lag of temperature gradient is negligible in present configuration. The effects of working angular frequency, nonlocal parameters, phase lag times, reflecting thermal boundaries and the type of incident waves on the propagation speeds, attenuation coefficients and reflection coefficients of harmonic waves are discussed and investigated graphically.