Piezoceramic Patches Research Articles

A Reliable Plain Solution for Rectangular Plates with Piezoceramic Patches

The present study investigates the behavior of a laminated composite plate with embedded or bonded piezoelectric materials. An exact mathematical model based on Reissner—Mindlin theory for plates (FSDT) has been developed for laminated composite plates with continuous piezoelectric layers. The flexural behavior has been solved based on Levy's method for plates. Therefore, the study has been limited to obtain exact solutions only for the cases of plates with at least two opposite simply supported edges, and only continuous piezoelectric layers. For a plate with piezoelectric patches, an approximate energy solution is presented, using Reissner—Mindlin theory, where the lateral displacement and the two bending rotations are expressed as infinite series. The point of merit for this model is its simplicity and reliability (depending on the number of terms) to solve a plate with any required boundary conditions and lay-ups. Furthermore, this model can be easily adapted to solve piezo-composite plates with an unlimited number of piezoelectric patches in arbitrary locations over the plate. A comprehensive parametric investigation has been performed to study the behavior of a plate actuated by extension or shear piezoelectric mechanisms. This investigation has been performed to yield results for plates with various boundary conditions and arbitrary patch locations.

Optimal design of smart panel using admittance analysis

Optimal configuration of piezoelectric shunt structures is obtained by analyzing admittance of the system. The dissipated energy in the shunt circuit is a function of admittance. Therefore, admittance was selected as the cost function in the process of optimization. Taguchi method was used to determine the optimal configuration of piezoceramic patch bonded on the host structure. Full three dimensional finite element models were analyzed to simulate vibration modes of smart panel and to obtain the admittances of the system. Numerical admittance was validated by experiment. After optimizing process using admittance, the optimal configuration of piezoceramic patch was obtained. It is observed that the performance of smart panel can be predicted by analyzing admittance of piezoelectric structure and admittance can be used as a design index of smart panel.

Health Monitoring of Composite Plates using Acoustic Wave Propagation, Continuous Sensors and Wavelet Analysis

Health monitoring of aerospace structures can be done passively by listening for acoustic waves generated by cracks, impact damage and delaminations, or actively by propagating diagnostic stress waves and interpreting the parameters that characterize the wave travel. This paper investigates modeling of flexural wave propagation in a plate and the design of sensors to detect damage in plates based on stress wave parameters. To increase understanding of the actual physical process of wave propagation, a simple model is developed to simulate wave propagation in a plate with boundaries. The waves can be simulated by applied forces and moments in the model either to represent passive damage growth or active wave generation using piezoceramic actuators. For active wave generation, the model considers a piezoceramic patch bonded perfectly to a quasi-isotropic glass-epoxy composite plate. Distributed sensors are used on the plate and are modeled as being constructed using active fiber composite and piezoceramic materials. For active wave generation, a moment impulse is generated by the actuation of a piezoceramic patch. The waves generated from the patch are detected by the distributed sensor. For passive sensing of acoustic waves, a step function is used to simulate an acoustic emission from a propagating damage. The resulting acoustic wave is measured by the distributed sensor and produces micro-strains in the sensor nodes. The strains produce a single voltage signal output from the distributed sensor. Computational simulations and animations of acoustic wave propagation in a plate are discussed in the article. A new method to locate the source of an acoustic emission using the time history of the dominant lower frequency components of the flexural wave mode detected by continuous sensors is also presented.

Noise Reduction Using Smart Panel with Shunt Circuit

Piezoelectric smart panels featuring shunt damping are designed and tested for broadband noise reduction. Electrical admittance is introduced to represent electromechanical coupling of piezoelectric structures. Admittance is used to predict the performance of piezoelectric shunt damping. The location, size, and rotational angle of piezoceramic patches on the host panel are optimized by taking the admittance as a cost function and by using the Taguchi method. The admittance is calculated by finite element method in the design stage and experimentally verified after the optimal configuration is found. Shunt performance of the smart panel is realized by vibration reduction in frequency domain. To illuminate the effect of noise reduction in the shunt system, a standard test setup according to SAE J1400 is used to measure the transmission loss and sound pressure distribution for the smart panel. In this paper, a broadband shunt technique for increasing transmission loss is experimentally investigated.

