A New Technique for the Design of Acoustic Matching Layers for Piezocomposite Transducers (original) (raw)
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Optimization of acoustic matching layers for piezocomposite transducers
2000 IEEE Ultrasonics Symposium. Proceedings. An International Symposium (Cat. No.00CH37121), 2000
At present, lot of piezoelectric broad band ultrasonic transducers use as active material piezoelectric ceramic composites. In a typical transducer based on piezocomposites the active material is mounted on a soft backing and one matching layer is placed on the front, radiating face, with the aim to match the acoustic impedance of the medium and to enlarge the bandwidth. In this paper an optimization work is shown to demonstrate that a composite configuration can be used in the matching layer in order to improve the efficiency and the band of the transducers. An approximated two-dimensional analytical model has been used to optimize the design of a composite-structured matching layer in the case of 2-2 composites, obtaining different results for the polymer and piezoceramic composite phases.
New Low-Q Ceramic Piezocomposites for Wide-Band Ultrasonic Transducer Applications
A new family of polymer-free ceramic piezocomposites with properties combining better parameters of PZT, PN type ceramics and 1-3 composites for wide-band NDT ultrasonic transducer applications is presented. New “damped by scattering” ceramic piezocomposites were developed based on the original microstructural design concept and characterized by previously unachievable low QM (QMt =2-3) combined with high piezoelectric (d33=250-350) and electromechanical (kt=0.45-0.5) parameters, high Curie point (340°C), low acoustic impedance (15-20 MRayl) in a wide working frequency range (0.2-12 MHz). Complex sets of elastic, dielectric, and piezoelectric parameters of the new piezocomposites were systematically studied using impedance spectroscopy approach and ultrasonic method. A line of wide-band NDT ultrasonic transducers with high sensitivity and resolution was manufactured and tested.
Piezocomposite transducer design and performance for high resolution ultrasound imaging transducers
International Journal of Computational Materials Science and Engineering
Piezocomposite design for dedicated ultrasonic imaging applications requires precise homogenization models for predicting the electromechanical characteristics of the new material. Thus, several homogenization models have been developed. As part of this work, we applied several analytical homogenization models for piezocomposite of 2–2 and 1–3 connectivities. To validate these analytical models, a comparative study was made between various models and experimental measurements. As a result, these homogenized electromechanical properties are effectively used for the calculation and comparison of electroacoustic response for typical transducers aimed at ultrasound imaging applications. An optimal design of transducer aimed at ultrasound imaging applications is proposed as a dedicated imaging performance index, elaborated through a trade-off between sensitivity and bandwidth.
Modeling and experimental study of transducers made with piezoelectric composite material
Le Journal de Physique IV, 1999
The topic of this work is the experimental and theoretical study of a cylindrical acoustic transducer made with a 1.3 piezoelectric composite material. This material consists in PZT ceramic rods embedded in a polymer matrix. A modeling of this ideal transversally periodic structure is proposed. It is based on a finite element approach derived from homogenization techniques mainly used for composite material studies. The analysis focuses on a representative unit cell with specific boundary conditions on the lateral surfaces taking accurately into account the periodicity of the structure. The first step proposed is the development of a tridimensional Fortran code especially adapted for this problem. It then allowed the set up of different nonredundant linear combinations of degrees of freedom that could be linked to the ANSYS FEM code allowing to progress toward the modeling of the complete problem. The motion of the faces of an experimental transducer vibrating in the quasi-static mode has been analyzed using Laser Doppler vibrometry technique. Experimental and modeling results are in good agreement and justify the proposed approach.
