Piezoelectric Lead Zirconate Titanate Research Articles

Bulk Acoustic Wave Diplexer for Medium Wave Application Based on Lead Zirconate Titanate Piezoelectric Material

Bulk Acoustic Wave Diplexer for Medium Wave Application Based on Lead Zirconate Titanate Piezoelectric Material

Interface debonding defect detection for CFST columns based on EMI measurements: Experiment, numerical simulation and blind inspection in practice

Concrete-filled steel tube (CFST) members have been widely used in skyscrapers and long-span bridges. Non-uniformly distributed hydration heat during curing, inadequate compaction during construction and unavoidable shrinkage and creep of mass concrete in service most likely lead to interface debonding defects between concrete core and steel tube, which has been a common concern. The development of effective non-destructive inspection methods for interface bonding condition of existing CFST members is critical. In this study, an interface debonding defect detection method based on electromechanical impedance (EMI) measurement using surface-mounted piezoelectric-lead-zirconate-titanate (PZT) sensors is proposed at first. Then, experimental study on the feasibility of the proposed approach is carried out with scaled CFST specimens with artificially mimicked interface debonding defects. EMI of surface-mounted PZT sensors at different frequency bands are measured and compared to verify the detectability of the proposed approach for the mimicked interface debonding defects. Thirdly, a multi-physics CFST-PZT coupling finite element model (FEM) with interface debonding defects is established, and EMI of surface-mounted PZT sensors at different locations is simulated. The influence of interface debonding defects on EMI measurements is illustrated. Finally, a blind inspection on the interface bonding condition of selected CFST columns in an existing skyscraper in service using the proposed approach is carried out. Both bonding and debonding defect in the tested CFST columns are detected correctly and validated with drilling hole observation. Experimental, numerical and engineering application results show the proposed approach is effective for interface debonding detection of CFST members and sensitive to minor debonding defect of 0.3 mm in CFST members.

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.

Interfacial debonding detection for steel-concrete composite structures part I: Benchmark test and signal calibration of contact and non-contact measurement

Interfacial bonding state is one of the crucial factors affecting the bearing capacity and durability of steel-concrete composite structures (SCCS). To achieve efficient interfacial debonding detection for SCCS, contact and non-contact method-based novel non-destructive test (NDT) is performed in this study. In order to figure out the dominant frequency and vibration mode of steel plate above interfacial debonding defects in SCCS, systematic theoretical analysis and finite element simulation are carried out. Then, the contact NDT experimental study is carried out utilizing piezoelectric lead zirconate titanate (PZT) sensors and acceleration meters. Conventional and high-frequency microphones, as well as high-precision scanning laser Doppler vibrometer (SLDV), are introduced for non-contact measurement. According to benchmark test on steel plate-bonded reinforced concrete cube with preset interfacial debonding defects in different dimensions, the signal calibration with Pearson correlation coefficient is further performed to quantitatively assess the variation and difference between contact and non-contact measurements. Research findings indicate that the synthetic experimental testing platform integrating contact vibration measurement, non-contact SLDV, and acoustic vibration measurement established in this study is capable of performing non-destructive tests using impact-response method, impact-echo technique, impact-acoustic vibration approach, and modal test simultaneously. Moreover, SLDV can precisely obtain the vibration mode of steel plates above interfacial debondings. Aided by high-precision scanning laser-based vibration measurement, the accuracy and efficiency of in-situ non-contact tests can be improved. The research findings in this study can provide practical guidance on non-destructive evaluation of interfacial damages in SCCS.

Crystallization of piezoceramic films on glass via flash lamp annealing

Integration of thin-film oxide piezoelectrics on glass is imperative for the next generation of transparent electronics to attain sensing and actuating functions. However, their crystallization temperature (above 650 °C) is incompatible with most glasses. We developed a flash lamp process for the growth of piezoelectric lead zirconate titanate films. The process enables crystallization on various types of glasses in a few seconds only. The functional properties of these films are comparable to the films processed with standard rapid thermal annealing at 700 °C. A surface haptic device was fabricated with a 1 μm-thick film (piezoelectric e33,f of −5 C m−2). Its ultrasonic surface deflection reached 1.5 μm at 60 V, sufficient for its use in surface rendering applications. This flash lamp annealing process is compatible with large glass sheets and roll-to-roll processing and has the potential to significantly expand the applications of piezoelectric devices on glass.

