Manufacture Of Transducers Research Articles

Повышение эффективности очистки канализационных труб

Today, the level of accessibility to water supply and sewage systems, their technical condition, and the quality of maintenance and cleaning are among the elements determining the quality of life in cities and small settlements. Efficient sewage systems are vital to maintaining environmental safety, the established sanitary norms, and the conditions of people’s comfortable accommodation. All these factors require the communal services of cities and megalopolises to maintain sewage systems in proper technical conditions, minimize operational costs, extend the service life of the systems, and organize and implement new treatment technologies. According to experts, the main enemy of the internal sewage systems is grease abundant in domestic wastewater. The initially warm wastewaters are soon cooled in the pipe, and grease impurities settle on the walls of the sewage pipe. The layer of grease deposits may trap other impurities, thus contributing to the formation of a larger and more complex clog. The development and implementation of new contemporary methods of treatment of sewage systems and, particularly, the use of ultrasonic vibrations reduces operational costs, extends the service life of the systems, and ensures environmental safety. For these purposes, the ultrasonic generator UZG-10 of 10 kW capacity was used, as well as the magnetostrictive ultrasonic transducer with a magnetoconductor with three rods. The middle rod is equipped with finished windings that rigidly connect the free ends of the other rods. The provided scheme of transducer manufacturing increases the efficiency of pipe treatment and significantly reduces energy costs.

Characterization of a Piezoelectric Acoustic Sensor Fabricated for Low-Frequency Applications: A Comparative Study of Three Methods.

Piezoelectric transducers are widely used for generating acoustic energy, and choosing the right radiating element is crucial for efficient energy conversion. In recent decades, numerous studies have been conducted to characterize ceramics based on their elastic, dielectric, and electromechanical properties, which have improved our understanding of their vibrational behavior and aided in the manufacturing of piezoelectric transducers for ultrasonic applications. However, most of these studies have focused on the characterization of ceramics and transducers using electrical impedance to obtain resonance and anti-resonance frequencies. Few studies have explored other important quantities such as acoustic sensitivity using the direct comparison method. In this work, we present a comprehensive study that covers the design, manufacturing, and experimental validation of a small-sized, easy-to-assemble piezoelectric acoustic sensor for low-frequency applications, using a soft ceramic PIC255 from PI Ceramic with a diameter of 10 mm and a thickness of 5 mm. We present two methods, analytical and numerical, for sensor design, followed by experimental validation, allowing for a direct comparison of measurements with simulated results. This work provides a useful evaluation and characterization tool for future applications of ultrasonic measurement systems.

Preparation of polyvinyl acetate composite as a new backing material for the manufacture of ultrasonic transducers

Polyvinyl acetate (PVAc) composites were loaded with varying amounts of nano-metal alloy (Ag–Sn–Cu–Pt) and stearic acid. They are used as backing materials for ultrasonic transducers to prevent back-echoes from reverberating into the piezoelectric element and to reduce noisy echoes. The novelty of this work is the usage of these newly prepared PVAc/alloy composites as backing material in ultrasonic transducers with a polyvinylidene fluoride (PVDF) active element. The X-ray diffraction (XRD) technique was used to examine the structure of the composites. The ultrasonic technique investigated the ultrasonic attenuation coefficient, the acoustic impedance, the mechanical properties, and other parameters. The transducers with the new backing composites gained high sensitivity, broadband, short ringing, and so on. These characteristics were improved by increasing the nano-metal alloy content in the backing composites. The study also proved the efficiency of the PVAc/alloy composite as new backing material in ultrasonic transducers.Graphical abstractSketch of fabricated ultrasonic transducers with backing materials from PVAc/alloy composites (B1, B2, B3, B4, B5, and B6) and their important features (BW is transducers’ band width and S is transducers’ sensitivity).

Micronized Recycle Rubber Particles Modified Multifunctional Polymer Composites: Application to Ultrasonic Materials Engineering.

