The capability of embedded piezoelectric wafer active sensors(PWAS)to perform in-situ nondestructive evaluation(NDE)for structural health monitoring(SHM)of reinforced concrete(RC)structures strengthened with fiber rei...The capability of embedded piezoelectric wafer active sensors(PWAS)to perform in-situ nondestructive evaluation(NDE)for structural health monitoring(SHM)of reinforced concrete(RC)structures strengthened with fiber reinforced polymer(FRP)composite overlays is explored.First,the disbond detection method were developed on coupon specimens consisting of concrete blocks covered with an FRP composite layer.It was found that the presence of a disbond crack drastically changes the electromecfianical(E/M)impedance spectrum lneasurcd at the PWAS terlninals.The spectral changes depend on the distance between the PWAS and the crack tip.Second,large scale experiments were conducted on a RC beam strengthened with carbon fiber reinforced polymer(CFRP)composite overlay.The beam was subject to an accelerated fatigue load regime in a three-point bending configuration up to a total of 807,415 cycles.During these fatigue tests,the CFRP overlay experienced disbonding beginning at about 500,000 cycles.The PWAS were able to detect the disbonding before it could be reliably seen by visual inspection.Good correlation between the PWAS readings and the position and extent of disbond damage was observed.These preliminary results demonstrate the potential of PWAS technology for SHM of RC structures strengthened with FRP composite overlays.展开更多
For traditional piezoelectric sensors based on poled ceramics,a low curie tem-perature(T_(c))is a fatal flaw due to the depolarization phenomenon.However,in this study,we find the low T_(c) would be a benefit for flex...For traditional piezoelectric sensors based on poled ceramics,a low curie tem-perature(T_(c))is a fatal flaw due to the depolarization phenomenon.However,in this study,we find the low T_(c) would be a benefit for flex-ible piezoelectric sensors because small alterations of force trig-ger large changes in polarization.BaTi_(0.88)Sn_(0.12)O_(3)(BTS)with high piezoelectric coefficient and low T_(c) close to human body temperature is taken as an example for materials of this kind.Continuous piezo-electric BTS films were deposited on the flexible glass fiber fabrics(GFF),self-powered sensors based on the ultra-thin,superflexible,and polarization-free BTS-GFF/PVDF composite piezoelectric films are used for human motion sensing.In the low force region(1-9 N),the sensors have the outstanding performance with voltage sensitivity of 1.23 V N^(−1) and current sensitivity of 41.0 nA N^(−1).The BTS-GFF/PVDF sensors can be used to detect the tiny forces of falling water drops,finger joint motion,tiny surface deformation,and fatigue driving with high sensitivity.This work provides a new paradigm for the preparation of superflexible,highly sensitive and wearable self-powered piezoelectric sensors,and this kind of sensors will have a broad application prospect in the fields of medical rehabilitation,human motion monitoring,and intelligent robot.展开更多
Structural health monitoring(SHM)is recognized as an efficient tool to interpret the reliability of a wide variety of infrastructures.To identify the structural abnormality by utilizing the electromechanical coupling ...Structural health monitoring(SHM)is recognized as an efficient tool to interpret the reliability of a wide variety of infrastructures.To identify the structural abnormality by utilizing the electromechanical coupling property of piezoelectric transducers,the electromechanical impedance(EMI)approach is preferred.However,in real-time SHM applications,the monitored structure is exposed to several varying environmental and operating conditions(EOCs).The previous study has recognized the temperature variations as one of the serious EOCs that affect the optimal performance of the damage inspection process.In this framework,an experimental setup is developed in current research to identify the presence of fatigue crack in stainless steel(304)beam using EMI approach and estimate the effect of temperature variations on the electrical impedance of the piezoelectric sensors.A regular series of experiments are executed in a controlled temperature environment(25°C–160°C)using 202 V1 Constant Temperature Drying Oven Chamber(Q/TBXR20-2005).It has been observed that the dielectric constantð"33 TÞwhich is recognized as the temperature-dependent constant of PZT sensor has sufficiently influenced the electrical impedance signature.Moreover,the effective frequency shift(EFS)approach is optimized in term of significant temperature compensation for the current impedance signature of PZT sensor relative to the reference signature at the extended frequency bandwidth of the developed measurement system with better outcomes as compared to the previous literature work.Hence,the current study also deals efficiently with the critical issue of the width of the frequency band for temperature compensation based on the frequency shift in SHM.The results of the experimental study demonstrate that the proposed methodology is qualified for the damage inspection in real-time monitoring applications under the temperature variations.It is capable to exclude one of the major reasons of false fault diagnosis by compensating the consequence of elevated temperature at extended frequency bandwidth in SHM.展开更多
We present a new polymer quartz piezoelectric crystal sensor that takes a quartz piezoelectric crystal as the basal material and a nanometer nonmetallic polymer thin film as the surface coating based on the principle ...We present a new polymer quartz piezoelectric crystal sensor that takes a quartz piezoelectric crystal as the basal material and a nanometer nonmetallic polymer thin film as the surface coating based on the principle of quartz crystal microbalance(QCM). The new sensor can be used to detect the characteristic materials of a volatile liquid. A mechanical model of the new sensor was built, whose structure was a thin circle plate composing of polytef/quartz piezoelectric/polytef. The mechanical model had a diameter of 8 mm and a thickness of 170 μm. The vibration state of the model was simulated by software ANSYS after the physical parameters and the boundary condition of the new sensor were set. According to the results of experiments, we set up a frequency range from 9.995850 MHz to 9.997225 MHz, 17 kinds of frequencies and modes of vibration were obtained within this range. We found a special frequency fspof 9.996358 MHz. When the resonant frequency of the new sensor's mechanical model reached the special frequency, a special phenomenon occurred. In this case, the amplitude of the center point O on the mechanical model reached the maximum value. At the same time, the minimum absolute difference between the simulated frequency based on the ANSYS software and the experimental measured stable frequency was reached. The research showed that the design of the new polymer quartz piezoelectric crystal sensor perfectly conforms to the principle of QCM. A special frequency value fspwas found and subsequently became one of the most important parameters in the new sensor design.展开更多
