Cylindrical Piezoelectric Transducer Research Articles

Vibration characteristics of a circular cylindrical panel piezoelectric transducer

We study the theory of the basic vibration characteristics of a circular cylindrical shell piezoelectric transducer. The linear theory of piezoelectricity is used. Both the free-vibration solution for resonant frequencies and modes as well as the electrically forced-vibration solution for admittance are obtained. Numerical results are presented.

Speckle Reduction in Near-field Image of Multimode Fiber with a Piezoelectric Transducer

We propose and experimentally demonstrate an effective method to reduce near-field speckle noise at the output of a 50 <TEX>${\mu}m$</TEX> graded index multimode fiber using a short cylindrical piezoelectric transducer(PZT) vibrating in the radial direction. The fiber was coiled as tightly as possible around the mandrel of the PZT and a periodic stretching effect was caused by the radial oscillations of the actuator. The output of the optical fiber using the He-Ne laser source was intensively observed by a CCD camera. By counting all the pixels corresponding to relative intensity graded into 256 levels in the selected area and by calculating standard deviation and mean value of the intensity, we could measure the speckle contrast and vibration effect quantitatively with reduction ratio of pixels and line profile of the illuminated region. It was clearly observed that the characteristics of the speckle pattern in the vibration-on state were significantly improved over that of the vibration-off state due to time-averaged smoothing.

Broadband transducers for underwater communications

Properties of underwater acoustic cylindrical piezoelectric (PZT) transducers currently used for broadband underwater communications with unmanned underwater vehicles (UUV) and new transducers under development utilizing single crystal relaxor ferroelectrics (PMN‐PT) with significantly higher material coupling coefficients and lower sound speed are presented. Characteristics including resonance frequency, coupling coefficient, transmit (TVR) and receive (OCVS) frequency response, maximum drive and achievable source levels, tuned and untuned power factor, and directivity factors are discussed. Results for experimental calibrations and field tests will be compared with detailed equivalent electrical circuit models of the transducer and transducer channel. Work supported in part by BTech Acoustics and Office of Naval Research.

Broadband multimode baffled piezoelectric cylindrical shell transducers

Hollow piezoelectric cylindrical shell transducers may be made directional for underwater acoustic applications by the use of suitable acoustical baffles and the operational bandwidth may be extended by using multiple resonant modes. A theoretical and experimental investigation was performed for circumferentially baffled piezoelectric cylindrical shell transducers operating in the zero and one modes of extensional vibration. The frequency responses and directivity patterns were analyzed under various conditions of energizing separate halves of electrodes. It was found that the broadest frequency response with nearly constant beamwidth can be obtained when the two halves of the piezoelectric ring are electromechanically excited 90 deg out-of-phase. The experimental results obtained with a proof-of-concept transducer were in good agreement with the theoretical predictions.

Compound piezoelectric cylindrical resonators as sensors of the rheological parameters of viscoelastic media

The electro-elastic behavior of a viscoelastically loaded layered cylindrical resonator (sensor) comprising two coupled hollow cylinders is presented. The inner cylinder is a piezoelectric ceramic tube. The outer cylinder is a non-piezoelectric (passive) metallic cylinder. An analytical formula for the electrical admittance of a compound layered cylindrical resonator loaded with a viscoelastic liquid is established. Admittance (conductance) diagrams were obtained using a continuum electromechanical model. The established analytical formulas enable the determination of the influence of the liquid viscosity, material, and geometrical parameters of a compound cylindrical resonator on the response characteristics of the compound sensor. In the paper, the sensor implications resulting from the performed analysis are described. Moreover, the algorithm of the method developed by the authors to evaluate the rheological parameters of a viscoelastic liquid is presented. Good agreement between the theoretical results and experimental data is shown. The analysis presented in this paper can be utilized for the design and construction of cylindrical piezoelectric viscosity sensors, annular accelerometers, filters, transducers, and multilayer resonators.