There is a growing interest in multifunctional composites and in the identification of novel applications for recycled materials. In this work, the design and fabrication of multiple particle-loaded polymer composites, including micronized rubber from end-of-life tires, is studied. The integration of these composites as part of ultrasonic transducers can further expand the functionality of the piezoelectric material in the transducer in terms of sensitivity, bandwidth, ringing and axial resolution and help to facilitate the fabrication and use of phantoms for echography. The adopted approach is a multiphase and multiscale one, based on a polymeric matrix with a load of recycled rubber and tungsten powders. A fabrication procedure, compatible with transducer manufacturing, is proposed and successfully used. We also proposed a modelling approach to calculate the complex elastic modulus, the ultrasonic damping and to evaluate the relative influence of particle scattering. It is concluded that it is possible to obtain materials with acoustic impedance in the range 2.35–15.6 MRayl, ultrasound velocity in the range 790–2570 m/s, attenuation at 3 MHz, from 0.96 up to 27 dB/mm with a variation of the attenuation with the frequency following a power law with exponent in the range 1.2–3.2. These ranges of values permit us to obtain most of the material properties demanded in ultrasonic engineering.

An improved nonlinear ultrasonic technique for detecting and monitoring impact induced damage in composite plates

An improved technique for sensing damage initiation and progression in thermoplastic resin composite plate specimens is presented in this study. The composite plate specimens are investigated by using a nonlinear ultrasonic (NLU) technique called Sideband Peak Count Index or SPC-I. The technique presented in this paper is an improvement from the previous SPC-I technique. This improved technique provides more reliable and consistent results and can monitor the damage progression over a wide range. In this paper the narrow band SPC-I technique is introduced to replace the conventional wide band SPC-I technique. The method implemented here is improved in three ways. First and foremost the narrow band SPC-I technique is introduced. Secondly, the non-permanently adhered gel coupled Lead-Zirconate-Titanate (PZT) transducers are used to reduce inconsistency in transducer adhesion and manufacturing. Lastly, higher sampling rate equipment is used for better signal resolution and peak counting. The experiments are performed on 4 sets of composite plate specimens fabricated using two composite fiber materials (Glass and Basalt) that have increasing levels of damage. The composite plate specimens were damaged by a falling weight impact machine with increasing impact energy (0 J, 10 J, 20 J and 30 J). The composite plate specimens were examined by propagating a narrow band chirp signal through the specimens using gel coupled transducers in a transmission mode setup. The received signals were recorded and analyzed using the NLU SPC-I technique. The modified SPC-I technique proposed in this paper can reliably and consistently detect both initiation and progression of damage in the composite plate specimens.

Axial guided wave characteristics in functionally graded one-dimensional hexagonal piezoelectric quasi-crystal cylinders

In one-dimensional hexagonal piezoelectric quasi-crystals, there exist the phonon–phason, electro–phonon, and electro–phason couplings. Therefore, the phonon–phason coupling and piezoelectric effects on axial guided wave characteristics in one-dimensional hexagonal functionally graded piezoelectric quasi-crystal (FGPQC) cylinders are investigated by utilizing the Legendre polynomial series method. The dispersion curves and cut-off frequencies are illustrated. Wave characteristics in three hollow cylinders with different quasi-periodic directions are comparatively studied. Some new wave phenomena are revealed: the phonon–phason coupling and piezoelectric effects on the longitudinal and torsional phonon modes (N = 0) vary as the quasi-periodic direction changes; the phonon–phason coupling effect on flexural–torsional modes in the r-, z-FGPQC hollow cylinders, and on flexural–longitudinal modes in ϑ-FGPQC hollow cylinders increases as N increases. The corresponding results obtained in this work lay the theoretical foundation for the design and manufacture of piezoelectric transducers with high resolution and energy-conversion efficiency.

PVDF Ultrasonic Sensors for In-Air Applications: A Review.

