This thesis deals with the generating electrical energy from vibrations from piezoelectric composite cantilever beam. A review of the piezoelectric materials is made. Then the analytical model of piezoelectric cantilever beam is presented, then the influence of parameters is inves-tigated. Case study with theoretic design of parameters on the specific source of vibration is also provided. Last part is the extension of model for the variable width of layers at cantilever

This thesis presents the design, modeling, and experiment of a novel pressure sensor using a dual-mode AT-cut quartz crystal resonator with beat frequency analysis based temperature compensation technique. The proposed sensor can measure pressure and temperature simultaneously by a single AT-cut quartz resonator. Apart from AT-cut quartz crystal, a newly developed Langasite (LGS) crystal resonator is also considered in the proposed pressure sensor design, since LGS can operate in a higher temperature environment than AT-cut quartz crystal. The pressure sensor is designed using CAD (computer aided design) software and CAE software - COMSOL Multiphysics. Finite element analysis (FEA) of the pressure sensor is performed to analyze the stress- strain of the sensor's mechanical structure. A 3D printing prototype of the sensor is fabricated and the proposed sensing principle is verified using a force-frequency analysis apparatus. Next to the 3D printing model verification, the pressure sensor with stainless steel housing has been fabricated with inbuilt crystal oscillator circuit. The oscillator circuit is used to excite the piezo crystal resonator at its fundamental vibrational mode and give the frequency as an output signal. Based on the FEA and experimental results, it has been concluded that the maximum pressure that the sensor can measure is 45 (psi). The pressure test results performed on the stainless steel product shows a highly linear relationship between the input (pressure) and the output (frequency).

This work presents an investigation of a piezoelectric sensor based energy harvesting system, which collects energy from the surrounding environment. Increasing costs and scarcity of fossil fuels is a great concern today for supplying power to electronic devices. Furthermore, generating electricity by ordinary methods is a complicated process. Disposal of chemical batteries and cables is polluting the nature every day. Due to these reasons, research on energy harvesting from renewable resources has become mandatory in order to achieve improved methods and strategies of generating and storing electricity. Many low power devices being used in everyday life can be powered by harvesting energy from natural energy resources. Power overhead and power energy efficiency is of prime concern in electronic circuits. In this work, an energy harvester is modeled and simulated in Simscape™ for the functional analysis and comparison of achieved outcomes with previous work. Results demonstrate that the harvester produces power in the 0 μW to 100 μW range, which is an adequate amount to provide supply to low power devices. Power efficiency calculations also demonstrate that the implemented harvester is capable of generating and storing power for low power pervasive applications.

Materiais piezocompósitos laminados são compostos por camadas de material piezelétrico, metálico e compósito (matriz epóxi com fibras de carbono ou de vidro), que possibilitam obter vantagens em relação aos materiais piezelétricos convencionais, permitindo obter características superiores que não podem ser conseguidas pelos seus componentes de forma isolada como, por exemplo, maior flexibilidade e resistência mecânica ou menor peso. Sob esse enfoque, este trabalho tem por objetivo o desenvolvimento de Estruturas Piezocompósitas Laminadas (EPLA) que consistem basicamente em estruturas multicamadas, através do projeto da sua resposta transiente e harmônica visando aplicações dinâmicas. Entre as potenciais aplicações dessas estruturas, tem-se atuadores, motores, sonares e dispositivos de coleta de energia (\"energy harvester\"), sendo de muito interesse a melhora das suas características dinâmicas e o seu desempenho. O projeto dinâmico de uma EPLA é complexo, porém pode ser sistematizado utilizando o Método de Otimização Topológica (MOT). O MOT é um método baseado na distribuição de material num domínio de projeto fixo com o objetivo de extremizar uma função de custo sujeita às restrições inerentes do problema, combinando algoritmos de otimização e de elementos finitos. A formulação de MOT para o projeto dinâmico de EPLA pretende determinar tanto a topologia ótima dos materiais nas diferentes camadas quanto o sinal de polarização do material piezelétrico e o ângulo da fibra na camada compósita, tendo como finalidade a maximização da amplitude de vibração em pontos determinados (em atuadores) ou da geração de energia elétrica a partir de excitações mecânicas (em coletores de energia). Além disso, é formulado um problema combinando os enfoques harmônico e transiente com o intuito de customizar a resposta da EPLA, de modo que, o nível da resposta seja o mesmo perante diferentes tipos de onda de excitação (transdutores multi-entrada). O trabalho inclui as etapas de projeto, simulação, fabricação e caracterização de protótipos. / Laminated piezocomposite materials are composed by layers of piezoelectric, metal and composite material (epoxy matrix