Добірка наукової літератури з теми "Piezoelectric ceramic sensor"

Owing to the high Curie temperature and good piezoelectric thermal stability, BiFeO3–BaTiO3 ceramics show great potentials for high-temperature piezoelectric sensor applications. In this paper, a compression-mode piezoelectric sensor was fabricated by the lead-free and high-temperature 0.75BiFeO3–0.25BaTiO3–MnO2 (BFBT25–Mn) ceramic and its sensitivity was characterized from room temperature to 550 °C over a frequency range of 200–1000 Hz. The output charge of the BFBT25–Mn piezoelectric sensor is independent of the measuring frequency at different temperatures. The maximum working temperature of the BFBT25–Mn piezoelectric sensor is 450 °C, about 250, 150, and 100 °C higher than those of these piezoelectric sensors fabricated by PZT-5A, BSPT64–Mn, and BSPT66–Mn ceramics, respectively. The temperature sensitivity coefficient from room temperature to 350 °C of the BFBT25–Mn piezoelectric sensor is 30% of that for the BSPT66–Mn sensor. Furthermore, the sensitivity of the BFBT25–Mn piezoelectric sensor is stable with the dwelling time at 400 °C. These results indicate that the BFBT25–Mn ceramic is a strong competitor for high temperature sensing applications.

Piezoelectric ceramics have good electromechanical coupling characteristics and a high sensitivity to load. One typical engineering application of piezoelectric ceramic is its use as a signal source for Weigh-In-Motion (WIM) systems in road traffic monitoring. However, piezoelectric ceramics are also sensitive to temperature, which affects their measurement accuracy. In this study, a new piezoelectric ceramic WIM sensor was developed. The output signals of sensors under different loads and temperatures were obtained. The results were corrected using polynomial regression and a Genetic Algorithm Back Propagation (GA-BP) neural network algorithm, respectively. The results show that the GA-BP neural network algorithm had a better effect on sensor temperature compensation. Before and after GA-BP compensation, the maximum relative error decreased from about 30% to less than 4%. The sensitivity coefficient of the sensor reduced from 1.0192 × 10−2/°C to 1.896 × 10−4/°C. The results show that the GA-BP algorithm greatly reduced the influence of temperature on the piezoelectric ceramic sensor and improved its temperature stability and accuracy, which helped improve the efficiency of clean-energy harvesting and conversion.

In the sensor system, the wave in the optical fibers conductivity will change when the surrounding medium is changed. Thus, minor changes according to the mechanical wave, optical fiber can be used to monitor changes in the surrounding environment. The working principle of the sensor system is the signal generator output signal transmitted to a piezoelectric ceramic. Because of the inverse piezoelectric effect of piezoelectric ceramics, conduction of the electrical signals can be converted to mechanical signals. The resulting mechanical wave transmitted to the other end of the piezoelectric ceramic by the optical fiber, and converted to an electrical signal. The proposed system consists of signal generator, a piezoelectric ceramic, fiber optics, oscilloscope. For investigation the performance of the sensor system the external point loading was applied. Results show that the sensor system can be successfully applied to the sensing the force value.

In this study, an acoustic emission (AE) sensor was fabricated using lead-free Ba(Zr0.2Ti0.8)O3–0.5(Ba0.7Ca0.3)TiO3 (BZT–BCT) ceramics. The acoustic and electromechanical properties of the AE sensor were determined by the shapes of the piezoelectric ceramics. To optimize the AE sensor performance, the shapes of the ceramics were designed according to various diameter/thickness ratios (D/T) = 0.5, 1.0, 1.5, 2.0, 2.5, 3.0. The BZT–BCT ceramic with D/T = 1.0 exhibited excellent values of a piezoelectric charge coefficient (d33), piezoelectric voltage coefficient (g33), and electromechanical coupling factor (kp), which were 370 (pC/N), 11.3 (10−3 Vm/N), and 0.58, respectively. Optimum values of resonant frequency (fr) = 172.724 (kHz), anti-resonant frequency (fa) = 196.067 (kHz), and effective electromechanical coupling factor (keff) = 0.473 were obtained for the manufactured BZT–BCT ceramic with D/T = 1.0. The maximum sensitivity and frequency of the AE sensor made of the BZT–BCT ceramic with a D/T ratio of 1.0 were 65 dB and 30 kHz, respectively.