Based on the needs of the oscillation equation and frequency stability, three oscillation conditions are proposed and have been experimentally verified for an electrode-separated piezoelectric sensor (ESPS ) in electr...Based on the needs of the oscillation equation and frequency stability, three oscillation conditions are proposed and have been experimentally verified for an electrode-separated piezoelectric sensor (ESPS ) in electrolyte solutions. The present paper covers the dependence of the minimum cell constant needed for the ESPS on solution conductivity. The oscillation conditions of the classical liquid piezoelectric sensor are discussed. The 'cease-to-oscillate' frequencies of the ESPS were measured.展开更多
An unexpected frequency response for a piezoelectric quartz crystal (PQC) sensor to liquid density and viscosity was reported. For a PQC oscillating in a liquid phase, the frequency shifts (?f ) show a wave-shape re...An unexpected frequency response for a piezoelectric quartz crystal (PQC) sensor to liquid density and viscosity was reported. For a PQC oscillating in a liquid phase, the frequency shifts (?f ) show a wave-shape response to liquid density (ρ) and viscosity (η) in fine structure, if the longitudinal wave effect was not eliminated. This result is different from the well-known linear relationship between of ?f and (ρη)1/2. An oscillating frequency-temperature curve of the sensor was observed and explained.展开更多
A piezoelectric sensor responsive to vitamin B 1 was fabricated based on the vitamin B 1 tetraphenylborate ion pair. The general performance characteristics of the sensor are presented here. The proposed sensor sho...A piezoelectric sensor responsive to vitamin B 1 was fabricated based on the vitamin B 1 tetraphenylborate ion pair. The general performance characteristics of the sensor are presented here. The proposed sensor showed a wide working pH range, a good sensitivity and selectivity. The response range is between 1 0×10 -7 -4 9×10 -5 mol/L with a detection limit of 8×10 -8 mol/L at pH 4 0. The selectivity should be attributed to the preferential adsorption of the component ion on the membrane/solution interface. The adsorption behavior of vitamin B 1 on the crystal surface was investigated with a quartz crystal impedance(QCI) system.展开更多
n oscillation condition was proposed and experimentally verified for an elec-troderaeparated piezoelectric sensor (ESPS) in non-electrolyte liquid, it was ex-pressed as , where C_s is the solution capaci-tance , R_q, ...n oscillation condition was proposed and experimentally verified for an elec-troderaeparated piezoelectric sensor (ESPS) in non-electrolyte liquid, it was ex-pressed as , where C_s is the solution capaci-tance , R_q, C_o and w are the motional resistance , static capacitance and resonant an-gle frequency of the crystal , respectively. And Y-tgθ, where θ is the phase shift inthe oscillator. The relationships between the minimum cell constant needed for ES-PS to oscillate and each of the following parameters, permittivity, density and vis-cosity of the liquid as well as the oscillator phase shift were discussed. The″ cease-to-oscillate″ frequency of ESPS was measured. The oscillation ability of ESPS in-creases with increasing permittivity or decreasing density and viscosity of the liq-uid. An oscillator with a larger Y value is helpful to drive ESPS.展开更多
Based on the two-dimensional constitutive relationships of the piezoelectric material, an analytical solution for an intelligent beam excited by a pair of piezoelectric actuators is derived. With the solution the forc...Based on the two-dimensional constitutive relationships of the piezoelectric material, an analytical solution for an intelligent beam excited by a pair of piezoelectric actuators is derived. With the solution the force and moment generated by two piezoelectric actuators and a pair of piezoelectric actuator/sensor are obtained. Examples of a cantilever piezo electric laminated beam or a simply supported piezoelectric laminated beam, applied with voltages, are given.展开更多
In vibration active control of composite structures, piezoelectricsensors/actuators are usually bonded to the surface of a host structure. Debonding of piezoelectricsensors/actuators can result in significant changes ...In vibration active control of composite structures, piezoelectricsensors/actuators are usually bonded to the surface of a host structure. Debonding of piezoelectricsensors/actuators can result in significant changes to the static and dynamic response. In thepresent paper, an novel Enhanced Assumed Strain(EAS) piezoelectric solid element formulation isdeveloped for vibration active control of laminated structures bonded with piezoelectric sensors andactuators. Unlike the conventional brick elements, the present formulation is very reliable, moreaccurate, and computationally efficient and can be used to model the response of shell structuresbesides thin plates. Delaminations are modeled by pairs of nodes with the same coordinates butdifferent node numbers, and numerical results demonstrate the performance of the element and theglobal and local effects of debonding sensors/actuators on the dynamics of the adaptive laminates.展开更多
