Piezoceramic Transducers Research Articles

ДИНАМИЧЕСКАЯ ОСЕСИММЕТРИЧНАЯ ЗАДАЧА ЭЛЕКТРОУПРУГОСТИ ДЛЯ ЖЕСТКО ЗАКРЕПЛЕННОЙ БИМОРФНОЙ ПЛАСТИНЫ

A nonstationary axisymmetric problem for a circular rigidly fixed bimorph plate consisting of a metal substrate and two piezoelectric elements is studied in this paper. Mechanical vibrations of the structure are made by the action of its end surfaces of electric potential, which is an arbitrary function of the radial coordinate and time. New closed solution is constructed in the framework of electrodynamics in three-dimensional statement by the consistent use of the method of incomplete separation of variables in the form of integral transformations. Consistently Hankel transformation with finite limits on the axial coordinate and generalized finite transformation (FIT) on the radial variable are applied. At each stage of the solution there is a procedure of standardization which allows the appropriate conversion algorithm. The calculated ratio for the components of the displacement vector and the electric field potential allow us to study the variation of the stress-strain state of the bimorph plate. The constructed solution provides an opportunity to make a qualitative and quantitative analysis of connection of electromechanical stress fields in composite laminated electroelastic structures that allow describing the work and finding the geometric characteristics of the typical elements of piezoceramic transducers of resonant and nonresonant classes. Based on the analysis results, it becomes obvious that there is the need for rigidly fixed bimorph systems for excitation of flexural vibrations of the split ring electrodes located on the faces of the piezoceramic plates and for the application of Timoshenko system of equations in applied theory for thin plates taking into account shear deformations. In addition, it became possible to obtain potential change laws, axial-vector components in the tensions and induction of electric field along the thin piezoceramic plate.

Method for calculation of piezoceramic transducer transmission characteristics in the mode of ultrasonic waves radiation. Part 1. Calculating the coefficient of electromechanical conversion

Definition for transmission characteristic of ultrasonic piezoelectric transducer is given in article and calculation of electromechanical transformation coefficient from electric input to the mechanic side of piezoelectric transducer is accomplished. Question of influence of liquid contact layer to frequencydependent variation of electromechanical transformation coefficient is described in first time. In case then area of mechanical contact with acoustic load have a finite size the liquid contact layer is the resonator of radial oscillation and it render a significant influence to frequency characteristic of piezoelectric oscillator. References 13, figures 7

Method for calculation of piezo-ceramic transducer transmission characteristics in the mode of ultrasonic waves excitation. Part2. Calculation of coefficient of mechanoacoustical converters in mode of normal Lamb wave excitation

Method for calculation of piezo-ceramic transducer transmission characteristics in the mode of ultrasonic waves excitation. Part2. Calculation of coefficient of mechanoacoustical converters in mode of normal Lamb wave excitation

Vibrational damage detection using fractal surface singularities with noncontact laser measurement

This study concerns damage detection in plate-type structures using fractal surface singularities with noncontact laser measurement of structural dynamic responses. The fractal dimension analysis aided by linear isomorphism is used to deal with mode shapes for a plate with damage. With this method, the linear isomorphism is utilized to remove the local extrema while preserving the damage information of a mode shape, giving a retrofitted mode shape. The retrofitted mode shape is processed by Katz’s fractal dimension analysis to produce a fractal dimension surface with its singular peak indicating the presence and location of the damage. In the method, a series of high-resolution mode shapes of the plate are used, which are acquired by using a noncontact measurement system consisting of a piezoceramic transducer as the actuator and a scanning laser vibrometer as the sensor. The capability of the method to locate and quantify damage is numerically demonstrated using a two-side-clamped aluminum plate with cracks of various depths; the efficacy of the method in identifying complex cracks is experimentally validated using a suspended aluminum plate bearing a cross-like crack. The numerical and experimental results show that the proposed method can accurately identify complex damage in plates, requiring neither benchmark models for the entire structure under investigation, or any prior knowledge of the material properties and the boundary conditions of the structure.