with carbon or glass fiber), which have advantages over conventional piezoelectric materials, because of their superior characteristics, which cannot be achieved by any of its components isolated, for example, more flexibility and strength and less weight. Under this approach, this work aims at the development of Laminated Piezocomposite Structures (LAPS) what primarily consist of multi-layer structures, through the transient and harmonic response design aiming at dynamic applications. Among the potential applications of these structures it can be cited actuators, motors, sonar devices and energy harvester, being of great interest the improvement of its dynamic characteristics and performance. The dynamic design of a LAPS is complex however it can be systematized by using the Topology Optimization Method (TOM). The TOM is a method based on the distribution of material in a fixed design domain with the aim of extremizing a cost function subject to constraints inherent to the problem by means of combining the optimization algorithms and the finite element method (FEM). The TOM formulation for the LAPS dynamic project aims to determine together the optimal topology of the materials for different layers, the polarization sign of the piezoelectric material and the fiber angle of the composite layer, in order to maximize the vibration amplitude at certain points (in actuators), or the generation of electrical energy from mechanical excitations (in energy harvesters). In addition, a TOM problem combining harmonic and transient approaches is formulated with the purpose of customizing EPLA response so that the response level is the same for different excitation waveforms (multi-entry transducers). The work includes design, simulation, manufacturing and characterization of prototypes.

The behaviour of a free-standing thin film differs from that of a film surface-bonded or embedded due to the boundary constraints. A general dearth of analytical models, in regard to prediction of the operational competence of a constrained Piezoelectric thin film, prevails. In conventional design of miniaturized thin film devices, several non classical effects, for instance the effect of boundary constraints, are not considered. To warrant the design and performance optimisation of thin film sensors, such effect must be taken into account in a forethoughtful manner. This thesis is an attempt to achieve such optimisation through modeling of thin films. The coupled problem of a film on a substrate is solved semi-analytically in theoretical cases; and by finite element analysis in realistic cases for damage identification in the host structure. We first propose a two-dimensional analytical model of a constrained Piezoelectric thin film embedded in a host. Analytical expressions of capacitance and voltage across the electrodes are obtained by assuming first order shear deformation across the film thickness. The bonding layer between the film and the substrate, which is assumed to be an equivalent single layer including electrodes, insulation layer, adhesive layer etc., is modeled by taking into account its viscoelastic property. Residual stress is incorporated in the constitutive model through equivalent residual strain. Simulations on 10 m thick PVDF and 100 mPZT films are conducted. They illustrate the dependence of voltage response and capacitance on the applied stress, as well as on the residual stress. A maximum percentage variation in capacitance, as compared to the conventional estimate, is about 2% in a PVDF film and +75% to-65% in a PZT film for various combinations of tensile stresses applied at the ends of the film. Effect of residual stress is also exemplified via comparative response of a 1 m PZT film deposited on Pt/Ti/Si(0 0 1), with and without residual stress. For this case, an almost +50% increase in the voltage and an equivalent drop in the capacitance is observed. Next, we look into the voltage response profile of this model by employing it as a sensor to identify a finite mode I and mode II sub-surface cracks in a finite size host. To model the embedded crack, additional perturbation functions in the displacement field due to linear elastic crack tips in an infinite solid under plane strain condition are introduced to accommodate the stress free conditions at its surfaces. The film model requires the interfacial displacement and traction conditions, which are obtained from the analysis of the host. The combined analysis of the film and crack models brings forth the voltage gradient along the film span as a direct indicator of the location of crack in the axial direction, whereas the voltage magnitude represents the size of the crack. Following this analysis, a quasi three-dimensional(3-D) model of a Piezoelectric thin film surface-bonded to the host structure is proposed. With due consideration of restriction on the thickness of the film, here the model is based on a reduced 3-D continuum mechanics approach. The displacement field in the film is assumed to vary according to the third-order shear deformation theory; and the electrical and mechanical boundary conditions on the surfaces of the film are accommodated in a consistent manner. The formulation yields a governing inhomogeneous system of second-order Partial Differential Equations(PDEs), which is dependent on the displacement field at the film-host interface through force terms. Semi-analytical expressions of potential