Concrete early-age strength monitoring using embedded piezoelectric transducers

At early ages of concrete structures, strength monitoring is important to determine thestructures’ readiness for service. Piezoelectric-based strength monitoring methods providean innovative experimental approach to conduct concrete strength monitoring at early ages.In this paper, piezoelectric transducers in the form of ‘smart aggregates’ are embedded intothe concrete specimen during casting. Piezoceramic materials can be used as actuators togenerate high frequency vibrating waves, which propagate within concrete structures;meanwhile, they can also be used as sensors to detect the waves. The smart aggregate isa one cubic inch, pre-cast concrete block with a wired, embedded PZT (leadzirconate titanate, a type of piezoceramic) patch. The strength development ofconcrete structures is monitored by observing the development of harmonic responseamplitude from the embedded piezoelectric sensor at early ages. From experimentalresults, the amplitude of the harmonic response decreases with increasing concretestrength. The concrete strength increases at a fast rate during the first few daysand at a decreasing rate after the first week. Concordantly, the amplitude of theharmonic response from the piezoelectric sensor drops rapidly for the first week andcontinues to drop slowly as hydration proceeds, matching the development of theconcrete strength at early ages. Concrete is heterogeneous and anisotropic, whichmakes it difficult to analyze mathematically. Fuzzy logic has the advantage ofconducting analysis without requiring a mathematical model. In this paper, a fuzzylogic system is trained to correlate the harmonic amplitude with the concretestrength based on the experimental data. The experimental results show that theconcrete strength estimated by the trained fuzzy correlation system matches theexperimental strength data. The proposed piezoelectric-based monitoring method has thepotential to be applied to strength monitoring of concrete structures at early ages.

Separation and Concentration of Particles in Fluid Using Ultrasonic Standing Wave

This paper presents the theory, design, and evaluation of a smart device for the enhanced separation of particles mixed in fluid. The smart device takes advantage of the ultrasonic standing wave, which was generated by the operation of a piezoceramic PZT patch installed in the smart device. The details of the device design including the electro-acoustical modelling for separation and PZT transducer are described at first. Based on this design, the separation device was fabricated and evaluated. In the experiments, an optical camera with a zoom lens was used to monitor the position of particles within the separation channel layer in the device. The electric impedance of the PZT patch bonded on the separation device was measured .The device shows a strong levitation and separation force against 50μm diameter particles mixed with water at the separation channel in the device. Experimental results also showed that the device can work at both heavy and light sand particles mixed with water due to the generated standing wave field in the separation channel.

Design and Analysis of a Biosensor Transducer with Multifunctions

This study deals with the development of a simple and multifunctional piezoelectric transducer, which can detect two or more species at one time. The transducer for testing consists of an aluminum cantilever beam and a piezoceramic patch. A piezoelectric impedance-based measurement technique is proposed for detecting a very small biospecies mass sensitively. Furthermore, two different types of biomembranes are coated on the beam so that they can detect two kinds of species without causing interference with each other. The problem as to how to determine the optimal positions for coating the membranes are investigated in detail by the finite element method (FEM). The numerical simulations showed a good agreement with the experimental results. Further, a concept for the design of a multifunctional transducer is proposed based on the mode function, and its validation is proved experimentally.

Elastic wave excitation in a layer by piezoceramic patch actuators

A mathematical model of an electromechanical system excited by piezoceramic patch actuators is developed. The model is based on the solution to the dynamic contact problem for a set of flexible strips interacting with a free elastic layer. Unlike the conventional models, which describe the mechanical part by the dynamic equations for beams, plates, or shels, the proposed model, in addition to the first fundamental modes, also takes into account the higher normal modes of an elastic waveguide. Results obtained with the proposed model and with the simplified models prove to be in good agreement in the low-frequency range. Numerical examples illustrate resonance energy radiation associated with higher modes of the laminate strip-layer structure, as well as the possibility to control its directivity.