Wind turbine blade damage detection using an active sensing approach

The wind energy sector is one of the fastest growing parts of the clean energy industry. As the wind energy sector grows, so does an increasing concern for the damage detection of wind turbine blades. This paper proposes an active sensing approach by utilizing piezoceramic transducers as actuators and sensors. The influence of the crack quantity, location, length and depth on the wave propagation was experimentally studied. Sweep sine signals ranging from 1 khz to 50 khz were used as input signals for active sensing. The change in the energy that propagated through the cracks was verified as feasible in detecting crack-related damage. An innovative polar plot analysis method based on Fast Fourier transform was developed to compare the minuscule difference between the damage signals and the baseline signal. The polar plot was able to make apparent differences in both the magnitude and the phase of the signals, which could be correlated to crack depth and plane geometry, respectively, based on the observation of the damage.

Studies on the polarisation behaviour of novel piezoelectric sensor modules

A novel approach to the manufacture of adaptive composite structures with integrated piezoelectric modules focusses on combining the previously separate production steps – production of the piezoceramic transducer, composite fabrication and integration of the transducers – into an efficient single-stage process. Based on the long fibre injection (LFI) technology, a novel multi fibre injection (MFI) method is developed. By integrating piezoceramic components like short fibres or pearls and suitable electrode structures into the composite, novel piezoelectric functional elements are created and embedded during the structure's manufacturing process. For the functionalisation of these elements, mainly to provide sensory properties, poling of the piezoceramic components during or after the production process is required. Based on initial simulations of electric field strength, poling process and resulting small signal properties, conclusions for an adapted poling strategy of these novel sensor modules are elaborated.

The Monitoring Method for Crack Damage of Concrete Structures Based on Piezoceramics Transducers

A method for monitoring the crack damage of concrete structure based on piezoceramics transducers was introduced in the paper. The PZT patches were packaged as smart aggregates which buried into concrete structures in pair. One is as actuator to transmit monitoring signals, and the other is as sensor to receive the monitoring signals. Sine sweep frequency wave was used as monitoring signal type, and its energy value was used as damage identification parameter. At last, a test was conducted to prove the effectiveness of monitoring method. The crack damage of a reinforced concrete beam under the load was monitored during the whole test process. The develop trend of damage identification parameter could reflect the develop trend of damage. The method proposed in the paper is feasible for crack damage monitoring of concrete structure.

Design, fabrication and characterization of a monolithic focusing piezoceramic transducer for an anisotropic material.

Piezoceramic transducers shaped as spherical caps are widely used to focus ultrasound waves in isotropic materials. For anisotropic materials, the sound wave surface is not spherical and the transducer surface should be adjusted to reproduce a portion of this wave surface to focus the emitted sound properly. In this article, we show how to design such a transducer and how to fabricate it in lab on a standard machine from a rod of raw piezo ceramic material. The main features of its electrical impedance response are well reproduced by a numerical model, allowing the identification of most of its vibrational modes. We finally measured the sound field emitted by such a transducer and found its focusing efficiency similar to that of spherical caps in isotropic media.

In situ characterization technique to increase robustness of imaging approaches in structural health monitoring using guided waves

The performance of guided wave imaging strategies used in Structural Health Monitoring relies on the accurate knowledge of mechanical properties for proper damage detection and localization. In order to increase the performance and robustness of such algorithms, it is desirable to implement autonomous approaches that can characterize the mechanical properties of the structure whatsoever the environmental and operational conditions. This article presents an innovative in situ and integrated characterization procedure based on guided waves that evaluates the thermo-mechanical properties of a structure when subjected to thermal variations prior to imaging using the same set of piezoceramic transducers used for imaging. These properties are then exploited in the damage imaging using a correlation-based algorithm (Excitelet) combined with the optimal baseline subtraction. The characterization strategy uses a genetic algorithm to identify the optimal set of mechanical properties leading to the best correlation between an analytical formulation of dispersed guided waves propagation and experimental measurements. The strategy is assessed experimentally on an aluminum plate with three sparse bonded piezoceramic transducers used for both characterization and imaging at various temperatures, representative of operational conditions of an aircraft. An artificial damage is subsequently introduced in the plate, and the effect of the accuracy of the mechanical properties estimation on imaging is assessed through the detection capability, positioning, accuracy, and correlation amplitude. The approach is then compared to three imaging methods, namely, baseline-free imaging, imaging without considering thermo-mechanical effects, and imaging using stretching methods traditionally used to compensate for temperature effects.

