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1
Liu, Guoning. "Application of fracture mechanics in electrical/mechanical failures of dielectrics /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?MECH%202006%20LIU.
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Joshi, Rucha. "Vibroacoustic source characterization of electrical pumps with application to residential dishwashers." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1555516017124571.
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Micski, Erik, and Ulrika Ottosson. "Calculation of Tidal Volume based on EMG-activity of the Diaphragm." Thesis, KTH, Skolan för teknik och hälsa (STH), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-210547.
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The objective of the thesis was to evaluate the possibility to calculate the unloading distribution between a ventilator and a patient using a new mathematical modelling of the breathing patterns. The modelling used today is considered to lack sufficient precision for clinical use, and is a somewhat simplified model. To evaluate the possibility of a new model, a volunteer test was carried out - recording data such as Edi, pressure, volume and flow. Using this data, and by using a more complex model, tidal volume was estimated and compared to the measured data. The results did not imply any improvement compared to the simpler model regarding the accuracy and the variability. However, more work should be done in this area, as time deficiency prevented further analysis.
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Olfati-Saber, Reza. "Nonlinear control of underactuated mechanical systems with application to robotics and aerospace vehicles." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/8979.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2001.Includes bibliographical references (leaves 308-316).
This thesis is devoted to nonlinear control, reduction, and classification of underactuated mechanical systems. Underactuated systems are mechanical control systems with fewer controls than the number of configuration variables. Control of underactuated systems is currently an active field of research due to their broad applications in Robotics, Aerospace Vehicles, and Marine Vehicles. The examples of underactuated systems include flexible-link robots, nobile robots, walking robots, robots on mobile platforms, cars, locomotive systems, snake-type and swimming robots, acrobatic robots, aircraft, spacecraft, helicopters, satellites, surface vessels, and underwater vehicles. Based on recent surveys, control of general underactuated systems is a major open problem. Almost all real-life mechanical systems possess kinetic symmetry properties, i.e. their kinetic energy does not depend on a subset of configuration variables called external variables. In this work, I exploit such symmetry properties as a means of reducing the complexity of control design for underactuated systems. As a result, reduction and nonlinear control of high-order underactuated systems with kinetic symmetry is the main focus of this thesis. By "reduction", we mean a procedure to reduce control design for the original underactuated system to control of a lowerorder nonlinear or mechanical system. One way to achieve such a reduction is by transforming an underactuated system to a cascade nonlinear system with structural properties. If all underactuated systems in a class can be transformed into a specific class of nonlinear systems, we refer to the transformed systems as the "normal form" of the corresponding class of underactuated systems. Our main contribution is to find explicit change of coordinates and control that transform several classes of underactuated systems, which appear in robotics and aerospace applications, into cascade nonlinear systems with structural properties that are convenient for control design purposes. The obtained cascade normal forms are three classes of nonlinear systems, namely, systems in strict feedback form, feedforward form, and nontriangular linear-quadratic form. The names of these three classes are due to the particular lower-triangular, upper-triangular, and nontriangular structure in which the state variables appear in the dynamics of the corresponding nonlinear systems. The triangular normal forms of underactuated systems can be controlled using existing backstepping and feedforwarding procedures. However, control of the nontriangular normal forms is a major open problem. We address this problem for important classes of nontriangular systems of interest by introducing a new stabilization method based on the solutions of fixed-point equations as stabilizing nonlinear state feedback laws. This controller is obtained via a simple recursive method that is convenient for implementation. For special classes of nontriangular nonlinear systems, such fixed-point equations can be solved explicitly ...
by Reza Olfati-Saber.
Ph.D.
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Jones, Dewi Ieuan. "Contributions to the application and implementation of control methods in electrical and mechanical systems." Thesis, Bangor University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395412.
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Sivabavanandan, Sivalingam. "Thermal energy storage application for load shifting and electrical demand management in Saudi Arabia." Thesis, Kingston University, 2005. http://eprints.kingston.ac.uk/35780/.
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Energy plays a major role in the economic prosperity of the Middle Eastern countries. Since the region is the largest oil producer of the world, it is less anticipated that these countries would ever be face with an energy crisis similar to the one experienced by the rest of the world during 1970s. The region was going through a chronic electricity demand supply crises with the demand for electrical energy in the rapidly expanding towns, cities and industries, far exceeding the power being made available. The relatively low electrical tariff also contributed to the increasing power demand due to wastage and uneconomical usage of electrical energy. The power generating companies and the Government authorities in the Middle East encouraged scientists and engineers to engage in ambitious Demand Side Management (DSM) programmes to develop novel ideas and new technologies to improve system efficiencies and to reduce energy consumption specifically in the field of refrigeration and air conditioning. The researcher began analysing the potential and possible applications of cool storage as a tool for Demand Side Management (DSM) in central air conditioning systems in the Middle East in 1991. The coupling of a refrigerated water storage tank or an ice storage tank to an air-cooled chiller plant, operated at night for load shifting, electrical peak demand reduction and energy conservation has been the major interest of investigation. The model project commissioned in 1996 used as a typical example to investigate electrical demand management for an office building in Riyadh, Saudi Arabia. The aim of this research was to develop new modified comfort cooling system coupled with a cool storage or commonly known as Thermal Energy Storage (TES) network. The research was expected to establish certain favouring conditions in relation to technical, economical and environmental criteria to make the TES application a viable option in comfort cooling systems in commercial buildings in the Middle East for electrical demand reduction, load shifting and energy conservation.
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Mehregany, Mehran. "Application of micromachined structures to the study of mechanical properties and adhesion of thin films." Thesis, Massachusetts Institute of Technology, 1986. http://hdl.handle.net/1721.1/15012.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1986.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING
Bibliography: leaves 131-141.
by Mehran Mehregany.
M.S.
8
Poljak, Daniel Oliver [Verfasser]. "Application of the method of Controlled Lagrangians: from mechanical to electrical systems / Daniel Oliver Poljak." Aachen : Shaker, 2012. http://d-nb.info/1052408443/34.
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Moosavi, Seyed Mahmoud. "DERIVATIVE-FREE KALMAN FILTER-BASED CONTROL OF NONLINEAR SYSTEMS WITH APPLICATION TO TRANSFEMORAL PROSTHESES." Cleveland State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=csu1502481884476173.
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Zuo, Lei 1974. "Optimal control with structure constraints and its application to the design of passive mechanical systems." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/68378.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.Page 214 blank.
Includes bibliographical references.
Structured control (static output feedback, reduced-order control, and decentralized feedback) is one of the most important open problems in control theory and practice. In this thesis, various techniques for synthesis of structured controllers are surveyed and investigated, including H2 optimization, H[infinity] optimization, L1 control, eigenvalue and eigenstructure treatment, and multiobjective control. Unstructured control-full- state feedback and full-order control-is also discussed. Riccati-based synthesis, linear matrix inequalities (LMI), homotopy methods, gradient- and subgradientbased optimization are used. Some new algorithms and extensions are proposed, such as a subgradient-based method to maximize the minimal damping with structured feedback, a multiplier method for structured optimal H2 control with pole regional placement, and the LMI-based H2/H[infinity]/pole suboptimal synthesis with static output feedback. Recent advances in related areas are comprehensively surveyed and future research directions are suggested. In this thesis we cast the parameter optimization of passive mechanical systems as a decentralized control problem in state space, so that we can apply various decentralized control techniques to the parameter design which might be very hard traditionally. More practical constraints for mechanical system design are considered; for example, the parameters are restricted to be nonnegative, symmetric, or within some physically-achievable ranges. Marginally statable systems and hysterically damped systems are also discussed. Numerical examples and experimental results are given to illustrate the successful application of decentralized control techniques to the design of passive mechanical systems, such as multi-degree-of-freedom tuned-mass dampers, passive vehicle suspensions, and others.
by Lei Zuo.
S.M.
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Liu, Xiaoxu. "Fault estimation and fault tolerant control with application to wind turbine systems." Thesis, Northumbria University, 2017. http://nrl.northumbria.ac.uk/35954/.
