Lead Zirconate Titanate Piezoelectric Ceramics Research Articles

Damage localization on reinforced concrete slab structure using electromechanical impedance technique and probability-weighted imaging algorithm

Damage localization plays a key role in structural damage identification and health monitoring. This paper proposed a new damage localization approach using electromechanical impedance/admittance (EMI/EMA) technique integrated with probability-weighted imaging algorithm based on Gaussian distribution. The proposed approach comprises five steps namely measurement of the EMA signature from an array of piezoelectric ceramic lead zirconate titanate (PZT) transducers, computation of statistic damage indicator, establishment of regression model for the indicator, damage visualization via Gaussian distribution and final damage localization. Experimental validation of the approach was conducted on a reinforced concrete (RC) slab with artificial crack damages detected by using an array of surface-bonded PZT patches. Comparative studies on localization accuracy were performed by utilizing root mean square deviation (RMSD), baseline-changeable RMSD namely RMSDk, mean absolute percentage deviation (MAPD) and correlation coefficient (CC). Experimental results demonstrated that the proposed approach could achieve precise localization of concrete crack with error as small as 0 mm, and that using RMSDk index exhibited the highest localization accuracy in average. The proposed approach promoted the capability of the EMI technique in characterization of concrete structural damages.

Evaluation of Damage Severity and Strength of Structural Member Using Macro‐Molecular PZT Sensor

AbstractThe structural health of various engineering systems has been easily monitored using macromolecular piezoelectric ceramic lead zirconate titanate (PZT) based electromechanical impedance (EMI) technique. It is in need to study the evaluation of various levels of damage and the present strength of structural systems to enhance the life of structures. Once damages occur, due to continuing usage they usually propagate in certain directions. Moreover, the increase in the severity of damages may lead to failure of the structural components or even the whole structure. Interaction between structure and PZT, which is found effective in EMI technique, is to identify effective damage detection. The macro‐molecular PZT's self‐actuating and sensing properties are utilized by the electromechanical impedance (EMI) method. The higher modes of vibration are locally activated by the local application of an AC source on the PZT transducers attached to the host structure. In this paper, the EMI technique using surface‐bonded PZT transducers is employed to obtain the structural health signature. The experiment is carried out on a real‐size concrete frame structure subjected to artificial damage to identify and locate the damages using frequency variations, and the severity is checked using extracted equivalent parameters; the damage index. This method also can identify hair‐like cracks at an early stage, which explains how it can shield the building from serious failures.

Influence of polyethylene content on preparation and properties of lead zirconate titanate piezoelectric ceramics via vat photopolymerization

Vat photopolymerization has garnered significant research interest due to its capabilities in achieving complicated designed structures and high resolution. However, there are still significant technical difficulties in manufacturing some piezoceramic parts because of the high refractive index and ultraviolet light absorptivity of these ceramic powders. Herein, we overcome this challenge for lead zirconate titanate (PZT) ceramics by introducing polyethylene (PE) additions with ultralow refractive index and UV light absorptivity into PZT slurries. As the PE content increases, the curing depth shows a clear upward trend. When the PE content is 30 vol%, the curing depth of PZT slurry could ensure the adequate interlayer combination. Besides, PZT ceramics with different volumes of porosity could be obtained by modulating PE content. The relative density of sintered PZT ceramics decreased from 83.12 % to 68.06 %. Furthermore, the samples with 30 vol% PE exhibited satisfactory dielectric and piezoelectric properties (ϵr =1911, tanδ=0.027, d33 = 308 pC/N, g33 = 1.82 × 10−2 Vm/N and d33g33= 5.61 × 10−12 m2/N). These results indicate that the addition of PE additives is an effective and universal approach to improve the curing depth of ceramic slurries and expand the range of processable materials for vat photopolymerization technologies.

