Dissertations / Theses on the topic 'Mechanicky princip'

Práce předkládá metody a výsledky návrhu, výroby a výzkumu pětiprsté protézy ruky. Inspirace jdoucí z přírody a z toho vyvozený princip použitého mechanizmu je uveden. Základní koncept řídícího schéma založeného na procesingu a ohodnocení EMG je navrhnut a implementován. Části senzorického systému protézy jsou navrhnuty a zahrnuty do rídícího algoritmu a shématu. Velké množství inovací a návrhů pro budoucí práce a výzkum jsou prezentovány, stejně tak komplexní analýza a diskuse dosažených a možných budoucích výsledků.

The glassy wormlike chain model is a highly successful phenomenological model recently introduced to describe anomalously slow subdiffusive dynamics in biopolymer networks and living cells. Here we extend this model by proposing a generic scheme how to include nonlinear plastic effects by introducing the possibility of force-dependent opening and closing of internal bonds. Further, we discuss physiological implications of this bond kinetics. Stability arguments lead us to the postulation of a “physiological sheet” in the parameter space. This sheet defines the set of parameters characterizing cells which are flexible enough to perform biological tasks while still being able to bear external perturbations characteristic of their surroundings and their internally generated prestress without damage. At the end of this contribution, we speculate about the connection between prestress and cell stiffness and about the mechanism by which the cell adapts to its mechanical environment.

This work presents the results of theoretical and experimental characterization of thermodynamic, mechanical and transport properties in polymer solvent systems. The polymer solvent pairs considered ranged to those in which the polymer is rubbery, to those in which the initially glassy polymeric matrix is plasticized by the action of the low molecular weight species. Advanced Equation of State models have been adopted for thermodynamic modeling,along with a rigorous procedure that enables to extend their applicability to the non equilibrium, glassy region. Mass sorption kinetics had been modeled with phenomenological models and with advanced kinetic models.
Questo lavoro verte sulla caratterizzazione teorica e sperimentale delle proprietà termodinamiche, meccaniche e di trasporto di sistemi polimero-solvente. In particolare sono stati presi in considerazione sia sistemi polimero-solvente in cui la matrice polimerica si trova allo stato di gomma, che sistemi in cui la matrice polimerica esibisce comportamento vetroso, nonché sistemi nei quali si verifica la transizione vetrosa indotta dall'effetto plasticizzante del solvente. La modellazione termodinamica è stata effettuata utilizzando equazioni di stato avanzate e metodi idonei ad estenderne il campo di utilizzo alla condizione di non equilibrio, propria dello stato vetroso. Cinetiche di assorbimento non Fickiane sono state modellate utilizzando approcci fenomenologici e modelli cinetici avanzati.

Following Exner et al. (Commun. Math. Phys. 26 (2014), no. 2, 531–541), we prove new Lieb-Thirring inequalities for a general class of self-adjoint, second order differential operators with matrix-valued potentials, acting in one space-dimension. This class contains, but is not restricted to, the magnetic and non-magnetic Schrödinger operators. We consider the three cases of functions defined on all reals, all positive reals, and an interval, respectively, and acquire three different kinds of bounds. We also investigate the spectral properties of a family of operators from conformal field theory, by proving an asymptotic phase-space bound on the eigenvalue counting function and establishing a number of spectral inequalities. These bound the Riesz-means of eigenvalues for these operators, together with each individual eigenvalue, and are applied to a few physically interesting examples.
Vi följer Exner et al. (Commun. Math. Phys. 26 (2014), nr. 2, 531–541) och bevisar nya Lieb-Thirring-olikheter för generella, andra gradens självadjungerade differentialoperatorer med matrisvärda potentialfunktioner, verkandes i en rumsdimension. Dessa innefattar och generaliserar de magnetiska och icke-magnetiska Schrödingeroperatorerna. Vi betraktar tre olika fall, med funktioner definierade på hela reella axeln, på den positiva reella axeln, samt på ett interval. Detta resulterar i tre sorters olikheter.  Vidare undersöker vi spektralegenskaperna för en klass operatorer från konform fältteori, genom att asymptotiskt begränsa antalet egenvärden med ett fasrymdsuttryck, samt genom att bevisa ett antal spektralolikheter. Dessa begränsar Riesz-medelvärdena för operatorerna, samt varje enskilt egenvärde, och tillämpas på ett par fysikaliskt intressanta exempel.