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In response to the high demand of the operation reliability by implementing real-time monitoring and system health management, the three-year PhD project focuses on developing robust fault diagnosis and fault tolerant control strategies for complex systems with high-nonlinearities, stochastic Brownian perturbations, and partially decoupled unknown inputs, which are then applied to wind turbine energy systems. Integration of serval advanced approaches, including the augmented system method, unknown input observer design, Takagi-Sugeno fuzzy logic, linear matrix inequality optimization, and signal compensation techniques enable us to achieve robust estimations of both the system states and the faults concerned simultaneously, while removing/reducing the adverse influences from faults to the system dynamics. Prior to the existing work, the considered unknown inputs can be partially decoupled rather than completely decoupled, which can meet a wider practical requirement. Moreover, the systems under investigation can be linear, Lipschitz nonlinear, quadratic inner-bounded nonlinear, high-nonlinear characterized by a Takagi-Sugeno fuzzy model, and stochastic with Brownian perturbations, which can cover a wide range of real industrial plants. Specifically, the augmented system method is used to construct an augmented plant with the concerned faults and system states being the augmented states. Unknown input observer technique is thus utilized to estimate the augmented states and decouple unknown inputs that can be decoupled. Linear matrix inequality approach is further addressed to ensure the stability of the estimation error dynamics and attenuate the influences from the unknown inputs that cannot be decoupled. As a result, the robust estimates of the faults concerned and system states can be obtained simultaneously. Based on the fault estimates, a signal compensation scheme is developed to remove/offset the effects of the faults to the system dynamics and outputs, leading to a stable dynamic satisfying the expected performance. A case study on a 4.8 MW wind turbine benchmark system is proposed to illustrate and demonstrate the proposed integrated fault tolerant control techniques. Takagi-Sugeno modelling of a wind turbine system is presented as a by-product. To summarize, the proposed integrated fault estimation and fault tolerant control strategy can handle a system with highly nonlinear dynamics in a strong disturbance/noise environment (e.g., partially-decoupled process disturbances and stochastic parameter perturbations), which is validated by a real-time wind turbine system. As a result, the presented methods/algorithms have enriched fault diagnosis and tolerant control theory with high-novelty and great potentials for practical applications.
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Menon, Manas Chandran. "Design of an instrumented multifunctional foot for application to a heavy duty mobile robot manufacturing system." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/45959.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.Includes bibliographical references (p. 56-57).
The design of a multifunctional foot for application to a mobile robotic system for heavy duty manufacturing is presented. The requirements for a target manufacturing task are presented and translated into requirements for the mobile robotic system, and specifically for the feet of this system. This includes: the ability of the feet to change frictional properties, the ability of the foot to operate without a direct power source, and load bearing requirements for heavy duty tooling. The mechanical design to meet these requirements for these feet is presented. Stability analysis is shown, and it is used to determine several design parameters to meet the goals of the project. The development of a series of iterations of prototypes is discussed. Manufacturing techniques, choice of materials, alignment strategies and assembly practices are explained. Appendices include information about several of the important design milestones. A sensing methodology is introduced. Computer simulations of magnetic fields to estimate the effectiveness of this methodology are performed. Experimental results are shown to match the simulations. A final functional prototype is shown. Testing is performed on this prototype to verify that it meets the functional requirements desired for the system.
by Manas Chandran Menon.
S.M.
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Yunus, Pg Hj Md Esa Al-Islam bin Pg Hj Md. "Carbon nanotube surfaces for low force contact application." Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/67624/.
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This thesis focuses on developing a testing method to estimate the mechanical and electrical characteristics of CNT-based contact surfaces. In particular the use of gold thin films deposited on a CNT forest has potential to offer a very effective contact surface. Two different pieces of experimental apparatus were used in this research to determine the mechanical and electrical properties of gold/multi-walled carbon nanotube (Au/MWCNT) composites: 1) a modified nano-indentation; and 2) a PZT actuator test rig. These apparatuses were used to mimic force-displacement and contact behaviour of the MEMS relay‟s contact at a maximum load of 1 mN with dry-circuit and hot-switched conditions. The surfaces were compared with reference Au-Au and Au-MWCNT contact pairs studied under the same experimental conditions. In the modified nano-indentation experiment, tests of up to 10 cycles were performed. The results showed that the Au-MWCNT pair electrical contact resistance improved when the Au-Au/MWCNT pair was used. Additionally the Au-Au/MWCNT pair electrical contact resistance (Rc) was comparable with the Au-Au contact pair. When the Au-Au/MWCNT composite surface is in contact with the Au hemispherical probe it provides a compliant surface. It conforms to the shape of the Au hemispherical probe. For a higher number of cycles, a PZT actuator was used to support Au/MWCNT planar coated surfaces. This surface makes electrical contact with a gold coated hemispherical probe to mimic the actuation of a MEMS relay‟s contact at higher actuation frequencies. This apparatus allows the performance of the contact materials to be investigated over large numbers of switching cycles. Different current loads were used in this experiment, 1mA, 10mA, 20mA and 50mA at 4V supply. The Rc of these surfaces was investigated as a function of the applied force under repeated cycles. Under current loads of 1mA and 10mA the Au/MWCNT composite surface provides a stable contact resistance of up to more than a million cycles and no degradation was observed on the surface. Compared with Au-Au contact pair, degradation occurred after 220 cycles. The Au-Au contact pair shows delamination of the Au surface on the probe. The possible reason is the softening or melting of the Au surface. Furthermore, under higher current loads of 20mA to 50mA, degradation had occurred after 50 million cycles (at 20mA) and degradation had occurred at around 45 to 150 cycles for 50mA to 30mA respectively. This is because of the softening or melting of the Au and Au fatigue after a large number of cycles. This study is the first step to show the potential of CNT surfaces as an interface in low force electrical contact applications. With this research, current trends in materials used on contacts and fabrication methods can be explored and even modified or adopted. The use of CNT‟s and their composites for contacts can be tested using the available apparatus to look at their performance and reliability in terms of mechanical and electrical properties. This is useful for MEMS contacts that form part of MEMS relay devices.
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McRae, Calum George Alexander. "Approaches to functional electrical stimulation induced cycling and application for the child with a spinal cord injury." Thesis, University of Glasgow, 2006. http://theses.gla.ac.uk/1526/.
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In the hope of more compact and user-friendly approaches to FES-cycling through the incorporation of modern sensor and computing technology, two new hip-angle-based strategies (both of which utilise a limb-mounted sensor) and a “traditional” crank-angle-based strategy have been developed and incorporated into a PDA-based multi-functional FES system. Through both simulation and tricycle-based experiments, all three approaches have been shown to provide practical stimulation activation timing. The second research focus concerns the development of two FES-cycling systems which are suitable for a spinal cord injured child, and methods to facilitate the intended use of both devices. A standard child’s tricycle has been modified with appropriate instrumentation for FES-cycling and testing involving its target population was carried out at a US-based paediatric research hospital. These experiments culminated in the demonstration of FES-cycling by an untrained seven year old T4/T6 (motor complete) subject, and the evolution of the device into one which should be able to meet the specific needs of spinal cord injured children. A second system with integrated motor has also been developed. As well as offering motor assistance, this device incorporates additional instrumentation to allow investigation into exercise and training capabilities. Experiments have been undertaken to validate this equipment and it is now ready for future pilot work involving paediatric subjects. The two research foci in this thesis represent what are, in our opinion, important routes that FES-cycling should take to progress into the home environment and also allow participation of a population who have potentially the most to gain from using it.
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Bull, James. "Application of Quantum Mechanics to Fundamental Interactions in Chemical Physics: Studies of Atom-Molecule and Ion-Molecule Interactions Under Single-Collision Conditions: Crossed Molecular Beams; Single-Crystal Mössbauer Spectroscopy: Microscopic Tensor Properties of ⁵⁷Fe Sites in Inorganic Ferrous High-Spin Compounds." Thesis, University of Canterbury. Department of Chemistry, 2010. http://hdl.handle.net/10092/4292.