Deep learning of electromechanical admittance data augmented by generative adversarial networks for flexural performance evaluation of RC beam structure

Deep learning networks facilitate automated damage identification and performance evaluation for concrete structures using electromechanical impedance/admittance (EMI/EMA) technique, while data quantity and quality limit the performance of such a data-driven network. For the first time, this paper proposed a data-augmentation approach using deep-convolutional admittance generative adversarial networks (AdmiGAN) to solve data deficiency and measurement inefficiency for deep learning-based flexural performance evaluation of reinforced concrete (RC) structures. In the approach, a new data normalization procedure was developed to collaboratively foster AdmiGAN-based EMA data synthesis, and synthetic datasets were fed into an adaptive convolutional neural network (CNN) for deep learning. Proof-of-concept experiment was conducted on a four-point bending RC beam structure, which was continuously monitored from initial loading to final failure by three surface-bonded piezoelectric ceramic lead zirconate titanate (PZT) patches. Qualitative detection of stress and damage was performed by traditional feature analysis of EMA signatures, automated performance evaluation was attempted by using CNN approach. Results demonstrated that the AdmiGAN required merely 5 groups of EMA signatures to generate high-accuracy dataset with 174 times of speed faster than conventional measurement method, and the AdmiGAN cooperated with CNN provided a new paradigm of data-driven structural performance evaluation with high accuracy, efficiency, and intelligence.

3D printing of lead zirconate titanate piezoelectric ceramics via digital light processing (DLP)

Research of piezoelectric ceramics via DLP technology has drawn considerable interest due to its high geometrical flexibility. However, the poor curing properties limit the use of DLP technology to fabricate piezoelectric ceramics. Herein, we overcome this challenge in prepared lead zirconate titanate (PZT) piezoelectric ceramics via DLP technology by incorporating ultralow refractive index and ultraviolet light absorptivity of soluble starch in PZT ceramic slurry. After the post-process, the relative density of printed PZT ceramic with 20 vol% soluble starch could reach about 89.51% of theoretical density. The printed PZT ceramic exhibits remarkable dielectric permittivity, remnant polarization, piezoelectric strain constant, piezoelectric voltage constant, figure of merit and electromechanical coupling factor of 2196, 35.56 μC/cm2, 373 pC/N, 1.92 × 10−2 Vm/N, 7.16 × 10−12 m2/N and 42.28%, respectively. The results achieved in this research indicate that our work provides a promising route for fabrication of advanced ceramics with high performance and designed complex structures by digital light processing.

A miniature longitudinal-bending hybrid linear ultrasonic motor inspired by the planar hinged five bar mechanism

Inspired by the double crank planar hinged five bar mechanism, a longitudinal-bending hybrid linear ultrasonic motor with compact miniature is proposed and tested. In order to realize miniaturization, it adopts a bonded-type structure. Four lead zirconate titanate (PZT) piezoelectric ceramics are distributed equally into two groups and bonded to the two ends of the metal frame, and then, two voltages with a phase difference of 90° are applied to each of the two groups of PZT ceramics. Subsequently, the first-order longitudinal vibration and second-order bending vibration generated by the motor combine with each other at the tip of the driving foot to form an elliptical motion trajectory. According to the theoretical kinematic analysis of the free beam, the initial structural dimensions of the motor were designed. Then, the initial dimensions of the motor were optimized, and the zero-order optimization algorithm was used to achieve the purpose of longitudinal and bending resonance of the motor, and finally, the optimal dimensions of the motor were obtained. A prototype of the designed motor was made, followed by experimental tests on the performance of the prototype, including mechanical output. The maximum motor speed without load at 69.4kHz is 134.57 mms-1. Under 200 Vpp voltage and 6 N preload, the output thrust of the motor is about 0.4 N at the maximum. The actual mass of the motor is about 1.6g; therefore, the thrust-to-weight ratio was calculated as 25.

Numerical and Experimental Research on Non-Reference Damage Localization Based on the Improved Two-Arrival-Time Difference Method.