Polyvinylidene fluoride (PVDF), a material with ferroelectric characteristics, is still extremely topical for the manufacturing of transducers, and different examples, some of which have been actively commercialized since the 1980s, are reported in the literature. In this work, we present a review focused on the PVDF technology for the manufacturing of in-air ultrasonic transducers, which found application in medical robotics, sonar systems, and automation industry (e.g., proximity sensors and obstacle detection). The aim is to provide a comprehensive view on the development of such ultrasonic transducers, highlighting the constructive choices and the advantages/disadvantages in a thorough and concise way.

Ultrasonic Transducer With Increased Exposure Power and Frequency up to 100 kHz.

A new design of a high-frequency piezoelectric transducer with a power from 70 to 1800 W (designed for radiation into liquids and gases of ultrasonic (US) vibrations in the frequency range of 30,…,100 kHz) is proposed. It is based on the principle of summation on a diametrically vibrating summing plate of vibrations of radially mounted Langevin transducers. The method of their design was created and the optimal design dimensions of the transducers were established. This made it possible to manufacture and research practical designs of transducers at frequencies of 30 and 90 kHz. The created transducers together with disk radiators allowed creating US vibrations of 155 dB in the gas at a frequency of 31.67 kHz and 151 dB at a frequency of 92.82 kHz. In this case, the power of the generated vibrations was limited by existing radiators of disk form and a small wave resistance of gas. As a result, the transducers provided radiation up to 1800 W at a frequency of 31.67 kHz and up to 250 W at a frequency of 92.82 kHz of acoustic power. The transducer can be used at processing of liquids, such as dispersion, emulsification, extraction, degassing of liquids, sterilization, and homogenization. The transducer can be used for agglomeration of suspended dispersed particles in gases, drying of various materials, and liquid spraying when exposed to gases. There are no restrictions on the number of simultaneously operating transducers. However, the overall dimensions exclude tight packaging. Therefore, its use in any array with a wavelength-oriented separation is not possible.

Model-Based Analysis and Regulating Approach of Air-Coupled Transducers with Spurious Resonance.

As an essential characteristic of air-coupled transducers, electrical impedance can provide valuable information for quality control during manufacturing of transducers. It is also found feasible to directly read the optimal operating frequency from the impedance plots when the resonance is independent of the others. However, the spurious resonance emerges when two neighboring resonances are closely spaced, resulting in distorted impedance and ambiguous optimal operating frequency. In this paper, the electrical impedance of air-coupled transducers with spurious resonance is modeled using the Butterworth–Van Dyke (BVD) equivalent circuit. Then model-based sensitivity analysis is performed to evaluate the mutual interference between adjacent resonances. Based on the analysis results, the prestress method is proposed to regulate and suppress the spurious resonance by adjusting the equivalent parameters of the BVD model. Experimental study was carried out on the response of the electrical impedance and the vibration velocity of the transducer with spurious resonance to pre-tightening force. The results show that the spurious resonance disappeared when the pre-tightening force was initially loaded. Moreover, the vibration velocity of two main resonance peaks increases about 45.6% and 33.9% as the pre-tightening torque increases to 0.25 N∙m. Hence it is validated that the proposed prestress method is efficient to suppress the spurious resonance and improve the transducers performance.

Graphene oxide conversion into controllably carboxylated graphene layers via photoreduction process in the inert atmosphere

