Design Of Ultrasonic Transducers Research Articles

Optimized Design of High-Temperature Resistant Air-Coupled Ultrasonic Transducer (ACUT) Based on Single Acoustic Matching Layer

Optimized Design of High-Temperature Resistant Air-Coupled Ultrasonic Transducer (ACUT) Based on Single Acoustic Matching Layer

Asymmetric-Backed Multi-Frequency Ultrasonic Transducer for Conformal Tumor Ablation.

Minimally invasive ultrasound ablation transducers have been widely studied. However, conventional designs are limited by the single working frequency, restricting their conformal ablation ability (i.e., ablation size and shape controllability). New multi-frequency ultrasonic transducer design method is proposed based on the asymmetric backing layer, which divides the transducer into non-backing-layer region (i.e., front-piezoelectric region) and backing-layer region (i.e., front-piezoelectric-backing region) with multiple local thickness mode resonant frequencies. Ablation zone can be controlled by exciting the local resonance within or between the regions, and its control flexibility is further enhanced by driven under a frequency modulation signal. Experiments and calculations are combined for verifying the proposal. The fabricated transducer with a Y-direction asymmetric backing layer shows five resonances, with two in each region and one resonance excited in both regions. Spatial ultrasound emission is demonstrated by acoustic measurements. Tissue ablation experiments verified spatial ablation zone control, and frequency modulation driving method enables the spatial transition of ablation zone from one region to the other, generating different ablation sizes and shapes. Finally, patient-specific simulations verified the effectiveness of conformal ablation. The proposed transducer enables flexible control of ablation zone. This study demonstrates a new method for conformal tumor ablation.

Measurement insights and error analysis of electronic parameters for ultrasonic transducers

Abstract Piezoelectric ultrasonic transducers with the function of energy conversation, as well as their numerous advantages in high-power density, quick response, flexible design, and service reliability, are involved in wide applications of industrial processing, precision driving, smart sensing, and medical services. The electromechanical equivalent circuit and Kirchhoff’s law indicate that mechatronics parameters are essential for performance evaluation, reliability analysis, and fault diagnosis of ultrasonic transducers. Importantly, the ultrasonic transducer is a time-variant system, data of one single parameter collected from a certain test cannot match with the data of another single parameter acquired from a different test. So, a synchronous and precise online measurement of electronic parameters is encouraged for performance evaluation and optimization design of ultrasonic transducers. With the combination of virtual instrument technology, an asynchronous measurement system of electrical excitation parameters for the ultrasonic transducers of linear driving motors was established in this study. Furthermore, the systematic measurement methods and error theory were illustrated, including the calculation methods and measuring circuits of electric signals. Experimental results proved that the proposed system and methods for measuring the input electronic power of ultrasonic transducer (e.g. effective value method for voltage and current, energy moment method for frequency, and spectrum analysis method for phase difference) are highly precise, quickly responsive, robust, and reliable for ultrasonic transducers. The findings of this study provide valuable references and suggestions for efficient, accurate, and online performance evaluation of ultrasonic transducers, particularly for piezoelectric transducers utilizing ultrasonic high-voltage exciting signals.

Optimal design of ultrasonic transducer based on multi-layer backing with adjustable impedance

Ultrasonic transducers, especially used in medical imaging, strike a balance between sensitivity and bandwidth to yield high-quality images. This challenge centers on the optimal transmission of acoustic energy across the layers of transducer. The backing layer stands as a critical component of transducers, orchestrating the conversion of acoustic impedance to enhance bandwidth. While traditional designs often utilize metal particle-polymer composites, issues arise from material limitations, complex fabrications, and deviations in sample properties. This study introduces an optimized multilayer backing (MLB) design using a metal-polymer structure. Implementing an equivalent circuit model, an MLB of epoxy-aluminum composite is designed. The ultrasonic transducer has an operating frequency of about 6 MHz, in which the backing layer is a stacking composite of 19.3 μm epoxy resin and 30 μm aluminum foil. Notably, this optimized design increased the -6dB bandwidth from 27.72 % to 33.44 % and verified its superior electro-acoustic performance based on ultrasonic imaging. Furthermore, this innovative design approach provides a wider range of acoustic impedance, improves the efficiency of ultrasonic energy transmission, and provides a streamlined approach to miniaturized transducer design.