Use of shunted shear-mode piezoceramics for structural vibration passive damping

This work presents, for the first time, simple theoretical and finite element investigations of the use of shear-mode piezoceramics for shunted passive vibration damping, leading to the so-called shear-mode shunted damping (SSD). Hence, its impedance-based formulation is first presented, then a simple finite element approach is described for its numerical implementation. Finally, the resistive SSD performance is evaluated and assessed on beams against the classical resistive extension-mode shunted damping (ESD). Preliminary results for the first three modes of a vibrating aluminium beam with sandwiched (axially polarized) and surface-bonded (through-the-thickness polarized) piezoceramic patches indicate that: (i) the generalised electromechanical coupling coefficient (EMCC) for SSD is more than three times higher than for ESD; (ii) the added resistive SSD is more than twelve times the classical resistive ESD; (iii) the amplitude reduction due to the SSD is more than two times that due to ESD. The shunted damping can be used either alone, when low-to-medium damping is required, or combined with an active damping as a complementary or fail-safe passive vibration damping solution.

General optimization of sizes or placement for various sensors/actuators in structure testingand control

In structural dynamics control and modal identification, the different types of sensors andactuators used and their location and size generally result in different frequencyresponse functions (FRFs) and thus affect the peak magnitude of each modeshown on the FRF curves. Consequently, this also affects the control effect forstructural dynamics due to the inadequate recognition of the contributions ofeach mode to the structural responses. This paper presents a general method ofoptimizing the location and the size of various types of sensor and actuator, such asaccelerometers, shakers, and force transducers as point-type sensors and actuators,and piezoceramic patches as distributed strain-type sensors and actuators forstructural excitation, testing, and control. Based on the concept of controllability andobservability in the control of the second order linear system, the general criterion isestablished considering the peak gain and the dc gain obtained based on the FRFs.Those FRFs that can be obtained by analysis or testing, when combined with theproposed objective criterion, provide a function for ranking the effectiveness ofalternative sensor/actuator locations and sizes, and hence a rational basis forchoosing their parameters. The method can be easily applied and has been proven tobe very promising on the optimal parameter selection for both point-type andstrain-type sensors and actuators. Finally, several case studies have been conducted todemonstrate the practicality of the proposed method together with experimental results.

Identification of the Location and Level of Damage in Multiple-Bolted-Joint Structures by PZT Actuator-Sensors

A piezoceramic (PZT) patch can be used simultaneously as an actuator and as a sensor for structural damage detection by utilizing its electromechanical coupling property. In this technique, a PZT actuator-sensor patch is bonded on a structure. Through the measurement of its electrical impedance, which is related to mechanical impedance of the structure being bonded, the change in structure properties due to damage can be detected. This paper presents the use of PZT actuator-sensors in conjunction with numerical model-based methodology in order to identify the location and level of the damage in multiple-bolted-joint structures. Laboratory experiments were performed on a two-joint and a four-joint aluminum beam, where the damage was simulated by loosening the bolts. The impedance was measured at high frequencies so that the wavelength of the excited motion is small and sensitive enough to detect local damage. Numerical models of structures were formulated by using a spectral element method, which has a high capability for high-frequency modeling. By utilizing the models, the location and level of the damage could be quantitatively identified.

Development of Piezoelectric Measuring Device for Evaluation of Polymer Gel Swelling Characteristics

This paper is concerned with the development of an in-situ measuring device for evaluating the swelling/desweling characteristic of temperature responsive polymer gels by the piezoelectric admittance measuring technique. The device is a simple cantilever type transducer, which consists of an aluminum cantilever beam, a piezoceramic patch and a probe coated with the polymer gel. The probe can be easily assembled to the cantilever transducer with a double-stick tape. In this paper, the characteristic of the transducer is investigated first with the aid of FEM analysis method. Based on the simulation results, a prototype piezo-transducer and probe coated by polymer gels are made. The characteristic of the gel is tested in situ experimentally. The results validated that the water content in the gel can be detected simply by the transducer. Furthermore, two kinds of membrane coating methods were investigated. The results obtained by the proposed transducer indicate that the directly coated gel membrane has higher temperature response in the water content than the pasted gel membrane.