difference and capacitance are obtained. This system is solved numerically for two unknown rotations about X and Y axes of the film by finite element method. A maximum variation of about 2.5% is obtained in the capacitance of a 10 m PVDF film, as compared to its conventional estimate. The operational performance of this model is assessed in terms of its voltage response over the film area for various displacement fields. Conformation of this response to the input displacement field attests to its mathematical integrity. Next, we ascertain the versatility of this model in its role as a sensor for Structural Health Monitoring. To deal with cracks in the host plate, finite size rectangular surfaces are introduced as crack faces. The film domain and the host domain are discretized with an a posteriori h-refinement strategy and compatible interfacial nodes at the film-host interface via finite element interpolation. The resulting coupled problem is solved by static finite element analysis. The nature of the voltage pattern over the film surface is peculiar to the mode of crack, and is a qualitative portrayal of its presence. To correlate the electric potential(voltage) –a distributed parameter – to the geometry and orientation of the crack, as well as to quantify it, electrostatic measures in terms of integrated potential difference and its spatial gradients on the film surface are proffered. The numerical implications of these measures are elicited through simulation results of various crack sizes in damaged and healthy hosts under identical conditions of stress and boundary. The pattern of these measures in a damaged host becomes oscillatory as compared to straight lines observed in a healthy host. Furthermore, the reduced 3-D model is extended to perform dynamic analysis with the inclusion of inertial terms in the governing equilibrium equations. Subsequently, the acceleration terms appear in the governing inhomogeneous system of PDEs in the force terms. Finite element analyses of this extended film model on an isotropic beam with surface and sub-surface cracks, and on a composite plate with delamination, are then performed in the time domain. In all cases, an excellent conformation of the voltage profile at any point in the film domain to the velocity profile at the corresponding point in the film-host interface is observed. Again, to quantify the extent of damage in the host, we proffer electrical measures based on the Lpnorm, of second order, of the voltage and its directional derivatives. We exemplify the numerical implications of these measures in the time domain through sensitivity analysis in regard to the defected areas, and their region of occurrence relative to the film sensor. The response of the film model educes that the relatively flat curves after the first incident pulse in a healthy structure shoots off to a monotonic pattern in damaged hosts. The measures depict high degree of sensitivity in regard to the variation in the area of damage of any nature. An apposition of the static and dynamic analyses is elaborated towards the end of this dissertation. It proves to be very insightful in the damage assessment of the host structure, for it shows the utility of the dynamic model to sense the location of the damage occurrence, whereas a more in-depth assessment on its nature and mode of the crack would demand a static analysis in its proximal regions. To sum up, in light of these models and the proposed measures, this thesis establishes salient justifications pertaining to their pragmatic significance. We believe that these results represent an important contribution towards the ongoing research on understanding the role of boundary constraints in mechanically thin Piezoelectric films.

Sensors is one of the major areas of current research. Thin film micro/nano sensors are gaining attention worldwide, as there is necessity of miniaturization. There are varieties of sensors available by utilizing different materials in bulk and thin film form for measuring parameters like temperature, pressure, flow, humidity etc. Apart from these, there are various sensors available to measure impact force. Impact sensor offers potential application possibilities in robotics, aerospace, structural & mechanical engineering and related areas. Many physical principles have been explored for the realization of impact sensor. The present thesis reports the efforts made in developing impact sensor using piezoelectric thin film. The necessary brief background information on impact sensors is presented in Chapter 1. This includes the description of available literature on impact sensors and their probable applications. In Chapter 2, a review of the various techniques such as thin film deposition techniques, film thickness measurement techniques, thin film characterization techniques, used in our work are explained in detail. Chapter 3 explains the direct and indirect methods of characterization used for confirming the piezoelectric property of zinc oxide thin films. The detailed experimental work carried out in realizing the impact sensor using piezoelectric thin films is presented in chapter 4. This includes design of the sensor, calibration setup used & the procedure followed and results obtained. Finally, we present the summary of the work carried out in the thesis, conclusions arrived at and the scope for carrying out further work in the direction of making the sensor more efficient.