The one-step method for graphene oxide (GO) simultaneous reduction and carboxylation via ultraviolet irradiation in the inert atmosphere has been reported. X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) data revealed that the proposed approach allows to obtain reduced graphene oxide (rGO) films, containing up to 10 at.% of carboxyl groups. The carboxyl groups concentration can be tuned within the range of 3 to 10 at.% by controlling the oxidation degree of the irradiated GO via the preliminary low-temperature air heating. Furthermore, no carboxylation effect is observed in the case of irradiation of the completely reduced GO films. This coincides with our previous results, validating the proposed model of GO carboxylation based on photoinduced conversion of basal-plane hydroxyl groups and ketones into carboxyl ones. Despite a different degree of carboxylation, all the obtained samples demonstrate almost complete elimination of basal plane groups and restoration of the graphene flakes aromatic structure. This fact is emphasized by the sheet resistance measurements, demonstrating that the obtained C-xy graphene exhibits high electrical conductivity. As a net result, the material obtained by the presented method shows promising applications in the manufacturing of biosensor transducers owing to both its conductive nature and presence of carboxyl groups, playing the role of the anchoring points for biomolecules.

Green’s function technique to model Love-type wave propagation due to an impulsive point source in a piezomagnetic layered structure

The crux of the present study is to unravel the concealed characteristics on the propagation behavior of Love-type wave through a piezomagnetic material (PMM) stratum overlying a functionally graded piezomagnetic material (FGPMM) substrate under the influence of an impulsive point source at its interfacial surface. Functional gradients in the substrate is due to the spatial variation in the elastic constants and density. The elasto-magneto-dynamical equations are laid down for the piezomagnetic medium. Green’s functions are derived for the layered structure taking a point force/point charge density at the interfacial surface into account. Dispersion equation of Love-type wave is obtained with aid of admissible boundary conditions and the well known properties of Green’s function. For sake of validation, the dispersion equation is reduced to fairly match with the classical Love wave equation. To demonstrate the analytical findings numerically and set forth the parametric effects, numerical data of two PMMs are undertaken for PMM stratum and FGPMM substrate. The graphical representations reveal that phase velocity of Love-type wave is significantly affected by the material constants and the functional gradients parameters allied with the piezomagnetic layered structure. The profound effects of piezomagnetic constants, magnetic permeabilities, magnifying gradient parameters and functional gradient parameter are portrayed by graphical means. A comparative analysis to trace out the piezomagnetic effect of the PMM stratum and FGPMM substrate is accomplished owing to their transverse isotropic orientational symmetry. This study may find noteworthy dynamic and practical applications towards manufacturing and optimization of piezomagnetic sensors and transducers. In addition, the obtained result may be useful for acquiring a better performance in surface acoustic wave devices and functionally graded material waveguides.

STUDY OF PULSE MODE OF PIEZOELECTRIC TRANSDUCER FOR ECHOSCOPE

The piezoelectric transducer of the echoscope intended for research of soft tissues of the person is considered. The active element of the transducer is a damped piezoceramic plate. As an exciting electric signal, an electric voltage pulse with a different number of half‑cycles at the natural frequency of the plate is selected. The pulse mode of the radiator operation is investigated. The amplitudes and durations of the probing acoustic signal are estimated depending on the duration of the exciting pulse. The dynamics of changes in the durations and amplitudes of the radiated acoustic pulses is studied. For various degrees of damping of the plate, the number of half‑cycles contained in the exciting signal, from which the emitter operates in a stationary mode, is determined. The obtained results can be used in the field of design and development of technology for manufacturing of broadband pulse piezoelectric transducers of ultrasonic medical echoscopes.

Lead-free porous and composite materials for ultrasonic transducers applications

The paper describes the results of the experimental study of the properties of piezoceramics, ceramic matrix composites “ceramics/crystal,” and porous ceramics based on lead-free sodium-lithium niobates (Na, Li)NbO3 and sodium-potassium niobates (Na, K)NbO3 compositions. The measurements of elastic, dielectric and piezoelectric parameters, as well as microstructural studies of experimental samples of lead-free porous piezoelectric ceramics and composites were performed. It was shown that the use of alkali metal niobates in the form of ceramic matrix composites and porous ceramics allows to increase the main functional parameters of these materials and makes them competitive with piezoceramics of the PZT system. The developed lead-free porous and composite materials have a unique combination of parameters and can be used for the manufacture of ultrasonic transducers and devices for a wide range of applications, including medical and nondestructive testing equipment.

