Thin Piezoelectric Plate Research Articles

Acoustic waves in structure “piezoelectric plate–polymeric nanocomposite film”

Paper is devoted to the investigation of SH 0 acoustic waves propagating in structure “piezoelectric plate–polymeric nanocomposite film”. The analysis was carried out by the example of the polymeric nanocomposite film based on high-pressure polyethylene with various contents of CdS nanoparticles and lithium tantalate and lithium niobate plate. The resonant attenuation of investigated waves for the certain ratios of plate and film thicknesses was found. The obtained results open the prospects of the development of structures for SH 0 waves consisting of nanocomposite polymeric substrates and thin piezoelectric plates. Such structures may be useful for development of various thermostable chemical and biological sensors and signal processing devices.

Asymptotic modeling of linearly piezoelectric slender rods

The piezoelectric thin plate modeling already derived by the authors is extended to rod-like structures. Two models corresponding to sensor or actuator behavior are obtained. The conditions of existence of non-local terms in the limit models are discussed. To cite this article: T. Weller, C. Licht, C. R. Mecanique 336 (2008).

Acoustic wave propagation in cubic piezoelectric semiconductor plates

Piezoelectric materials can be either dielectric or semiconductors. An acoustic wave propagating in a piezoelectric crystal is usually accompanied by an electric field. When the crystal is also a semiconductor, the electric field produces currents and space charges, resulting in dispersion and acoustic loss. The interaction between a travelling acoustic wave and mobile charges in piezoelectric semiconductors is currently called the acoustoelectric effect. It was shown experimentally and proved theoretically that an acoustic wave travelling in a piezoelectric semiconductor can be amplified by the application of an initial dc electric field. Piezoelectric semiconductors devices often have structural design of plates or rods. Here we study the thin piezoelectric semiconductor plates. Two‐dimensional equations for coupled extensional, flexural and thickness‐shear motions are obtained systematically from the three‐dimensional equations by retaining lower order terms in power series expansions in the plate thickness coordinate. The two‐dimensional equations are specialized to crystals of cubic (43m) symmetry. Propagation of extensional, flexural and thickness‐shear waves and their amplification by a dc electric field are analyzed.

Influence of polymeric nanocomposite film on acoustic waves in piezoelectrics

At present the attention of researchers is attracted by investigation of multilayer acoustical waveguides with using of well known as well as novel materials. Also in present time there exist a lot of papers devoted to novel nanocomposite polymeric materials. But the influence of such materials on parameters of acoustic waves in piezoelectrics did not study. In this connection the paper is devoted to theoretical investigation of acoustic waves in structure “piezoelectric - polymeric nanocomposite film.” The analysis was carried out by the example of polymeric nanocomposite film with various contents of Fe and CdS nanoparticles and lithium niobate plate or substrate. As a result of conducted calculation the velocity and attenuation per wavelength have been found for acoustic waves propagating in aforementioned structure. The conducted analysis has showed that for certain value of nanocomposite film thickness d the attenuation of investigated waves has the resonant behavior. The obtained results allow choose such values of d for which the acoustic wave does not practically attenuate in the presence of the film. This opens, for example, the prospects of development of undisturbed substrates of nanocomposite materials for thin piezoelectric plates. This work is supported by RFBR 06-08-01011, RNP.2.1.1.8014 (Russia), contract 2007-3-1.3-07-15-036 (Russia).

CrossRef Listing of Deleted DOIs

The finite element formulation for analyzing static damage near a conducting crack in a thin piezoelectric plate is established from the virtual work principle of piezoelectricity. The damage fields under various mechanical and electrical loads are calculated carefully by using an effective iterative procedure. The numerical results show that all the damage fields around a crack tip are fan-shaped and the electric field applied has great influence on the mechanical damage, which is related to the piezoelectric properties.

Effect of a liquid on the characteristics of antisymmetric lamb waves in thin piezoelectric plates

The effect of a perfectly elastic nonviscous nonconducting liquid on the characteristics of a zero-order antisymmetric Lamb wave (the A 0 wave) in a 128YX LiNbO3 plate, whose thickness is small compared to the wavelength, is studied both theoretically and experimentally. A method for calculating the velocity and attenuation of this wave depending on the value of the parameter hf (h is the plate thickness and f is the wave frequency) is proposed. In addition, the characteristics of an A 0 wave in a piezoelectric plate that is in contact with two different perfectly elastic nonviscous nonconducting liquids on its two sides are investigated. A possibility for the development of a proximate analyzer of liquids on the basis of such a structure is indicated.

Effect of metallization on the power flow angle of SH0 waves in thin piezoelectric plates

The anisotropy of the angle between the phase and group velocity (power flow angle, PFA) as well as the influence of electrical boundary conditions on this angle have been studied for shear-horizontal fundamental (SH0) acoustic waves in thin piezoelectric plates of lithium niobate (LNO) and potassium niobate (KNO). Both LNO and KNO crystals possess orientations at which the PFA for SH0 waves reaches large values (17° and 48°, respectively). It is established that metallization of the piezoelectric plate surface can significantly change PFA values, in particular, by 18° and 55° for Y-X + 25° cut plates of LNO and KNO, respectively.