In this paper, a calibration mechanism of sensor based on artificial polycrystalline piezoelectric material and a kind of micro-voltage output system have been designed through understanding the characteristics and the parameters of the capacitive displacement sensor, so as to achieve the sensor calibration interval reaches the piezoelectric ceramic resolution of 5 nm. Through the measured values in the condition that 10mV/100mV is input to piezoelectric ceramic, it can be seen that the design meets the initial requirements. Such mechanism can be used for the calibration of a variety of high-precision sensors; however, it must be used in a stable environment.

In this paper, some smart sensors or material used to make the smart sensors, such as piezoresistance composite, piezoelectric polymer, piezoelectric cement and corrosion monitoring sensor, developed by Harbin Institute of Technology were introduced. Piezoresistance composite is made with carbon nanotube and resin, one character of the work is the carbon nanotube is orientation arranged by magnetic field. Piezoelectric polymer is made with PZT particles and PVDF, in order to improve its performance a few carbon nanotube are also mixed in the composite. Piezoelectric cement is one kind of sensing material whose primary raw materials are cement and piezoelectric ceramic particles (or fiber). The sensing performance of piezoelectric cement is coming from its functional phase, the piezoelectric ceramic. The corrosion monitoring sensor is made with solid-state reference electrode, whose surface is one kind of binary alloy membrane produced with physical vapor deposition technology. The main producing technology, performance and applications of above sensors were introduced in this paper.

Among the photothermal methods, the photopyroelectric (PPE) technique is a suitable method to determine thermal properties of different kinds of samples ranging from solids to liquids and gases. Polyvinylidene difluoride (PVDF) is one of the most frequently used pyroelectric sensors in PPE technique but has the disadvantage that it can be easily deformed by the sample weight. This deformation could add a piezoelectric effect to the thermal parameters assessment; also PVDF has a narrow temperature operation range when compared with ceramic pyroelectric sensors. In order to minimize possible piezoelectric effects due to sensor deformation, a ceramic of lanthanum modified lead zirconate (PLZT) was used as pyroelectric sensor in the PPE technique. Then, thermal diffusivity of some liquid samples was measured, by using the PPE configuration that denominated the thermal wave resonator cavity (TWRC), with a PLZT ceramic as pyroelectric detector. The performance obtained with the proposed ceramic in the TWRC configuration was compared with that obtained with PVDF by using the same configuration.

Abstract In this work the design aspects of a piezoelectric-based resonance ceramic pressure sensor made using low-temperature co-fired ceramic (LTCC) technology and designed for high-temperature applications is presented. The basic pressure-sensor structure consists of a circular, edge-clamped, deformable diaphragm that is bonded to a ring, which is part of the rigid ceramic structure. The resonance pressure sensor has an additional element – a piezoelectric actuator – for stimulating oscillation of the diaphragm in the resonance-frequency mode. The natural resonance frequency is dependent on the diaphragm construction (i.e., its materials and geometry) and on the actuator. This resonance frequency then changes due to the static deflection of the diaphragm caused by the applied pressure. The frequency shift is used as the output signal of the piezoelectric resonance pressure sensor and makes it possible to measure the static pressure. The characteristics of the pressure sensor also depend on the temperature, i.e., the temperature affects both the ceramic structure (its material and geometry) and the properties of the actuator. This work is focused on the ceramic structure, while the actuator will be investigated later.