Characterization of Piezoelectric Material Parameters Through a Global Optimization Algorithm

Better understanding of the loss mechanisms and higher confidence in material data for piezoelectric materials are very important for transducer manufacturers. In this paper, a method is described to characterize these loss mechanisms using a global optimization algorithm, a 1-D equivalent circuit, and a simple experimental measurement. Two different cost functions were used in the optimization algorithm, one based on impedance and the other based on admittance. The sensitivities of these cost functions to the parameters being characterized are shown to be nonuniform. The results are compared to the results obtained from a local optimization method to show the advantage of using a global optimization algorithm. A way to quantify the uncertainty of the results is introduced by looking at the difference between the results obtained from the two different cost functions. It is shown here that the more ambient noise there is in the data, the wider the gap between the results found by the two cost functions. However, although the results from the individual cost functions diverge from the correct values with increasing noise, the average of the two cost function results remains within $5\%$ of the original value. Hence, even with noise in the measured data, the use of two cost functions can yield accurate material parameters.

A reconfigurable miniaturized transducer based on rotating coils for testing particle accelerator magnets

The design of a reconfigurable transducer, based on rotating coils realized by printed circuit board (PCB), is proposed for testing magnets in particle accelerators. Despite classical rotating coils, the sensitivity of this transducers is not completely established with the design. Different configurations allow to tune sensitivity to the specific components of the magnetic flux density to be measured. At this aim, specific field harmonics such as dipole, quadrupole, sextupole, octupole, and decapole can be suppressed. Thus, the same accuracy level can be ensured in measuring the field quality of several types of magnets.In this paper, first, conventional design criteria are recalled. Then, the design of the reconfigurable transducer based on four coils to suppress undesired field harmonics, from dipole up to decapole, is illustrated. The possibility of using both radial and tangential geometry, without affecting compensation quality, is highlighted too. Finally, a metrological analysis about the transducer manufacturing is reported, proving that the uncertainty arising from the PCB production is made negligible.

Performance comparison of 2-1-3, 1-3 and 1-3-2 piezoelectric composite transducers by finite element method

1-3 type, 1-3-2 type and 2-1-3 type piezoelectric composites are three proper smart materials for the design and manufacture of ultrasonic transducers. They have been proposed in different stages but possess similar properties. Compared with the initial 1-3 type composite, 1-3-2 composite is of higher mechanical stability. Compared with 1-3-2 composite, 2-1-3 composite has lower manufacturing difficulty. In this paper, a comparative study on these three composites in terms of receiving transducer material properties is presented. Finite element method (FEM) has been adopted to calculate longitudinal velocity, thickness electromechanical coupling coefficient and voltage receiving sensitivity. It is concluded that for a large aspect ratio $\alpha=1$, the performance of 2-1-3 composite transducer is much better than that of 1-3 and 1-3-2 composite transducers. The thickness electromechanical coupling coefficient of 2-1-3 composite transducer is about 5.58 times that of 1-3 composite transducer and 7.42 times that of 1-3-2 composite transducer. The voltage receiving sensitivity at 2 kHz of 2-1-3 composite transducer is 13.1 dB higher than that of 1-3-2 composite transducer and 12.3 dB higher than that of 1-3 composite transducer.