New method of change in temperature coefficient delay of acoustic waves in thin piezoelectric plates

As is well-known, the development of high-effective and thermostable acoustic devices assumes using the acoustic waves with high coefficient of electromechanical coupling (K2) and low temperature coefficient of delay (TCD). At present, it also is well-known that fundamental shear horizontal (SH0) acoustic waves in thin piezoelectric plates possess by significantly more electromechanical coupling compared to surface acoustic waves (SAW) in the same material. However, although the value of TCD of SH0 waves is insignificantly less than for SAW, this is not enough for development of thermostable devices. This paper suggests a new way of decreasing TCD of SH0 waves in piezoelectric plates at a high level of electromechanical coupling. This way assumes to use the structure containing the piezoelectric plate and liquid with the special dependence of permittivity on temperature. Theoretical and experimental investigation showed that, for SH0 wave in YX LiNbO3 plate at hf = 700 m/s (h = plate thickness, f = wave frequency) the presence of butyl acetate can decrease the value of TCD by six times at K2 = 30%. In a whole the obtained results open the wide prospect of using SH0 wave in thin piezoelectric plate for development of high effective and thermo-stable acoustic devices.

Gravimetric sensitivity of acoustic waves in thin piezoelectric plates in the presence of liquids

The effect of a dielectric weight load on the zero-order acoustic modes in a thin piezoelectric plate of lithium tantalate (LiTaO3) was theoretically studied, and the change in this sensitivity in the presence of a liquid was estimated. The gravimetric sensitivity has a complicated frequency spectrum and also depends on the plate thickness and on the load material. The presence of a liquid can significantly increase the sensitivity of zero-order acoustic modes in a piezoelectric plate with respect to a dielectric weight load.

Electro-mechanical equivalent circuit of a piezoelectric ceramic thin circular ring in radial vibration

The radial vibration of a piezoelectric ceramic thin circular ring polarized in the thickness direction is studied. Its electro-mechanical equivalent circuit is derived, the resonance and anti-resonance frequency equations are obtained, and the relationship between the resonance frequencies and the material parameters and the geometrical dimensions is analyzed. It is illustrated that the first radial resonance frequency of a solid piezoelectric thin plate is larger than that of a hollow piezoelectric thin ring with the same outer radius. When the radius ratio is increased, the first radial resonance frequency is decreased. The relationship between the second radial resonance frequency and the radius ratio is complex. When the radius ratio is smaller than the definite value, the second radial resonance frequency is decreased as the radius ratio is increased; while when the radius ratio is larger than this value, the second radial resonance frequency is increased as the radius ratio is increased. When the radius ratio is larger than a definite value, the second radial resonance frequency is larger than that of a solid plate with the same outer radius. When the radius ratio limits one, the second radial resonance frequency limits infinity.

Scaled-boundary method in electroelasticity of thin plates

The paper discusses the scaled-boundary method as applied to electroelastic problems. As an example, the stress-intensity factor is calculated for a thin rectangular piezoelectric plate with an edge crack

Nondestructive testing in human teeth using a leaky Lamb wave device

A Lamb wave interdigital transducer mounted on a layered substrate composed of two plates, a thin piezoelectric ceramic plate and an acrylic plate, operating at a liquid–solid boundary, is investigated for ultrasonic nondestructive testing of the layer thickness in human teeth. A higher-order mode having a phase velocity higher than the longitudinal wave velocity in the human teeth can be used for nondestructive testing. In the combination of the two layers, the fourth mode of leaky Lamb wave is most favorable for a frequency-controllable radiation angle of an ultrasound beam into a water layer as an acoustic coupler. In the configuration of an acoustic delay line, the layer-thickness measurement in vivo, evaluated from the time interval between two reflected ultrasound echoes, is successfully realized under a thin water layer as the acoustic coupler.

Boundary-layer of torsion in a piezoelectric material with a symmetry of order six

An analytical model for the boundary-layer of torsion in a piezoelectric thin plate with a symmetry of order six is proposed on the basis of the method of asymptotic expansions. The local behaviour of the three-dimensional solution of the problem of linear piezoelectricity is formulated in the vicinity of the lateral contour of the plate, and the solution of the problem for the boundary-layer of torsion is then obtained. However, we denote that full proof of the theorems is not given in this paper. Only hints of the proof are given.

An extension of the J-integral to piezoelectric materials

This paper provides an analysis of the crack propagation criterion for a thin piezoelectric plate with a symmetry of order six. On the basis of Gol’denveizer’s asymptotic integration method or Destuynder’s unidirectional zoom technique, we obtain an extension of the purely mechanical J-integral to piezoelectric materials, with a dependence of the gradient of energy of the plate only on zeroth order terms of asymptotic expansions.