Radiation field angled horn antenna with a piezoceramic transducer with radial polarization

Radiation field angled horn antenna with a piezoceramic transducer with radial polarization

Acoustic properties of cylindrical piezoceramic transducer using unloaded design

Acoustic properties of cylindrical piezoceramic transducer using unloaded design

The effect of crosstalk in a circular transducer array on ultrasound transmission tomography of breast

Various types of undesirable crosstalk can occur in ultrasonic arrays consisting of a number of elementary piezoelectric transducers. Crosstalk is a result of deficiency in electrical or mechanical isolation between array elements. It is a function of proximity between piezoelectric transducers of the array or between connections. Small piezoceramic transducers tightly located inside of a circle (cylinder or sphere in 3-D systems) are mostly used for in vivo ultrasound tomography imaging of breast tissue. This means that proper switching of transducers makes it possible to quickly acquire tomographic transmission and reflection data for all directions around the object. A problem with such arrangements is the occurrence of crosstalk, which introduce specific errors to measurement data. Transmission and reflection tomographic images reconstructed based on ultrasonic measurements with crosstalk are distorted in a characteristic way. This work analyzes the effect of crosstalk in a circular transducer array on ultrasound transmission tomography imaging—especially, when used for examination of breast tissue.

Fatigue Monitoring of Double Surface Defects Using PZT Based Electromechanical Impedance and Digital Image Correlation Methods

Most of the engineering failures especially in mechanical and aerospace industry are due to the fatigue. Fatigue cracks and their propagation can be monitored by observing changes in the structural stiffness resulting from strength reduction as a function of the number of loading cycles. This monitoring can be observed using piezoceramic (PZT) transducer based electromechanical impedance (EMI) technique, and digital image correlation (DIC) system which uses variations on structural surface. The fatigue load usually aggravates the fracture if any defects pre-exist in the structure. The present work monitors multiple-crack emanating from electrode sparked multiple plane defects which are induced in to the specimens prior to the fatigue test, using EMI technique and DIC system. The fracture occurs much below the ultimate stress for the structures which already have defects as in the present case. EMI technique uses signature comparison of healthy and cracked state of the structure to depict crack growth. Initial detection of surface hair-line cracks from the corners of induced defects and their propagation till merging and subsequent failure were explained by signature variations and DIC techniques. Thus, a signal processing technique EMI, and image processing technology DIC were found to complement each other in prediction of early crack and their appearance on surface of the specimens.

Physical fields of hydroacoustic antenna consisting of the angle of the horn and the piezoceramic transducer with a circumferential po-larization

Considered hydroacoustic antenna consisting of the angle of the horn reflector soft type and placed in his mouth cylindrical piezoceramic transducer with a circumferential polarization. Thus the design of the transmitter can be power or compensating type.The problem was solved by methods related fields and analytical expressions describing the physical fields of the horn antenna – acoustic, mechanical and electrical. These fields are presented in the form of expansions in series of the wave functions of the circular cylindrical coordinate system with unknown expansion coefficients which are determined from the boundary conditions and the matching conditions at the interfaces between fields areas. Solution is reduced to an infinite system of linear algebraic equations.References. 4, Fig. 2.

To the question about radiation of acoustic fields by the cylindrical piezoceramic transducers of different constructions

Using the method of equivalent electromechanical circuits were obtained solution of "pervasive" problem of sound radiation by cylindrical piezoceramic transducers of non-compensated and compensated power structures, in the construction of which is used longitudinal and transverse piezoelectric effect. Using these correlation were calculated numerical characteristics of sound fields of such transducers and made comparative analysis of acoustic properties of non-compensated and compensated designs in a wide frequency range depending on the type of piezoelectric , mechanical quality factor values , geometrical sizes of transducers and characteristics of the medium filling the internal volume of transducers.Also, the comparative analysis of the acoustic properties of cylindrical piezoceramic transducer of such design calculated by related fields and by equivalent circuits. It is shown that the results of the calculation is almost equivalent only when the magnitude of the mechanical quality factor is higher than Qм=80¸100.References 7, figures 10, table 1.