Design, evaluation and experiment of a dual-frequency ultrasonic transducer for aluminum wedge bonding

Design, evaluation and experiment of a dual-frequency ultrasonic transducer for aluminum wedge bonding

Simulation and experimental investigation of the effects of subdicing on a single element transducer

Structure design of medical ultrasonic transducers is of prime importance, as it not only affects the transducer's imaging performance, but also limits its application scene and scope. In this paper, a single element transducer with subdicing is fabricated and its performance is studied using finite element method. In addition, the comparison transducers (CPTs) are fabricated as well as single element transducers with and without subdicing the element. The experimental results show that by subdicing the element with cut width 120 μm and cut depth 500 μm of the single transducer with a center frequency of 8 MHz and dimension of 2 mm × 0.9 mm × 1.2 mm, the center frequency reduced by up to 58.3 %, the −6 dB bandwidth increased by up to 48.7 %, but the echo signal amplitude reduced by 52.4 %. Compared to CPT-5, the volume of the subdicing transducer reduced by 94.6 %, the center frequency reduced by 4.3 %, the −6 dB bandwidth increased by 1.26 times, the transmitted pulse signal length decreased by 50 %, and the echo signal amplitude achieved 28 % of CPT-5. Therefore, the proposed subdicing transducer may have great potential for miniaturization and close-range imaging.

Intelligent Optimization Design of a Phononic Crystal Air-Coupled Ultrasound Transducer.

To further improve the operational performance of a phononic crystal air-coupled ultrasonic transducer while reducing the number of simulations, an intelligent optimization design strategy is proposed by combining finite element simulation analysis and artificial intelligence (AI) methods. In the proposed strategy, the structural design parameters of 1-3 piezoelectric composites and acoustic impedance gradient matching layer are sampled using the optimal Latin hypercube sampling (OLHS) method. Moreover, the COMSOL software is utilized to calculate the performance parameters of the transducer. Based on the simulation data, a radial basis function neural network (RBFNN) model is trained to establish the relationship between the design parameters and the performance parameters. The accuracy of the approximation model is verified through linear regression plots and statistical methods. Finally, the NSGA-II algorithm is used to determine the design parameters of the transducer. After optimization, the band gap widths of the piezoelectric composites and acoustic impedance gradient matching layer are increased by 16 kHz and 13.5 kHz, respectively. Additionally, the -6 dB bandwidth of the transducer is expanded by 11.5%. The simulation results and experimental results are consistent with the design objectives, which confirms the effectiveness of the design strategy. This work provides a feasible strategy for the design of high-performance air-coupled ultrasonic transducers, which is of great significance for the development of non-destructive testing technology.

Physical and dynamic characteristics of high-amplitude ultrasonic wave propagation in nonlinear and dissipative media

This study presents a comprehensive investigation into the soliton solutions for the Khokhlov–Zabolotskaya–Kuznetsov ([Formula: see text]) problem using the Bernoulli sub-equation function approach, generalized Kudryashov method, and Homotopy perturbation method. The [Formula: see text] equation, a nonlinear wave equation that governs the propagation of high-amplitude ultrasonic waves through nonlinear media, is studied in detail. Perturbation theory and asymptotic expansions are employed to derive approximate solutions for the [Formula: see text] problem. These methodologies offer valuable insights into the behavior of ultrasonic waves in different media, thereby facilitating the optimization of ultrasonic transducer design and enhancing the precision of ultrasonic imaging systems. The analytical and semi-analytical methods utilized for solving the [Formula: see text] equation are computationally efficient and serve as valuable resources for researchers and engineers working in the field of ultrasonics. The outcomes of this study carry significant implications for the understanding of ultrasonic wave behavior in nonlinear and dissipative media, ultimately contributing to the development of more accurate and efficient ultrasonic imaging techniques.

Design and Analysis of Ultrasonic Composite Transducer with a Quarter-wave Taper Transition Horn

Based on the electromechanical equivalent circuit theory, equations related to the resonance frequency and the magnifying coefficient of a quarter-wave vibrator and a quarter-wave taper transition horn were deduced, respectively. A series of 3D models of ultrasonic composite transducers with various conical section length was also established. To reveal the influences of the conical section length and the prestressed bolt on the dynamic characteristics (resonance frequency, amplitude, displacement node, and the maximum equivalent stress) of the models and the design accuracy, finite element (FE) analyses were carried out. The results show that the addition of prestressed bolt increases the resonance frequency and causes the displacement node on the center axis to move towards the small cylindrical section. As the conical section length rises, the increment of resonance frequency reduces and tends to a stable value of 360 Hz while the displacement of the node on the center axis becomes lager and gradually approaches 1.5 mm. Furthermore, the amplitude of the output terminal is stable at 16.18 μm under 220 V peak-topeak (77.8 VRMS) sinusoidal potential excitation. After that, a prototype was fabricated and validated experiments were conducted. The experimental results are consistent with that of theory and simulations. It provides theoretical basis for the design and optimization of small-size, large-amplitude, and high-power composite transducers.