The identification of damage based on Lamb waves can hardly avoid obtaining the reference signal under healthy conditions. A non-reference damage localization (NRDL) method is proposed in this paper. The NRDL method is established by the improved two-arrival-time difference method (2/ATDM) and BFGS method. The layout principles of the piezoelectric ceramic lead zirconate titanate (PZT) transducer array in the specimen are proposed. In contrast to existing methods, the damage outside the array in the specimen is identified based on the NRDL. The full-area damage location in the specimen is realized. Furthermore, the optimization of the excitation signal center frequency and transducer array layout is carried out. The damage location accuracy is greatly improved.

Influence of Multidirectional Oscillations on Output Characteristics of Inertial Piezoelectric Platform

A piezoelectric platform driven by a multifunctional piezoelectric actuator is used to investigate the influence of multidirectional oscillations on the output characteristics of an inertial piezoelectric platform. Multidirectional oscillations can be generated by the vibration PZT (lead zirconate titanate piezoelectric ceramics) element of the actuator while the platform is driven by the actuation PZT element. The output characteristics are tested with the changing amplitude and frequency of multidirectional oscillations. An interesting phenomenon is observed when the amplitude or frequency is larger than specific values: The sticking and sliding displacements decrease quickly, and the step distance drops to zero rapidly; in other words, the oscillations determine the displacement response. The oscillation perpendicular to the contact plane is selected to switch friction and alleviate the inherent defects of the inertial platform. The response displacement is measured under a voltage of 600 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p-p</sub> and a frequency of 1 Hz; the linear fitting is carried out, and the calculated correlation coefficient is improved from 0.987 to 0.995 by using friction switching; and a larger output force is also obtained. The results indicate that friction switching can be applied to obtain a high linearity displacement output and a large output force for the inertial platform.

Multi-material fused filament fabrication of flexible 3D piezoelectric nanocomposite lattices for pressure sensing and energy harvesting applications

Flexible three-dimensional (3D) piezoelectric sensors and energy harvesters are in great demand for wireless and low power consumption human health monitors, artificial skins and soft robots. In this work, a multi-material fused filament fabrication (FFF) 3D printing technique is used to fabricate 3D piezoelectric and flexible nanocomposite structures with integrated electrodes by utilizing a developed piezoelectric nanocomposite filament and a commercially available conductive nanocomposite filament. The developed piezoelectric nanocomposite filament consists of flexible polyurethane (TPU) matrix and 30 vol% (maximum allowable content) of piezoelectric ceramic lead zirconate titanate (PZT) nanoparticle fillers. The fabricated and poled TPU/30vol%PZT piezoelectric nanocomposite has an elongation at break strain ∼56% and a d33 value 6.8 pC/N. Four types of 3D piezoelectric nanocomposite lattices including simple cubic, body-centered cubic, cuboctahedron and octet truss are fabricated and tested along with a fully dense solid counterepart. Under the same maximum applied compressive force, the octet truss piezoelectric nanocomposite lattice generates two times higher voltage output than the fully dense solid counterpart. As a demonstration for the potential applications, a multi-material 3D printed flexible piezoelectric nanocomposite shoe sole made of the octet truss infill pattern can generate a peak-to-peak voltage (Vpp) ∼20 V through a typical human stomp. Our approach can open a new avenue for design and manufacturing of flexible piezoelectric devices for sensing and energy harvesting applications.

Automated identification of compressive stress and damage in concrete specimen using convolutional neural network learned electromechanical admittance