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.

A Deep Learning Approach for Autonomous Compression Damage Identification in Fiber-Reinforced Concrete Using Piezoelectric Lead Zirconate Titanate Transducers.

Effective damage identification is paramount to evaluating safety conditions and preventing catastrophic failures of concrete structures. Although various methods have been introduced in the literature, developing robust and reliable structural health monitoring (SHM) procedures remains an open research challenge. This study proposes a new approach utilizing a 1-D convolution neural network to identify the formation of cracks from the raw electromechanical impedance (EMI) signature of externally bonded piezoelectric lead zirconate titanate (PZT) transducers. Externally bonded PZT transducers were used to determine the EMI signature of fiber-reinforced concrete specimens subjected to monotonous and repeatable compression loading. A leave-one-specimen-out cross-validation scenario was adopted for the proposed SHM approach for a stricter and more realistic validation procedure. The experimental study and the obtained results clearly demonstrate the capacity of the introduced approach to provide autonomous and reliable damage identification in a PZT-enabled SHM system, with a mean accuracy of 95.24% and a standard deviation of 5.64%.

A Gas Flow Measurement System Based on Lead Zirconate Titanate Piezoelectric Micromachined Ultrasonic Transducer.

Ultrasonic flowmeter is one of the most widely used devices in flow measurement. Traditional bulk piezoelectric ceramic transducers restrict their application to small pipe diameters. In this paper, we propose an ultrasonic gas flowmeter based on a PZT piezoelectric micromachined ultrasonic transducer (PMUT) array. Two PMUT arrays with a resonant frequency of 125 kHz are used as the sensitive elements of the ultrasonic gas flowmeter to realize alternate transmission and reception of ultrasonic signals. The sensor contains 5 × 5 circular elements with a size of 3.7 × 3.7 mm2. An FPGA with a resolution of ns is used to process the received signal, and a flow system with overlapping acoustic paths and flow paths is designed. Compared with traditional measurement methods, the sensitivity is greatly improved. The flow system achieves high-precision measurement of gas flow in a 20 mm pipe diameter. The flow measurement range is 0.5-7 m/s and the relative error of correction is within 4%.

Flexure-critical stress and damage identification in RC beam structure using embedded piezoelectric transducers: 2D modelling and experimental investigations

This paper proposed a real-time identification approach of flexure-critical stress and damage in reinforced concrete (RC) beam structure using embedded Piezoelectric lead Zirconate Titanate (PZT) transducers. Effect of structural stress and damage were theoretically incorporated into mechanical impedance to derive a novel two-dimensional (2D) embedded PZT-structure interaction model. Analytical analysis was conducted to calculably interpret the identification of tensile/compressive stress and damage based on the electromechanical admittance (inverse of impedance, EMA) signatures. The proposed approach was validated by experiment on an RC beam subjected to four-point bending test, which was continuously monitored by cement-embedded PZT (CEP) transducers. Analytical and experimental results showed that resonance peak and frequency shift of the EMA spectrums of CEPs exhibited converse behaviors when responding to tension and compression stresses, while typical frequency decrease and peak increase accurately indicated the occurrence of initial cracking. Comparative studies also revealed that CEPs were superior to visual inspection and bonded PZT transducer in identification of concrete cracking, and that located in compressive zone was more efficacious in prediction of the forthcoming yield and final failure of the RC beam. Results of this study cogently demonstrated the potentialities of CEP transducer as a means of on-line monitoring of stress/damage in flexure-critical RC infrastructures.

Solar cell micro crack detection technique using electromechanical impedance and finite element analysis

Electromechanical impedance (EMI) is one of the modern techniques employed in the field of structural health monitoring (SHM) and has witnessed a great expansion in many domains due to its ability to ensure continuous monitoring and high reliability with a lower cost. Hence, the purpose of this study is to investigate the effectiveness of EMI in monitoring and detecting pre-existing cracks in the silicon layer of the photovoltaic (PV) solar cells. Indeed, a detailed finite element analysis (FEA) on the effect of piezoelectric lead zirconate titanate (PZT) patch shape on the EMI of crystalline-silicon (c-Si) layer of the PV solar cells were performed. The typical structure (c-Si + PZT) of different scenarios were stimulated by giving a lower voltage and high frequency as input data to extract the EMI signature as an explainable output result. Different models were investigated based on PZT patch types and crack position in the silicon layer. The results indicate that the EMI technique is effective in detecting crack, even in its incipient stage. The analysis suggests using a higher frequency range (350–650 kHz) for characterizing damage with an invisible depth due to the higher sensitivity of the EMI technique in this specific frequency.