"1998"--T.p. / Thesis (PhD)--Macquarie University, School of Mathematics, Physics, Computing and Electronics, 1999. / Includes bibliographical references. / Introduction -- A Michelson interferometer for measurement of piezoelectric coefficients -- The piezoelectric coefficient of gallium arsenide -- Extensional piezoelectric coefficients of gallium nitrides and aluminium nitride -- Shear piezoelectric coefficients of gallium nitride and aluminium nitride -- Electrostriction in gallium nitride, aluminium nitride and gallium arsenide -- Summary and prognosis. / The present work represents the first use of the interferometric technique for determining the magnitude and sign of the piezoelectric coefficients of III-V compound semiconductors, in particular gallium arsenide (GaAs), gallium nitride (GaN), and aluminium nitride (AIN). The interferometer arrangement used in the present work was a Michelson interferometer, with the capability of achieving a resolution of 10⁻¹³ m. -- The samples used were of two types. The first were commercial wafers, with single crystal orientation. Both GaAs and GaN were obtained in this form. The second type of sample was polycrystalline thin films, grown in the semiconductor research laboratories at Macquarie University. GaN and AIN samples of this type were obtained. -- The d₁₄ coefficient of GaAs was measured by first measuring the d₃₃ value of a [111] oriented sample. This was then transformed to give the d₁₄ coefficient of the usual [001] oriented crystal. The value obtained for d₁₄ was (-2.7 ± 0.1) pmV⁻¹. This compares well with the most recent reported measurements of -2.69 pmV⁻¹. The significance of the measurement is that this represents the first time this coefficient has been measured using the inverse piezoelectric effect. -- For AIN and GaN samples, the present work also represents the first time their piezoelectric coefficients have been measured by interferometry. For GaN, this work presents the first reported measurements of the piezoelectric coefficients, and some of these results have recently been published by the (Muensit and Guy, 1998). The d₃₃ and d₃₁ coefficients for GaN were found to be (3.4 ± 0.1) pmV⁻¹ and (-1.7 ± 0.1) pmV⁻¹ respectively. Since these values were measured on a single crystal wafer and have been corrected for substrate clamping, the values should be a good measure of the true piezoelectric coefficients for bulk GaN. -- For AIN, the d₃₃ and d₃₁ coefficients were found to be (5.1 ± 0.2) pmV⁻¹, and (-2.6 ± 0.1) pmV⁻¹ respectively. Since these figures are measured on a polycrystalline sample it is quite probable that the values for bulk AIN would be somewhat higher. / The piezoelectric measurements indicate that the positive c axis in the nitride films points away from the substrate. The piezoelectric measurements provide a simple means for identifying the positive c axis direction. -- The interferometric technique has also been used to measure the shear piezoelectric coefficient d₁₅ for AIN and GaN. This work represents the first application of this technique to measure this particular coefficient. The d₁₅ coefficients for AIN and GaN were found to be (-3.6 ± 0.1) pmV⁻¹ and (-3.1 ± 0.1) pmV⁻¹ respectively. The value for AIN agrees reasonably well with the only reported value available in the literature of -4.08 pmV⁻¹. The value of this coefficient for GaN has not been measured. -- Some initial investigations into the phenomenon of electrostriction in the compound semiconductors were also performed. It appears that these materials have both a piezoelectric response and a significant electrostrictive response. For the polycrystalline GaN and AIN, the values of the M₃₃ coefficients are of the order of 10⁻¹⁸ m²V⁻². The commercial single crystal GaN and GaAs wafers display an asymmetric response which cannot be explained. / Mode of access: World Wide Web. / Various pagings ill

Low-power requirements of contemporary sensing technology attract research on alternate power sources that can replace batteries. Energy harvesters function as power sources for sensors and other low-power devices by transducing the ambient energy into usable electrical form. Energy harvesters absorbing the ambient vibrations that have potential to deliver uninterrupted power to sensing nodes installed in remote and vibration rich environments motivate the research in vibrational energy harvesting. Piezoelectric bimorphs have been demonstrating a pre-eminence in converting the mechanical energy in ambient vibrations into electrical energy. Improving the performance of these harvesters is pivotal as the energy in ambient vibrations is innately low. The present work is organized in three major sections: firstly, audit of the energy available in a vibrating source and design for effective transfer of the energy to harvesters, secondly, design of vibration energy harvesters with a focus to enhance their performance, and lastly, identification of key performance metrics influencing conversion efficiencies and scaling analysis for MEMS harvesters. Typical vibration levels in stationary installations such as surfaces of blowers