The finite element dynamic model for integrated structures containing distributed piezoelectric sensors and actuators ( S/As ) is formulated with a new piezoelectric plate bending element in this paper. The problem of...The finite element dynamic model for integrated structures containing distributed piezoelectric sensors and actuators ( S/As ) is formulated with a new piezoelectric plate bending element in this paper. The problem of active vibration control and suppression of integrated structures is investigated under constant gain negative velocity feedback control law. A general method for active vibration control and suppression of integrated structures is presented. Finally, numerical example is given to illustrate the validity of the method proposed in this paper.展开更多
This paper presents a new pattern recognition system for Chinese spirit identification by using the polymer quartz piezoelectric crystal sensor based e-nose. The sensors are designed based on quartz crystal microbala...This paper presents a new pattern recognition system for Chinese spirit identification by using the polymer quartz piezoelectric crystal sensor based e-nose. The sensors are designed based on quartz crystal microbalance(QCM) principle,and they could capture different vibration frequency signal values for Chinese spirit identification. For each sensor in an8-channel sensor array, seven characteristic values of the original vibration frequency signal values, i.e., average value(A),root-mean-square value(RMS), shape factor value(S_f), crest factor value(C_f), impulse factor value(I_f), clearance factor value(CL_f), kurtosis factor value(K_v) are first extracted. Then the dimension of the characteristic values is reduced by the principle components analysis(PCA) method. Finally the back propagation(BP) neutral network algorithm is used to recognize Chinese spirits. The experimental results show that the recognition rate of six kinds of Chinese spirits is 93.33% and our proposed new pattern recognition system can identify Chinese spirits effectively.展开更多
A two-year field observation of saltation activity was carried out at Tazhong area, the hinterland area of the Taklimakan Desert with highly frequent dust storms. From 1 September 2008 to 31 August 2010, a piezoelectr...A two-year field observation of saltation activity was carried out at Tazhong area, the hinterland area of the Taklimakan Desert with highly frequent dust storms. From 1 September 2008 to 31 August 2010, a piezoelectric saltation sensor (Sensit) was used to continuously collect the data on saltation activity at a level sand surface. Analysis on the data suggests that saltation activity can occur at any time of the year when conditions are favorable; however, the necessary conditions are rarely satisfied in most time. In the daytime of spring or summer, saltation activity can persist even over a continuous one-hour-or-so period. It is found that, from 1 September 2008 to 31 August 2010, saltation activity accounts for more than 3% of the total yearly time, and it tends to peak in spring and summer months with strong winds. During winter months when winds are weak, however, it is often at a minimum. It seems that precipitation does not appear to be significant in reducing saltation activity in arid regions like Tazhong.展开更多
With the rapid development of internet of things,self-powered touch sensors made of piezoelectric fluorinated polymers have attracted significant interest because they can constantly convert mechanical energy into ele...With the rapid development of internet of things,self-powered touch sensors made of piezoelectric fluorinated polymers have attracted significant interest because they can constantly convert mechanical energy into electrical energy without external power supply.However,it is still challenging to fabricate fluorinated polymer films with good adhesion and high output performance with a large-scale and low-cost method while maintaining high transparency,which are extremely important for simultaneous optical detection and electromechanical transduction.In this work,we demonstrate that the incorporation of a molecular ferroelectric-dabcoHReO_(4)(DH)into poly(vinylidene difluoride)(PVDF)solution enables high-throughput and low-temperature processing of flexible and transparent piezoelectric films by scalable processing method.The effects of multiaxial DH are multiple.First,DH can trigger the phase transition of PVDF fromα-toβ-phase and realize the orderly orientation of PVDF,which guarantees higher piezoelectric performance without any additional electrical poling process.Second,the hydrophilic nature of DH can improve the adhesion properties of PVDF,which in turn improve the stability and durability of the devices.By optimizing the fabrication processes,the transmittance of the piezoelectric touch sensors based on PVDF films and Ag nanowires coated poly(ethylene terephthalate)electrodes can be higher than 94%.The piezoelectric voltage constant g;of the transparent films can reach to 1.2 V·m·N;,which is at least three times higher than the commercially available PVDF films obtained by stretching.These results indicate that the flexible piezoelectric sensors have potential applications in transparent electronic devices for mechanical sensing and energy harvesting.展开更多
The frequency responses of a langasite crystal microbalance (LCM) in liquid phase were investigated. It was shown that the LCM possessed much stronger oscillating ability in liquid phase than that of the commonly us...The frequency responses of a langasite crystal microbalance (LCM) in liquid phase were investigated. It was shown that the LCM possessed much stronger oscillating ability in liquid phase than that of the commonly used quartz crystal microbalance (QCM). The frequency shifts of the LCM to the changes in mass loading, as well as viscosity and density of the liquid were measured. The LCM was applied to monitor the adsorption process of an ionic liquid film to ethanol vapor.展开更多