Structural Health Monitoring of Fiber-Reinforced Concrete Prisms with Polyolefin Macro-Fibers Using a Piezoelectric Materials Network under Various Load-Induced Stress

This experimental study investigates the influence of synthetic macro-fibers added in fiber-reinforced concrete (FRC) prismatic specimens on their flexural response and overall cracking performance. Application of a novel structural health monitoring (SHM) system that implements the electromechanical impedance (EMI) technique and the use of piezoelectric lead zirconate titanate (PZT) transducers installed in the FRC prisms are also included. The applied PZT-enabled EMI-based monitoring system was developed to diagnose damage and the overall performance in reinforced concrete (RC) structural members subjected to cyclic repeated loading, simulating seismic excitations in existing RC buildings. The paper also aims to determine the sensitivity of the real-time, wireless, and portable monitoring technique corresponding to the location, the distance, the direction of polarization of the PZT transducers and the location and magnitude of damage due to flexural cracking. Further, the influence of the effect of stresses corresponding at various loading levels and the observed changes in the ΕΜΙ frequency response of the PZT transducers are also examined. Test results indicated that cracking detection is achieved using this SHM system by prompt damage level assessment due to the FRC’s flexural load at early seismic loading stages in existing RC buildings.

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.

Parametric analysis of RSB sensors for concrete strength monitoring using hybrid EMI and WP techniques: Numerical investigation

The strength of concrete after its casting increases with time up to a certain limit due to continuous hydration reactions in the cement matrix. To measure the rate of strength development and ultimate capacity of concrete, a novel health monitoring method using Reusable smart bolt (RSB) piezoelectric sensor is proposed in the present paper. The smart piezoelectric Lead zirconate titanate (PZT) patch-based Electro-mechanical impedance (EMI) and Wave propagation (WP) techniques are utilised for accessing the health of concrete at 1, 3, 5, 7, 14, 21 & 28 days of concrete hydration. Firstly, the PZT patch-based sensing capabilities are validated with the experimental results from literature by modelling concrete cube for EMI and beam for WP results. Then, a total of 31 finite element models of concrete cubes having different RSB configurations were taken into consideration for sensor design and optimization. In EMI technique, the shifting of conductance signatures and relative resonance frequency are measured, whereas in WP technique, the shift of P-wave velocity peaks between actuator and sensor is estimated for all the models. The sensitivity of outputs is measured by plotting statistical Root mean square deviation (RMSD) index which proven the efficacy of employing RSB sensors for monitoring concrete strength-development during early-hydration ages with good correlations. Overall, the EMI-identified RMSD plotted for conductance shows 327 % more sensitivity than WP-identified relative change of P-wave velocity in monitoring concrete strength development using RSB sensors.

Bottom-up micromachined PZT film-based ultrasonic microphone with compressible parylene tube

This paper reports on a micromachined ultrasonic microphone using a bottom-up fabrication scheme. Starting with a 4 μm-thick titanium foil as the substrate, each functional film and key element was added to the foil substrate to complete the ultrasonic microphone. The piezoelectric lead zirconate titanate film hydrothermally grown on the patterned substrate with low residual stress effectively deflected the unimorph-sensing cantilever array of the microphone under ultrasound pressure. The created cantilever array structure secured on a 250 μm-thick SU8 hollow plate formed an ultrasonic microphone plate that was tested with a sensitivity of −60 dBV Pa−1 at 21 kHz (with 0 dB gain amplification) and an operation bandwidth of 5–55 kHz. Different thicknesses of parylene films ranging from 0.5 to 2 μm overlaid over the entire sensing region and converted the cantilever-to-diaphragm-structured microphone for further investigation. An enhanced result was observed when the deposited parylene film thickness was in the submicron range. The sensitivity of the microphone can be further enhanced by up to 33% by adding a parylene-film-made compressible tube to act as a Helmholtz resonator (HR). The HR model was discussed and compared with the experimental results. The output amplitude of the developed microphone assembled with the compressible tube demonstrates a 15 dB increase compared to that of a commercial capacitive MEMS ultrasonic microphone.