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As part of this project and in preparation for future experimental studies of gas-phase ion-molecule reactions, extensive modification and characterization of the crossed molecular beam machine in the Department of Chemistry, University of Canterbury has been carried out. This instrument has been configured and some
preliminary testing completed to enable the future study of gas-phase ion-molecule collisions of H⁺₃ and Y⁻ (Y
= F, Cl, Br) with dipole-oriented CZ₃X (Z = H, F and X = F, Cl, Br). Theoretical calculations (ab initio
and density functional theory) are reported on previously experimentally characterized Na + CH₃NO₂, Na + CH₃NC, and K + CH₃NC systems, and several other systems of relevance. All gas-phase experimental and theoretical studies have the common theme of studying collision orientation dependence of reaction under singlecollision
conditions. Experimental measurements, theoretical simulations and calculations are also reported on some selected ferrous (Fe²⁺) high-spin (S=2) crystals, in an attempt to resolve microscopic contributions of two fundamental macroscopic tensor properties: the electric-field gradient (efg); and the mean square displacement (msd) in the case when more than one symmetry related site of low local point-group symmetry contributes to the same quadrupole doublet. These determinations have been made using the nuclear spectroscopic technique of Mössbauer spectroscopy, and complemented with X-ray crystallographic measurements.
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Parro, Rocco John III. "THE MECHANICAL PROPERTIES OF AMORPHOUS SILICON CARBIDE FILMS DEPOSITED BY PECVD AND RF SPUTTERING FOR APPLICATION AS A STRUCTURAL LAYER IN MICROBRIDGE-BASED RF MEMS." Case Western Reserve University School of Graduate Studies / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1270241057.
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Neal, John. "Experimental Investigation of a Hybrid Energy Storage System in an Engine Stop-Start Application." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1367432710.
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Qin, Zhenpeng. "Modeling of Ion Transport for Micro/Nano Size Particles in Coulter Counter Application." University of Akron / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=akron1240858653.
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El, zein Racha. "Solid supported lipid monolayer : From biophysical properties to sensor application." Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4014/document.
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Le but de ce projet est d'étudier les propriétés mécaniques et électriques d'une monocouche de phospholipide supportée sur silicium en vue de son utilisation comme diélectrique de grille dans un biocapteur à transistor à effet de champ. Ces monocouches de 3nm sont formées par fusion de vésicules. Les lipides utilisés possèdent des triples liaisons dans leurs chaînes alkyles permettant une polymérisation radicalaire. Nous montrons que la polymérisation stabilise la monocouche à l'air et améliore sa résistance mécanique. Les mesures ont été réalisées par mesure de force par AFM, la force de ‘rupture' de la monocouche par la pointe AFM augmentant après polymérisation. L'étude de la force en fonction de la vitesse d'approche de la pointe nous a permis de montrer que la rupture de la couche est un phénomène activé qui dépend de la vitesse. Nous avons pu ainsi déterminer pour chacune des deux surfaces, polymérisées ou pas, l'énergie d'activation de rupture de la couche du système couche/pointe et une estimation du module de Young. Ces grandeurs qui augmentent après polymérisation montrent une amélioration des propriétés mécaniques. Nous nous intéressons également aux propriétés électriques de ces monocouches. Nous avons réalisé des mesures Courant-Tension I(V) à partir desquelles nous avons pu déterminer la résistance de la couche, les densités de courant de fuite et la tension de claquage. Les résultats obtenus démontrent que ces monocouches ultrafines possèdent de très bonnes propriétés isolantes. De plus nous avons révélé la propriété très intéressante d'auto-régénération de la monocouche isolante après claquage à l'air, à température ambiante en quelques minutes seulementThe main goal of this project was to study the electrical and mechanical properties of a solid supported lipid monolayer in order to use it as a dielectric insulator in a Field Effect Transistor based biosensor. The 3 nm lipid monolayer supported on silicon was obtained by the vesicle fusion method. DC8,9PC phospholipids containing acetylenic moiesties were selected. The lipid monolayer was stabilized on the substrate by two-dimensional polymerization in the plane of the layer. We demonstrate that this polymerization stabilizes the monolayer in air. Force measurements realized by AFM on both polymerized and non-polymerized layers demonstrated a net improvement of the nano-mechanical resistance of the layer after polymerization with a net increase of the force required to rupture the layer. Measurements realized at different loading rates have evidenced the fact that the monolayer rupture is an activated process that depends on the loading rate. For both types of layers, we have determined the intrinsic rupture activation energy of the tip–layer system as well as their Young modulus. These two physical quantities increase after polymerization and demonstrate a net improvement of the mechanical properties of the polymerized monolayer. The electrical properties of these layers have also been investigated. Current-Voltage measurements were done on the monolayer in the air at room temperature. The differential resistance, the leakage current, the breakdown voltages were measured and showed that the polymerized monolayer behaves as a good electric insulator. In addition, we demonstrated a very interesting property of autonomic self-healing after electrical breakdown
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Comby, Dassonneville Solène. "Développement et application d'un nanoindenteur in situ MEB couplé à des mesures électriques." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAI047/document.
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L’essor de la demande actuelle pour des matériaux architecturés, en microélectronique par exemple, ou pour des matériaux de structure, nécessite le développement d’outils de caractérisation toujours plus performants. Dans cette optique, un instrument de caractérisation multifonctionnel basé sur un couplage mécanique / électrique, a été développé au laboratoire SIMaP. Le cœur de ce dispositif est un nanoindenteur in situ FEG-SEM (Field Emission Gun Scanning Electron Microscope) couplé à des mesures électriques. Ce travail est porté par trois principales motivations: (1) L’étude du comportement mécanique d’objets petites échelles, (2) L’apport des données électriques à l’analyse quantitative du comportement mécanique pendant l’indentation, en particulier pour obtenir une meilleur estimation de l’aire de contact, (3) L’étude locale des propriétés électroniques d’empilements de films minces. L’intégration in situ SEM a été validée et permet un positionnement des indents avec une précision meilleure que 100 nm, autorisant ainsi l’étude des propriétés mécaniques à l’échelle submicrométrique. La rapidité des essais permet également des mesures statistiques. Des caractérisations mécaniques ont été menées aussi bien sur des échantillons composites massifs que sur des ilots d’or submicrométriques. Pour ce dernier cas, malgré la nature stochastique de leur comportement mécanique, une loi déterministe a pu être extraite des données mécaniques. Des mesures 3D-BCDI (Bragg Coherent Diffraction Imaging) au synchrotron ont été réalisées sur certains ilots avant et après chargement mécanique, révélant une germination de dislocations avant l’avalanche de grandes déformations plastiques. En parallèle de cette étude, des mesures électriques ont été réalisées pendant l’indentation de divers échantillons. Des mesures de nanoindentation résistive ont ainsi été effectuées sur des métaux nobles (Au) ou recouverts de leur oxyde natif (Cu, Al), soit à l’état de monocristal massif ou de film polycristallin. Les résultats quantitatifs soulignent l’importance de la présence d’une couche d’oxyde sur la réponse électrique. En présence d’un oxyde, l’interface pointe / échantillon semble être le lieu d’importantes réactions électrochimiques. En l’absence d’oxyde, la résistance mesurée peut être entièrement décrite par un modèle analytique. Dans ce cas, l’aire de contact électrique peut être prédite à partir des mesures de résistance. Enfin, des mesures capacitives ont été réalisées sur des structures MOS avec différentes épaisseurs d’oxyde. Les résultats expérimentaux sont parfaitement décrits par un modèle analytique, ce qui ouvre la voie à des mesures locales de permittivité diélectrique sous contrainte mécaniqueThe increasing demand for multifunctional materials has become a recurrent challenge for a wide panel of application fields such as microelectronics and structural applications. Within the frame of this project, a multifunctional characterisation set-up has been developed at SIMaP lab, mainly based on the electrical / mechanical coupling. The heart of this device is an in situ FEG-SEM (Field Emission Gun Scanning Electron Microscope) nanoindenter coupled with an electrical measurement apparatus. This work has threefold objectives: (1) The investigation of mechanical behavior of small scale systems, (2) The input of electrical data to the quantitative analysis of mechanical behavior during indentation, in particular to obtain a better estimation of the contact area (3) The local study of electronic properties of thin film stacks. SEM integration of the device has been validated and indent positioning with a precision better than 100 nm is successfully obtained. This performance allows the studies of mechanical properties at submicrometric length scale, with a high throughput allowing statistical measurements. Various bulk composite materials have been characterized as well as submicrometric gold islands on sapphire. In the latter case, despite the stochastic nature of their mechanical behavior, a deterministic law has been extracted. 3D-BCDI (Bragg Coherent Diffraction Imaging) experiments have been performed on a few islands at synchrotron facility to investigate the crystal state before and after mechanical loading. These experiments reveal initial dislocation nucleation prior to large deformation bursts. In parallel to this study, electrical measurements have been performed during indentation on various cases. Resistive-nanoindentations have been performed on noble metals (Au) and natively oxidized metals (Cu, Al), either as bulk single crystals or as polycrystalline thin films. Qualitative results emphasize the importance of the oxide layer on the electrical response. In the presence of an oxide layer, strong electrochemical reactions seem to occur at the tip-to-sample interface. When no oxide is involved, the measured resistance can be fully described by an analytical model and the computed electrical contact area is successfully validated with residual areas measurements. Finally, capacitive measurements have been performed on MOS structures with various oxide thicknesses. Experimental results have been well described by analytical modelling, which paves the way for quantitative local dielectric permittivity measurements under mechanical loading
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BAMDAD-SOOFI, JAHANSHAH. "Performances mecaniques du rotor d'une eolienne darrieus et application a "aeolia 3" en fonctionnement." Paris, ENSAM, 1986. http://www.theses.fr/1986ENAM0006.
