Investigation of the electrochemical coupling coefficient of acoustic waves in thin potassium niobate plates

The characteristics of antisymmetric and symmetric Lamb waves, as well as quasi-shear-horizontal waves, propagating in thin potassium niobate plates are investigated theoretically. It is found that the square of the electromechanical coupling coefficient of acoustic waves in such plates can reach 100% in certain directions. The results obtained indicate that potassium niobate is a highly promising material for creating various acoustoelectronic devices. Pis’ma Zh. Tekh. Fiz. 25, 67–70 (April 26, 1999)     

Propagation of acoustic waves in unsaturated porous media

A mathematical model of propagation of acoustic waves in a proous medium saturated with a two-phase mixture is proposed. The mechanism of initiation of slow motion as a result of prolonged nondestructive acoustic action is analyzed. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 71, No. 3, pp. 433–440, May–June, 1998.     

On the possibility of acoustic probing of gas wells

The possibility of probing the critical areas of gas wells using acoustic signals is analyzed. The results of investigations on the evolution of acoustic waves in cylindrical channels with permeable portions surrounded by a porous space are presented. The quantitative and qualitative features of the dynamics of waves as a function of the state of an inhomogeneous porous medium are established. Results showing that the state of the reservoir characteristics of rocks has a substantial influence on the evolution of acoustic signals are obtained. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 4, pp. 118–126, July–August, 2007.     

Influence of the Piezoelectric Effect on the Propagation of Elastic Waves in Cubically Anisotropic Piezoelectrics

Using bismuth germanate as an example, it has been shown that longitudinal and quasitransverse waves propagating in the (11ˉ0) crystallographic plane of a cubically anisotropic medium are piezoelectrically active. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 3, pp. 167–170, May–June, 2005.     

Mechanism of initiation of acoustic emission in crystallization and melting of a substance. II

In[Inzh.-Fiz. Zh.,73,No. 5, 1064–1072 (2000)], the authors investigated one of the possible mechanisms of initiation of the acoustic effect of crystallization (melting) of substances, which was based on the assumption of a stepwise character of motion of the crystal-melt interface. In the present work, consideration is given to another mechanism of initiation of the acoustic effect of crystallization, which is based on the concept of possible enhancement of waves propagating in the liquid and in the crystal during the motion of their interface. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 5, pp. 1073–1079, September–October, 2000.     

Numerical determination of modal dispersion and AE signal characterization in waveguides through LBIE/BEM and time–frequency analysis

In the present paper a meshless local boundary integral equation (LBIE) method is employed for the numerical determination of dispersion curves in plate like waveguides. Next, the LBIE method is properly combined with the boundary element method (BEM) for the characterization of acoustic emission signals derived from nucleating surface-breaking and body cracks in plate-like waveguides being in contact with a fluid. The time history of the propagating guided waves is computed by means of either the LBIE method or the hybrid LBIE/BEM scheme and the representation of mode dispersion is accomplished through the Reassigned Smoothed Pseudo Wigner–Ville time–frequency analysis. The effectiveness of the method is demonstrated through representative numerical examples.     

Stress-strain state of the surface of a circular cylindrical shell under the action of acoustic waves

We present the results of an investigation of the stress-strains state of a mechanical system consisting of two coaxial circular cylinders connected by an elastic link under the action of external acoustic pressure waves. We establish regularities of the appearance of displacements of the elements of the surface of the circular cylinders and the characteristics of the state of the entire mechanical system under acoustic loading. Translated from Problemy Prochnosti, No. 3, pp. 139–144, May–June, 1997.     

Analysis of three-dimensional wave motions in a cubically anisotropic thermoelastic medium with allowance for the relaxation time of thermal disturbances

Formulas for the coordinates of points of a cubically anisotropic thermoelectric medium, which determine the geometry of wave fronts excited by a lumped disturbance source, have been obtained. The three-dimensional fronts of a quasilongitudinal modified elastic wave, a modified thermal wave, and quasitransverse elastic waves propagating in lead have been constructed. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 4, pp. 808–813, July–August, 2008.     

Finite Element Evaluation of Acoustic Energy Penetration of Partially Submerged Tube Bundles

In this paper, the finite element software ANSYS is used to model ultrasonic waves propagating through a liquid volume containing partially submerged tubes. An immersible transducer is used to generate the waves. The goal of the investigation is to find an appropriate excitation frequency in order to perform ultrasonic cleaning of the tubes. Modal analysis of the coupled tubes–liquid system is conducted to evaluate the dynamic behavior of the tube structures under ultrasonic wave excitations. The frequency at which the acoustic waves efficiently penetrate the tube array with least energy loss and least deformation to tube structures is obtained, and will be used to probe the capability and the potential of utilizing ultrasonic energy as a non-destructive technique for cleaning tube bundles.     

Qualitative properties of optimum acoustic structures

Problems of optimum synthesis of layered structures exposed to acoustic waves are investigated. Qualitative laws governing the interrelationship between the parameters in structures that realize the limiting possibilities for control of the energy characteristics of acoustic waves are established. A numerical example is given. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 71, No. 5, pp. 902–905, September–October, 1998.     