and ducts, and in mobile platforms such as light and heavy transport vehicles, are determined by measuring the acceleration signal. The frequency content in the signal is determined from the Fast Fourier Transform. A method of determining the energy associated with the vibrating source and the associated power using power spectral density of the signal is proposed. Power requirements of typical sensing nodes are listed with an intent to determine the adequacy of energy harvesting. Effective transfer of energy from a given vibration source is addressed through the concept of dynamic vibration absorption, which is a passive technique for suppressing unintended vibrations. Optimal absorption of energy from a vibration source entails the determination of absorber parameters such as resonant frequency and damping. We propose an iterative method to obtain these parameters for a generic case of large number of identical vibration absorbers resembling harvesters by minimizing the total energy absorbed by the system. The proposed method is verified by analysing the response of a set of cantilever absorber beams placed on a vibrating cantilever plate. We find, using our method, the values of the absorber mass, resonant frequency and damping of the absorber at which significant amount of energy supplied to the system flows into the absorber, a scenario which is favourable for energy harvesting. We emphasize through our work that monitoring energies in the system and optimizing their flow is both rational and vital for designing multiple harvesters that absorb energy from a given vibration source optimally. Enhancing the performance of piezoelectric energy harvesters through a multilayer and, in particular, a multistep configuration is presented. Partial coverage of piezoelectric material in steps along the length of a cantilever beam results in a multistep piezoelectric energy harvester. We find that the power generated by a multistep beam is almost twice of that generated by a multilayer harvester made out of the same volume of polyviny-lidine fluoride (PVDF), further corroborated experimentally. Improvements observed in the power generated prove to be a boon for weakly coupled, low pro le, piezoelectric materials. Thus, in spite of the weak piezoelectric coupling observed in PVDF, its energy harvesting capability can be improved significantly by using it in a multistep piezoelectric beam configuration. Besides, the effect of piezoelectric step length and thickness in a piezoelectric unimorph harvester and performance metrics such as piezoelectric coupling factor and efficiency of conversion are presented. Modeling of a hybrid energy harvester composed of piezoelectric and electromagnetic mechanisms of energy conversion motivated by the need to determine the contribution of each domain to the power generated by the harvester is presented, particularly, when multiple domains exist in a single harvester. Two exclusive schemes of energy transduction are represented using equivalent circuits, which allow modeling any additional transduction scheme employed in the hybrid harvester with relative ease. Furthermore, a method of determining optimal loads in the respective domains using the equivalent circuit of the hybrid harvester is presented. Four different hybrid energy harvesters were fabricated and evaluated for their performance in comparison with that estimated from the proposed models. Additionally, scaling laws for hybrid energy harvesters are presented. The power developed by both piezoelectric and electromagnetic domains is observed to decrease with width and length cubed. Power indices and figures of merit in a hybrid harvester are proposed and are used to estimate the efficiencies of the four fabricated hybrid harvesters. The important design parameters for micro scale harvesting are identified by performing scaling analysis on MEMS piezoelectric harvesters. Performance of energy harvesters is directly related to the harvester attributes, viz., size, material, and end-mass. Depending on the contribution from each attribute, the power developed by MEMS harvesters can vary widely. A novel method of delineating the power developed by a harvester using five exclusive factors representing scaling, composition, inertia, material, and power (SCIMP) factors is presented. Although the proposed method can be extended to bi-morph and multilayer harvesters, in the present work, we elucidate it by applying it to a MEMS unimorph. We also present a unique coupling factor that ensures maximum power factor in a harvester. As any tiny increment in the power generated would considerably improve the power densities of MEMS harvesters, we focus on enhancing the power developed by maximizing each of the five exclusive factors irrespective of material and size. Furthermore, we demonstrate the competence of the proposed method by applying it on nine different MEMS harvesters reported in the literature. Considering the close match between the reported and predicted performance, we emphasize that monitoring the proposed factors is sufficient to attain the best performance from a harvester.