Dynamic characteristics of piezoelectric cylindrical transducers with radial polarization

This paper presents the radial vibration characteristics of piezoelectric cylindrical transducers. Taking into account the piezoelectric anisotropy, dynamic differential equations of piezoelectric radial motion have been derived in terms of radial displacement and electric potential. Applying mechanical and electric boundary conditions has yielded a characteristic equation for radial vibration of the radially polarized piezoelectric cylinder. Theoretical calculations of the fundamental natural frequency have been compared with numerical and experimental results for transducers of several sizes, and have shown a good agreement.

Basic Characteristics of Axial Scanner of Optical Coherence Tomography with Cylindrical Piezoelectric Transducer

We have investigated the basic characteristics (scan depth, linearity, and stability) of a piezoelectric axial scanner (PAS) composed of optical fibers wound around a cylindrical piezoelectric transducer. The scan depth due to the stretching of the fibers is decreased to 77.5% by the photoelastic effect. With the application of a high voltage pseudo-triangular signal to two PASs, a scan depth of 2 mm and scan rate of 2,000 lines/s were achieved and used to acquire a cross-sectional image of an in vivo human finger with a measurement time of 0.5 s.

실린더형 압전소자 광지연선을 이용한 광 간섭형 단층촬영(OCT) 시스템 제작

원통형의 압접소자를 이용한 광지연선을 사용하여 광 간섭형 단층촬영 시스템을 제작하였다. 광지연선은 18 m 길이의 단일 모드 광섬유를 압전소자의 둘레에 134회 감아 구성하였으며 0.78 mm의 광경로 길이변화를 얻었다. 제작한 광 간섭형 단층촬영 시스템은 신호 대 잡음비 96.9 dB, 종방향 분해능 <TEX>$18.6{\pm}0.5\;{\mu}m$</TEX>, 횡방향 분해능 <TEX>$5\;{\mu}m$</TEX>의 특성을 보였다. We demonstrate a compact optical coherence tomography(OCT) system based on the optical fiber delay line controlled by a cylindrical piezo-electric transducer(PZT). An 18-m length of single mode fiber is wrapped under constant tension around a PZT. Approximately 134 windings are used. Wraps of the long length of fiber allow the small expansion of the PZT to be magnified to an optical path length delay of 0.78 m. The OCT system shows characteristics for 2-dimensional imaging, exhibiting 96.9dB of signal-to-noise ratio(SNR), <TEX>$18.6{\pm}0.5\;{\mu}m$</TEX> of axial resolution, and <TEX>$5\;{\mu}m$</TEX> of lateral resolution with samples.

광간섭 단층촬영(OCT)용 PZT 광경로 지연기에서의 편광모드 분산 및 열요동 보상

광간섭 단층촬영(OCT)용으로 원통형 압전소자(PZT)와 단일모드 광섬유를 이용한 광경로 지연기를 제작하여 그 특성을 분석하였다. 광경로 지연기에서 발생하는 편광모드 분산은 편광조절기로 조절하였고, 열요동을 2중 광경로 지연기를 구성하여 최소화하였다. 이중 광경로 지연기는 단일 광경로 지연기에 비해 2배의 측정 깊이와 속도를 구현하여 <TEX>$18.6\pm0.5{\mu}m$</TEX>의 해상도. 측정 깊이 1.68 mm, 측정 녹도 360.4 mm/s를 각각 얻었다. We have fabricated and characterized optical delay lines for optical coherence tomography, which is composed of cylindrical PZT(piezoelectric transducer) and single mode optical fiber. The polarization mode dispersion from the optical delay lines was compensated by the polarization controllers. By applying the duplex optical delay line, we minimized the thermal drift due to optical delay lines and obtained the scan range of 2 times that of a single optical delay line. The OCT system showed resolution of <TEX>$18.6\pm0.5{\mu}m$</TEX>, scanning range of 1.68mm, and scanning speed of 360.4mm/s.