For the first time, this paper proposed a simple two-dimensional convolutional neural network (2-D CNN) integrated with electromechanical admittance (EMA, inverse of impedance) to detect compressive stress and load-induced damages of concrete cubic structure subjected to applied loading, which was attempted to solve the difficulty for stress/damage quantification merely based on traditional EMA technique. It automatically resolved the raw EMA signatures with no need of complex transformation or manual feature extraction. In the experimentation, the whole process of the structural states from initial loading to fatal failure was monitored via using surface-bonded piezoelectric ceramic lead zirconate titanate (PZT) transducer. Independent EMA databases were established at each stress/damage state of the structure. Qualitative detection of stress development and cracking damage progression as three stages of failure mode was analysed via using characteristics of EMA spectra encompassing resonant frequency and amplitude values. Quantifiable assessment of stress level and damage severity was attempted using the raw EMA signatures learned by the proposed CNN model without signal pre-processing. Experimental results demonstrated that EMA signature was sensitive to stress variations in concrete and its cracking, expansion and propagation. The proposed approach possessed excellent accuracy and efficiency superior to traditional root mean square deviation (RMSD)-based one for quantification on compressive stress and damage state changes in the specimen, which potentially provided an alternative paradigm of data-driven stress/damage identification in concrete structures.

Study on pre-damage diagnosis and analysis of adhesively bonded smart PZT sensors using EMI technique

The electro-mechanical impedance technique (EMI) is one of the best methods for continuous structural health monitoring (SHM) by embedding a smart piezoelectric ceramic Lead Zirconate Titanate (PZT) sensor or pasting it over the surface of the structure. The smart PZT transducer is intensely affected by the adhesive bonding condition between the PZT patch and the host structure. The current paper studies the damage-diagnosis process of the coupled electro-mechanical behavior of an adhesively bonded smart PZT transducer. The inverse of impedance signatures is used for investigating pre-damage diagnosis and analysis of surface-mounted PZT transducer. A parametric study on the variation of adhesive property is carried out to overcome the shear lag effect. The novel contribution of this paper discusses a methodology for an early diagnosis of damage in the PZT transducer and adhesive bond layer during the SHM process. Firstly, the damage is introduced to the PZT patch and bonding layer, and the corresponding EMI signatures are obtained using numerical modeling and simulations. The damage detection using susceptance is discussed for lower frequencies from 0 to 20 kHz. It is observed that the change in susceptance signature is not large enough to detect adhesive debonding. Subsequently, the conductance signatures are utilized for the investigation. It is observed that damage in the adhesive layer and PZT patch cause upward or downward shift with no alteration along the horizontal direction. It helps to detect sensor breakage and adhesive debonding effectively. Secondly, the simulation results are verified using the theoretical analysis for the single piezo configuration by improved continuum-based impedance equations. A modified dual piezo configuration is investigated to validate the proposed method. Experimental investigation on PZT-bonded aluminum plate involving perfectly bonded, adhesive debonding, and sensor breakage conditions are conducted to verify the process. It is found that the real part of the admittance signature is reliable and critical in sensor diagnosis, and sensor faults of debonding and breakage can be identified and differentiated. It also validates the semi-analytical work results. Therefore, the proposed methodology for pre-diagnosing damage present in the smart PZT sensor and adhesive layer using the EMI technique can be utilized for effective SHM.

Modeling, identification and optimization of damage deterioration in the bolted repaired metallic plate

The in situ detection of the damaged aluminum alloy plate with bolted patch is numerically and experimentally studied based on a surface-mounted piezoelectric ceramic lead zirconate titanate (PZT) elements. The contact effects between the bolts, repair patch and host structure are considered. The convergence analysis, range-frequency analysis and pretension force analysis are discussed. The numerical results are good agreement with those of the experiments. The damage identification indexes are introduced for damage detection. It indicates the numerical simulation is effective for the damage deterioration of bolted repaired structures. The location of the PZT transducer is discussed to optimize the process.

Irradiation behavior and recovery effect of ferroelectric properties of PZT thin films* *Project supported by the National Natural Science Foundation of China (Grant No. 51802056), the Science Foundation of the National Key Laboratory of Science and Technology on Advanced Composites in Special Environments, and the Key Laboratory of Micro-systems and Micro-structures Manufacturing (Harbin Institute of Technology), Ministry of Education, China.