Structural health monitoring employs different tools and techniques to provide a prediction for damages that occur in various structures.Damages such as debond and cracks in concrete-filled steel tube column(CFST)are ...Structural health monitoring employs different tools and techniques to provide a prediction for damages that occur in various structures.Damages such as debond and cracks in concrete-filled steel tube column(CFST)are serious defects that threaten the integrity of the structural members.Ultrasonic waves monitoring applied to the CFST column is necessary to detect damages and quantify their size.However,without appropriate signal processing tools,the results of the monitoring process could not be crucial.In this research,a monitoring process based on a Multiphysics numerical simulation study was carried out.Two signal processing tools:short time Fourier transform(STFT)and Welch Power Spectral Density Estimate(PSD)were used to analyse the captured raw signals.The STFT spectrogram was effective in identifying the different size of damage based on a graphical interpretation.The results show that the increasing of frequency of the excited signal give a better results.The increase in peak magnitude values in Welch PSD was found to be proportionate to the change in damage length whereas the damage depth has a less effect.The results for the crack size identification were less promising than those of debond damage because of the different type of the signal’s propagation path.Simulation process conducted by COMSOL software has proved the validity of the adopted signal processing techniques in detecting such damages in CFST columns.展开更多
Bird strike studies on typical aluminium leading edges of the Horizontal Tail (HT) with and without Glass Fibre Shape Memory Polymer (GF-SMP) layers are carried out. A one-fifth scaled model of HT is designed and fabr...Bird strike studies on typical aluminium leading edges of the Horizontal Tail (HT) with and without Glass Fibre Shape Memory Polymer (GF-SMP) layers are carried out. A one-fifth scaled model of HT is designed and fabricated. The parameters like bird dimension and energy requirements are accordingly scaled to conduct the bird strike tests. Two leading-edge components have been prepared, namely one with AL 2024-T3 aluminium alloy and the other specimen of the same dimension and material, additionally having GF-SMP composite layers inside the metallic leading edge, in order to enhance its impact resistance. Bird strike experiments are performed on both the specimens, impacting at the centre of the leading edge in the nose tip region with an impact velocity of 115 m/s. The test component is instrumented with linear post-yield strain gauges on the top side and the PZT sensors on the bottom. Furthermore, the impact scenario is monitored using a high-speed camera at 7000 fps. The bird strike event is simulated by an equation of state model, in which the mass of the bird is idealized using smooth particle hydrodynamics element in PAMCRASH<sup>?</sup><sup> </sup>explicit solver. The strain magnitude and its pattern including time duration are found to be in a good correlation between test and simulation. Key metrics are evaluated to devise an SHM scheme for the load and impact event monitoring using strain gauges and PZT sensors. GF-SMP layers have improved the impact resistance of the aluminium leading edge which is certainly encouraging towards finding a novel solution for the high-velocity impact.展开更多
During the whole service lifetime of aircraft structures with composite materials,impacts are inevitable and can usually cause severe but barely visible damages.Since the occurrences of impact are random and unpredict...During the whole service lifetime of aircraft structures with composite materials,impacts are inevitable and can usually cause severe but barely visible damages.Since the occurrences of impact are random and unpredictable,it is a hotspot direction to develop an online impact monitoring system that can meet strict limitations of aerospace applications including small size,light weight,and low power consumption.Piezoelectric(PZT)sensor,being able to generate impact response signals with no external power and cover a large-scale structure with only a small amount of them,is a promising choice.Meanwhile,for real systems,networks with multiple nodes are normally required to monitor large-scale structures in a global way to identify any impact localization confliction,yet the existing studies are mostly evaluated with single nodes instead of networks.Therefore,in this paper,based on a new low-power node designed,a Bluetooth-based digital impact monitoring PZT sensor network is proposed for the first time with its global confliction-solving impact localization method.Evaluations of the system as a network are researched and analyzed on a complex real aircraft wing box for a global confliction-solving impact localization,showing a satisfying high accuracy.展开更多
Fabric-based composites with superior mechanical properties and excellent perceptive function are highly desirable.However,it remains a huge challenge to attain structure-function integration,especially for hybrid fab...Fabric-based composites with superior mechanical properties and excellent perceptive function are highly desirable.However,it remains a huge challenge to attain structure-function integration,especially for hybrid fabric composites.Herein,a skin-inspired interface modification strategy is proposed toward this target by constructing a hybrid smart fabric system consisting of two types of smart fabrics:carbon nanotube(CNT)/MXene-modified aramid fabrics and zinc oxide nanorod(ZnO NR)-modified carbon fabrics.Based on that,flexible piezoelectric pressure sensors with skin-like hierarchical perception interfaces are fabricated,which demonstrate superb sensitivity of 2.39 V·kPa^(-1)and are capable of various wearable monitoring tasks.Besides,the interface-modified hybrid fabric reinforced plastics can also be fabricated,which are proven to possess 13.6%higher tensile strength,10.1%elastic modulus.More impressively,their average energy absorption can be improved by 111.9%,accompanied with inherent damage alert capability.This offers a paradigm to fabricate structure-function integrated hybrid smart fabric composites for the smart clothing and intelligent aerial vehicles.展开更多