Generation of nonstationary waves by a thick-walled piezoceramic cylinder excited by electric signals

Coupled electroelasticity theory, acoustic approximation, and two-wire transmission line theory are used to study the generation of waves by a submerged cylindrical piezoelectric transducer connected by a cable to a source of nonstationary electric signals. The problem is reduced to a system of integral Volterra equations using the Laplace transform and analytical inversion of boundary conditions. The results of calculations for different cable lengths are presented

Measurements of mutual radiation impedance in arrays of piezoelectric cylindrical shell transducers

We present our recent experimental results of the mutual radiation impedance of piezoelectric cylindrical shell transducers in arrays using the Z- and V-methods previously reported by the authors [J. Acoust. Soc. Am. 112, 2407 (2002)]. The mutual radiation impedance in an array of two coaxially aligned cylindrical transducers was determined as a function of separation distance. The results obtained by both methods are in good agreement with the calculations based on the analytical equations for a similar array developed by D. H. Robey [J. Acoust. Soc. Am. 27, 706–710 (1955)]. The mutual radiation impedances in other array geometries including planar and curved arrays of cylindrical shell transducers, in which there is no known analytical solution, were also measured by the same methods in our underwater test facility. [Work supported in part by ONR 321 SS.]

Effects of coupled vibrations in cylindrical shell transducers

Coupled vibrations in cylindrical transducers can have unwanted effects on the resulting radiation or reception of sound. An investigation of vibrations of piezoelectric cylindrical shell transducers using analytical and experimental methods shows the presence of an additional flexural resonant mode that was not previously reported [see J. F. Haskins and J. L. Walsh, ‘‘Vibrations of ferroelectric cylindrical shells with transverse isotropy,’’ J. Acoust. Soc. Am. 29, 6 (1957)]. The additional flexural mode can be strongly coupled to radial and axial modes in cylindrical shells with finite thickness. The effect can be substantial, resulting in unwanted resonances that may be in the frequency band of interest for both projectors and receivers. An equivalent circuit is derived, which describes the cylindrical transducer operation taking into account the effect of coupled vibrations. The results of calculations in terms of resonant frequencies and frequency responses for both transmit and receive modes are in good agreement with experiments. The overall performance of the cylindrical shell transducer can be greatly enhanced by using cylinders of appropriate height to diameter aspect ratio. [Work supported in part by ONR 321SS.]

Cylindrical transducers to generate and detect axisymmetric waves in a pipe

This paper presents the radial vibration characteristics of piezoelectric cylindrical transducers and the application of the transducers to the generation and detection of axisymmetric longitudinal waves in a pipe. Dynamic differential equations of piezoelectric radial motion derived in terms of radial displacement and electric potential and mechanical and electric boundary conditions have yielded a characteristic equation for radial vibration of the radially polarized piezoelectric cylinder. Theoretical calculations of the fundamental natural frequency have been compared with numerical and experimental results for transducers of several sizes, and have shown a good agreement. It has been shown that the piezoelectric natural frequency of the fundamental mode for radial vibration in a cylindrical transducer depends mostly on the radius rather than on the thickness of the cylinder. Experiments have been performed in empty and water-filled pipes equipped with the transducers that were used for transmitting and receiving axisymmetric elastic waves in the pipe wall. The measured wave speeds have been compared with the analytical ones. This work has demonstrated the feasibility of using cylindrical transducers and pipe waves for the determination of the mass density and, eventually, the flow rate of the liquid in a pipe.

Space distribution of harmonic mode vibration amplitudes in nonlinear finite piezoelectric transducer

Nonlinear elastic vibrations of cylindrical piezoelectric transducers are investigated both experimentally and theoretically. A particular behaviour, that relates the space distribution of the fundamental mode vibration to those of the second and third harmonic components, is observed. A simplified physical interpretation of the phenomenon is given.