Lead zirconate titanate piezoelectric ceramics have important applications in space and aerospace technology, but the effect and physical mechanism of charged particle radiation on their performance yet to be clarified. In this study, we characterized PbZr0.52Ti0.48O3 (PZT) thin films, and changes in the ferroelectric properties of the films before and after electron and proton irradiation were investigated. The natural and heat treatment recoverability of the ferroelectric properties were studied, and the damages and mechanisms of different types of radiation in PZT films were also investigated. The results show that, in addition to ionization damages, electron irradiation causes certain structural damage on the PZT film, and the large structural damage caused by proton irradiation reduces drastically the ferroelectricity of the PZT film.

Experimental study on fatigue degradation of piezoelectric energy harvesters under equivalent traffic load conditions

The fatigue life of piezoelectric energy harvesters (PEHs) under traffic load remains unclarified despite increasing research. Lead zirconate titanate (PZT) piezoelectric ceramics are widely used in PEHs, owing to their excellent piezoelectric properties. In this study, we fabricated a PZT-5H piezoelectric transducer, showing excellent performance, loaded it 10 million times under equivalent traffic loads, and investigated its ultimate fatigue life under intermittent and persistent loading. The micromechanism of fatigue depolarization and effects of different excitation loads and frequencies on the fatigue life of PZT-5H were studied. The degradation rate was 32.37% after 10 million intermittent loads (equivalent to 3 years of road traffic load), but reached 96.6% after 81 h of persistent loading. The fatigue degradation rate increased with increasing excitation loads and frequencies. Thus, PZT-5H piezoelectric transducers can replace disposable batteries for longer service life, if watt level output power is obtained.

Paste extrusion 3D printing and characterization of lead zirconate titanate piezoelectric ceramics

The additive manufacturing of piezoelectric ceramic Lead Zirconate Titanate (PZT) through paste extrusion 3D printing was demonstrated. Different paste compositions with varied water weight content were studied to find a composition suitable for printing. The pastes were evaluated in terms of their viscosities, yield stresses, and stability when aged. Furthermore, the material properties of the ceramics produced through paste extrusion were characterized and compared with those of ceramics fabricated through a conventional die pressing method. Paste extruded PZT with achieved densities as high as 94.9% of the theoretical density after sintering, which nearly matched the 95% density attained by the pressed samples. Upon poling, the paste extruded PZT piezoelectric ceramics attained piezoelectric coefficients and dielectric constants that were close to the values of die pressed samples. As near full density PZT ceramics were successfully fabricated through paste extrusion, this work paves the way for piezoelectric ceramics with application-driven geometry designs for sensors, actuators, and energy harvesters.

A novel approach to improving the electromechanical properties of PZT-based piezoelectric ceramics via a grain coating modification strategy

In the present work, we used a hybrid ceramic fabrication technology to synthesize lead zirconate titanate (PZT) piezoelectric ceramics coated with yttrium oxide–stabilized zirconia (YSZ) powders (PZT@YSZ). The tailoring effects of the YSZ grain coating layer were investigated systematically. The results demonstrate that the mechanical properties of the modified PZT ceramics were successfully improved, which is mainly attributed to the synergistic effect of reinforced martensitic transformation toughening, micro-crack toughening, and second-phase dispersion toughening of the YSZ grain coating layer. More importantly, the piezoelectric properties of the PZT@YSZ ceramics, such as d33, kp, strain (S), strain hysteresis Hs, and d33*, have no declined, instead, have improved significantly. This is due to the coexistence of the rhombohedral-tetragonal phase of PZT in the PZT@YSZ ceramics, which is confirmed by Rietveld refinements in X-ray diffraction. Furthermore, the breakdown strength of the PZT@YSZ ceramics increased by 28%, a result of the reduction in grain size. This work describes an effective approach to simultaneously toughening PZT-based piezoelectric ceramics and enhancing their piezoelectric properties.