Technique for Impact Localization on Carbon Fiber Laminate Sheets: il problema affrontato è stato quello della localizzazione di un impatto a bassa energia (simulati con sfere in caduta libera) su strutture planari in materiale polimerico rinforzato con fibra di carbonio (CFRP) per mezzo della formula di triangolazione di Tobias sviluppando un nuovo algoritmo “di verosimiglianza” per l’estrazione del tempo di arrivo differenziale (DToA) da una coppia di sensori piezoelettrici flessibili incollati alla superficie del materiale. In particolare, è stata fatta la caratterizzazione della lastra in CFRP in termini di diagramma delle velocità di propagazione delle onde di Lamb. L’algoritmo ha reso indipendente la valutazione del DToA dal tipo di trasduttore utilizzato, ha migliorato la stima l’accuratezza delle coordinate di impatto. I parametri da inserire nel sistema di elaborazione sono minimi e sono stati migliorati i tempi di elaborazione. Sono state sviluppate nuove geometrie per i sensori in PVDF. Infine, è stato popolato un data base con i segnali acquisiti ed estratti dati statistici con i quali è stato possibile valutare l’algoritmo e confrontarlo con il metodo classico a soglia fissa per lastre in CFRP. Analysis of the errors in the estimation of impact positions in plate-like structure through the triangulation formula: l’attività di ricerca si è svolta concentrandosi sullo studio di una sperimentazione che diminuisse i parametri di incertezza. È stata condotta quindi un’analisi degli errori nella stima della posizione di impatto su alluminio attraverso la formula di triangolazione. Inizialmente, al fine di ridurre l’incertezza sulla generazione degli impatti con sfere in caduta libera, è stato realizzato un sistema meccanico, completo di elettronica di pilotaggio, per la generazione di impatti controllati e ripetibili. Il lavoro si è concentrato su una semplice procedura di laboratorio basata su un set-up con una coppia di sensori posizionati simmetricamente rispetto al punto di impatto, per stimare l'incertezza del DToA e la velocità di propagazione. Successivamente dallo studio del modello matematico di triangolazione sono stati individuati ed indagati, in modo simulato, i due fattori che ne influiscono sulla stima: il tempo differenziale di arrivo (DToA) ad ogni coppia di sensori dell’array e l’incertezza sulla stima della velocità di gruppo delle onde guidate di Lamb. Le prove sperimentali per la misura della velocità delle onde di Lamb e per la stima del DToA, sono state fatte su di una lastra di alluminio di spessore 1.4 mm con sensori piezoelettrici commerciali. Poiché l'errore per la stima DToA dipende anche dal tipo di elaborazione del segnale adottato, tra i molti metodi riportati in letteratura per la stima del DToA, abbiamo analizzato e confrontato tre metodi: l'attraversamento di una soglia predeterminata, il metodo di correlazione e l’algoritmo di “verosimiglianza” sviluppato in [A1]. Per il rilevamento dell'incertezza della velocità di propagazione, sono state calcolate le curve di dispersione della piastra di alluminio ed i risultati sono stati poi confrontati con le misurazioni sperimentali. Inoltre, un'analisi teorica ha mostrato come gli errori che influenzano il DToA e la velocità di propagazione agiscano sulla stima del punto di impatto nella formula di triangolazione. L'analisi dell'errore di posizionamento, nell’ottica di un utilizzo di configurazione multisensoriale, è considerata utile per la progettazione di un sistema di monitoraggio strutturale (SHM).

