Design Of Piezoelectric Transducers Research Articles

Vibration Modeling and Design of Piezoelectric Floating Mass Transducer for Implantable Middle Ear Hearing Devices

In this paper, a simple piezoelectric floating mass transducer (PFMT) for implantable middle ear hearing devices (IMEHDs) is proposed and its modeling and designing are studied. The transducer which can be implanted in the meddle ear consists of a PMN-PT multi-layered piezoelectric actuator, an elastic material, and a metal case. The proposed transducer has a simple structure and the force generated from the piezoelectric actuator is efficiently transferred to the ossicles of the middle ear. For the analysis of the vibration characteristics, the transducer attached on the ossicle is simplified into a simple mechanical model considering the mass of an incus. And the vibration displacement of the model is calculated using computer simulation and verified by the experimental results. It is shown that the designed PFMT can allow implantation in the middle ear cavity and provide a sufficiently high output of more than 100nm of vibration displacement. Plus, it is verified that the vibration characteristics of PFMT can be controlled through adjustment of the metal case size and the elastic material of the transducer.

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.

Piezoelectric actuator design for ultrasonically assisted deep hole drilling

From different chipping machining processes it is known that a superposition of the cutting kinematics with additional vibration energy increases material removal rate and tool life. Concerning the deep drilling process in the scope of smallest diameters from 0.9 to 6 mm insights to this so called hybrid processes are still awaited. Preliminary investigations indicated that here is high, so far unused potential. The goal of current research is an increase in effectiveness of the deep hole drilling process by superimposing additional vibration energy in ultrasonic frequency range by means of a piezoelectric transducer and low-frequency vibrations in the range of acoustic frequencies as well. Positive effects can appear in a couple of areas, e.g. achievable surface quality, feeding force, drilling torque, shape and length of chips, feasibility of machining ceramic materials and tool wear. This paper describes mainly the ultrasound conform design of the vibration unit. Furthermore issues of contactless energy transfer into a rotating tool and model based design of piezoelectric transducers will be addressed.

Optimal Data Selection for Piezoelectric Material Characterization

AbstractIn the simulation and design of piezoelectric transducers the exact knowledge of the entries in the material tensors ‐ the elastic, dielectric and piezoelectric coupling coefficients ‐ is an important prerequisite. Our task is the identification of these coefficients from indirect measurements, namely electric impedance data at different frequencies. This leads to a parameter identification problem for a system of coupled PDEs, which we solve by regularized Newton iterations. A crucial issue is the selection of frequencies at which measurements are taken. Here, we discuss the problem of choosing these frequencies in an optimal way to preserve efficiency of our identification scheme while improving reliability of the reconstruction results. For this purpose, we formulate this task as an optimization problem with PDE constraints and propose two approaches for its solution. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Piezoelectric transducer design via multiobjective optimization

The design of piezoelectric transducers is usually based on single-objective optimization only. In most practical applications of piezoelectric transducers, however, there exist multiple design objectives that often are contradictory to each other by their very nature. It is impossible to find a solution at which each objective function gets its optimal value simultaneously. Our design approach is to first find a set of Pareto-optimal solutions, which can be considered to be best compromises among multiple design objectives. Among these Pareto-optimal solutions, the designer can then select the one solution which he considers to be the best one. In this paper we investigate the optimal design of a Langevin transducer. The design problem is formulated mathematically as a constrained multiobjective optimization problem. The maximum vibration amplitude and the minimum electrical input power are considered as optimization objectives. Design variables involve continuous variables (dimensions of the transducer) and discrete variables (the number of piezoelectric rings and material types). In order to formulate the optimization problem, the behavior of piezoelectric transducers is modeled using the transfer matrix method based on analytical models. Multiobjective evolutionary algorithms are applied in the optimization process and a set of Pareto-optimal designs is calculated. The optimized results are analyzed and the preferred design is determined.