Acoustic properties of cylindrical piezoceramic emitters with power and compensated design with longitudinal and transverse piezoe-lectric effect

The numerical analysis of the properties of sound fields, generated by cylindrical piezoceramic transducers, power and compensated design has been done. Different compaunds of piezoceramics and various schemes of constructing oscillation systems has been analyzed, allowing to implement in the transducer longitudinal or transverse piezoeffect. The influence in the sound field made by the changes in the geometric form of the transducer has been discovered. Comparative analysis of the frequency dependence of the sound fields allowed us to establish a number of subtle effects in their formation, depending both on the type of construction, and the kind of the piezoelectric effect and compound of piezoceramics used.Reference 3, figures 9, table 1.

High Temperature Dynamic Pressure Measurements Using Silicon Carbide Pressure Sensors

Un-cooled, MEMS-based silicon carbide (SiC) static pressure sensors were used for the first time to measure pressure perturbations at temperatures as high as 600 °C during laboratory characterization, and subsequently evaluated in a combustor rig operated under various engine conditions to extract the frequencies that are associated with thermoacoustic instabilities. One SiC sensor was placed directly in the flow stream of the combustor rig while a benchmark commercial water-cooled piezoceramic dynamic pressure transducer was co-located axially but kept some distance away from the hot flow stream. In the combustor rig test, the SiC sensor detected thermoacoustic instabilities across a range of engine operating conditions, amplitude magnitude as low as 0.5 psi at 585 °C, in good agreement with the benchmark piezoceramic sensor. The SiC sensor experienced low signal to noise ratio at higher temperature, primarily due to the fact that it was a static sensor with low sensitivity.

Rezonansowy układ LCL w zastosowaniach przemysłowych

The paper presents chosen applications of LCL resonant circuit. Its induction heating application results in easy modular system designing and allows creating the resonant converter with variable frequency. Application of ultrasonic power systems allows efficient filtration of higher harmonics of the inverter output voltage waveform and the construction of resonant converters for virtually constant frequency equal to the frequency of mechanical resonance piezoceramic transducer. The VSI-LCL IH system operation principles and the basic analytical analysis are described. The experimental and simulations test have been made. The research results are shown. (LCL Resonant Circuit Industrial Applications).

Adaptive Model Predictive Vibration Control of a Cantilever Beam with Real-Time Parameter Estimation

This paper presents an adaptive-predictive vibration control system using extended Kalman filtering for the joint estimation of system states and model parameters. A fixed-free cantilever beam equipped with piezoceramic actuators serves as a test platform to validate the proposed control strategy. Deflection readings taken at the end of the beam have been used to reconstruct the position and velocity information for a second-order state-space model. In addition to the states, the dynamic system has been augmented by the unknown model parameters: stiffness, damping constant, and a voltage/force conversion constant, characterizing the actuating effect of the piezoceramic transducers. The states and parameters of this augmented system have been estimated in real time, using the hybrid extended Kalman filter. The estimated model parameters have been applied to define the continuous state-space model of the vibrating system, which in turn is discretized for the predictive controller. The model predictive control algorithm generates state predictions and dual-mode quadratic cost prediction matrices based on the updated discrete state-space models. The resulting cost function is then minimized using quadratic programming to find the sequence of optimal but constrained control inputs. The proposed active vibration control system is implemented and evaluated experimentally to investigate the viability of the control method.

Innovative Data Fusion Enabled Structural Health Monitoring Approach

Piezoceramic-based active sensing is a useful approach to structural health monitoring. This approach often involves a large number of distributed piezoceramic transducers. It may be confusing to incorporate each sensor data. It is desired to develop an automated health monitoring approach to obtain a comprehensive and accurate health monitoring result by simultaneously interpreting data from all sensors. In this paper, an innovative data fusion enabled structural health monitoring (SHM) approach based on the Dempster-Shafer (D-S) evidence theory is proposed to obtain comprehensive SHM results for a distributed sensor network in a civil infrastructure. Considering that evidence from multiple different information sources (sensor data) has different levels of significance, not all evidence is equivalently effective for the final decision. A weighted fusion damage index (WFDI) is proposed to perform damage identification based on the authors’ recently developed piezoceramic-based smart aggregates. Experimental data of a two-story concrete frame was used to study the effectiveness of the proposed weighted fusion damage index. Analyses show that the proposed weighted fusion damage index can reveal the damage status of different areas of the frame. The results are consistent with the visual inspection of the cracks on the concrete frame.