Materiais piezocompósitos laminados são compostos por camadas de material piezelétrico, metálico e compósito (matriz epóxi com fibras de carbono ou de vidro), que possibilitam obter vantagens em relação aos materiais piezelétricos convencionais, permitindo obter características superiores que não podem ser conseguidas pelos seus componentes de forma isolada como, por exemplo, maior flexibilidade e resistência mecânica ou menor peso. Sob esse enfoque, este trabalho tem por objetivo o desenvolvimento de Estruturas Piezocompósitas Laminadas (EPLA) que consistem basicamente em estruturas multicamadas, através do projeto da sua resposta transiente e harmônica visando aplicações dinâmicas. Entre as potenciais aplicações dessas estruturas, tem-se atuadores, motores, sonares e dispositivos de coleta de energia (\"energy harvester\"), sendo de muito interesse a melhora das suas características dinâmicas e o seu desempenho. O projeto dinâmico de uma EPLA é complexo, porém pode ser sistematizado utilizando o Método de Otimização Topológica (MOT). O MOT é um método baseado na distribuição de material num domínio de projeto fixo com o objetivo de extremizar uma função de custo sujeita às restrições inerentes do problema, combinando algoritmos de otimização e de elementos finitos. A formulação de MOT para o projeto dinâmico de EPLA pretende determinar tanto a topologia ótima dos materiais nas diferentes camadas quanto o sinal de polarização do material piezelétrico e o ângulo da fibra na camada compósita, tendo como finalidade a maximização da amplitude de vibração em pontos determinados (em atuadores) ou da geração de energia elétrica a partir de excitações mecânicas (em coletores de energia). Além disso, é formulado um problema combinando os enfoques harmônico e transiente com o intuito de customizar a resposta da EPLA, de modo que, o nível da resposta seja o mesmo perante diferentes tipos de onda de excitação (transdutores multi-entrada). O trabalho inclui as etapas de projeto, simulação, fabricação e caracterização de protótipos. / Laminated piezocomposite materials are composed by layers of piezoelectric, metal and composite material (epoxy matrix with carbon or glass fiber), which have advantages over conventional piezoelectric materials, because of their superior characteristics, which cannot be achieved by any of its components isolated, for example, more flexibility and strength and less weight. Under this approach, this work aims at the development of Laminated Piezocomposite Structures (LAPS) what primarily consist of multi-layer structures, through the transient and harmonic response design aiming at dynamic applications. Among the potential applications of these structures it can be cited actuators, motors, sonar devices and energy harvester, being of great interest the improvement of its dynamic characteristics and performance. The dynamic design of a LAPS is complex however it can be systematized by using the Topology Optimization Method (TOM). The TOM is a method based on the distribution of material in a fixed design domain with the aim of extremizing a cost function subject to constraints inherent to the problem by means of combining the optimization algorithms and the finite element method (FEM). The TOM formulation for the LAPS dynamic project aims to determine together the optimal topology of the materials for different layers, the polarization sign of the piezoelectric material and the fiber angle of the composite layer, in order to maximize the vibration amplitude at certain points (in actuators), or the generation of electrical energy from mechanical excitations (in energy harvesters). In addition, a TOM problem combining harmonic and transient approaches is formulated with the purpose of customizing EPLA response so that the response level is the same for different excitation waveforms (multi-entry transducers). The work includes design, simulation, manufacturing and characterization of prototypes.

This theis deals with the general overview of the piezoelectric theory, focused both on the mathematical description and on the attributes of piezoelectric materials. It further focuses on the description of piezoelectric resonators with a more detailed explantation of their equivalent scheme and measurement methods of its single elements. The practical part of the thesis rests on the proposal of a measurement apparatus which will serve to measuring the equivalent circuit piezoelectric resonator elements. The realization of the apparatus and its functionality testing are described. In the experimental part of the thesis, the measured rates are processed and levels of the electric equivalent circuit elements of the used piesoelectric resonator for the basic and the two higher closest resonance frequency are set. The measured results are compiled into a standard measurement protocol. This thesis should place basics to the growing laboratory. It should also be a source of necessary theoretical and practical information for this lab.