Cylindrical Piezoelectric Transducer Research Articles

Coupled vibration of a radially polarized piezoelectric cylinder with a co-axial elastic cylinder of varying height.

The cylindrical piezoelectric transducer has the advantages of large radiation area, high electromechanical coupled coefficient, and omni-direction radiation along the radius. In this paper, a piezoelectric transducer consisting of a radially polarized piezoelectric cylinder and an outer metal cylinder of varying height is presented. The metal cylinder of varying height is approximated as the radial superposition of multiple uniform height metal cylinders, and the equivalent impedance of the transducer's coupled vibration is obtained by using the impedance matrix method, and then the resonance frequency, anti-resonance frequency, effective electromechanical coupled coefficient, and displacement amplification coefficient are obtained. In this paper, the relationship between the vibration characteristics of the cylindrical piezoelectric transducer and its geometric dimensions is studied. An experimental sample of the transducer is fabricated and assembled, and its electrical impedance curve is measured. The measured results are in good agreement with the simulation results and the theoretical calculation results. The displacement distribution of the radiation surface of the transducer at resonance frequency is measured, which verifies that the two coupled vibration modes of the transducer can be effectively excited.

Controlling Speckle and Resolution of Reconstructed Images by Vibrating Multimode Optical Fiber with a Cylindrical Piezoelectric Transducer in Electro-Holography

Controlling Speckle and Resolution of Reconstructed Images by Vibrating Multimode Optical Fiber with a Cylindrical Piezoelectric Transducer in Electro-Holography

Finite element-based diffraction correction for piezoelectric transducers accounting for diffraction at transmission, propagation, and reception.

Existing diffraction correction models for ultrasonic transmit-receive measurement systems rely on simplifying assumptions with respect to the boundary conditions at the transmitter or receiver. Common simplifications include approximating the sound field radiated by a piezoelectric transducer using a baffled piston model and assuming that the receiver's electrical response is proportional to the spatially averaged free-field pressure over its front surface. In many applications, such simplifications may be adequate, but their validity and accuracy need to be evaluated and quantified. Here, a diffraction correction model utilizing the full set of electrical and mechanical boundary conditions at the transmitter and receiver is presented, avoiding these simplifications. The model is based on finite element modeling of coaxially aligned piezoelectric transducers in a fluid medium. Comparison is made with existing models for an example case of cylindrical piezoelectric ceramic disk transducers operating in air at 50-300 kHz and 0.03-2 m apart, relevant for, e.g., sound velocity and absorption measurements in fluids and ultrasonic gas flow metering. In the near-field, errors introduced by the simplifications are up to 3 dB and 47° for the first radial resonance. Generally, such errors are application-specific and depend on distance, frequency, transducer construction, vibration pattern, and medium properties.

High-frequency inlaid cylindrical piezoelectric transducer for high-sensitivity acoustics

This work develops a high-frequency high-sensitivity inlaid cylindrical hydroacoustic transducer by enhancing the electromechanical coupling coefficient, amplifying stress, and adopting circumferential inlaid techniques. Equivalent circuit and finite element simulation methods were used to determine the optimum parameters of the unit, then the transducer was fabricated. Tests show that the resonant frequency of every array unit was 220 kHz. The maximum emission voltage response and reception sensitivity were respectively about 172 dB and −177 dB, with emission and reception bandwidths both about 40 kHz at 3 dB loss. The horizontal and vertical beamwidths were 15° and 4° for each unit respectively.

Spatial and temporal localization of ultrasonic heating effect using cylindrical standing waves

The aim of this work was to develop a new method alternative to high intensity focused ultrasound for spatial and temporal localization of ultrasonic heating effects using cylindrical standing waves. Computer simulations and experimental validation of the standing cylindrical waves generation and the viscoelastic media heating inside a cylindrical piezoelectric transducer were carried out.

Cylindrical Piezoelectric PZT Transducers for Sensing and Actuation.

Piezoelectric transducers have numerous applications in a wide range of sensing and actuation applications. Such a variety has resulted in continuous research into the design and development of these transducers, including but not limited to their geometry, material and configuration. Among these, cylindrical-shaped piezoelectric PZT transducers with superior features are suitable for various sensor or actuator applications. However, despite their strong potential, they have not been thoroughly investigated and fully established. The aim of this paper is to shed light on various cylindrical piezoelectric PZT transducers, their applications and design configurations. Based on the latest literature, different design configurations such as stepped-thickness cylindrical transducers and their potential application areas will be elaborated on to propose future research trends for introducing new configurations that meet the requirements for biomedical applications, the food industry, as well as other industrial fields.