Ferroelectric ceramics are very promising materials for a variety of piezoelectric applications such as high permittivity dielectrics, piezoelectric sensors, piezoelectric/electrostrictive transducers, actuators, electro-optic devices, etc. Among the commercially viable ferroelectric ceramics, the lead-zircon ate-titivate Pb(Zr1-xTix)O3 (PZT) based ceramics have dominated the market due to their superior piezoelectric and dielectric property along with other advantages like high electromechanical coupling, ease of processing and low cost. However, the toxicity of lead based materials, and its volatility at processing temperatures is a serious health and environmental concern. Several legislations against lead-based products have been passed all over the world in order to encourage identification of alternative lead-free materials for these applications. As a consequence, there has been a remarkable surge in efforts by researchers on identifying lead-free alternatives for piezoelectric applications. A larger emphasis has been placed on perovskite based ceramics since in addition to possessing excellent properties, their relatively simple structure facilitates understanding structure-property relationships which are important for developing novel high performance materials. Na1/2Bi1/2TiO3 (NBT) and its solid solutions are one of the leading classes of perovskite ceramics, which show promising ferroelectric, piezoelectric and dielectric property thereby having the potential to replace PZT based ferroelectrics. The parent compound NBT is ferroelectric with large ferroelectric polarization (~40 C/cm2), promising piezoelectric properties with 0.08% maximum strain and longitudinal piezoelectric coefficient (d33) ~ 80 pC/N. Though NBT was discovered nearly six decades ago, a clear understanding of its structure remained elusive for a long time since different characterization techniques yielded contradicting reports on its structure and nature of phase transformation. However, rapid advances in characterization techniques in recent years have led to uncovering of new results, thereby shedding light on the true structure of NBT. X-ray and neutron diffraction studies in the past have shown that NBT exhibits rhombohedral (R3c) structure at room temperature, which undergoes a gradual transformation into tetragonal (P4bm) structure at ~230oC. However, recent characterization of both single crystal and powder of NBT using high resolution x-ray diffraction showed that the room temperature structure is not purely rhombohedral and the structure can be better modeled with a monoclinic (Cc) structure. In contrast to x-ray and neutron diffraction, electron diffraction studies have shown evidence for the presence of planar disorders, corresponding to in-phase octahedral tilts in the sample which cannot be accounted for by either R3c or Cc structure. In addition, EXAFS, x-ray and neutron total scattering studies, diffuse scattering studies, etc. have shown that the structural parameters obtained from bulk diffraction techniques are significantly different from the local structure of the material. Similar ambiguities have been observed even in NBT based solid solutions like BaTiO3, K1/2Bi1/2TiO3, etc. which show enhanced properties at the morphotropic phase boundary (MPB). A major breakthrough in understanding the structural complexity involved in NBT based solid solutions was achieved when it was found that the structure of the MPB compositions were sensitive to electric field. This led to solving the mystery behind the appearance of cubic-like phase at some of the MPB compositions where the application of electric-field resulted in the transformation of the structure into a co-existence of rhombohedral and tetragonal phases. Observation of an electric-field-induced structural transition at the MPB compositions was expected, because the MPB signifies instability in the system and even a minor external force can significantly influence the system. However, we have found that the structure of even pure NBT is significantly influenced by electric field and the framework of this thesis is based on this particularly important result. The intrinsic tendency of the electric field to affect the structure of NBT is a major factor which needs to be considered when studying similar phase transitions in the MPB compositions of NBT-substituted systems also. This was not taken into account by other research groups, and they assumed that the instability associated with the MPB was the only major factor involved in the electric-field induced transitions. A simple but highly effective strategy of grinding the electrically poled pellet into fine powder and then collecting x-ray diffraction patterns, facilitated elimination of preferred orientation in the sample. Thus, structural analysis by Rietveld refinement was possible even on the poled sample, which has not been carried out by any other groups on any ferroelectric ceramics so far. The initial part of the thesis deals with addressing the structural complexity of pure NBT, wherein the effect of electric field on the bulk structure as well as the local structure was studied in great detail. Later on, similar concepts are used to investigate BaTiO3 and K1/2Bi1/2TiO3 substituted NBT also. The first chapter of the thesis provides a brief introduction to the field of ferroelectrics, perovskite structure and their phase transition. An exposure to concepts like relaxor ferroelectrics, morphotrophic phase boundary, octahedral tilting, etc. has been provided. Then, a detailed overview of the existing literature related to the structure of NBT and its phase transition studies with temperature has been discussed. The details of the experimental procedures, characterization techniques used, and some theory behind these techniques have been provided in chapter 2. The third chapter deals with the room temperature structural characterization of pure NBT using techniques like x-ray diffraction, neutron diffraction, electron diffraction and EXAFS analysis. The results of these structural characterizations are also complemented with first-principles calculation study of the ground state structure of NBT, dielectric and ferroelectric characterization, and ageing studies. While x-ray and neutron diffraction clearly established electric-field induced structural transition from a monoclinic (Cc) to rhombohedral (R3c) structural transition, first principles calculation showed that the monoclinic phase is not stable and hence cannot be the ground state structure of NBT. Also, the possibility of the monoclinic features appearing in the x-ray diffraction solely due to micro structural effects by nano-sized domains was discussed. Comparison of electron diffraction of poled and unpoled samples of NBT showed that the in-phase tilted regions were greatly suppressed in the poled samples. Even HRTEM images showed that the unpoled samples had a very high concentration of strain heterogeneity in them, which was absent in the poled samples. This gave a direct evidence of correlation between observation of monoclinic phase and the presence of in-phase tilted regions in the unpoled samples. It was proposed that the strain caused by these in-phase tilted disorders caused distortion in the original rhombohedral lattice thereby making the structure appear monoclinic. Application of electric field causes the in-phase octahedral tilt disorders to vanish, thereby even the monoclinic features observed in the XRD also disappear. The fourth chapter discusses the consequences of poling on the high temperature phase transition behavior of NBT. We have used temperature dependent x-ray and neutron diffraction, Raman spectroscopy and EXAFS analysis whose results were correlated with the anomalies observed in temperature dependent dielectric and polarization studies. We found that the poled sample shows a sharp anomaly at the depolarization temperature (Td) in all the characterization techniques used, in contrast to a diffuse or negligible effect seen in the unpoled sample. The depolarization temperature was found to be associated with introduction of structural disorder in the sample in the form of in-phase octahedral tilts. This also gave rise to a normal to relaxor ferroelectric transition at Td, and this relaxor behavior persisted even after cooling the sample to room temperature. An intermediate cubiclike phase was observed from x-ray diffraction at around 300C wherein the rhombohedral phase vanishes and the tetragonal phase begins to appear. Even single crystal study of NBT in the past showed sudden disappearance of the domains at 300C, even though they were visible at both above and below this temperature. This effect was called isotropization, and was postulated to arise due to extremely small domains which made the system isotropic. However, our neutron diffraction pattern showed that in-phase tilted superlattice reflections persisted at this temperature which meant that the structure was not truly cubic at this temperature. Further, a neutron diffraction study at higher temperatures showed that the in-phase tilted superlattice reflections persisted even above the cubic phase transition temperature, in corroboration with similar reports from high temperature electron diffraction. Chapter five deals with the BaTiO3 substituted NBT system, which has gained tremendous interest in the last decade as a viable piezoelectric ceramic for commercial applications. Though a large number of groups have already carried out exhaustive studies on this system, most of the work concentrated mainly on the MPB compositions which showed enhanced piezoelectric properties. In this chapter, we highlight some important findings in the pre-MPB and post-MPB compositions. Using room-temperature and high temperature x-ray diffraction, we show that there exists a subtle compositional phase boundary at x = 0.03, which disappears upon poling the sample. While the monoclinic phase in pure NBT becomes cubiclike at this composition, the depolarization temperature (Td) also slightly increases up to this composition and then decreases upon further Ba substitution. Similar studies were also carried out with compositions containing slightly excess bismuth in them (0.1 mol %), whose purpose was to negate the effects of Bi-vaporization during sintering. It was found that while the compositional phase boundary remained essentially unchanged, there was a decrease in Td for all the compositions. It was also realized that the addition of excess bismuth improved the overall piezoelectric property of the system. Studies on higher compositions of Ba in the post-MPB regions further revealed two additional compositional phase boundaries. A criticality in the coercive field and spontaneous tetragonal strain was observed at x = 0.2, which was found to be associated with crossover from a long-period modulated tetragonal phase (for x < 0.2) to a no modulated tetragonal phase (for x > 0.2). Near the BT rich end (x ~ 0.7), the system exhibits a crossover from normal to a diffuse/relaxor ferroelectric transition with increasing Na1/2Bi1/2 substitution. The onset of relaxor state by Na1/2Bi1/2 substitution on the Ba-site, was shown to increase the spontaneous tetragonal strain in the system. This was because of the enhancement in the covalent character of the A-O bond by virtue of the Bi+3 6s2 lone pair effect, and it also led to a sudden increase in the tetragonal-to-cubic transition temperature. This was in contrast to other chemical modifications of BT reported in the past (like Zr, Sn, Sr, etc.) where the relaxor state is accompanied by a weakening of the ferroelectric distortion and a decrease in the critical temperature. Finally, chapter six covers the effect of electric field induced phase transition in K1/2Bi1/2TiO3 substituted NBT. Visual observation showed that while the compositions (x < 0.2) behaved similar to pure NBT, wherein the structure became purely rhombohedral upon poling, the effect of electric field was negligible in the post-MPB compositions (x > 0.2). In addition, the peaks in the annealed samples were considerably overlapping which made identifying the structural transitions at the MPB compositions difficult using Rietveld analysis. However, comparison of the FWHM of the {200}pc peaks of compositions x < 0.2 showed that the FWHM began to increase suddenly for x > 0.15 indicating emergence of the tetragonal phase. Also, all the compositions showed an increase in the {200}pc peak FWHM by 0.03 after poling. The depolarization temperature showed only slight variation in the pre-MPB compositions, but showed a minimum at the MPB compositions. Temperature dependent dielectric studies further showed that for the post-MPB compositions, the system remains relaxor even after poling.