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Etude des contraintes et des deformees du rotor pour toute situation de fonctionnement optimal, suivant trois etapes de recherche: 1. Analyse de fabrication des pales d'aeolia 3 (forme troposkienne de construction, parametres geometriques, contraintes normales dues au procede de cintrage). 2. Analyse du comportement statique du rotor. 3. Analyse du comportement dynamique des pales en fonctionnement (y compris l'arret) avec determination des modes propres du rotor et des deformees modales. Deux methodes de calcul, toutes deux matricielles, ont ete etudiees selon les besoins en rapidite du calcul et de sa mise au point et selon les besoins de precision des resultats
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Laurent, Fabrice. "Croissance de nanotubes de carbone sur des fibres de carbone : application aux matériaux composites." Thesis, Mulhouse, 2016. http://www.theses.fr/2016MULH7632/document.
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Le travail présenté dans ce mémoire de thèse s’est inscrit dans le cadre du développement de la technologie flamme oxyacétylénique pour la synthèse de nanotubes de carbone (NTC) au Laboratoire de Physique et Mécanique Textile. La simplicité et l’originalité de ce procédé en font un candidat très sérieux pour envisager la mise en œuvre d’un pilote industriel pour la production de fibres de renforcement multidimensionnelles, notamment composées de fibres de carbone sur lesquelles ont cru de nanotubes de carbone. Ce travail a consisté à :- Réaliser une étude bibliographique sur les procédés de croissance de NTC,- Etablir la preuve de concept de la croissance des nanotubes sur des fibres,- Concevoir et réaliser un dispositif assurant une bonne maîtrise de la croissance,- Mettre au point le procédé de croissance sur des fibres,- Identifier les principaux paramètres influençant la qualité et la quantité des nanotubes,- Caractériser les nanotubes obtenus,- Faire croître ces nanotubes sur des fibres de carbone,- Intégrer des nouveaux matériaux multidimensionnels dans des matrices afin de réaliser des matériaux composites structurels,- Caractériser ces matériaux,- Décrire les mécanismes de croissance dans la flamme.Notre effort a porté sur le traitement des fibres avant exposition à la flamme et à évaluer les conditions de croissance des NTC en faisant varier notamment, la température d’exposition des fibres et la qualité des catalyseurs de croissance. Après synthèse des NTC sur les fibres de carbone et leur caractérisation nous avons réalisé des matériaux composites. Nous avons mesuré que les NTC améliorent significativement le module d’Young des composites mais altèrent sensiblement la contrainte à la rupture. Les propriétés électriques longitudinales et transversales sont améliorées d’un facteur 8 et 5 respectivement. Nous avons proposé des mécanismes de croissance des NTC. Ces mécanismes sont directement en relation avec propriétés physiques et chimiques des particules de catalyseurThe research presented in this work aims to develop the oxyacetylene flame method for the Carbon Nanotubes (CNT) synthesis at the Laboratory of Physics and Mechanics of Textiles. The simplicity and the degree of innovation of this process make of it a serious candidate for manufacturing a pilot in order to produce new kind of tridimensional material made of CNT having grew on carbon fibres. This work consisted of:- Make a bibliographic study,- Establish a proof of concept of the growth of CNT,- Design and manufacture a device allowing process control,- Setup the process of growth on the fibres,- Identify the main parameters influencing CNT quality and quantity,- Characterize CNT,- Assume the CNT growth on carbon fibers,- Integrate these multidimensional materials into an organic matrix to realize structural composite materials,- Characterize these materials,- Describe and explain the growth mechanism in the flame.First, we focused our work on the fibres chemical treatment before flame exposition to evaluate the NTC growth conditions by varying notably, the fibres exposition temperature and the quality of the catalysts. After, the NTC syntheses on carbon fibres (CF) was done. The multidimensional product was characterized par various examinations and analyses. Composite materials were molded with epoxy resin to evaluate mechanical properties of NTC-FC. Young’s modulus was increased and tensile strength at break decreased. Transverse and longitudinal electrical properties were increased by 500 to 800 % respectively. Finally, we proposed NTC growth mechanisms. They are directly linked to the chemical and physical catalyst particles properties
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Tardieu, Simon. "Fils conducteurs composites (microfils d'argent - cuivre) pour application en champs magnétiques intenses." Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30186.