Harvesting energy of flow-induced vibrations using cylindrical piezoelectric transducers

Piezoelectric transducers are used to harvest the energy of Flow-Induced Vibrations, FIVs. These transducers are mainly in the shape of a cantilever beam, although a cylindrical piezoelectric transducer has rarely been used. This work discusses the use of cylindrical piezoelectric transducers to harvest the energy of FIVs. Two cylinders made from Lead Zirconate Titanate, PZT, underwent closed-circuit wind-tunnel tests at wind speeds of 1 up to 7 m/s. The electric load was varied for each cylinder from 200 up to 800 kilo-Ohms. The cylinders had diameters of forty and ten millimetres and aspect ratios of one and three, respectively. It was possible to dissipate electric energy at a power of 370.6 pW across the load using the forty-millimetre-diameter cylinder at a flow speed of 1 m/s and a load resistance of 200 kΩ.

A Wind Tunnel Study of the Flow-Induced Vibrations of a Cylindrical Piezoelectric Transducer.

Piezoelectric transducers are used as a sensing device to study the fluids’ motion. Moreover, they are used as a harvester of energy of Flow-Induced Vibration (FIV). The current FIV harvesters in the literature rely on piezoelectric cantilevers coupled with a bluff body that creates flow instabilities. This paper studies the use of piezoelectric cylinders as a novel transducer in the field of fluid mechanics, where the transducer makes use of its bluff geometry to create instability. The study was based on wind tunnel measurements performed on four piezoelectric cylinders of different sizes over a speed range of 1–7 m/s. The paper looks at the variation of the generated voltage across the Reynolds number. It also compares the spectra of the generated open-circuit voltage to the turbulence spectra features known from the literature.

Experimental validation of axially polarized multilayer piezoelectric composite cylindrical transducers with adjustable multifrequency

The axially polarized multilayer piezoelectric composite cylindrical transducers with adjustable multifrequency capability have been proposed by adjusting the external electric resistance and the ratio of piezoelectric layer numbers between the actuator part and the sensor part, which have promising potential in designing the novel cymbal transducer for underwater sound projector and ultrasonic radiator applications. In the previous studies, the multilayer models were established to guide the design of the transducers with arbitrary layer number, and analyzed the dynamic characteristics theoretically. In this work, an experimental study is performed to validate the theoretical models and predictions. Piezoelectric rings with multiple concentric annular electrodes are designed to characterize the multilayer piezoelectric composite cylindrical transducers. The top surface of the piezoelectric rings is divided into two separate parts. One part is covered by multiple concentric annular electrodes, corresponding to the piezoelectric layers, and the other part is uncovered, corresponding to the elastic layers. Four prototypes are fabricated and each consists of four concentric annular electrodes. The impedance spectra are measured by the impedance analyzer to obtain the resonance and anti-resonance frequencies. Effects of two adjusting methods on the dynamic characteristics are evaluated experimentally. The experimental results basically coincide with the theoretical ones. This comprehensive experimental work assures the feasibility of using axially polarized multilayer piezoelectric composite cylindrical transducers with adjustable multifrequencies and confirms the benefit of the developed theoretical models for guiding the fabrication and optimization of this type of transducers.

The Potential of Cylindrical Piezoelectric Transducers for High-Frequency Acoustic Energy Harvesting

The work presented in this paper studies the potential of cylindrical piezoelectric transducers for harvesting high-frequency acoustic energy. The cylinder was made of a modified PZT (lead zirconate titanate) and had the shape of a squared cylinder with a side length of 4 cm and a wall thickness of 1 mm. The study used open-circuit measurements to study the relationship between the sound wavelength and the cylinder size and its effect on the performance of energy harvesting. The cylinder was found to give the best performance at a frequency of 20 kHz. In addition to open-circuit measurements, closed-circuit measurements were performed to demonstrate the ability to dissipate energy harvested from 20 kHz sound waves across an electric load. The load was designed in a series of experimental steps that aimed at optimizing an impedance-matched energy harvester. Finally, the cylinder was tested at the optimized load conditions, and it was possible to harvest and store energy with a power of 67.6 μW and harvesting efficiency of 86.1%.