Monitoring high-temperature vibrations is critical in aerospace engineering,industrial manufacturing,and energy production,where harsh conditions necessitate robust vibration sensors for detecting anomalous signals.Ho...Monitoring high-temperature vibrations is critical in aerospace engineering,industrial manufacturing,and energy production,where harsh conditions necessitate robust vibration sensors for detecting anomalous signals.However,the accuracy of such sensors is often compromised by crosstalk between temperature and vibration signals.This study introduces a high-temperature vibration sensor based on langasite(LGS)surface acoustic wave(SAW)technology,designed to withstand temperatures up to 500℃.The sensor demonstrates high sensitivity,ranging from 12.54 kHz/g at 25℃ to 15.63 k Hz/g at 500℃.A comprehensive mechanical and electrical coupling model for the SAW vibration sensor was developed by integrating theoretical equations with numerical simulations to optimize the sensor's performance.Additionally,a novel decoupling algorithm for temperature and vibration was established,achieving thermomechanical decoupling with precise vibration parameters.Experimental results indicated a maximum relative deviation of 4.67%for the algorithm.In conclusion,the proposed LGS SAW vibration sensor emerges as a promising solution for the accurate detection of multiple parameters in high-temperature vibration monitoring.展开更多
基金the National Seienee Foundation through grants NSF#CMS-9908293 and NSF INT-9904493the Federal Highway Administration and the South Carolina Department of TransPortation(projeet Number 614)
文摘The capability of embedded piezoelectric wafer active sensors(PWAS)to perform in-situ nondestructive evaluation(NDE)for structural health monitoring(SHM)of reinforced concrete(RC)structures strengthened with fiber reinforced polymer(FRP)composite overlays is explored.First,the disbond detection method were developed on coupon specimens consisting of concrete blocks covered with an FRP composite layer.It was found that the presence of a disbond crack drastically changes the electromecfianical(E/M)impedance spectrum lneasurcd at the PWAS terlninals.The spectral changes depend on the distance between the PWAS and the crack tip.Second,large scale experiments were conducted on a RC beam strengthened with carbon fiber reinforced polymer(CFRP)composite overlay.The beam was subject to an accelerated fatigue load regime in a three-point bending configuration up to a total of 807,415 cycles.During these fatigue tests,the CFRP overlay experienced disbonding beginning at about 500,000 cycles.The PWAS were able to detect the disbonding before it could be reliably seen by visual inspection.Good correlation between the PWAS readings and the position and extent of disbond damage was observed.These preliminary results demonstrate the potential of PWAS technology for SHM of RC structures strengthened with FRP composite overlays.
基金This work is financially supported by the basic research project of science and technology of Shanghai(No.20JC1415000)National Natural Science Foundation of China(Nos.11874257 and 52032012)the Fund for Science and Technology Innovation of Shanghai Jiao Tong University.
文摘For traditional piezoelectric sensors based on poled ceramics,a low curie tem-perature(T_(c))is a fatal flaw due to the depolarization phenomenon.However,in this study,we find the low T_(c) would be a benefit for flex-ible piezoelectric sensors because small alterations of force trig-ger large changes in polarization.BaTi_(0.88)Sn_(0.12)O_(3)(BTS)with high piezoelectric coefficient and low T_(c) close to human body temperature is taken as an example for materials of this kind.Continuous piezo-electric BTS films were deposited on the flexible glass fiber fabrics(GFF),self-powered sensors based on the ultra-thin,superflexible,and polarization-free BTS-GFF/PVDF composite piezoelectric films are used for human motion sensing.In the low force region(1-9 N),the sensors have the outstanding performance with voltage sensitivity of 1.23 V N^(−1) and current sensitivity of 41.0 nA N^(−1).The BTS-GFF/PVDF sensors can be used to detect the tiny forces of falling water drops,finger joint motion,tiny surface deformation,and fatigue driving with high sensitivity.This work provides a new paradigm for the preparation of superflexible,highly sensitive and wearable self-powered piezoelectric sensors,and this kind of sensors will have a broad application prospect in the fields of medical rehabilitation,human motion monitoring,and intelligent robot.
基金the National Science and Technology Major Project of China(No.2018ZX04011001)for this study。
文摘Structural health monitoring(SHM)is recognized as an efficient tool to interpret the reliability of a wide variety of infrastructures.To identify the structural abnormality by utilizing the electromechanical coupling property of piezoelectric transducers,the electromechanical impedance(EMI)approach is preferred.However,in real-time SHM applications,the monitored structure is exposed to several varying environmental and operating conditions(EOCs).The previous study has recognized the temperature variations as one of the serious EOCs that affect the optimal performance of the damage inspection process.In this framework,an experimental setup is developed in current research to identify the presence of fatigue crack in stainless steel(304)beam using EMI approach and estimate the effect of temperature variations on the electrical impedance of the piezoelectric sensors.A regular series of experiments are executed in a controlled temperature environment(25°C–160°C)using 202 V1 Constant Temperature Drying Oven Chamber(Q/TBXR20-2005).It has been observed that the dielectric constantð"33 TÞwhich is recognized as the temperature-dependent constant of PZT sensor has sufficiently influenced the electrical impedance signature.Moreover,the effective frequency shift(EFS)approach is optimized in term of significant temperature compensation for the current impedance signature of PZT sensor relative to the reference signature at the extended frequency bandwidth of the developed measurement system with better outcomes as compared to the previous literature work.Hence,the current study also deals efficiently with the critical issue of the width of the frequency band for temperature compensation based on the frequency shift in SHM.The results of the experimental study demonstrate that the proposed methodology is qualified for the damage inspection in real-time monitoring applications under the temperature variations.It is capable to exclude one of the major reasons of false fault diagnosis by compensating the consequence of elevated temperature at extended frequency bandwidth in SHM.
基金Project supported by the National High Technology Research and Developmem Program of China ~Grant No. 2013AA030901).