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Le LNCMI-Toulouse produit les champs magnétiques non-destructifs pulsés parmi les plus puissants du monde (98,8 T). Les fils conducteurs utilisés dans les bobines qui génèrent ces champs magnétiques nécessitent une contrainte à la rupture élevée afin de résister aux forces de Lorentz. De plus, pour obtenir une durée d'impulsion la plus longue possible, ces conducteurs doivent avoir une résistivité électrique la plus proche possible de celle du Cu pur. Le LNCMI et le CIRIMAT explorent la conception et la préparation de fils nano-composites à matrice Cu par une combinaison de métallurgie des poudres, de frittage SPS et de tréfilage. Les poudres composites à faibles teneurs en Ag (< 10 % vol. Ag) sont préparées en dispersant des microfils d'Ag (diamètre 200 nm, longueur 30 µm) synthétisés au CIRIMAT dans une poudre commerciale de Cu sphérique (diamètre 0,5-1 µm). Les poudres ainsi obtenues sont consolidées par SPS sous forme de barreaux. Ceux-ci sont étirés sans rupture, jusqu'à l'obtention de fils fins (diamètre 1 - 0,2 mm) dont la microstructure est sous la forme de grains ultrafins de Cu (200 - 400 nm) allongés sur plusieurs micromètres dans le sens de l'étirage. Les microfils d'Ag sont dispersés le long des joints de grains du Cu. La mesure de la résistivité électrique et de la contrainte à la rupture des fils (à 293 K et 77 K) a permis de déterminer que les fils contenants seulement 1 % vol. Ag présentent le meilleur compromis contrainte à la rupture / résistivité (1100 MPa / 0,49 µÔmega.cm à 77 K). La formation d'un alliage Cu/Ag lors du frittage SPS a pour conséquence une augmentation notable de la résistivité électrique des fils et doit donc être évitée. Une matrice de Cu avec une distribution bimodale de la taille des grains permet de réduire la résistivité électrique tout en conservant une haute contrainte à la rupture (1080 MPa / 0,45 µÔmega.cm à 77 K). Les fils nano-composites Ag-Cu présentent une contrainte à la rupture équivalente à celle des fils d'alliage Cu/Ag contenant environ 20 fois plus d'Ag élaborés par fusion et solidification, mais présentent une résistivité électrique environ 1,5 fois plus faibleLNCMI-Toulouse produces some of the most intense non-destructive pulsed magnetic fields in the world (98.8 T). The wires used in coils which generate these magnetic fields require high ultimate tensile strength (UTS) in order to resist the Lorentz forces. Moreover, to obtain the longest possible pulse duration, these wires must have an electrical resistivity closest to that of pure Cu. LNCMI and CIRIMAT explore the design and preparation of Cu-based nanocomposite wires obtained by a combination of powder metallurgy, Spark Plasma Sintering (SPS) and wire-drawing. Composite powders with low Ag contents (< 10 % vol. Ag) are prepared by dispersing Ag microwires (diameter 200 nm, length 30 µm) synthesized at CIRIMAT in a commercial spherical Cu powder (diameter 0.5-1 µm). The so-obtained composite powders are consolidated by SPS in the form of cylinders. These cylinders are drawn, without breaking, in the form of fine wires (1 - 0.2 mm). The microstructure of the wires is made up of Cu ultrafine grains (200 - 400 nm) elongated over several micrometers in the drawing direction. Ag microwires are dispersed along the grain boundaries of Cu. The measurement of the electrical resistivity and the UTS of the wires (at 293 K and 77 K) shows that the wires containing only 1 vol. % Ag present the best compromise between high UTS and low electrical resistivity (1100 MPa / 0.49 µÔmega.cm at 77 K). The formation of Cu/Ag alloys during the SPS cycle significantly increases the resistivity of the wires and thus must be avoided. A Cu matrix with a bimodal grain size distribution makes it possible to reduce the electrical resistivity of the wires while keeping high UTS (1080 MPa / 0.45 µÔmega.cm at 77 K). Ag-Cu nanocomposite wires present high UTS, equivalent to that of Cu/Ag alloy wires containing about 20 times more Ag produced by melting and solidification, but their electrical resistivity is about 1.5 times lower
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Chelaghma, Saber Ayoub. "Fonctionnalisation de composites C/PEKK pour application aérospatiale : caractérisation, modélisation et influence sur les propriétés du composite." Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30362.
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La réduction du poids des avions est l'un des grands défis de l'industrie aérospatiale. Afin d'atteindre les objectifs ambitieux en matière de consommation de carburant et de réduction des émissions, des composites renforcés de fibres de carbone, ont été introduits sur le marché. Ces matériaux suscitent un intérêt croissant, néanmoins, ils possèdent une faible conductivité électrique, ne permettant pas de garantir une protection contre la foudre. Pour cette raison, les composites chargés de particules conductrices font l'objet d'activités de recherche en cours. L'objectif est le développement de composites multifonctionnels avec des propriétés électriques accrues. Pour l'heure, la matrice thermoplastique de référence est le PEEK mais ce polymère reste toutefois cher, et sa température d'élaboration élevée. Dans ce but, des matrices thermoplastiques, telles que le PEKK, sont à nouveau étudiées. Entre la matière première et la pièce finale, la matrice thermoplastique subit plusieurs cycles de traitement à haute température (imprégnation, consolidation, procédés d'assemblage) au cours desquelles sa capacité à cristalliser évolue sans cesse. Afin d'évaluer l'impact du procédé et des constituants du composite sur les propriétés du composite, la cristallisation a fait l'objet d'une attention particulière. Deux dispositifs expérimentaux complémentaires ont été utilisés afin de caractériser la cristallisation : une platine chauffante, permettant d'appliquer un cycle thermique et d'observer la cristallisation en microscopie optique ainsi que la calorimétrie différentielle à balayage. L'influence des fibres de carbone et des particules conductrices sur la cinétique de cristallisation a été évaluée. Une diminution des temps de cristallisation a été observée à travers l'augmentation du taux de germination. Les données recueillies ont servi à développer un modèle de cinétique de cristallisation identifié à travers une approche originale en se basant sur des données microscopiques et enthalpiques. Ce modèle permet de prédire les cinétiques de cristallisation des composites à matrice PEKK mais il ne permet pas de rendre compte de la microstructure finale engendrée. Or, cette dernière a un impact non négligeable sur les propriétés mécaniques comme cela a été prouvé à travers des essais de nano-indentation. Pour prévoir la microstructure finale, un modèle basé sur l'approche pixel coloring a été développé. L'influence des fibres de carbone a été introduite à travers la formation d'une phase transcristalline. Une bonne corrélation est constatée entre l'approche analytique, la simulation et les données expérimentales en termes de cinétique de cristallisation. Des caractérisations mécaniques et électriques ont été effectuées afin d'évaluer les performances de ces nouveaux matériaux. Sur les matériaux étudiés, la réponse mécanique n'est pas homogène comme observé sur des essais de traction suivis en stéréo-corrélation. L'étude de la santé matière montre l'existence de défauts, en particulier, à l'échelle de la microstructure. Afin de prendre en compte ces particularités, il est ainsi nécessaire de décrire plus finement la microstructure. Pour cela, la tomographie à rayons X a été utilisée afin de caractériser le composite. Les récents développements de cette technique permettent, en combinaison avec des outils de segmentation, de reconstruire une géométrie représentative du matériau. Cette géométrie est utilisée pour simuler le comportement mécanique ainsi que la cristallisation. Les simulations numériques d'un VER sont capables de prédire les propriétés d'un pli, puis celles du stratifié. Cette modélisation multi-échelle pourrait réduire le nombre et le coût des campagnes expérimentales. Ainsi, déterminer les propriétés de la structure finale en se basant sur des caractérisations et simulations à l'échelle de la microstructure est un enjeu scientifique et industriel stratégique. Ce travail constitue une contribution vers cette approcheReducing aircraft weight is one of the major challenges facing the aerospace industry. In order to achieve the ambitious goals of fuel consumption and emission reduction, carbon-fiber reinforced composites have been introduced to the market. These materials are attracting increasing interest, however, they have low electrical conductivity to ensure protection against lightning strike. For this reason, composites filled with conductive particles are the subject of ongoing research activities. The objective is the development of multifunctional composites with enhanced electrical properties. Actually, the most used thermoplastic matrix is PEEK, but this polymer remains expensive, and its processing temperature is high. For this purpose, thermoplastic matrices, such as PEKK, are again studied. Between the raw material and the final part, the thermoplastic matrix undergoes several thermal steps with high temperature exposure (impregnation, consolidation, forming and assembly processes) during which its ability to crystallize evolves continuously. In order to evaluate the impact of the process and the composite constituents on its properties, crystallization has been the subject of particular attention. Two complementary experimental devices were used to characterize the crystallization. The heating stage, allows to apply a thermal cycle and observe the crystallization in optical microscopy and differential scanning calorimetry. The influence of carbon fibers and conductive fillers on the crystallization kinetics was evaluated. A decrease in crystallization times was observed through the increase of the nucleation rate. The collected data were used to develop a kinetic model identified through an original approach based on microscopic data. This model makes it possible to predict the crystallization kinetics of PEKK composites. Nevertheless, it does not make it possible to predict the final microstructure. However, the microstructure has a significant impact on mechanical properties as it has been proven through nano-indentation tests. To predict the final microstructure, a model based on the pixel coloring approach has been developed. The influence of carbon fibers has been introduced through the formation of a transcrystalline phase. A good correlation is found between the analytical approach, the simulation and the experimental data in terms of crystallization kinetics. Mechanical and electrical characterizations were performed to evaluate the performance of these new materials. On the studied materials, the mechanical response is not homogeneous as observed on tensile tests followed in stereo-correlation. The study of matter health shows the existence of defects, in particular, at the microstructure level. In order to take this particularity into account, it is thus necessary to describe the microstructure more finely. For this, X-ray tomography was used to characterize the composite. Recent developments in this technique allow, in combination with segmentation tools, to reconstruct a representative geometry of the material. This geometry is used to simulate the mechanical behaviour as well as the crystallization. The numerical simulations of an RVE are able to calculate the properties of a ply, then those of a laminate. This multi-scale modelling could reduce the number and cost of experimental campaigns. Thus, determining the properties of the final structure based on characterizations and simulation at the microstructure scale is a strategic scientific and industrial issue. This work is a contribution towards this approach
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Arnaud, Claire. "Fils conducteurs nanostructurés (cuivre et composites nanotube de carbone - cuivre) pour application en champs magnétiques intenses." Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30216/document.