A flexible piezoelectric transducer design for efficient generation and reception of ultrasonic Lamb waves

This paper describes the development of a flexible piezoelectric transducer for the generation and detection of ultrasonic symmetrical Lamb waves in plate-like structures. This piezoplatelet transducer structure comprises an array of miniature piezoceramic plates embedded within a soft setting polymer filler material, combining the efficiency of the active piezoceramic phase with a degree of flexibility, which is a function of the platelet/polymer dimensions. For many condition-monitoring applications, the generation of ultrasonic Lamb waves is often appropriate, and this was achieved by incorporating interdigital design techniques via the transducer electrode pattern. The performance of the piezoplatelet transducer structure was evaluated using a combination of linear systems and finite-element modeling, substantiated by experimental results. Importantly, the transducer is shown to operate as an ensemble of platelets, each operating in the thickness mode and well decoupled from neighboring piezoelectric elements. Using this transducer configuration, an unimodal s1 Lamb wave, at 1.45 MHz, has been generated and detected in a 3-mm thick steel plate. Furthermore, a propagation distance of almost 1 m was recorded for s0 Lamb wave generation/detection in a fiber-reinforced composite plate.

Double frequency piezoelectric transducer design for harmonic imaging purposes in NDT

Harmonic imaging (HI) has emerged as a very promising tool for medical imaging, although there has been little published work using this technique in ultrasonic nondestructive testing (NDT). The core of the technique, which uses nonlinear propagation effects arising in the medium due to the microstructure or the existence of defects, is the ability to design transducers capable of emitting at one frequency and receiving at twice this frequency. The transducers that have been used so far are usually double crystal configurations with coaxial geometry, and commonly using a disc surrounded by a ring. Such a geometry permits the design of broadband transducers if each transducer element is adapted to the medium with its corresponding matching layers. Nevertheless, the different geometry of the emission and reception apertures creates difficulties when resolving the images. In this work, a new transducer design with different emission and reception apertures is resented. It makes use of the traditional construction procedures used to make piezocomposite transducers and the well-known theory of the mode coupling in piezoelectric resonators when the lateral dimensions are comparable with the thickness of the piezoceramic. In this work the design, construction, and characterization of a prototype to be used in NDT of metallic materials is presented. The acoustic field is calculated using water as a propagation medium, and these theoretical predictions then are compared with the experimental measurements. The predicted acoustic performances for the case of propagation in stainless steel are shown.

Design of compact piezoelectric transducers for shock wave applications

The application of focused intense sound pulses to treat several orthopedic diseases has gained in importance during the past years. Self-focusing piezoelectric transducers known from ESWL are not well suited for this purpose due to their size. Therefore compact transducers have to be designed. This implies an increase of the pressure pulse amplitude generated at the radiating surface. A stacked placement of two piezoelectric layers driven by two high-voltage pulses with an adjustable delay accomplishes this. Several designs are presented here representing transducers of different sizes. In principle piezoelectric transducers have the ability to vary the pressure pulse shape to a wider extent than other shock wave sources. Based on FEM simulations of the transducer the influence of some driving parameters, like a variation of the interpulse delay or shape of the driving voltage, on the resulting focal pressure signal is demonstrated. The results show the feasibility to control some parameters of the signal, for example the peak negative pressure amplitude. This possibility could provide new aspects in basic research as well as in clinical applications.

Effect of Q in Piezoelectric Transducers Based on Pb0.88 (Ln)0.08 Ti0.98 Mn0.02 O3 (Ln = La, Eu, Nd, Sm, Gd) Ceramics Used in Human Tissue

The dependence of the mechanical quality factor Q is used in the design of piezoelectric transducers based on PbTiO 3 modified by the partial substitution of rare earths for Pb. The Pb 0.88 (Ln) 0.08 Ti 0.98 Mn 0.02 O 3 system (Ln = La, Eu, Nd, Sm, Gd) ceramics are studied in the design of medical ultrasound transducers used in human tissue. The Q value indicates the lack of balance between the piezoelectric ceramic acoustic impedence and the acoustic impedance of the mean wich is in contact with the ceramic. This impedance relationship is important when are designed medical ultrasound transducers used in pulse-echo or continuous Doppler effect systems. The equation of Filipczynsky et al . is used to obtain the Q of ultrasonic transducers coupled acoustically and the electromechanical coupling factor k t (thickness dilatational vibration). Particular case, is when the Eu substitutes for Pb, the ceramic presents ultrahigh electromechanical anisotropy k t /k p M X . Coupling factor for planar extensional vibration k p M 0.