Systematic electromechanical transfer matrix model of a novel sandwiched type flexural piezoelectric transducer

Sandwiched type flexural piezoelectric transducers are used in many applications due to their excellent output performances. However, the design and manufacture of traditional sandwiched type flexural piezoelectric transducers always have specific requirements on the flexural piezoelectric ceramics with complex polarizations and configurations, seriously limiting their applications. To reduce these special requirements, a novel sandwiched type flexural piezoelectric transducer in which common rectangular piezoelectric plates with a single polarization are adopted is proposed in this paper. By applying excitation signals with different temporal phases to the rectangular piezoelectric plates, the proposed transducer features the ability to generate flexural vibration, longitudinal vibration, and composite longitudinal-flexural vibration. To lower the computational efforts of the finite element analysis, a general systematic electromechanical model is carried out for the proposed transducer utilizing the transfer matrix method. The developed systematic transfer matrix model provides an available approach for simultaneously coupling the mechanical and electrical properties to adequately reveal the dynamic behavior of the proposed transducer operating in flexural vibration mode. To validate the proposed model, dynamic behaviors of the sandwiched piezoelectric transducer in flexural vibration are calculated and compared with the finite element simulation results. The results demonstrate that the proposed transfer matrix model is valid and effectively reduces the computational efforts. In addition, vibration characteristics of the transducer prototype are experimented, and results verified the feasibility of the transducer design and the effectiveness of the developed transfer matrix model.

Calculation of Volumetric Sound Field of Pulsed Air-Coupled Ultrasound Transducers Based on Single-Plane Measurements.

Quantitative and reproducible air-coupled ultrasound (ACU) testing requires characterization of the volumetric pressure fields radiated by ACU probes. In this paper, a closed-form reradiation method combining the Rayleigh-Sommerfeld integral and time-reversal acoustics is proposed, which allows calculation of both near- field and far-field based on a single-plane measurement. The method was validated for both 3-D (circular, square) and 2-D (rectangular) planar transducers in the 50-230 kHz range. The pressure fields were scanned with a calibrated microphone. The measurement window was at least four times the size of the transducer area and the grid step size was one third of the wavelength. Best results were observed by acquiring the measurement plane at near-field distance. The method accurately reproduces pulsed ultrasound waveforms and pressure distributions (RMSE <2.5% in far field and <5.5% in near field), even at the transducer radiation surface. The effects of speed of sound drifts during the scan in the pressure were negligible (RMSE <0.3%). The reradiation method clearly outperforms conventional baffled piston models. Possible applications are transducer manufacture control (imperfections at radiation surface) and calibration (on-axis pressure, side lobes, and beamwidth) together with generation of accurate source functions for quantitative nondestructive evaluation inverse problems.

The effect of flexoelectricity on domain switching in the vicinity of a crack in ferroelectrics

Ferroelectrics are widely used in the manufacture of transducers, actuators, and memory devices, due to their attractive electromechanical properties. However, the reliability and failure of devices is greatly dependent on their brittleness. In view of the fact that both the polarization distribution and elastic field are at nanoscale and vary greatly in the vicinity of the crack tip, flexoelectricity is expected to strongly affect the domain configuration. In this work, Ginzburg-Landau (TDGL) theory and the phase field method (PFM) are employed to analyze the influence of flexoelectric effect on the domain switching process in the vicinity of the crack tip of ferroelectric materials. The results obtained show that, the domain configuration would become asymmetric with increasing flexoelectric coefficients, and the flexoelectric effect has a larger influence on the polarization field than on the elastic field in the vicinity of the crack tip of ferroelectric materials.

Polarized shear waves in functionally graded piezoelectric material layer sandwiched between corrugated piezomagnetic layer and elastic substrate

This article investigates the propagation behaviour of horizontally polarized shear waves in a layered composite structure. In the considered model, a functionally graded piezoelectric material layer is sandwiched between corrugated piezomagnetic layer and elastic substrate. Method of separation of variables is used to obtain the displacement components in all three mediums. Dispersion relation has been established in the determinant form for the two cases, magneto-electrically open case and magneto-electrically short case. Effects of material gradient (of functionally graded piezoelectric material layer), corrugation parameters and layer width are distinctly marked and represented graphically. This study finds its application towards manufacturing and optimization of piezoelectric sensors and transducers. Also, the obtained result may be utilized for acquiring a better performance in surface acoustic wave devices.