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Afin de produire des champs magnétiques intenses (100 T), les fils conducteurs utilisés dans les bobines pulsées doivent présenter une contrainte à la rupture élevée et une très faible résistivité électrique. Le LNCMI et l'équipe NNC du CIRIMAT explorent des solutions originales basées sur l'élaboration de fils de cuivre nanostructuré et de fils nanocomposites nanotube de carbone - cuivre (NTC-Cu) par la combinaison originale du spark plasma sintering (SPS) et de l'étirage à température ambiante. Des barreaux de cuivre ont été élaborés par SPS à partir de poudres commerciales micrométriques. La croissance cristalline est très faible et la taille des grains de cuivre est 10 fois plus petite que celle des précurseurs de fils classiques. Les barreaux ont été étirés, sans rupture, sous forme de fils de diamètre décroissant (jusqu'à 0,198 mm) et de plusieurs mètres de long. Les grains ultrafins de Cu sont fortement allongés dans la direction de l'étirage. Aucune macle n'a été observée. Tous nos fils de cuivre présentent une résistance à la rupture en traction (à 293K et 77K) supérieure à celle des fils préparés à partir d'un précurseur de cuivre OFHC classique, ce qui pourrait résulter de la combinaison de l'écrouissage et des mécanismes d'Orowan. La résistivité électrique des fils est environ 12% plus élevée que celle des fils de cuivre OFHC. Pour les composites NTC-Cu, une adaptation de la méthode de mélange (fonctionnalisation des NTC biparois et à huit parois, mélange, cryogénisation, lyophilisation, réduction sous H2) a permis de produire des lots de poudre de 14 g en ayant une dispersion homogène des NTC. Du fait de la très faible teneur en carbone (= 1%), la préparation des barreaux puis des fils par les méthodes employées pour le cuivre pur est possible sans modification. La contrainte maximale à la rupture des fils NTC-Cu est supérieure (10-25%) à celle des fils de cuivre correspondants. Les NTC ont peu d'influence sur la microstructure du cuivre et leur probable alignement permet de bénéficier de leur grande résistance en traction. La résistivité est légèrement supérieure à celle des fils de cuivre correspondants (environ 12% à 77K). Le dernier chapitre est consacré à la préparation d'éprouvettes " os-de-chien " (Cu et NTC-Cu) directement par SPS " near-net-shape ". Nous avons mis en évidence l'influence de la nature du matériau dans lequel est usinée la matrice (graphite ou WC-Co) sur la microstructure, la microdureté et la contrainte à la rupture, pour un même cycle de frittageIn order to produce high magnetic fields (100 T), the conducting wires used in pulsed coils must show both a high tensile strength and very low electrical resistivity. The LNCMI and NNC team of CIRIMAT explore creative solutions based on the development of nanostructured copper wires and carbon nanotube - copper (CNT-Cu) nanocomposite wires by the original combination of spark plasma sintering (SPS) and room-temperature wire-drawing (WD). Copper cylinders were prepared by SPS of micrometric commercial powders. Crystal growth is very low and the copper grains size is 10 times lower than for conventional wire precursors. The cylinders were wire-drawn, without breaking, into wires of decreasing diameter (down to 0.198 mm) and several meters long. The ultrafine Cu grains are highly elongated in the WD direction. No twinning was observed. Our copper wires show an ultimate tensile strength (UTS) at 293K and 77K higher than those for wires prepared from conventional OFHC copper, which could result from the combination of strain hardening and Orowan mechanisms. The electrical resistivity is about 12% higher than those for the OFHC wires. For the CNT-Cu nanocomposites, an adaptation of preparation route (functionalization of double-walled and eight-walled CNTs, mixing, freeze-drying, H2 reduction) resulted in the production of 14 g powder batches with a homogeneous dispersion of the CNTs. Due to the very low carbon content (= 1%), the preparation of the cylinders and wires by the methods used for pure copper is possible without modification. The UTS of the CNT-Cu wirers is 10-25% higher than for the corresponding copper wires. The CNTs have little influence on the Cu microstructure and their probable alignment allows one to benefit from their high tensile strength. The electrical resistivity is only moderately higher than for the corresponding copper wires (about 12% at 77K). The last chapter was devoted to the preparation of "dog-bone" Cu and CNT-Cu test samples by "near-net-shape" SPS. We have brought to the fore the influence of the nature of the die (graphite or WC-Co) on the microstructure, microhardness and tensile strength, for the same sintering cycle
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Márquez, Costa Juan Pablo. "Caractérisation et modélisation des interfaces dans les composites organiques stratifiés à haute température : Application à la tenue au feu des structures aéronautiques PhyFire LOT 2 - Développement de modèles de comportement du composite Caractérisation en température de la ténacité en mode II des interfaces des CMO en utilisant l’effet Joule Caractérisation du comportement visqueux des interfaces CMO et influence sur la propagation de délaminage Convention PhyFIRE 2 - LOT 2 : Développement d’un cadre de modélisation pour les matériaux composites Durabilité des matériaux composites en conditions extrêmes : vers la prédiction des propriétés de tenue au feu Durability of Composite Materials under Severe Temperature Conditions : Influence of Moisture Content and Prediction of Thermo- Mechanical Properties During a Fire Towards the Prediction of Sandwich Composites Durability in Severe Condition of Temperature : A New Numerical Model Describing the Influence of Material Water Content during a Fire Scenario." Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2021. http://www.theses.fr/2021ESMA0004.
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Dans le cadre de la tenue au feu des matériaux composites, il est nécessaire d’évaluer la dégradation de leurs propriétés thermiques et mécaniques due à des pertes de masse, de la fissuration matricielle et/ou des délaminages. Néanmoins, peu d’études dans la littérature sur la tenue en température des composites aéronautiques concernent le comportement mécanique et la rupture des interfaces avant toute dégradation thermique, sujet qui est l’objet principal de ce travail. Ainsi, l’objectif est de proposer un modèle de prévision de rupture concernant tant l’amorçage que la propagation du délaminage pour des chargements thermomécaniques. Ce travail a porté en grande partie sur la caractérisation des propriétés d’interfaces à l’aide d’une analyse d’essais de propagation de fissure en mode II pour des éprouvettes chauffées par effet Joule. Ces analyses numériques montrent que le comportement du pli n’explique pas la réponse macroscopique pseudo-ductile observée expérimentalement. Ainsi, une méthode de dialogue essai-calcul, comparant les champs cinématiques mesurés par corrélation d’images numériques et ceux simulés par éléments finis, souligne l’importance du comportement visqueux à l’échelle de l’interface.C’est par une approche similaire de type FEMU que les paramètres d’une loi de rupture de type cohésif ont été identifiés en température et en tenant compte des différentes sources d’incertitude. Ce travail met en évidence la similitude entre le cisaillement plan et hors plan, tant sur le comportement que sur la rupture. En parallèle, l’analyse d’essais de tenue en température par impact laser a permis d’établir un critère d’amorçage par une approche couplée en contrainte et en énergie. Une confrontation de ce critère aux paramètres de la loi de zone cohésive identifiés précédemment permet de discuter de l’échelle de modélisation de l’interfaceWithin the framework of the fire resistance of composite materials, it is necessary to assess the degradation of their thermal and mechanical properties due to mass losses, matrix cracking and/or delamination cracks. Nevertheless, few studies in the literature about the temperature resistance of aeronautical composites concern the mechanical behaviour and the rupture of interfaces before any thermal degradation,subject which is the main topic of this work. Thus, the objective is to propose a failure model concerning both the delamination crack initiation and growth under thermomechanical loads. Much of this work has focused on the characterisation of interface properties using an analysis of mode II crack propagation tests for Joule heated specimens. These numerical analyses show that the ply behaviour does not explain the macroscopic pseudo-ductile response observed experimentally. Thus, a test-calculation dialog method, comparing the kinematic fields measured by digital images correlation and those simulated by finite elements, underlines the importance of the viscous behaviour at the interface scale. By a similar FEMU approach the parameters of a cohesive-type fracture law have been identified in temperature and taking into account the different sources of uncertainty. This work highlights the similarity between plane and out-of-plane shearing, both on behaviour and on failure. In parallel, the analysis of temperature resistance tests by laser impact made it possible to establish a crack initiation criterion by a coupled stress and energy approach. A comparison of this criterion with the parameters of the cohesive zone law previously identified makes it possible to discuss about the modeling scale of the interface
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Camilo, Rúben Filipe Xavier. "Projeto e modelação de linhas elétricas de média e alta tensão até 60Kv." Master's thesis, 2021. http://hdl.handle.net/10400.26/35683.