Perovskites are an interesting class of materials that have tremendous applications as actuators, sensors and in photovoltaics. Lead based perovskites exhibit piezoelectricity and other interesting properties and thus have conquered the ceramic industry for a long time. Lead free piezoelectric perovskites are the need of the hour because lead based piezoceramics are toxic and a danger to the environment. There are various contenders of lead free alternatives of lead zirocnate-titnate (PZT) based ceramics including potassium-sodium niobate, barium titanate, bismuth based perovskites that exhibit similar piezoelectric and ferroelectric properties in comparison to PZT ceramics. These lead free piezoceramics and their important properties and respective applications such as sensors, transducers and actuators, is briefly explored in this chapter.

Perovskites are an interesting class of materials that have tremendous applications as actuators, sensors and in photovoltaics. Lead based perovskites exhibit piezoelectricity and other interesting properties and thus have conquered the ceramic industry for a long time. Lead free piezoelectric perovskites are the need of the hour because lead based piezoceramics are toxic and a danger to the environment. There are various contenders of lead free alternatives of lead zirocnate-titnate (PZT) based ceramics including potassium-sodium niobate, barium titanate, bismuth based perovskites that exhibit similar piezoelectric and ferroelectric properties in comparison to PZT ceramics. These lead free piezoceramics and their important properties and respective applications such as sensors, transducers and actuators, is briefly explored in this chapter.

Research topics related to the production of nanocomposites are the most important directions of development of new semiconductor engineering, ensuring high nanocomposites obtaining useful properties in the scope of biophysical characteristics, biomedical and piezoelectric applications. We present two case studies as Hydroxyapatite are in medical applications and aluminum nitride as acoustic wave sensor. Hydroxyapatite, is the main inorganic structure of the tooth enamel and bone and is a biomaterial that is commonly used in biomedical applications that involve bone substitution, drug delivery and bone regeneration because of its excellent biocompatibility, high bioactivity and good osseoconductivity. Since the past decade. Aluminum nitride (AlN), an electrical insulating ceramic with a wide band gap of 6.3 eV, is a potentially useful dielectric material very important in fields such as optoelectronic and micro electronics.

Research topics related to the production of nanocomposites are the most important directions of development of new semiconductor engineering, ensuring high nanocomposites obtaining useful properties in the scope of biophysical characteristics, biomedical and piezoelectric applications. We present two case studies as Hydroxyapatite are in medical applications and aluminum nitride as acoustic wave sensor. Hydroxyapatite, is the main inorganic structure of the tooth enamel and bone and is a biomaterial that is commonly used in biomedical applications that involve bone substitution, drug delivery and bone regeneration because of its excellent biocompatibility, high bioactivity and good osseoconductivity. Since the past decade. Aluminum nitride (AlN), an electrical insulating ceramic with a wide band gap of 6.3 eV, is a potentially useful dielectric material very important in fields such as optoelectronic and micro electronics.