文摘We present a new polymer quartz piezoelectric crystal sensor that takes a quartz piezoelectric crystal as the basal material and a nanometer nonmetallic polymer thin film as the surface coating based on the principle of quartz crystal microbalance(QCM). The new sensor can be used to detect the characteristic materials of a volatile liquid. A mechanical model of the new sensor was built, whose structure was a thin circle plate composing of polytef/quartz piezoelectric/polytef. The mechanical model had a diameter of 8 mm and a thickness of 170 μm. The vibration state of the model was simulated by software ANSYS after the physical parameters and the boundary condition of the new sensor were set. According to the results of experiments, we set up a frequency range from 9.995850 MHz to 9.997225 MHz, 17 kinds of frequencies and modes of vibration were obtained within this range. We found a special frequency fspof 9.996358 MHz. When the resonant frequency of the new sensor's mechanical model reached the special frequency, a special phenomenon occurred. In this case, the amplitude of the center point O on the mechanical model reached the maximum value. At the same time, the minimum absolute difference between the simulated frequency based on the ANSYS software and the experimental measured stable frequency was reached. The research showed that the design of the new polymer quartz piezoelectric crystal sensor perfectly conforms to the principle of QCM. A special frequency value fspwas found and subsequently became one of the most important parameters in the new sensor design.
文摘Based on the needs of the oscillation equation and frequency stability, three oscillation conditions are proposed and have been experimentally verified for an electrode-separated piezoelectric sensor (ESPS ) in electrolyte solutions. The present paper covers the dependence of the minimum cell constant needed for the ESPS on solution conductivity. The oscillation conditions of the classical liquid piezoelectric sensor are discussed. The 'cease-to-oscillate' frequencies of the ESPS were measured.
基金supported by the National Natural Science Foundation of China(No.20275021)
文摘An unexpected frequency response for a piezoelectric quartz crystal (PQC) sensor to liquid density and viscosity was reported. For a PQC oscillating in a liquid phase, the frequency shifts (?f ) show a wave-shape response to liquid density (ρ) and viscosity (η) in fine structure, if the longitudinal wave effect was not eliminated. This result is different from the well-known linear relationship between of ?f and (ρη)1/2. An oscillating frequency-temperature curve of the sensor was observed and explained.
基金Supported by the National Natural Science Foundation of China( No.2 0 0 75 0 0 7)
文摘A piezoelectric sensor responsive to vitamin B 1 was fabricated based on the vitamin B 1 tetraphenylborate ion pair. The general performance characteristics of the sensor are presented here. The proposed sensor showed a wide working pH range, a good sensitivity and selectivity. The response range is between 1 0×10 -7 -4 9×10 -5 mol/L with a detection limit of 8×10 -8 mol/L at pH 4 0. The selectivity should be attributed to the preferential adsorption of the component ion on the membrane/solution interface. The adsorption behavior of vitamin B 1 on the crystal surface was investigated with a quartz crystal impedance(QCI) system.
文摘n oscillation condition was proposed and experimentally verified for an elec-troderaeparated piezoelectric sensor (ESPS) in non-electrolyte liquid, it was ex-pressed as , where C_s is the solution capaci-tance , R_q, C_o and w are the motional resistance , static capacitance and resonant an-gle frequency of the crystal , respectively. And Y-tgθ, where θ is the phase shift inthe oscillator. The relationships between the minimum cell constant needed for ES-PS to oscillate and each of the following parameters, permittivity, density and vis-cosity of the liquid as well as the oscillator phase shift were discussed. The″ cease-to-oscillate″ frequency of ESPS was measured. The oscillation ability of ESPS in-creases with increasing permittivity or decreasing density and viscosity of the liq-uid. An oscillator with a larger Y value is helpful to drive ESPS.
文摘Based on the two-dimensional constitutive relationships of the piezoelectric material, an analytical solution for an intelligent beam excited by a pair of piezoelectric actuators is derived. With the solution the force and moment generated by two piezoelectric actuators and a pair of piezoelectric actuator/sensor are obtained. Examples of a cantilever piezo electric laminated beam or a simply supported piezoelectric laminated beam, applied with voltages, are given.
文摘In vibration active control of composite structures, piezoelectricsensors/actuators are usually bonded to the surface of a host structure. Debonding of piezoelectricsensors/actuators can result in significant changes to the static and dynamic response. In thepresent paper, an novel Enhanced Assumed Strain(EAS) piezoelectric solid element formulation isdeveloped for vibration active control of laminated structures bonded with piezoelectric sensors andactuators. Unlike the conventional brick elements, the present formulation is very reliable, moreaccurate, and computationally efficient and can be used to model the response of shell structuresbesides thin plates. Delaminations are modeled by pairs of nodes with the same coordinates butdifferent node numbers, and numerical results demonstrate the performance of the element and theglobal and local effects of debonding sensors/actuators on the dynamics of the adaptive laminates.
文摘The finite element dynamic model for integrated structures containing distributed piezoelectric sensors and actuators ( S/As ) is formulated with a new piezoelectric plate bending element in this paper. The problem of active vibration control and suppression of integrated structures is investigated under constant gain negative velocity feedback control law. A general method for active vibration control and suppression of integrated structures is presented. Finally, numerical example is given to illustrate the validity of the method proposed in this paper.