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A presente dissertação de mestrado tem como principal objetivo, o desenvolvimento de um projeto de uma linha aérea de alta tensão 60 kV, efetuando-se o estudo das metodologias, cálculos e dimensionamentos de acordo com as diretrizes da EDP-Distribuição, do regulamento de segurança de linhas elétricas de alta tensão (RSLEAT) e utilizando critérios de projetista.
Foi ainda desenvolvida uma aplicação implementada em ambiente de simulação Matlab, com o intuito de sistematizar o cálculo e projetos futuros. Esta aplicação permite também efetuar o estudo do comportamento das flechas das catenárias em função da variação da temperatura ambiente e do respetivo comprimento de vão. Estes modelos foram sustentados com base num projeto real, o qual consiste numa linha aérea de transporte de energia elétrica com um comprimento de 16.1 km, uma potência de transporte de 38 MVA e com uma tensão de transporte de 60 kV. Este projeto foi estabelecido tendo por base no regulamento de segurança de linhas elétricas de alta tensão, cumprindo todos os requisitos técnicos relativamente às localizações dos apoios, distâncias mínimas exigidas para as estruturas e para o meio envolvente.The main objective of this master's thesis is the development of a high-voltage 60 kV overhead power line project, carrying out its study of methodologies, calculations and performing dimensioning according to EDP-Distribuição guidelines, high-voltage power line safety regulation (RSLEAT) and using designer criteria. An application was also developed and implemented in Matlab simulation environment, with the purpose of systematizing the calculation and future projects. This application allows the study of the behaviour of overhead catenaries sags, according to the variation of the ambient temperature and the respective span length. These models were supported based on a real project, which consists of an overhead power line with a length of 16.1 km, a transport power of 38 MVA and a transport voltage of 60 kV, this project was established based on the safety regulations for high voltage power lines, fulfilling all the technical requirements regarding the locations of the supports, minimum distances required for the structures and the surrounding environment.
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Αθανασόπουλος, Νικόλαος. "Calculation of electrical conductivity and electrothermal analysis of multilayered carbon reinforced composites: application to damage detection." Thesis, 2013. http://hdl.handle.net/10889/6142.
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During this thesis, it has been proved that the electrical conductivity of multilayered and electrically anisotropic carbon fiber materials can be expressed by an equivalent second order tensor, which is equal to sum of each layer’s electrical conductivity tensor. The aforementioned equivalent electrical conductivity tensor is valid assuming that the material’s thickness is negligible compared to the other dimensions of the body. The mathematical expression for the prediction of the electrical conductivity of a multilayered material for any stacking sequence, is based on the electric current conservation, and was validated using different methods. Each layer’s electrical conductivity was experimentally studied at the two principal directions. Transverse to the fibers’ direction, an empirical model was developed for the prediction of the electrical conductivity as a function of the layer’s thickness, of the fibre volume fraction and of temperature. All cases involved the study of multidirectional and unidirectional carbon fiber materials without the presence of matrix (porous form – CF preform) as well as in the presence of polymeric matrix (CFRP).
The validation of the equivalent tensor was achieved through three different ways: a) through the measurement of the electric resistance, for various stacking sequences, b) through the Joule heating effect, by recording and comparing the developing temperature field to the respective numerically calculated, c) through 3D numerical models which approximate the analytical solution of the 2D domain problem. Moreover using the finite difference method, certain electrothermal models were developed in order to study the temperature field for different stacking sequences. The electrical problem can be expressed by an elliptic PDE, for the case where the material is electrically anisotropic and homogeneous, or non-homogeneous. On the other hand, the transient heat transfer problem involves the case where the material is thermally anisotropic and homogeneous. Using the equivalent tensor, the 3D domain problem is simplified to a 2D domain problem resulting in less computational requirements for the solution of the problem.
The present research study could be used in a plethora of application, such as the development of carbon fibre reinforced heating elements (direct heating CFRP molds) as well as damage detection in multidirectional composite materials with electrical conductive
reinforcement.Κατά τη διάρκεια της παρούσας διδακτορική διατριβής, αποδείχθηκε ότι η ηλεκτρική αγωγιμότητα των πολύστρωτων και ηλεκτρικά ανισότροπων υλικών με ίνες άνθρακα, μπορεί να εκφραστεί από έναν ισοδύναμο τανυστή δεύτερης τάξης, ο οποίος είναι το άθροισμα των τανυστών κάθε στρώσης. Ο ισοδύναμος τανυστής ισχύει υποθέτοντας ότι το πάχος συγκριτικά με τις υπόλοιπες διαστάσεις του υλικού είναι πολύ μικρό. Η μαθηματική έκφραση με την οποία μπορεί να προβλεφθεί η ηλεκτρική αγωγιμότητα ενός πολύστρωτου υλικού για οποιαδήποτε αλληλουχία στρώσεων αποδείχτηκε με συστηματικό τρόπο και βασίζεται στην αρχή διατήρησης του ηλεκτρικού φορτίου. Η ηλεκτρική αγωγιμότητα κάθε στρώσης μελετήθηκε πειραματικά στις δύο κύριες διευθύνσεις. Κάθετα στη διεύθυνση των ινών αναπτύχθηκε ένα εμπειρικό μοντέλο πρόβλεψης της ηλεκτρικής αγωγιμότητας συναρτήσει του πάχους της στρώσης, της περιεκτικότητας σε ίνες άνθρακα και της θερμοκρασίας. Σε όλες τις περιπτώσεις μελετήθηκαν πολύστρωτα υλικά ινών άνθρακα χωρίς μήτρα (πορώδης μορφή-CF preforms) και με πολυμερική μήτρα (CFRPs). Η επιβεβαίωση της εγκυρότητας του ισοδύναμου τανυστή έγινε με τρεις διαφορετικούς τρόπους: α) μέσω μετρήσεων της ηλεκτρικής αντίστασης, για διαφορετικές αλληλουχίες στρώσεων, β) μέσω του φαινομένου Joule, καταγράφοντας και συγκρίνοντας το αναπτυσσόμενο θερμοκρασιακό πεδίο με το θερμοκρασιακό πεδίο που υπολογίζεται αριθμητικά, γ) μέσω τρισδιάστατων αριθμητικών μοντέλων όπου τείνουν στην αναλυτική λύση του δισδιάστατου προβλήματος. Στη συνέχεια αναπτύχτηκαν ηλεκτροθερμικά μοντέλα με τη μέθοδο των πεπερασμένων διαφορών με σκοπό τη μελέτη του θερμοκρασιακού πεδίου για διαφορετικές αλληλουχίες στρώσεων. Το ηλεκτρικό πρόβλημα εκφράζεται από μία ελλειπτική διαφορική εξίσωση όπου το υλικό είναι ηλεκτρικά ανισότροπο και ομογενές ή μη ομογενές ενώ το θερμικό πρόβλημα είναι θερμικά ανισότροπο και ομογενές. Χρησιμοποιώντας τον ισοδύναμο τανυστή το τρισδιάστατο πρόβλημα μετατρέπεται σε ένα δισδιάστατο πρόβλημα με αποτέλεσμα να απαιτούνται λιγότεροι πόροι για την επίλυση του προβλήματος. Η συγκεκριμένη εργασία μπορεί να χρησιμοποιηθεί σε μία πληθώρα εφαρμογών όπως στην ανάπτυξη και στη λειτουργία θερμαινόμενων στοιχείων ενισχυμένων με ίνες άνθρακα (καλούπια όπου το θερμαντικό στοιχείο το αποτελούν οι ίνες άνθρακα) αλλά και στην ανίχνευση βλάβης συνθέτων υλικών με αγώγιμη ενίσχυση.