CONCRETE CORE DEFECTS TOMOGRAPHIC IMAGINATION FOR MESOSCALE CFST MEMBERS USING STRESS WAVE MEASUREMENT

To visualize concrete core void defects in concrete-filled steel tube (CFST) members considering the mesoscale heterogeneity and randomness of concrete core is critical in practice. A stress wave travelling time tomography imagination method using piezoelectric-lead-zirconium-titanate (PZT) patches as actuators or sensors is proposed and validated numerically. A two-dimensional (2D) multi-physics and mesoscale coupling CFST-PZT model composed of number of PZT actuators and sensors, steel tubes, and concrete core with randomly distributed circular aggregates is established. The first stress wave arrival times of the mesoscale coupling CFST-PZT model without or with a concrete core void defect are recorded by PZT sensors when a PZT actuator is excited by pulse signals. A random walking algorithm (RWA) with the Snell laws is employed to determine the shortest wave travel path between each PZT actuator and each PZT sensor. Finally, the velocity fields of the mesoscale coupling models are identified using a simultaneous iterative reconstruction technique (SIRT) to minimize the difference between the first arrival time of the stress wave and the shortest wave travel time. Results show that the location and dimension of the void defect in the models with heterogeneous concrete core can be imaged with acceptable resolution.

Electro-Mechanical Impedance-Based Structural Health Monitoring of Fiber-Reinforced Concrete Specimens under Four-Point Repeated Loading

Fiber Reinforced Concrete (FRC) has shown significant promise in enhancing the safety and reliability of civil infrastructures. Structural Health Monitoring (SHM) has recently become essential due to the increasing demand for the safety and sustainability of civil infrastructures. Thus, SHM provides critical benefits for future research to develop more advanced monitoring systems that effectively detect and diagnose the damage in FRC structures. This study investigates the potential of an Electro-Mechanical Impedance (EMI) based SHM system for detecting cracks in FRC prisms subjected to four-point repeated loading. For the needs of this research, an experimental investigation of three FRC specimens with the dimensions 150 × 150 × 450 (mm) were subjected to three different loading levels where no visual cracks formed on their surface. Next, prisms were subjected to reloading until they depleted their load-carrying capacity, resulting in pure bending fracture at the mid-span. A network of nine cement paste coated Piezoelectric lead Zirconate Titanate (PZT) transducers have been epoxy bonded to the surface of the FRC prisms, and their frequency signal measurements were utilized for quantitative damage assessment. The observed changes in the frequency response of each PZT sensor are evaluated as solid indications of potential damage presence, and the increasing trend connotes the severity of the damage. The well-known conventional static metric of the Root Mean Square Deviation (RMSD) was successfully used to quantify and evaluate the cracking in FRC specimens while improving the efficiency and accuracy of damage detection. Similarly, the dynamic metric of a new statistical index called “moving Root Mean Square Deviation” (mRMSD) was satisfactorily used and compared to achieve and enhance accuracy in the damage evaluation process.

Additive Manufacturing of Piezoelectric Niobium-Doped Lead Zirconate Titanate (PZT-N) by Binder Jetting

Binder jetting is an emerging indirect additive manufacturing technique for ceramic materials, which could be employed to produce application-oriented designed components impossible to achieve with traditional processes and featuring enhanced performances. In our study, niobium-doped lead zirconate titanate (PZT-N) powder, usually processed through the standard press-and-sinter route, was employed as the raw material. First, the powder was characterized in terms of granulometry and flowability to assess its suitability for the printing process. Then, shaping by binder jetting was studied, and the effect of three levels of binder saturation (75–90–105%) on the green bodies was assessed. Finally, the microstructure of the sintered samples was studied using SEM, to investigate the effect of thermal treatments on the grain size distribution and residual porosity (~40%). The piezoelectric properties were measured and compared to those of conventionally processed material. The piezoelectric charge and voltage constants (d33 and g33) were evaluated to determine the possible use of printed parts as porous piezoelectric components to be exploited in hydrophones in the direct mode.