UNIDIMENSIONAL MODELING AND CONSTRUCTION OF A 1-3 PIEZOELECTRIC COMPOSITE TRANSDUCER
2000
In many applications, such as medical imaging and nondestructive testing, broadband ultrasonic transducers capable of producing short pulses are required. Combining a piezoelectric element and a passive polymer to form a piezoelectric composite allows the development of transducers with high bandwidth and sensitivity, and low radial coupling. This work presents the modeling and construction of an ultrasonic transducer using a 1-3 piezoelectric composite. A simple physical model is used to calculate the effective properties of the composite. This model can be applied when the lateral spatial scale of the composite is sufficiently small so that the composite can be treated as an effective homogeneous medium. The effective properties are used in a distributed matrix model to calculate the electrical impedance of the composite. It is used the dice-and-fill technique to construct a 1-3 lead zirconate titanate(PZT)/epoxy 800 kHz, 20 mm diameter composite. The simulated results of the electrical impedance are compared with the experimental results measured by an impedance analyzer equipment. Finally, the ultrasonic transducer is constructed using the piezoelectric composite. The impulse response of the transducer is measured and compared with the theoretically obtained using the distributed matrix model. The experimental results show excellent agreement with the simulated ones. , Ouro Preto, MG
Design considerations for 1-3 composites used in transducers for medical ultrasonic imaging
Ceramic polymer piezoelectric composites with 1-3 connectivity have become an important tool in the design and manufacture of thickness mode transducers for medical diagnostic ultrasonic imaging. The major reasons for this are that, relative to piezoelectric ceramics alone, the composite can be designed with higher thickness coupling coefficient. acoustic impedance can be more closely matched to human tissue, arid low frequency lateral resonances can be suppressed. These improvements can lead to higher sensitivity and bandwidth in the transducer and reduce ringing due to unwanted modes of vibration. This paper compares annular array transducers made from ceramics alone to those made with composites to demonstrate the advantages of composites, and examines some of the trade-offs involved in optimizing composite designs for this application. Effects of varying Young's modulus and Poisson's ratio of the polymer phase on coupling coefficient and high frequency lateral resonances of the composite are presented.
Manufacturing and experimental investigation of 2-2 piezocomposite transducer arrays
The relative lack of experimental data relative to 2-2 piezocomposites stimulated the present experimental investigation of the vibration behaviour of 2-2 PZT-polymer composite transducers array for clinical ultrasound equipments, that was carried on for several prototypes having the same dicing pitch of 0,11 mm and different volume fractions and thickness values. Many array transducers were manufactured from the 2-2 plates, with subsequent deposition of the electrodes by a second dice-and-fill technique with pitch of 0,245 mm. In these latter conditions, the 2-2 plate becomes an "asymmetric" 1-3 composite and thus a more complex vibration pattern of the structure should be expected. Several cases of different volume fractions of 2-2 plate were investigated (70, 65, 60, 50 and 40 percent) and for each volume fractions several composite transducer arrays having the thickness mode resonance within the range from 2,6 MHz to 8 MHz were manufactured and analyzed. Measurements w...
A 3D model of new composite ultrasonic transducer
Journal of Computational Electronics, 2017
A three-dimensional (3D) model of a high-power ultrasonic, composite, unidirectional transducer is proposed in this paper. The proposed 3D Matlab/Simulink model of the composite transducers predicts the thickness and the radial modes of oscillation as well as their mutual couplings. This longitudinal, prestressed, asymmetrical, piezoelectric transducer, which consists of two active piezoelectric layers, front, back and central oscillating metal mass, is realized. Due to its special structure, the central mass is not bounded using a bolt and performs unidirectional piston motion as compression and expansion occur in cycles keeping the axial dimension of the transducer roughly constant because of mutually opposite polarization of active elements. The electromechanical equivalent circuit of the transducer, representing one-dimensional (1D) model, is derived first and is also presented in this paper, while the resonance frequency equation is obtained analytically. Few composite transducers are designed and manufactured. Their resonance frequencies are measured and compared with the analytically obtained results for a large number of electrical connection combinations. In order to demonstrate the capabilities and limitations of the 1D model, comparison with the results from the 3D model are made. Results show that the measured frequencies are in good correspondence with the analytically obtained from 1D model only for the thickness modes and from the 3D model for the thickness and the radial modes of oscillation and their mutual coupling.
High frequency piezo-composite transducer array designed for ultrasound scanning applications
Proceedings of the IEEE Ultrasonics Symposium
A 20 MHz high density linear array transducer is presented in this paper, This array has been developed using an optimized ceramic-polymer composite material. The electro-mechanical behaviour of this composite, especially designed for high frequency applications, is characterised and the results are compared to theoretical predictions. To support this project, a new method of transducer simulation has been implemented. This simulation software takes into account the elementary boundary phenomena and allows prediction of inter-element coupling modes in the array. The model also yields realistic computed impulse responses of transducers, A miniature test device and water tank have been constructed to perform elementary acoustic beam pattern measurements. It is equipped with highly accurate motion controls and a specific needle-shaped target has been developed. The smallest displacement available in the three main axes of this system is 10 microns. The manufacturing of the array transd...