Propagation of a Mode-II crack in a viscoelastic medium with different bulk and shear relaxation

A solution for a crack propagating under shear-loading in an isotropic viscoelastic medium with different relaxation under volume and shear deformations is presented. The medium is infinite and the semi-infinite crack propagates along the x ₁-axis at constant speed V, which may take any value up to the speed of dilatational waves. The requisite Riemann–Hilbert problem for the steady-state case has been solved and the asymptotics of the stress component σ₁₂ directly ahead of the crack and at infinity have been obtained.     

Formulation and validation of Berenger's PML absorbing boundary forthe FDTD simulation of acoustic scattering

Berenger's perfectly matched layer (PML) absorbing boundary condition for electromagnetic (EM) waves is derived to absorb 2-D and 3-D acoustic waves in finite difference time domain (FDTD) simulation of acoustic wave propagation and scattering. A PML medium suitable for acoustic waves is constructed. Plane wave propagation in the PML medium is solved for both 2-D and 3-D cases and explicit FDTD boundary conditions are derived. The equations show that a matched PML medium is a perfect simulation of free space in that a plane wave does not change its direction of propagation or its speed when it propagates from free space into a matched PML medium. FDTD simulation of a pulsed point source propagating in two dimensions is carried out to test the performance of the PML boundary for acoustic waves. Results show that an eight layer PML boundary condition reduces the reflected error 40 dB over Mur's second order boundary condition     

Scattering of acoustic waves from inhomogeneities of the velocity field of a moving medium

It is demonstrated that acoustic waves propagating in a moving liquid can be scattered on inhomogeneities of the velocity field of the medium, and a theory of such scattering is developed. The obtained estimates show the possibility of acoustic diagnostics of the velocity field inhomogeneities in moving media.     

Acoustic channels and lenses in a medium with inhomogeneous velocity field

A homogeneous moving medium can feature waveguide propagation of acoustic oscillations, provided that the velocity of medium is inhomogeneous. A waveguide of a finite length is equivalent to a lens. The waveguides and lenses are nonreciprocal, whereby their characteristics are significantly different for the acoustic waves propagating in opposite directions. Estimates are obtained and the possible applications are discussed.     

Superposition principle in acoustics

Using the effect of the nonstationary frequency shift of acoustic waves in a medium with spatially and temporally varying properties, a theoretical estimate is made of the deviation from the superposition principle for an acoustic wave propagating in the field of another continuous plane wave.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 43, No. 5, pp. 826–833, November, 1982.     

Influence of a thin conducting transverse layer on the properties of quasitransverse shear waves and Lamb waves in gallium arsenide plates

An investigation was made of the influence of a thin conducting surface layer on the damping and velocity of acoustic waves in gallium arsenide plates. It was observed that the square of the coefficient of electromechanical coupling for specific directions of propagation of Lamb waves and quasitransverse shear waves is an order of magnitude higher than that for surface acoustic waves. Thus, the conductivities of the substrate and the surface layer have a stronger influence on the damping of waves in the plates than in the case of surface acoustic waves. Pis’ma Zh. Tekh. Fiz. 25, 38–43 (February 12, 1999)     

Investigation of the propagation of an ultrasound pulse in a dispersed fractal medium

Results are presented of an experimental determination of the fractal parameters of crushed sand particles. Results of measurements of the propagation of an acoustic pulse through a mass of sand having various degrees of dispersion are used to determine the fractional exponent in the dependence of the propagation velocity on the ultrasound wavelength. A wave equation in fractional derivatives is proposed to describe the propagation of ultrasonic waves in a dispersed medium. Pis’ma Zh. Tekh. Fiz. 25, 14–18 (June 12, 1999)     

Quantitative visualization of ultrasonic acoustic waves by means of digital laser speckle-technologies

An original version of digital laser speckle photography has been used for visualization and quantitative diagnosis of acoustic waves in liquids in the megahertz frequency range. Standing acoustic waves were generated in tanks of special configuration which permitted obtaining analytical dependences of refraction angles of the probe laser radiation on the wave intensity. These refraction angles were determined experimentally by the change in contrast of the speckle fields arising in the scattered probe radiation and recorded by means of high-resolution digital CCD matrices. Quantitative diagnosis of the pressure and velocity fields in acoustic waves was carried out by measuring the deformation of the laser intensity correlation functions in recorded speckle fields. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 2, pp. 229–239, March–April, 2008.     

Radial-slit erosion discharge

A new type of erosion discharge, which is distinguished by the stability of the formation and ease of observation of its nonequilibrium plasma in the form of radially propagating, solitary waves, is described. Pis’ma Zh. Tekh. Fiz. 25, 58–61 (June 26, 1999)     

Amplitude-dependent attenuation of compressive waves in curved granular crystals constrained by elastic guides

We study the wave propagation in a curved chain of spherical particles constrained by elastic guides under the axial impact of a falling mass. We characterize the force transmission properties of the chain by varying the striker’s mass and the chain’s curvature. Experimental tests demonstrate amplitude-dependent attenuation of compressive waves propagating through the curved chain. In particular, we observe that the curved systems present an improved transmission of small dynamic disturbances relative to that of strong excitations, resulting from the close interplay between the granular particles and the softer elastic medium. We also find that the transmission of the compressive waves through the chains is dependent on the initial curvature imposed to the system. Numerical simulations, based on an approach that combines discrete element and finite element methods, corroborate the experimental results. The findings suggest that hybrid structures composed of granular particles and linear elastic media can be employed as new passive acoustic filtering materials that selectively transmit or mitigate excitations in a desired range of pressure amplitudes.