Vibration and acoustic radiation characteristics of cylindrical piezoelectric transducers with circumferential steps

Circular cylindrical transducers have a wide range of applications in ultrasound generation. Introducing axial or circumferential stepped-thickness variations affects the performance of these transducers. This paper investigates the effect of circumferential stepped-thickness variations on the vibration and acoustic characteristics of a circular cylindrical piezoelectric shell. FEM software ANSYS is used to simulate these characteristics and experiments are performed to validate the simulations. Stress concentration levels due to these steps are observed in order to avoid exceeding the material limit. The results show that these steps can excite certain mode shapes which produce strong ultrasound fields and these modes have circumferential wave numbers commensurate with the number of stepped regions. These steps localize the vibration within the thin-walled regions leading to higher amplitude acoustic waves produced by constructive interference. Superiority of a circumferentially stepped transducer over an axially stepped one is demonstrated in this study through a much more uniform acoustic field along the length of the transducer as well as a lower frequency of operation at the intended mode shape. The effect of input excitation is also investigated and it is shown that introducing circumferential steps is more effective in terms of acoustic amplification than increasing the input excitation for the uniform-thickness transducer.

Studies on a Piezoelectric Cylindrical Transducer for Borehole Dipole Acoustic Measurements

In this article, a novel design of a piezoelectric dipole transducer is proposed for formation acoustic velocity measurement in the vicinity of a borehole with a frequency range of 0.4–6 kHz. The transducer which actuates a cylindrical shell to generate a pure dipole mode wave by using multiple piezoelectric bender bars is analyzed theoretically and simulated numerically by using the finite element method (FEM). Moreover, the transducer is fabricated and tested to compare with the numerical simulation results, which shows that the test and simulation results are in good agreement. Finally, compared with numerical simulation results of the traditional dipole transducer, it is shown that the proposed dipole transducer has higher transmitting sensitivities than commonly used ones, especially in low frequency responses. This work lays a foundation for the new development of the transducer in borehole dipole acoustic shear wave measurements. Especially, in a slow formation where the shear wave velocity is lower than that of compressional wave in the borehole fluid, the transducer could be used for highly efficient shear wave velocity measurements.

Computer simulations of a viscoelastic media heating by standing cylindrical ultrasound waves

This work is devoted to computer simulations of a viscoelastic media heating by standing cylindrical ultrasonic waves generated inside a cylindrical piezoelectric transducer with radial polarization. The transducer is assumed to operate on wall-thickness vibrational mode. Acoustic simulations were performed with the aid of two software packages: k-wave (acoustic simulations) and FeniCS (thermal simulations).

Acoustic radiation characteristics of piezoelectric shells with internal and external axial stepped-thickness configurations

Using stepped-thickness variations, this work aims at amplifying the strength of the focused acoustic field generated inside a hollow piezoelectric cylindrical tube transducer without increasing the driving power. This requires a full understanding of the vibration and acoustic radiation characteristics of various configurations of piezoelectric tube transducers with internal and external axial stepped-thickness variations. A uniform-thickness cylindrical shell is machined at specific regions to acquire a stepped-thickness cylindrical shell with thin-walled regions. The design procedure includes determining the location and number of these thin regions. ANSYS software is used to determine the frequencies and mode shapes of various configurations of these shells. However, stress concentration, as an important design consideration, is also scrutinized at the step regions to avoid exceeding the material fatigue limit. An optimum design configuration for the stepped-thickness transducer is identified. Stronger acoustic fields are obtained using geometrical variations without any increase in the driving power. The simulations are validated experimentally with reasonable agreement.

Physical Characteristics of and Transient Response from Thin Cylindrical Piezoelectric Transducers Used in a Petroleum Logging Tool.

We report on a transient response model of thin cylindrical piezoelectric transducers used in the petroleum logging tools, parallel to a recently established transient response model of thin spherical-shell transducers. Established on a series of parallel-connected equivalent-circuits, this model provides insightful information on the physical characteristics of the thin cylindrical piezoelectric transducers, i.e., the transient response, center-frequency, and directivity of the transducer. We have developed a measurement system corresponding to the new model to provide a state-of-the-art comparison between theory and experiment. We found that the measured results were in good agreement with those of theoretical calculations.

On the reducing of the acoustic signal length from the piezoelectric transducers of the sea ice monitoring systems

The solution of navigation problems the ice situation problems in the Arctic region need to study the acoustic parameters and local reflective properties of ice in real conditions. Information about the local sea ice acoustic properties essentially helps to solve the problems of statistical forecasting of reflective and scattering properties of ice cover. The successful solution of these problems mostly depends on the metrological parameters of the probing signals emitted by the primary piezoelectric transducers. This means, that to increase the resolution of the control and measuring equipment it is better to radiate and to receive short acoustic pulses. The article presents the results of analysis the pulse mode of operation of cylindrical piezoelectric transducers designed to measure the velocity of sound in sea ice. To reduce the length of acoustic pulses, an inductive-resistive load is connected to the electrical input of the radiator. The length and the amplitude of the emitted acoustic pulse were estimated using equivalent circuits of piezoelectric transducers and a spectral method based on the Fourier transforms. The optimal parameters of the electrical circuit, ensuring the minimum length of the acoustic pulses are calculated. The technique of possible measurements is described. The results are presented in the most general form, making possible to use them within different frequency ranges.