Optimization of elastic wave propagation in a reconfigurable medium by genetic algorithms with adaptive mutation probability

We introduce a reconfigurable medium for the manipulation of elastic propagation properties of Lamb waves. It is based on a shape memory polymer (SMP) with temperature-dependent Young’s modulus. Waves are excited by a laser pulse and detected by a laser vibrometer. A two-dimensional temperature field is controlled by a scanning heating laser. We use genetic algorithms to determine optimal distributions of mechanical properties for the following criteria: the wave amplitude has to be maximized at a given location and at the same time minimized at one or two other locations. Due to the reconfigurability of the medium, the optimization process is performed directly on the object of optimization, and not on a numerical or analytical representative, based on a direct measurement of the fitness. The optimized configuration makes the waves propagate away from (or around) the point of minimization towards the point of maximization. We improve the genetic algorithm by adapting the mutation probability of individual genes according to specific criteria, which depend on the surrounding genes (distributed in two dimensions). This provides the advantages: concentrating the mutations in the areas of genetic inconsistencies and counterbalancing the error of the fitness measurement. The method is applicable for the intelligent design of wave energy harvesters, ultrasonic transducers, and analogue wave computing devices.

High Acoustic Impedance and Attenuation Backing for High-Frequency Focused P(VDF-TrFE)-Based Transducers.

Backing materials with tailored acoustic properties are beneficial for miniaturized ultrasonic transducer design. Whereas piezoelectric P(VDF-TrFE) films are common elements in high-frequency (>20 MHz) transducer design, their low coupling coefficient limits their sensitivity. Defining a suitable sensitivity-bandwidth trade-off for miniaturized high-frequency applications requires backings with impedances of >25 MRayl and strongly attenuating to account for miniaturized requirements. The motivation of this work is related to several medical applications such as small animal, skin or eye imaging. Simulations showed that increasing the acoustic impedance of the backing from 4.5 to 25 MRayl increases transducer sensitivity by 5 dB but decreases the bandwidth, which nevertheless remains high enough for the targeted applications. In this paper, porous sintered bronze material with spherically shaped grains, size-adapted for 25-30 MHz frequency, was impregnated with tin or epoxy resin to create multiphasic metallic backings. Microstructural characterizations of these new multiphasic composites showed that impregnation was incomplete and that a third air phase was present. The selected composites, sintered bronze-tin-air and sintered bronze-epoxy-air, at 5-35 MHz characterization, produced attenuation coefficients of 1.2 and >4 dB/mm/MHz and impedances of 32.4 and 26.4 MRayl, respectively. High-impedance composites were adopted as backing (thickness = 2 mm) to fabricate focused single-element P(VDF-TrFE)-based transducers (focal distance = 14 mm). The center frequency was 27 MHz, while the bandwidth at -6 dB was 65% for the sintered-bronze-tin-air-based transducer. We evaluated imaging performance using a pulse-echo system on a tungsten wire (diameter = 25 μm) phantom. Images confirmed the viability of integrating these backings in miniaturized transducers for imaging applications.

Ultrasonic Transducers for In-Service Inspection and Continuous Monitoring in High-Temperature Environments.

The inspection of structures operating at high temperatures is a major challenge in a variety of industries, including the energy and petrochemical industries. Operators are typically performing nondestructive evaluations using ultrasound to monitor component thicknesses during scheduled shutdowns, thereby ensuring safe operation of their plants. However, despite being costly, this calendar-based approach may lead to undetected corrosion, which can potentially result in catastrophic failures. There is therefore a need for ultrasonic transducers designed to withstand permanent exposure to high temperatures, so as to continuously monitor the remnant thicknesses of structures in real time. This paper discusses the design of a heat-resistant ultrasonic transducer based on a piezoelectric element. The piezoelectric material, the electrodes, the backing layer, the wires and the casing are presented in detail from the acoustic and thermal expansion point of view. Four transducers optimized for 3 MHz were manufactured and tested to destruction in different conditions: (1) 72-h temperature steps from room temperature to 750 ∘C, (2) thermal cycles from room temperature to 500 ∘C and (3) 60 days of continuous operation at >550 ∘C. The paper discusses the results, as well as the effect of temperature over time on the properties of the transducer.