Numerical analysis of the properties of slit electroacoustic waves

The properties of slit electroacoustic waves that propagate in a system of two semi-infinite piezoelectric media separated by a vacuum gap, in a system consisting of a thin piezoelectric plate and a semi-infinite piezoelectric medium separated by a gap, and in a system consisting of two thin piezoelectric plates separated by a vacuum gap are studied. The process of transformation of slit electroacoustic waves to generalized surface acoustic waves or to Lamb waves is considered.

Operational Performance of A0-mode Lamb Wave Interdigital Transducers Under Water-Loaded Condition

The operational performance of an A0-mode Lamb wave interdigital transducer is described in a delay line structure. The delay line is composed of two interdigital transducers (IDTs) on a thin piezoelectric ceramic plate, under the air- or water-loaded condition. The A0-mode Lamb wave device has two frequency ranges in the forms of nonleaky and leaky Lamb waves. The boundary frequency is related to the longitudinal wave velocity in water. The basic performance of the A0-mode delay line is presented with measured results in the vicinity of the transition region, where the A0-mode Lamb wave velocity is near the longitudinal wave velocity in water. The A0-mode IDT operates efficiently as an underwater transducer with a shallow radiation angle in the operation region as the leaky wave.

Piezoelectric ceramic rectangular transducers in flexural vibration

Based on the equivalent elastic method and coupled vibration theory, an analytic method is presented to study the flexural vibration of rectangular transducers consisting of piezoelectric ceramic thin plates. By introducing a mechanical coupling coefficient, the flexural vibration of the piezoelectric ceramic rectangular thin plate is reduced to two simple, one-dimensional flexural vibrations of narrow piezoelectric ceramic strips. The resonance frequency equations for the piezoelectric ceramic rectangular thin-plate transducers in flexural vibration are derived under the free and simply supported boundary conditions analytically. The relationship between the resonance frequency and the flexural vibrational order, the geometrical shape, and the dimensions of the piezoelectric ceramic rectangular thin-plate transducer is analyzed. It is demonstrated that the one-dimensional vibrational theory for the flexural vibration of a narrow piezoelectric ceramic strip and the stripe-mode flexural vibrational theory for the piezoelectric ceramic rectangular thin plate can be derived directly from the theory obtained in this paper. Experimental results show that the measured resonance frequencies of the piezoelectric ceramic rectangular thin-plate transducers in flexural vibration under free-boundary conditions are in good agreement with the calculated results. The method presented in this paper can be used in the resonance frequency analysis of vibrating systems in coupled vibration.

High-Speed Thin Ultrasonic Spindle Motor and Its Application

In this paper, we report an ultrasonic motor capable of high-velocity revolution applicable for long continuous high operation as a microfan. This study is a response to the new challenge of developing a new field of applications for an ultrasonic motor. Ultrasonic motors using a longitudinal-flexural coupling-vibration mode of a thin plate with a vibrating piece or step-horn are considered. A stator vibrator consists of a metal plate sandwiched by two thin unipoled piezoelectric ceramic plates, the electrodes of which are not divided, and this ultrasonic motor can be driven by a single ac source. Not only the coupling between a longitudinal vibration and flexural one but also the transformation of a longitudinal vibration velocity by a vibrating piece λ/4 long and step-horn λ/2 long are used. They will be effective at making the rotary speed fast. As a result, an ultrasonic motor 0.55 mm thick rotated a shaft 1.5 mm in diameter over 8,000 rpm under conditions of an applied voltage of 30 Vp-p and an input power of only 0.16 W.

Moving-Speed Measurement Using Leaky Lamb Wave Interdigital Transducers

A technique for measuring the moving target speed is described using an ultrasound device, composed of two leaky Lamb wave interdigital transducers (IDTs) and a thickness-mode transducer on a thin piezoelectric ceramic plate. The thickness-mode transducer located between the two IDTs radiates an ultrasound beam into a liquid in the thickness direction of the piezoelectric substrate. The IDT functions as a detector of the ultrasound signal reflected in an oblique direction from a moving medium in the liquid. The reflected delayed-output has a frequency shift via a Doppler effect, corresponding to the moving speed of the reflection object. Basic performances of the device with two IDTs and the central thickness-mode transducer and the measured results of the moving speed of a metal disk are presented for the first antisymmetrical Lamb wave mode with the highly dispersive property.

Reflection of normal acoustic waves in thin plates from a grating with a periodically distributed mechanical load

Reflection of zero-order normal acoustic waves excited in a thin piezoelectric plate from a set of conducting strips of a finite thickness is studied both theoretically and experimentally. The analysis shows that the effects produced by the short-circuiting of the plate surface and by the elastic load on the impedance ratio of adjacent plate segments are in opposition to each other. These effects can be commensurable, and, hence, for each wave type, there is a certain value of the strip thickness at which the reflection coefficient becomes equal to zero. The experimental results obtained for a shear horizontal normal wave (an SH0 wave) propagating in a lithium niobate plate are in good agreement with the theory and justify the use of the equivalent-circuit model in analyzing the properties of reflectors of the type under study.