Numerical and experimental research on damage shape recognition of aluminum alloy plate based on Lamb wave

The structure health monitoring (SHM) system with Lamb waves technique is studied numerically and experimentally in this paper. A damage shape recognition algorithm (DSRA) is developed for the hole on aluminum alloy plate specimen. The proposed DSRA is established based on the two arrival time difference method (2/ATDM) and Lagrangian optimization method. This method captures the damage shape by describing the coordinates of the reflection point from the piezoelectric ceramic lead zirconate titanate (PZT) transducers to the damage edge. 2/ATDM provides a way to obtain coordinate points by the arrival time which is determined by Lamb waves. And the coordinate points are optimized by the Lagrangian optimization method. A numerical model is established to simulate the proposed experiment process. Its convergence rate of mesh size and time steps is investigated, and the numerical results are verified by these of experiment. Hence, the shape recognition of damage occurring at an arbitrary position and that of irregular damage are studied by the proposed numerical and experiment methods.

Heteroepitaxy of flexible piezoelectric Pb(Zr0.53Ti0.47)O3 sensor on inorganic mica substrate for lamb wave-based structural health monitoring

Active Lamb wave detection is an effective and simple monitoring method for structural health monitoring (SHM). Piezoelectric lead zirconate titanate (PZT) ceramics are most commonly used as transducers to excite and receive Lamb wave. However, due to their hardness, thickness and brittleness, PZT ceramics are severely limited in detecting damage on curved surface structures. Herein, we report that flexible PZT film sensor is an excellent candidate for receiving Lamb wave used in Lamb wave-based SHM of aircraft. An improved piezoelectric coefficient d33 (~130 pm V−1) is obtained in epitaxial PZT films grown on flexible inorganic mica substrates via van der Waals heteroepitaxy. Superior stable ferroelectricity and piezoelectricity retain in flexible PZT film after bending 104 cycles under a radius of 8 mm. As proven by experiment and simulation, flexible PZT film is demonstrated as an ultrasonic sensor with high sensitivity to be bonded on the curved aluminum plate for Lamb wave-based damage monitoring. Our work demonstrates that flexible PZT films have enormous potential for real-time light-weight and high-sensitivity receiver sensors for the SHM of aging aircraft.

State-Space Modeling and Active Vibration Control of Smart Flexible Cantilever Beam with the Use of Finite Element Method

The aim of this study is to design a Linear Quadratic Regulator (LQR) controller for the active vibration control of a smart flexible cantilever beam. The mathematical model of the smart beam was created on the basis of the Euler-Bernoulli beam theory and the piezoelectric theory. State-space and finite element models used in the LQR controller design were developed. In the finite element model of the smart beam containing piezoelectric sensors and actuators, the beam was divided into ten finite elements. Each element had two nodes and two degrees of freedom were defined for each node, transverse displacement, and rotation. Two Piezoelectric ceramic lead Zirconate Titanate (PZT) patches were affixed to the upper and lower surfaces of the beam element as pairs of sensors and actuators. The location of the piezoelectric sensor and actuator pair changed and they were consecutively placed on the fixed part, the middle part, and the free end of the beam. In each case, the design of the LQR controller was made considering the first three dominant vibratory modes of the beam. The effect of the position of the sensor-actuator pair on the beam on the vibration damping capability of the controller was investigated. The best damping performance was found when the sensor-actuator pair was placed at the fixed end.

Failure mechanism analysis and experimental study of lead zirconate titanate actuators in piezoelectric micro jetting valve

Piezoelectric ceramics have recently become one of the most common materials in electromechanical industries, especially in the microelectronic packaging industry. In a jetting dispenser, the presence of imbalanced stress-induced defects in such materials prevents them from providing high stability during the jetting dispensing process. In this work, lead zirconate titanate piezoelectric ceramics (PZT ceramics) were used to actuate the amplifying mechanism of the jetting dispenser. However, during the cyclic dispensing, several ceramics were found to be damaged. In order to figure out what actually caused the damage, analytical and experimental studies were carried out to acquire characteristics of PZT ceramics with damages, and simulation studies of overstress were also performed. Details of the damage characteristics in PZT ceramics are discussed in this paper. This work will improve the stability and life of the piezoelectric dispenser and further promote its wide application in various fields.