Design of a novel 2D ultrasonic transducer for 2D high-frequency vibration–assisted micro-machining

Ultrasonic vibration–assisted machining (VAM) is a process in which a tool or workpiece is vibrated using ultrasonic frequency small-amplitude vibrations to improve cutting performance, and an ultrasonic transducer usually generates these vibrations. This study investigates how two-dimensional vibrations are generated using axially polled piezoceramics. Modifying the wave propagation in geometric ways by creating a notch at the front mass, the longitudinal response excited by the axially polled piezoceramic discs can be converted into combined longitudinal and bending vibrations at the transducer front mass. Finite element analysis (FEA) software COMSOL is used to study wave propagation, and ANSYS is used to optimize the transducer’s mechanical structure, while an equivalent circuit approach is used to analyze the electrical impedance spectra and confirm its resonance frequency. An experimental analysis of impedance response and amplitude of generated vibrations using the novel 2D ultrasonic transducer is conducted to validate the numerical and analytical results, which shows that resonance frequency results are in very good agreement with the theoretical model. Finally, the proposed design is validated by preliminary test results that demonstrate its performance and principles.

Design and test of a small high frequency ultrasonic cleaning transducer

In order to solve the problem of cleaning of complex surfaces and micro blind holes in industrial products, a small high frequency ultrasonic cleaning transducer was designed and tested. Firstly, the finite element model of the transducer was established, and the influence of structural parameters on the first order longitudinal vibration frequency was analyzed. By adjusting the structural parameters of the transducer, the first order longitudinal vibration frequency of the transducer was determined to be 58716hz.The harmonic response of the transducer was analyzed. The results showed that when the voltage amplitude applied on the piezoelectric ceramic sheet was 80V, the transducer produced resonance at 58716 Hz, and the end face of the front cover of the transducer produced an axial displacement of about 3.34 µm . The transducer was made according to the theoretical analysis results, and the frequency sweep test was carried out on the transducer. The theoretical analysis results were consistent with the test results, which showed that the designed small high frequency ultrasonic cleaning transducer could meet the requirements of high frequency cleaning.

Nonlinear Equivalent Circuit of High-Power Sandwich Piezoelectric Ultrasonic Transducer.

In the theoretical design and analysis of the sandwich piezoelectric ultrasonic transducer, the transducer is considered to be an ideal linear system, where the dielectric, piezoelectric, and mechanical losses are neglected. However, when the transducer is driven at high power, the losses are becoming several times higher comparing them to low signal measurements, and the transducer works in a nonlinear state. In order to predict the performance of the transducer at high power, the nonlinear parameters (complex constants) of the piezoelectric materials are introduced. The corresponding nonlinear equivalent longitudinal wave sound velocity and the nonlinear equivalent longitudinal wavenumber of the piezoelectric ceramics are derived. Then, the nonlinear equivalent circuit (NEC) and the nonlinear resonance frequency equation of the high-power sandwich piezoelectric ultrasonic transducer that related with the losses are deduced. Then, the nonlinear finite element model (NFEM) of the transducer is constructed. The performance parameters of the transducer obtained by the NEC method and the finite element (FE) method are compared with each other, and consistent results have been achieved by two methods. Finally, the contribution of various losses is obtained through theoretical calculation, simulation, and experimental measurement, and the correctness of the theoretical model in this article is verified.

Design and Fabrication of 15-MHz Ultrasonic Transducers Based on a Textured Pb(Mg1/3Nb2/3)O3-Pb(Zr, Ti)O3 Ceramic.