Effect of Q in Piezoelectric Transducers Based on Pb0.88 (Ln)0.08 Ti0.98 Mn0.02 O3 (Ln = La, Eu, Nd, Sm, Gd) Ceramics Used in Human Tissue

The dependence of the mechanical quality factor Q is used in the design of piezoelectric transducers based on PbTiO 3 modified by the partial substitution of rare earths for Pb. The Pb 0.88 (Ln) 0.08 Ti 0.98 Mn 0.02 O 3 system (Ln = La, Eu, Nd, Sm, Gd) ceramics are studied in the design of medical ultrasound transducers used in human tissue. The Q value indicates the lack of balance between the piezoelectric ceramic acoustic impedence and the acoustic impedance of the mean wich is in contact with the ceramic. This impedance relationship is important when are designed medical ultrasound transducers used in pulse-echo or continuous Doppler effect systems. The equation of Filipczynsky et al . is used to obtain the Q of ultrasonic transducers coupled acoustically and the electromechanical coupling factor k t (thickness dilatational vibration). Particular case, is when the Eu substitutes for Pb, the ceramic presents ultrahigh electromechanical anisotropy k t /k p M X . Coupling factor for planar extensional vibration k p M 0.

Characterization of piezoceramic rectangular parallelepipeds by means of a two-dimensional model.

The characterization of piezoelectric resonators is a field of intense scientific work; moreover, clear and accepted IEEE and IEC Standards have been published, showing the concepts and routes to perform the complete characterization of piezoelectric resonators. All of the accepted procedures define some resonator geometries, each of them related with a set of parameters, that can be obtained following resonance measurements at the corresponding resonance frequencies. The basis of the standards is the existence, for each geometry, of well-defined modes that have been analytically solved. The development of multi-dimensional models of the waves' propagation in piezoceramic materials opens the possibility of characterizing piezoelectric resonators with geometries different from those recommended in the standards. In this paper, a two-dimensional model, which takes into account the mechanical and dielectric losses, has been used to characterize piezoceramics with the shape of a regular parallelepiped. A set of elastic, dielectric, and piezoelectric parameters, which are useful for piezoelectric transducer design, can be obtained. For a given sample, the measured input electrical impedance is used to obtain the parameters by means of a fitting process with the corresponding model output. The results obtained with low and high loss materials show that the parameters found have values similar to those obtained following the procedures and geometries recommended by the standards. This procedure permits the characterization of materials when the manufacturing procedure does not allow the fabrication of the shapes recommended by the standards, making it a useful tool for transducer manufacturers and material scientists.

Design considerations for piezoelectric polymer ultrasound transducers

Much work has been published on the design of ultrasound transducers using piezoelectric ceramics, but a great deal of this work does not apply when using the piezoelectric polymers because of their unique electrical and mechanical properties. The purpose of this paper is to review and present new insight into seven important considerations for the design of active piezoelectric polymer ultrasound transducers: piezoelectric polymer materials selection, transducer construction and packaging requirements, materials characterization and modeling, film thickness and active area design, electroding selection, backing material design, and front protection/matching layer design. Besides reviewing these design considerations, this paper also presents new insight into the design of active piezoelectric polymer ultrasonic transducers. The design and fabrication of an immersible ultrasonic transducer, which has no adhesive layer between the active element and backing layer, is included. The transducer features direct deposition of poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymer onto an insulated aluminum backing substrate. Pulse-echo tests indicated a minimum insertion loss of 37 dB and -6 dB bandwidth of 9.8 to 22 MHz (71%). The use of polymer wear-protection/quarter-wave matching layers is also discussed. Test results on a P(VDF-TrFE) transducer showed that a Mylar/sup TM/ front layer provided a slight increase in pulse-echo amplitude of 15% (or 1.2 dB) and an increase in -6 dB pulse-echo fractional bandwidth from 86 to 95%. Theoretical derivations are reported for optimizing the active area of the piezoelectric polymer element for maximum power transfer at resonance. These derivations are extended to the special case for a low profile (i.e., thin) shielded transducer. A method for modeling the non-linear loading effects of a commercial pulser-receiver is also included.