A smart device for particle separation in water using ultrasonic standing waves

This paper presents the theory, design, and evaluation of a smart device for the enhanced separation of particles mixed in fluid. The smart device takes advantage of the ultrasonic standing wave, which was generated by the operation of a piezoceramic PZT patch installed in the smart device. The details of the device design including the electro-acoustical modelling for separation and PZT transducer are described. Based on this design, the separation device was fabricated and evaluated. In the experiments, an optical camera with a zoom lens was used to monitor the position of interested particles within the separation channel layer in the device. The electric impedance of the PZT patch bonded on the separation device was measured. The device shows a strong levitation and separation force against 50 μm diameter particles mixed with water at the separation channel in the device. Experimental results also showed that the device can work with both heavy and light sand particles mixed with water due to the generated standing wave field in the separation channel.

Proposed piezoceramic excitation for translational and rotational mobility measurements

A piezoceramic excitation approach is proposed that allows for a convenient measurement of translational and rotational structural mobility. This article focuses on verifying the ability of piezoceramic patches, when aligned in certain formations, to mimic normal force and moment excitation and allow easy measurement of translational and rotational structural mobility. Depending on the orientation of the patches on a thin, clamped-clamped beam, a normal force, bending moment or torsional moment is created and accelerometers are used to measure the mobility at the center point of the beam. The experimental measurements are compared to numerical results from a finite element program to verify the efficacy of the piezoceramic patches in exciting a structure. The specific arrangements of the patches are able to excite the desired modes and measurements agree well with the numerical model. This method combined with the proposed array could be placed at any point on a structure to excite the structure and measure the translational and rotational point structural mobility.

Control of enclosed sound fields using zero spillover schemes

In this article, a combined analytical and experimental study conducted on the feasibility of implementing a zero spillover scheme for active structural acoustic control is presented. The aim of this effort is to actively control sound fields inside a three-dimensional rectangular enclosure into which noise is transmitted through a flexible boundary. Piezoceramic patches, which are mounted on the flexible boundary, are used as actuators, and microphones, which are placed inside and outside the enclosure, are used as sensors. In the experiments, an attenuation ranging up to 18.1 dB is obtained for narrowband disturbances and an attenuation of 8.3 dB is obtained for broadband excitation in the frequency range of 40 Hz⩽ f⩽230 Hz. The role of inherent acoustic feedback in designing the control scheme is also examined and discussed.

Finite element formulation for composite plates with piezoceramic layers for optimalvibration control applications

A finite element (FE) formulation for piezoceramic laminated structures is derived, whichincludes plate elements that are developed using shear deformation (Mindlin plate) theoryfor each layer of the composite plate. In order to ensure shear continuity at the interface, aconstraining matrix is introduced that defines the displacement field for eachindividual layer. The proposed model is applicable to both thick and thin plates whereelectromechanical coupling is present due to the piezoelectric effect. A combination offour-node Lagrange bilinear and eight-node serendipity quadratic elements are usedfor deriving the matrices and vectors necessary for approximating the solution.Electromechanical coupling terms model the orthotropic piezoelectric properties , and there is an orthotropic formulation for the mechanical propertiesof each plate layer. The proposed FE model is compared to FE modelsbased on thin plate theory with isotropic piezoelectric actuation(g31 = g32) and isotropic material properties. Modeling accuracy is evaluated bycomparison with experimental measurements. A passive control application ispresented that is based on shunting one of the piezoceramic patches with aLR (inductor and resistor) circuit; a linear quadratic regulator is added to the shuntto enable active control. An optimization study for hybrid control is presentedwhere all of the control parameters, including active feedback gain, passive shuntinductance and resistance, are optimized numerically; the response of the structure toan impulse disturbance is simulated for both controlled and uncontrolled cases.

Effect of electromechanical coupling on static deformations and natural frequencies

A two-way coupled electromechanical theory is used to study static deformations and free vibrations of a laminated hybrid rectangular plate comprised of either piezoceramic (PZT) layers or patches embedded at arbitrary locations in graphite/epoxy layers. A first-order shear deformation theory is used to develop equations for the plate which are solved by the finite-element method (FEM) using eight-node isoparametric elements. Static deflections and natural frequencies computed with open-circuited PZT layers are found to differ significantly from those of grounded PZT layers.