Electromechanical equivalent circuit of the radially polarized cylindrical piezoelectric transducer in coupled vibration.

Electromechanical equivalent circuit of the radially polarized cylindrical piezoelectric transducer in coupled vibration is obtained. The equivalent elasticity method is used to analyze the coupled vibration. It is an approximate analytical method, ignoring the shear and torsion stresses and strains, dividing the coupled vibration into the extensional radial and longitudinal vibrations. A mechanical coupling coefficient is introduced to connect these two equivalent vibrations. According to the electromechanical equivalent circuit, the resonance frequency equations as functions of the frequency and the mechanical coupling coefficient are acquired. The sound pressure level and far field sound pressure distribution for the transducer in water are simulated. It is demonstrated that the radiation range of the cylindrical transducer is larger than that of the ring-type transducer. Several prototypes of the transducer are fabricated; the radial and longitudinal resonance frequencies are measured. The experimental resonance frequencies are in good agreement with the analytical results. The acquisition of the electromechanical equivalent circuit contributes to analyzing the electromechanical characteristics of the radial polarized cylindrical transducer.

Finite element simulation of ultrasonic standing wave fields inside cylindrical piezoelectric transducers

At the present work, we have studied high-intensity ultrasound fields of standing cylindrical waves, generated by cylindrical piezoelectric transducer with radial polarization in its internal volume filled by liquid. The paper is focused on the study of length-extensional and thickness vibrational modes of cylindrical piezoelectric transducer. We have performed the finite-element simulations of standing cylindrical waves formation inside the cylindrical transducer filled with a liquid by those oscillation modes of piezoelectric cylinder using ANSYS software package and compared effectiveness of different regimes of standing waves generation.

Electromechanical equivalent circuit and coupled vibration of the radially composite cylindrical piezoelectric transducer

Electromechanical equivalent circuit for the radially composite cylindrical piezoelectric transducer in coupled vibration is deduced. The transducer is composed of a piezoelectric cylinder sandwiched by two concentric metal cylinders. Equivalent elasticity method is used to study the coupled vibrations of the three cylinders. A ratio named the mechanical coupling coefficient is introduced to divide the coupled vibration into the radial and longitudinal vibrations. The electromechanical equivalent circuits for the transducer and the resonance frequency equations are obtained. When the height is close to the radius of the transducer, the coupling between the radial vibration and the longitudinal vibration is strong. The thicker is the piezoelectric cylinder, the larger is the effective electromechanical coupling coefficient. Several prototypes of the transducer are fabricated. It is demonstrated that the theoretical resonance frequencies are in good agreement with the numerical and experimental results.

Effects of electrodes and electrical connections of piezoelectric layers on dynamic characteristics of radially polarized multilayer piezoelectric cylindrical transducers

Piezoelectric cylindrical transducer is a type of excellent smart devices that can generate radial sound radiation due to its unique structural characteristics and has been widely used for ultrasonic and underwater sound applications. In the design of a piezoelectric cylindrical transducer, especially with the multilayer structure, the electrodes and electrical connections of piezoelectric layers are two key factors affecting the device performance but have not been well evaluated, which result in the inaccurate prediction of dynamic characteristics. This work establishes the exact theoretical models for radially polarized multilayer piezoelectric cylindrical transducers by taking into account the electrodes and electrical connections of piezoelectric layers. Based on the plane stress assumption, the dynamic solutions of the models are derived. Analytical expressions of electric impedances are also derived to obtain the resonance frequencies. In addition, the analytical solutions are validated using the special example in the earlier work and comparing them with the finite element analysis results. Subsequently, the effects of the electrodes and electrical connections of piezoelectric layers on the dynamic characteristics of the transducer are analyzed and discussed. The results show that the electrode thickness, the electrode type, and the parallel and series connections significantly affect the transducer’s performance, thus providing useful guidelines in the design of piezoelectric cylindrical transducers. This work contributes to an overall analysis on the dynamic characteristics of the radially polarized multilayer piezoelectric cylindrical transducers, which is very helpful to improve the performance of two-dimensional emitter and receiver in underwater sound and ultrasonic applications.