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Chen, Qian. "Reset control systems: Stability, performance and application." 2000. https://scholarworks.umass.edu/dissertations/AAI9988771.
Full textAbstract:
Linear time invariant (LTI) control design is the most widely applied control design technique. But it has inherent limitation. In LTI feedback control systems, high-frequency loop gain is linked to both low-frequency loop gain and stability margins through Bode's gain-phase relationship. This linkage results in trade-offs among competing performance specifications. Reset control design is a great candidate of improving this limitation. The basic idea of reset control is to reset the state of a linear controller to zero whenever its input meets a threshold. Such a reset controller is introduced in feedback control systems with the aim of providing better trade-offs between competing specifications than could be achieved using linear controllers. There have been some successful experimental applications of reset control technique which demonstrate its benefit. However, during the past three decades, there is a lack of theoretical results for reset control systems. For example, none of the experimental reset control applications can provide formal proof of stability and theoretic analysis of performance. Dedicated to solving this problem, this dissertation performs theoretic analysis of the stability and performance of reset control systems. A complete set of theoretic results on the stability and time-domain performance are developed. These results build a solid theoretic base for the further and wider application of reset control system. Also, reset control design is successfully applied to the speed control of a rotational flexible mechanical system with supporting theoretic analysis. This experiment demonstrates the benefit of reset control design over LTI control design and the effectiveness of the theoretic results.
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Huang, Chin-Hao, and 黃志豪. "Study of application of 3D integration mapping of mechanical and electrical construction projects." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/08895237141402879218.
Full textAbstract:
碩士國立交通大學
工學院碩士在職專班工程技術與管理組
99
Recently, the scale of electronic-industry factories is getting larger. Also, the timeliness of completing projects, the complexity of projects, and the demands of related professional knowledge increase. Meanwhile, construction companies face stringent circumstances, due to rise of raw-materials and increasing of competition among same traders. Therefore, the resulting-profit for construction projects comes from effective management presently. Because of the restriction of diverse in species, complicated in construction, and limitation of constructing-time, the constructing quality and overall construction time of electromechanical systems are highly affected if lack of comprehensive spatial conformity complete in advance. There are many shortcomings of common used 2D drawing system in mechanical and electrical construction drawings as lack of ability for representing the complicated spatial relationship among various components. Advanced 3D drawing system has been energetically developed and applied in many fields nowadays. The aim of this work is to investigate and utilize 3D drawing system in 3D mapping integration of mechanical and electrical construction projects. A real electromechanical project is employed as studying case herein and required man-hours are compared between use of 2D and 3D systems. The simulated results reveal that 3D drawing system is feasible for complicated electromechanical systems in constructing level. Also, some constructing conflicts can be detect and solve in advance.
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Chen, Jyun-Yu, and 陳俊宇. "BIM Application for Identification and Elimination of Electrical and Mechanical Conflicts in Building Construction." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/tq33b3.
Full textAbstract:
碩士國立臺灣大學
土木工程學研究所
105
A building will not be completed without the mechanical, electrical and plumbing (MEP) system. The mechanical and electrical systems are to the construction as organs are to the human body, and the plumbing systems which build up the connections are the nerves and vessels. As the quality of constructions improving, the complexity of the MEP systems increases, interface conflicts come along. MEP are currently designed with 2D graphing; this derives issues on error identification, communication, interface integration, information storage, which may easily result in delay, disputes, discrepancies between sites and designs. Building Information Modeling (BIM) can manage visualization and information storage, hence, may efficiently mitigate the problems addressed. Designing MEP system with the aid of BIM has become an inevitable trend. BIM has not yet been well developed in Taiwan. Although some customers have demanded using BIM in the contract, it takes time for traditional constructions to change. Traditional techniques are still existing, competitive barriers and promotion of the software are yet to be overcome. BIM can convert the tradition 2D diagram into 3D view with its visualization function, therefore, may mediate the interface conflicts. However, the software application currently requires the experience of the engineers and a larger amount of workforce to eliminate the conflicts. The purpose of this research is to make the BIM application more efficient by standardizes the process of the MEP elimination measure with a case study. A detailed record of problems encountered and solutions were kept during the research for further studies in the future.
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Chuang, Jui-Hung, and 莊睿紘. "Application of AHP in the Subcontract Planning - A Case Study of the Electrical and Mechanical Engineering." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/85313590011532743659.
Full textAbstract:
碩士國立高雄應用科技大學
工業工程與管理系
99
Division of labor is a trend and has a significant role in the effects of manufacturing industry for a long time. With the growth of national economic and the amazing architecture around the world, more and more enormous and complex projects are now presented and created worldwide. Mechanical and electrical engineering plays as a key factor in the controlling of entirety building. In this study, Analytic Hierarchy Process is utilized to devise and analysis a survey on the basis of the important layers and elements. The results can be established by an efficient system of subcontract planning model, and improve the decision performance of subcontract planning of mechanical and electrical engineering in Taiwan.
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Hanusa, Paul Jeffrey. "A practical application of a force feedback control system for a mechanical, 3-fingered, dextrous hand." Thesis, 1992. http://hdl.handle.net/1911/13654.
Full textAbstract:
The trajectory planning and control system for a mechanical, 3-fingered, dextrous hand are analyzed and implemented. The forward and inverse kinematics of the fingers are derived and used to analyze the capabilities of the hand. The simple and effective grasping strategy employs minimal trajectory planning and relies solely on force feedback to define finger position and orientation. A force feedback controller is implemented on the hand which allows independent control of each finger. The hand is used in conjunction with a robotic arm to execute various tasks which require hand dexterity.
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Chen, Kuei-Yin, and 陳貴英. "An application of lean management in the procurement of electrical and mechanical engineering：a case study on L.T company." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/8gfp5p.
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Sitole, Soumitra. "Application and Evaluation of Lighthouse Technology for Precision Motion Capture." 2018. https://scholarworks.umass.edu/masters_theses_2/715.
Full textAbstract:
This thesis presents the development towards a system that can capture and quantify motion for applications in biomechanical and medical fields demanding precision motion tracking using the lighthouse technology. Commercially known as SteamVR tracking, the lighthouse technology is a motion tracking system developed for virtual reality applications that makes use of patterned infrared light sources to highlight trackers (objects embedded with photodiodes) to obtain their pose or spatial position and orientation. Current motion capture systems such as the camera-based motion capture are expensive and not readily available outside of research labs. This thesis provides a case for low-cost motion capture systems. The technology is applied to quantify motion to draw inferences about biomechanics capture and analysis, quantification of gait, and prosthetic alignment. Possible shortcomings for data acquisition using this system for the stated applications have been addressed. The repeatability of the system has been established by determining the standard deviation error for multiple trials based on a motion trajectory using a seven degree-of-freedom robot arm. The accuracy testing for the system is based on cross-validation between the lighthouse technology data and transformations derived using joint angles by developing a forward kinematics model for the robot’s end-effector pose. The underlying principle for motion capture using this system is that multiple trackers placed on limb segments allow to record the position and orientation of the segments in relation to a set global frame. Joint angles between the segments can then be calculated from the recorded positions and orientations of each tracker using inverse kinematics. In this work, inverse kinematics for rigid bodies was based on calculating homogeneous transforms to the individual trackers in the model’s reference frame to find the respective Euler angles as well as using the analytical approach to solve for joint variables in terms of known geometric parameters. This work was carried out on a phantom prosthetic limb. A custom application-specific motion tracker was also developed using a hardware development kit which would be further optimized for subsequent studies involving biomechanics motion capture.