Ultrasound medical imaging is an entrenched and powerful tool for medical diagnosis. Image quality in ultrasound is mainly dependent on performance of piezoelectric transducer elements, which is further related to the electromechanical performance of the constituent piezoelectric materials. With rising need for piezoelectric materials with better performance and low cost, a highly 〈001〉 textured piezo ceramic, Pb(Mg1/3Nb2/3)O3-Pb(Zr, Ti)O3, has been developed. Recently, textured ceramic materials can be produced at low cost and exhibit high piezoelectric strain constants and large electromechanical coupling coefficients. In this work, 15-MHz ultrasonic transducers with an effective aperture of 2.5 mm in diameter based on these highly 〈001〉 textured ceramics have been successfully fabricated. The fabricated transducers achieved a central frequency of 15 MHz, a fractional bandwidth of 67% (at -6 dB), a high effective electromechanical coupling coefficient [Formula: see text] of 0.55, and a low insertion loss (IL) of 21 dB. Ex vivo ultrasonic imaging of a porcine eyeball was used to assess the tomography quality of the transducer. The results show that utilized textured ceramic has a great potential in developing ultrasonic devices for biomedical imaging purposes.

Design and 3D FEM Analysis of a Flexible Piezoelectric Micromechanical Ultrasonic Transducer Based on Sc-Doped AlN Film.

In this paper, a flexible piezoelectric micromachined ultrasonic transducer (PMUT) based on Scandium (Sc)-doped Aluminum Nitride (AlN) film was designed and modeled by the three-dimensional finite element method (3D-FEM). The resonant frequency of 218.1 kHz was reported. It was noticeable that a high effective electromechanical coupling coefficient (k2eff) of 1.45% was obtained when a combination of a flexible PI and a thin Si layer was used as the PMUT supporting structure layer. Compared with a pure Si supporting layer counterpart, the coupling coefficient had been improved by 110.68%. Additionally, the increase of Sc doping concentration in AlN film further enhanced the device electromechanical coupling coefficient and resulted in an improvement for transmitting/receiving sensitivity of the proposed flexible PMUT. When the doping concentration of Sc reached 30%, the emission sensitivity was as large as 1.721 μm/V, which was 2.86 times greater than that of conventional AlN film-based PMUT. The receiving sensitivity was found to be 2.11 V/KPa, which was as high as 1.23 times the performance of an undoped device. Furthermore, the bending simulation result showed that the proposed flexible PMUT device can maintain a good mechanical stability when the bending radius is greater than 1.5 mm. The simulation of sound field characteristics demonstrated that the flexible PMUT based on AlScN could receive stable sound pressure signals under the bending radius of 1.5 cm.

Design and 3D printing of waveguide-based ultrasonic longitudinal-torsional transducers for medical needle insertion

This paper presents a new waveguide-based longitudinal-torsional (L&T) ultrasonic transducer. For synchronization of both the longitudinal and the torsional vibrations, a new circular array of helical structures was designed and developed. The array of helical structures is used as an effective waveguide to constrain the wave propagations to achieve harmonic longitudinal-torsional vibration. Analytical modeling of the new design is presented for synchronous L&T vibration conversion. A finite element (FE) analysis was used to optimize the geometric design of the new L&T transducer. The new design was fabricated using a selective laser melting (SLM) additive manufacturing (AM) process. Lab experiments were conducted to measure the impedance and vibration performance of the novel fabricated transducers and validate the L&T transducer design. The results show that the new waveguide-based transducer is promising to deliver synchronized L&T vibration with high vibrational power efficiency. The new L&T ultrasonic transducer can be developed for a vibratory needle insertion device, effectively reducing insertion force and bending.

Non-continuous furcation phenomenon of SH dispersion curves in magneto-electro-elastic alloy plate with negative magnetic permeability

Inspired by recent work on Lamb waves in magneto-electro-elastic plate (Xiao et al., 2016), in the present work we studied the non-continuous furcation phenomenon of Shear Horizontal (SH) dispersion curves in 40%BaTiO3–60%CoFe2O4 alloy. The SH modes in this magnetostrictive alloy introduce new non-continuous furcation curves that are a remarkable phenomenon when compared to available data. Although (Xiao et al.,2016) did not conclude explicitly the exact and obvious cause of this phenomenon, it seems clear to us that it is closely related to negative magnetic permeability. Even using the negative value of this magnetic permeability, however, the available data is contradictory. Therefore, an investigation into the veracity of the accurate trajectories under this condition was imperative. The obtained observations may serve as a useful reference for the design of ultrasonic transducers for non-destructive evaluation (NDE) in industry.

Design and 3d Printing of Waveguide-Based Ultrasonic Longitudinal-Torsional Transducers for Medical Needle Insertion

Design and 3d Printing of Waveguide-Based Ultrasonic Longitudinal-Torsional Transducers for Medical Needle Insertion