Ferroelectric materials are widely investigated due to their excellent properties and versatile applications. At present, the dominant materials are lead-containing materials, such as Pb (Zr,Ti)O3 solid solutions. However, the use of lead gives rise to environmental concerns, which is the driving force for the development of alternative lead-free ferroelectric materials. (Bi0.5Na0.5)TiO3-based ceramics are considered to be one of the most promising lead-free materials to replace lead-containing ferroelectric ceramics due to their excellent ferroelectric properties, relaxation characteristics, and high Curie point. After decades of efforts, great progress has been made in the phase structure characterization and properties improvement of BNT based ceramics. However, most of the studies on BNT system mainly focuses on its piezoelectric properties and application of piezoelectric sensors and strain actuators, little attention is paid to its ferroelectric properties and related applications. In this chapter, new BNT-based ceramics via composition modification and special focuses on the ferroelectric properties, phase transition behaviors under external fields and related applications, such as application in energy storage, pulsed power supply and pyroelectric detection were proposed.

Piezoelectric sensors are used in many structural health monitoring (SHM) methods to interrogate the condition of the structure to which the sensors are affixed or imbedded. Among SHM methods utilizing thin wafer piezoelectric sensors (PWAS), electro-mechanical impedance monitoring is seen as a promising approach to assess structural condition in the vicinity of a sensor. Using the converse and direct piezoelectric effects, this health monitoring method utilizes mechanical actuation and electric voltage to determine the impedance signature of the structure. If there is damage to the structure, there will be a change in the impedance signature. It is important to discern between actual damage and environmental effects on the piezoelectric ceramic sensors and the structure. If structural health monitoring is to be implemented in space structures on orbit, it is imperative to determine the effects of the extreme space environment on piezoelectric sensors and the structures to which they are affixed. The space environment comprises extreme temperatures, vacuum, atomic oxygen, microgravity, micro-meteoroids and debris, and significant amounts of radiation. Radiation in space comes from three sources: solar events, background cosmic radiation, and trapped particles in the Van Allen Belts. Radiation exposure to structures on orbit will vary significantly depending on the duration of the flight and the altitude and inclination of the orbit. In this contribution, the effect of gamma radiation on piezoelectric ceramic sensors and space grade aluminum is investigated for equivalent gamma radiation exposure to 3-months, six-months, and 1-year on Low Earth Orbit (LEO). An experiment was conducted at White Sands Missile Range, Gamma Radiation Facility using Cobalt-60 as the source of radiation. A free PWAS and a PWAS bonded to a small aluminum beam were exposed to increasing levels of gamma radiation. Impedance data were collected for both sensors after each radiation exposure. The total radiation absorbed dose was 200 kRad (Si) by the end of the experiment. The results show that piezoelectric ceramic material is affected by gamma radiation. Over the course of increasing exposure levels to Cobalt-60, the impedance frequency of the free sensor increased with each absorbed dose. The impedance measurements of the sensor bonded to the aluminum beam reflects structural and sensor’s impedance. The data for this sensor show an increase in impedance amplitude with each level of absorbed dose. The mechanism at work in these impedance changes is suggested and future experimental work is identified. A survey of previous results of radiation exposure of piezoelectric ceramic sensors and aluminum alloys is presented and are compared to previous studies.

Abstract Large area 1–3 composite piezoelectric transducer panels have been produced by Materials Systems Inc. (MSI). These SonoPanels™ measure 250 × 250 mm and have excellent response as underwater actuators as well as sensors. Piezocomposite panel manufacturing has been facilitated by an injection molding technology for fabricating net-shape lead zirconate titanate (PZT) ceramic preforms. An array of fifteen 250 × 250 mm 1–3 composite actuator panels, integrated with surface mounted pressure and velocity sensors, has been attached to a steel backing structure. The array has been evaluated for underwater active surface control applications at the Naval Research Laboratory. Sensor-actuator coupling was investigated, with good agreement between calculated and measured performance.

Abstract In this paper, a digital regulator is designed and experimentally implemented for a smart structure featuring piezoelectric sensors and actuators using optimal multivariable control techniques. The controller consists of a linear quadratic regulator with output weightings and a state estimator, Luenberger observer. The structure is a cantilever beam synthesized with two sets of sensor/actuator PZT ceramic piezoelectric plates bonded to the beam surface at the high strain locations corresponding to the first and second vibration modes. Equations of motion of the beam are developed using finite beam element model. The model includes the mass and rigidity of the PZT ceramics. Experimental results of two regulators differing in the number of modes considered are presented and discussed. The results proved the applicability of the concept and the stability and robustness of the control algorithm.