Design of piezocomposite materials and piezoelectric transducers using topology optimization— Part III

Currently developments of piezocomposite materials and piczoelectric actuators have been based on the use of simple analytical models, test of prototypes, and analysis using the finite element method (FEM), usually limiting the problem to a parametric optimization. By changing the topology of these devices or their components, we may obtain an improvement in their performance characteristics. Based on this idea, this paper discusses the application of topology optimization combined with the homogenization method and FEM for designing piezocomposite materials. The homogenization method allows us to calculate the effective properties of a composite material knowing its unit cell topology. New effective properties that improves the electromechanical efficiency of the piezocomposite material are obtained by designing the piezocomposite unit cell. This method consists of finding the distribution of the material and void phases in a periodic unit cell that optimizes the performance characteristics of the piezocomposite. The optimized solution is obtained using Sequential Linear Programming (SLP). A general homogenization method applied to piczoelectricity was implemented using the finite element method (FEM). This homogenization method has no limitations regarding volume fraction or shape of the composite constituents. The main assumptions are that the unit cell is periodic and that the scale of the composite part is much larger than the microstructure dimensions. Prototypes of the optimized piezocomposites were manufactured and experimental results confirmed the large improvement.

Design of piezocomposite materials and piezoelectric transducers using topology optimization—Part II

Design of piezocomposite materials and piezoelectric transducers using topology optimization—Part II

Design of piezocomposite materials and piezoelectric transducers using topology optimization—Part I

Design of piezocomposite materials and piezoelectric transducers using topology optimization—Part I

Design of piezoelectric transducers using topology optimization

Among other applications piezoelectric transducers are widely used for acoustic wave generation and as resonators. These applications require goals in the transducer design such as high electromechanical energy conversion for a certain transducer vibration mode, specified resonance frequencies and narrowband or broadband response. In this work, we have proposed a method for designing piezoelectric transducers that tries to obtain these characteristics, based upon topology optimization techniques and the finite element method (FEM). This method consists of finding the distribution of the material and void phases in the design domain that optimizes a defined objective function. The optimized solution is obtained using sequential linear programming (SLP). Considering acoustic wave generation and resonator applications, three kinds of objective function were defined: maximize the energy conversion for a specific mode or a set of modes; design a transducer with specified frequencies and design a transducer with narrowband or broadband response. Although only two-dimensional plane strain transducer topologies have been considered to illustrate the implementation of the method, it can be extended to three-dimensional topologies. Transducer designs were obtained that conform to the desired design requirements and have better performance characteristics than other common designs.

Design of piezoelectric sandwich ultrasonic transducers with large cross-section

The coupled vibration of piezoelectric sandwich ultrasonic transducers with large cross-section was studied. The transducer consists of two piezoelectric ceramic circular plates with central holes, metal head and tail with rectangular cross-section. When the vibration coupling coefficients and the equivalent elastic constants were introduced, the coupled vibration of the transducer was divided into two vibrations: the longitudinal vibration along the central axis, and the lateral vibration perpendicular to the axis. The frequency equation was derived by means of the apparent elasticity method. Compared with one-dimensional theory, no limitations are imposed on the lateral dimensions of the transducer. Compared with numerical methods, the computation is time-saving. It is shown that the resonant frequencies obtained from the frequency equation are in better agreement with the measured results than those from one-dimensional theory.

Design of Composite Piezoelectric Transducers

Design of Composite Piezoelectric Transducers

Dipole horn piezoelectric electro-acoustic transducer design

A piezoelectric electro-acoustic device for converting an electric signal into an acoustic vibration and/or for converting acoustic vibrations into an electric signal is disclosed. The device employs at least two opposing concave membranes having a single axis of elongation tangent to the curvature thereof. The membranes face each other and are connected to electrodes. Upon changes in electric current provided to the membranes, the membranes will vibrate towards one another to thereby displace air located between the surfaces thereof. This dipole horn structure provides a high conversion efficiency as well as a true 360° acoustic response.

Optimizing the performance of piezoelectric drivers that use stepped horns

An analysis is presented for the design of piezoelectric transducers in a sandwich configuration using a stepped horn as a particle velocity amplifier. The condition for maximum power delivery to the load impedance is established in terms of the parameters of the horn and the piezoelectric material. As an example, the method of false position is used to find solutions numerically for the dimensions of a horn suitable for radiating into steam.