Tracking Control of a Piezoceramic Actuator With Hysteresis Compensation Using Inverse Preisach Model

This paper presents the classical Preisach hysteresis modeling and tracking control of a curved pre-stressed piezoceramic patch actuator system with severe hysteresis. The actuator is also flexible with very small inherent damping. It has potential applications in active antennas. A series of tests are conducted to study the hysteresis properties of the piezoceramic actuator system. The numerical expressions of the classical Preisach model for different input variations are presented. The classical Preisach model is applied to simulate the static hysteresis behavior of the system. Higher order hysteresis reversal curves predicted by the classical Preisach model are verified experimentally. The good agreement found between the measured and predicted curves showed that the classical Preisach model is an effective mean for modeling the hysteresis of the piezoceramic actuator system. Subsequently, the inverse classical Preisach model is established and applied to cancel the hysteresis the piezoceramic actuator system for the real-time microposition tracking control. In order to improve the control accuracy and to increase damping of the actuator system, a cascaded PD/lead-lag feedback controller is designed with consideration of the dynamics of the actuator. In the experiments, two cases are considered, control with major loop hysteresis compensation, and control with minor loop hysteresis compensation. Experimental results show that RMS tracking errors are reduced by 50% to 70% if the hysteresis compensation is added in the feedforward path in both cases. Therefore, hysteresis compensation with the feedback controller greatly improves the tracking control accuracy of the piezoceramic actuator.

Manufacturing and Testing of Active Composite Panels with Embedded Piezoelectric Sensors and Actuators

This work presents the manufacturing and testing of active composite panels (ACPs) with embedded piezoelectric sensors and actuators. The composite material employed here is a plain weave carbon/epoxy prepreg fabric with 0.30 mm ply thickness. A cross-ply type stacking sequence is employed for the ACPs. The piezoelectric flexible patches employed here are Active Fiber Composite (AFC) piezoceramics with 0.33 mm thickness. Composite layers with openings are used to fill the space around the embedded piezo patches to minimize the problems associated with ply drops in composites. The AFC piezoceramic patches were embedded inside the composite laminate. High-temperature wires were soldered to the piezo leads, insulated from the carbon substructure by high-temperature materials, and were taken out of the composite laminates employing cutout hole, molded-in hole, and embedding techniques. The laminated ACPs with their embedded piezoelectric sensors and actuators were vacuum bagged and co-cured inside an autoclave employing the cure cycle recommended by the composite material supplier. The Curie temperature of the embedded piezo patches should be well above the curing temperature of the composite materials as was the case here. The capacitance of the piezoelectric patches was measured before and after cure for quality control. The manufactured ACPs were trimmed and then tested for their functionality. A finite element analysis (FEA) model was developed to verify the free expansion of the AFC FEA. Next, the FEA model of the manufactured ACP was developed based on the AFC FEA free expansion model and was employed to test the functionality of the AFCs embedded within the ACPs. Both static and dynamic FEA results of the modeled ACPs showed very good agreements with their corresponding experimental results. Finally, vibration suppression as well as simultaneous vibration suppression and precision positioning tests, using Hybrid Adaptive Control (HAC), were successfully conducted on the manufactured ACP beams and their functionality was further demonstrated. The advantages and disadvantages of ACPs with embedded piezoelectric sensor and actuator patches manufactured employing the abovementioned three wires out techniques are also presented in terms of manufacturing and performance.

Lamb waves for the non-destructive inspection of monolithic and sandwich composite beams

The aim of the current study is to develop a cost and time effective inspection strategy for in-service health monitoring of composite structures. An experimental study is presented, that demonstrates the potential of low-frequency Lamb waves being used for the inspection of monolithic and sandwich composite beams. Small and unobtrusive piezoceramic patches are used to generate and capture flexural waves propagating through the structure at low frequencies. Multidirectional carbon fibre reinforced plastic beams of various lay ups are tested for the detection of matrix cracking, delaminations and broken fibres. The technique is also successfully applied to the damage inspection of composite sandwich beams.