In-situ cure monitoring of thick CFRP using multifunctional piezoelectric-fiber hybrid sensor network

Conventional process monitoring techniques rely on point or line measurements and can only monitor very limited physical quantities during the curing process. In this study, an innovative multifunctional piezoelectric-fiber hybrid sensor network is developed for global monitoring of multiple physical quantities during the curing cycle of thick carbon fiber-reinforced polymer (CFRP) composites. Three different approaches based on non-invasive and integrated piezoelectric lead-zirconate-titanate (PZT) sensor network are effectively developed to track the degree of cure and key steps via the velocity and amplitude of the received guided wave. The bare and encapsulated fiber optic sensors are woven into the fabrics along the through-thickness direction before liquid composite molding processing to monitor the key steps and the development of temperature and cure-induced strain gradient. Efforts are also made to perform three-dimensional curing imaging from the measurements of the developed sensor network. Experimental validation demonstrates the effectiveness of the proposed piezoelectric-fiber hybrid sensor network for in-situ and real-time monitoring of multiple physical quantities during cure, contributing to the advancement in smart manufacturing and life-cycle structural health monitoring of composites.

Feasibility of Stress Wave-Based Debond Defect Detection for RCFSTs Considering the Influence of Randomly Distributed Circular Aggregates with Mesoscale Homogenization Methodology.

In order to efficiently investigate the effect of the mesoscale heterogeneity of a concrete core and the randomness of circular coarse aggregate distribution on the stress wave propagation procedure and the response of PZT sensors in traditional coupling mesoscale finite element models (CMFEMs), firstly, a mesoscale homogenization approach is introduced to establish coupling homogenization finite element models (CHFEMs) with circular coarse aggregates. CHFEMs of rectangular concrete-filled steel tube (RCFST) members include a surface-mounted piezoelectric lead zirconate titanate (PZT) actuator, PZT sensors at different measurement distances, a concrete core with mesoscale homogeneity. Secondly, the computation efficiency and accuracy of the proposed CHFEMs and the size effect of representative area elements (RAEs) on the stress wave field simulation results are investigated. The stress wave field simulation results indicate that the size of an RAE limitedly affects the stress wave fields. Thirdly, the responses of PZT sensors at different measurement distances of the CHFEMs under both sinusoidal and modulated signals are studied and compared with those of the corresponding CMFEMs. Finally, the effect of the mesoscale heterogeneity of a concrete core and the randomness of circular coarse aggregate distribution on the responses of PZT sensors in the time domain of the CHFEMs with and without debond defects is further investigated. The results show that the mesoscale heterogeneity of a concrete core and randomness of circular coarse aggregate distribution only have a certain influence on the response of PZT sensors that are close to the PZT actuator. Instead, the interface debond defects dominantly affect the response of each PZT sensor regardless of the measurement distance. This finding supports the feasibility of stress wave-based debond detection for RCFSTs where the concrete core is a heterogeneous material.

An Electromechanical Impedance-Based Application of Realtime Monitoring for the Load-Induced Flexural Stress and Damage in Fiber-Reinforced Concrete

Effective real-time structural health monitoring in concrete structures is paramount to evaluating safety conditions and the timely maintenance of concrete structures. Especially, the presence of discrete fibers in fiber-reinforced concrete restrains crack propagation into small and thin cracks, which increases the difficulty in detecting damage. In this study, an array of piezoelectric lead zirconate titanate (PZT) transducers was applied to study the effects of external load-induced flexural stress and damage in fiber-reinforced concrete beams using the electromechanical impedance (EMI) or electromechanical admittance (EMA) methods. Beams were subjected to a four-point bending test under repeatable loading, while PZTs evaluated corresponding flexural stress and induced damage simultaneously. Due to the influence of the medium’s stress fields in the different types of wave propagation in structural elements, PZT transducers measurements are accordingly affected under variable stress fields, in addition to the effect of the higher level of damage that occurred in the medium. According to the results of the tests, variation in EMA signatures, following flexural stress and gradual damage changes, provided convincing evidence for predicting stress and damage development.