이방성을 고려한 원통형 압전 변환기의 반경방향 진동 특성 해석

This paper presents the analysis fur the radial vibration characteristics of cylindrical piezoelectric transducers. Taking into account the piezoelectric anisotropy, the differential equations of piezoelectric radial motion have been derived in terms of radial displacement and electric potential. Applying mechanical and electric boundary conditions has yielded a characteristic equation for radial vibration. Numerical analysis also has been carried out by using the finite element method. Theoretical calculations of the fundamental natural frequency have been compared with the experimental observations for transducers of several sizes. Comparison with the previous report of theoretical analysis simplifying the piezoelectric anisotropy into isotropy concludes that isotropic analysis is a reasonable process to predict the vibration characteristics of piezoelectric transducers.

Radial vibration characteristics of piezoelectric cylindrical transducers

Radial vibration characteristics of piezoelectric cylindrical transducers

Cylindrical acoustic levitator/concentrator having non-circular cross-section

A low-power, inexpensive acoustic apparatus for levitation and/or concentration of aerosols and small liquid/solid samples having particulates up to several millimeters in diameter in air or other fluids is described. It is constructed from a commercially available, hollow piezoelectric crystal which has been formed with a cylindrical cross-section to tune the resonance frequency of the breathing mode resonance of the crystal to that of the interior cavity of the cylinder. When the resonance frequency of the interior cylindrical cavity is matched to the breathing mode resonance of the cylindrical piezoelectric transducer, the acoustic efficiency for establishing a standing wave pattern in the cavity is high. By deforming the circular cross-section of the transducer, the acoustic force is concentrated along axial regions parallel to the axis of the transducer. The cylinder does not require accurate alignment of a resonant cavity. The concentrated regions of acoustic force cause particles in the fluid to concentrate within the regions of acoustic force for separation from the fluid.

A combined resonance-Doppler technique for studying bubble evolution in liquids

Gas bubbles in liquids have been studied for decades with a variety of optical and acoustic techniques. The evolution of a bubble consists of several stages, including formation and growth at a nozzle, detachment and resonance, and rise towards terminal velocity. Most existing techniques can monitor only a single aspect of the bubble behaviour. This work describes an acoustic technique to monitor all stages of an air bubble's evolution. The technique uses a combination of passive acoustic listening and active ultrasonic Doppler observation to study millimetre-sized air bubbles in liquid. A hollow cylindrical piezoelectric transducer, located around the nozzle used to produce the bubbles, detects the resonance of the bubble following its detachment. An ultrasonic Doppler system, positioned several centimetres above the nozzle, monitors both the growth and the rise of the bubble, including shape oscillations and the terminal velocity through the use of joint time-frequency analysis. Because all aspects of the bubble evolution are affected by the properties of the liquid, by monitoring the bubble evolution with this technique the rising bubble can potentially be used as a tool to characterize the liquid.

원통형 압전 변환기의 반경방향 고유진동 특성 연구

This paper presents the characteristics of the radial nitration of cylindrical piezoelectric transducers. The differential equations of piezoelectric radial motion have been derived in terms of the radial displacement and electric potential, which are functions of the radial and axial coordinates. Applying mechanical and electrical boundary conditions has yielded the characteristic equation of radial vibration. Numerical results of the natural frequencies have been compared with the experimental observations reported earlier for the transducers of several sizes, and have shown a good agreement for the fundamental mode. The paper discusses the dependence of the natural frequencies on the radius and thickness of the piezoelectric cylinders and the difference between Piezoelectric and elastic resonances.

DYNAMICAL ANALYSIS OF A CYLINDRICAL PIEZOELECTRIC TRANSDUCER

In the present paper, the vibration of a cylindrical piezoelectric transducer induced by applied voltage, which can be used as the stator transducer of a cylindrical micromotor, is studied based on shell theory. The transducer is modelled as a thin elastic cylinder. The properties of the vibration modes of the transducer, such as mode frequencies and amplitude ratios of the mode shapes, are determined following Galerkin method. The response of the transducer under the four electric sources with 90° phase difference is then obtained by the modal summation method. With the results, the performance of the transducer under the electric sources can be estimated. The present work provides a general and precise theoretical modelling on the dynamical movement of the transducer.