基金Project supported by the National High Technology Research and Development Program of China(Grant No.2013AA030901)the Fundamental Research Funds for the Central Universities,China(Grant No.FRF-TP-14-120A2)
文摘This paper presents a new pattern recognition system for Chinese spirit identification by using the polymer quartz piezoelectric crystal sensor based e-nose. The sensors are designed based on quartz crystal microbalance(QCM) principle,and they could capture different vibration frequency signal values for Chinese spirit identification. For each sensor in an8-channel sensor array, seven characteristic values of the original vibration frequency signal values, i.e., average value(A),root-mean-square value(RMS), shape factor value(S_f), crest factor value(C_f), impulse factor value(I_f), clearance factor value(CL_f), kurtosis factor value(K_v) are first extracted. Then the dimension of the characteristic values is reduced by the principle components analysis(PCA) method. Finally the back propagation(BP) neutral network algorithm is used to recognize Chinese spirits. The experimental results show that the recognition rate of six kinds of Chinese spirits is 93.33% and our proposed new pattern recognition system can identify Chinese spirits effectively.
基金funded by the National Natural Science Foundation of China (41175017,41175140)the R & DSpecial Fund for Public Welfare Industry (meteorology)(GYHY201006012,GYHY201106025)
文摘A two-year field observation of saltation activity was carried out at Tazhong area, the hinterland area of the Taklimakan Desert with highly frequent dust storms. From 1 September 2008 to 31 August 2010, a piezoelectric saltation sensor (Sensit) was used to continuously collect the data on saltation activity at a level sand surface. Analysis on the data suggests that saltation activity can occur at any time of the year when conditions are favorable; however, the necessary conditions are rarely satisfied in most time. In the daytime of spring or summer, saltation activity can persist even over a continuous one-hour-or-so period. It is found that, from 1 September 2008 to 31 August 2010, saltation activity accounts for more than 3% of the total yearly time, and it tends to peak in spring and summer months with strong winds. During winter months when winds are weak, however, it is often at a minimum. It seems that precipitation does not appear to be significant in reducing saltation activity in arid regions like Tazhong.
基金financially supported by the National Natural Science Foundation of China(Nos.51973150,51473112 and 21674076)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(No.19KJA320009)a Project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)。
文摘With the rapid development of internet of things,self-powered touch sensors made of piezoelectric fluorinated polymers have attracted significant interest because they can constantly convert mechanical energy into electrical energy without external power supply.However,it is still challenging to fabricate fluorinated polymer films with good adhesion and high output performance with a large-scale and low-cost method while maintaining high transparency,which are extremely important for simultaneous optical detection and electromechanical transduction.In this work,we demonstrate that the incorporation of a molecular ferroelectric-dabcoHReO_(4)(DH)into poly(vinylidene difluoride)(PVDF)solution enables high-throughput and low-temperature processing of flexible and transparent piezoelectric films by scalable processing method.The effects of multiaxial DH are multiple.First,DH can trigger the phase transition of PVDF fromα-toβ-phase and realize the orderly orientation of PVDF,which guarantees higher piezoelectric performance without any additional electrical poling process.Second,the hydrophilic nature of DH can improve the adhesion properties of PVDF,which in turn improve the stability and durability of the devices.By optimizing the fabrication processes,the transmittance of the piezoelectric touch sensors based on PVDF films and Ag nanowires coated poly(ethylene terephthalate)electrodes can be higher than 94%.The piezoelectric voltage constant g;of the transparent films can reach to 1.2 V·m·N;,which is at least three times higher than the commercially available PVDF films obtained by stretching.These results indicate that the flexible piezoelectric sensors have potential applications in transparent electronic devices for mechanical sensing and energy harvesting.
基金supported by the National Natural Science Foundation of China(No.20275021)the Open Foundation of the State Key Laboratory of Chemo/Biosensing and Chemometrics,Hunan University.
文摘The frequency responses of a langasite crystal microbalance (LCM) in liquid phase were investigated. It was shown that the LCM possessed much stronger oscillating ability in liquid phase than that of the commonly used quartz crystal microbalance (QCM). The frequency shifts of the LCM to the changes in mass loading, as well as viscosity and density of the liquid were measured. The LCM was applied to monitor the adsorption process of an ionic liquid film to ethanol vapor.
文摘Structural health monitoring employs different tools and techniques to provide a prediction for damages that occur in various structures.Damages such as debond and cracks in concrete-filled steel tube column(CFST)are serious defects that threaten the integrity of the structural members.Ultrasonic waves monitoring applied to the CFST column is necessary to detect damages and quantify their size.However,without appropriate signal processing tools,the results of the monitoring process could not be crucial.In this research,a monitoring process based on a Multiphysics numerical simulation study was carried out.Two signal processing tools:short time Fourier transform(STFT)and Welch Power Spectral Density Estimate(PSD)were used to analyse the captured raw signals.The STFT spectrogram was effective in identifying the different size of damage based on a graphical interpretation.The results show that the increasing of frequency of the excited signal give a better results.The increase in peak magnitude values in Welch PSD was found to be proportionate to the change in damage length whereas the damage depth has a less effect.The results for the crack size identification were less promising than those of debond damage because of the different type of the signal’s propagation path.Simulation process conducted by COMSOL software has proved the validity of the adopted signal processing techniques in detecting such damages in CFST columns.
文摘Bird strike studies on typical aluminium leading edges of the Horizontal Tail (HT) with and without Glass Fibre Shape Memory Polymer (GF-SMP) layers are carried out. A one-fifth scaled model of HT is designed and fabricated. The parameters like bird dimension and energy requirements are accordingly scaled to conduct the bird strike tests. Two leading-edge components have been prepared, namely one with AL 2024-T3 aluminium alloy and the other specimen of the same dimension and material, additionally having GF-SMP composite layers inside the metallic leading edge, in order to enhance its impact resistance. Bird strike experiments are performed on both the specimens, impacting at the centre of the leading edge in the nose tip region with an impact velocity of 115 m/s. The test component is instrumented with linear post-yield strain gauges on the top side and the PZT sensors on the bottom. Furthermore, the impact scenario is monitored using a high-speed camera at 7000 fps. The bird strike event is simulated by an equation of state model, in which the mass of the bird is idealized using smooth particle hydrodynamics element in PAMCRASH<sup>?</sup><sup> </sup>explicit solver. The strain magnitude and its pattern including time duration are found to be in a good correlation between test and simulation. Key metrics are evaluated to devise an SHM scheme for the load and impact event monitoring using strain gauges and PZT sensors. GF-SMP layers have improved the impact resistance of the aluminium leading edge which is certainly encouraging towards finding a novel solution for the high-velocity impact.
基金supported by the National Natural Science Foundation of China(Nos.51921003,51975292 and 52275153)the Outstanding Youth Foundation of Jiangsu Province of China(No.BK20211519)+2 种基金the Research Fund of State Key Laboratory of Mechanics and Control of Mechanical Structures,China(Nanjing University of Aeronautics and Astronautics,No.MCMS-I-0521K01)the Fund of Prospective Layout of Scientific Research for Nanjing University of Aeronautics and Astronautics,Chinathe Priority Academic Program Development of Jiangsu Higher Education Institutions,China。
文摘During the whole service lifetime of aircraft structures with composite materials,impacts are inevitable and can usually cause severe but barely visible damages.Since the occurrences of impact are random and unpredictable,it is a hotspot direction to develop an online impact monitoring system that can meet strict limitations of aerospace applications including small size,light weight,and low power consumption.Piezoelectric(PZT)sensor,being able to generate impact response signals with no external power and cover a large-scale structure with only a small amount of them,is a promising choice.Meanwhile,for real systems,networks with multiple nodes are normally required to monitor large-scale structures in a global way to identify any impact localization confliction,yet the existing studies are mostly evaluated with single nodes instead of networks.Therefore,in this paper,based on a new low-power node designed,a Bluetooth-based digital impact monitoring PZT sensor network is proposed for the first time with its global confliction-solving impact localization method.Evaluations of the system as a network are researched and analyzed on a complex real aircraft wing box for a global confliction-solving impact localization,showing a satisfying high accuracy.
基金supported by the National Natural Science Foundation of China(Nos.52205298,52375280 and 51775022)Project funded by China Postdoctoral Science Foundation(Nos.2022M710302 and 2022TQ0023)the Fundamental Research Funds for the Central Universities.
文摘Fabric-based composites with superior mechanical properties and excellent perceptive function are highly desirable.However,it remains a huge challenge to attain structure-function integration,especially for hybrid fabric composites.Herein,a skin-inspired interface modification strategy is proposed toward this target by constructing a hybrid smart fabric system consisting of two types of smart fabrics:carbon nanotube(CNT)/MXene-modified aramid fabrics and zinc oxide nanorod(ZnO NR)-modified carbon fabrics.Based on that,flexible piezoelectric pressure sensors with skin-like hierarchical perception interfaces are fabricated,which demonstrate superb sensitivity of 2.39 V·kPa^(-1)and are capable of various wearable monitoring tasks.Besides,the interface-modified hybrid fabric reinforced plastics can also be fabricated,which are proven to possess 13.6%higher tensile strength,10.1%elastic modulus.More impressively,their average energy absorption can be improved by 111.9%,accompanied with inherent damage alert capability.This offers a paradigm to fabricate structure-function integrated hybrid smart fabric composites for the smart clothing and intelligent aerial vehicles.
基金supported by the National Natural Science Foundation of China(Grant Nos.U1837209 and 52105594)the Fundamental Research Program of Shanxi Province(Grant No.20210302124274)+4 种基金the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi(Grant No.2023L361)the Outstanding Young Talents Support Plan of Shanxi Provincethe Young Sanjin Scholar Distinguished Professor Plan of Shanxi Provincethe Innovative Research Group Project of the National Natural Science Foundation of China(Grant No.51821003)the Shanxi‘1331 Project’Key Subjects Construction。
文摘Monitoring high-temperature vibrations is critical in aerospace engineering,industrial manufacturing,and energy production,where harsh conditions necessitate robust vibration sensors for detecting anomalous signals.However,the accuracy of such sensors is often compromised by crosstalk between temperature and vibration signals.This study introduces a high-temperature vibration sensor based on langasite(LGS)surface acoustic wave(SAW)technology,designed to withstand temperatures up to 500℃.The sensor demonstrates high sensitivity,ranging from 12.54 kHz/g at 25℃ to 15.63 k Hz/g at 500℃.A comprehensive mechanical and electrical coupling model for the SAW vibration sensor was developed by integrating theoretical equations with numerical simulations to optimize the sensor's performance.Additionally,a novel decoupling algorithm for temperature and vibration was established,achieving thermomechanical decoupling with precise vibration parameters.Experimental results indicated a maximum relative deviation of 4.67%for the algorithm.In conclusion,the proposed LGS SAW vibration sensor emerges as a promising solution for the accurate detection of multiple parameters in high-temperature vibration monitoring.