V současnosti je velmi aktuálním tématem generování elektrické energie z alternativních zdrojů, zejména z vibrací. Zařízení, která přeměňují mechanickou energii na elektrickou, využívají často ke své činnosti piezoelektrický jev. Pro optimální nastavení takového elektromechanického měniče pro danou aplikaci je třeba mít k dispozici výpočtový model, který bude schopný postihnout všechny klíčové aspekty jeho provozu. Tato práce se tedy zabývá vytvořením takovéhoto nástroje, který je schopen komplexně popsat elektromechanickou odezvu studovaného piezoelektrického měniče energie v podobě vetknutého, vícevrstvého keramického nosníku s piezoelektrickými vrstvami. Uvažovaná vícevrstvá konstrukce je během své činnosti vystavena kinematickému buzení a je rovněž zatížena tepelnou zbytkovou napjatostí vznikající při její výrobě. Vytvořený výpočtový model využívá klasickou laminátovou teorii k určení statické elektromechanické odezvy dané konstrukce. Elektromechanická odezva při kmitání uvažované konstrukce v ustáleném stavu je získána s využitím Hamiltonova variačního principu a teorie kmitání prutů. Vytvořený výpočtový model je dále schopen odhadnout zdánlivou lomovou houževnatost dané vícevrstvé konstrukce pomocí metody váhových funkcí. Výstupy vytvořeného výpočtového modelu jsou ověřeny s využitím numerických simulací na bázi MKP a dostupných experimentálních výsledků. V diplomové práci je následně vytvořený výpočtový model aplikován při hledání optimálního rozložení jednotlivých vrstev konkrétního vícevrstvého nosníku s cílem maximalizovat jeho elektrický výkon a odolnost vůči šíření povrchových trhlin, resp. vzniku křehkého lomu. Tohoto cíle je dosaženo pomocí vhodného rozložení tepelných zbytkových napětí v jednotlivých vrstvách uvažované konstrukce (řízeného použitými materiály a tloušťkami jednotlivých vrstev).

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.
Includes bibliographical references.
Postural synergies describe characteristic patterns of actuation in human hands arising from biomechanical constraints, physical tendon coupling, and neurological control schemes. Often, a small number of synergies contain much of the information required to describe an entire human hand posture, with 80% or more of the total information encoded in only two component values. Synergies have commonly been used to identify hand shapes with minimal processing power. However, they can also be used to recreate postures in robot hands, by allowing a mechanical implementation of inter-finger coordination. This can provide benefits of reduced cost, compact size, and decreased actuator count. In this paper, a novel mechanism is proposed to drive a dexterous, versatile, 17 degree-of-freedom robot hand using only two DC motors. Posture data was collected with a dataglove, and analyzed using principal components analysis to determine the postural synergies. The synergies are then mechanically hardwired into the driving mechanism, resulting in a concept dubbed eigenpostures.
(cont.) Two eigenpostures effectively recreate the entire posture set. Several observations and suggestions are presented on tendon-drive robotic hand design in general, and also specifically targeted towards synergy- or eigenposture-based design. Avenues for further research into synergy mechanism design are proposed, including a powerful concept incorporating k-means clustering with principal components analysis to distinguish between high-precision and low-precision tasks, and greatly reduce overall error.
by Christopher Yeates Brown.
S.M.

Magister Educationis - Med
The purpose of this study was to investigate the effect of the conceptual-change teaching strategy on the Principle of Conservation of Mechanical Energy in the absence of dissipative forces. Specifically, the study used the scientific investigation and interactive simulations in the teaching of the Principle of Conservation of Mechanical Energy concepts. The research design adopted for the study was a case study in which a mixed method approach was used. A sample of thirty learners was purposively selected from a grade 10 Physical Sciences class in the rural Eastern Cape. Data were collected using the pre-test, concept map and semi-structured interviews. The pre-test and the concept map were systematically assessed for validity and reliability by involving experts in Science Education and through pilot study. Mean, standard deviation and thematic analysis were employed in the analysis of data. The quantitative results indicated that learners who held to their alternative conceptions hinder their learning and understanding of scientific concepts. Results also indicated a significant improvement in the learners' understanding of the energy concept and its conservation after the use of the conceptual change strategy. The qualitative results indicated that learners learn better through the conceptual change approach as learners are actively involved in restructuring their conceptual framework and the knowledge gained becomes more meaningful. Learners find the conceptual change approach effective as it is motivational and engages them in dialogues and debates that iron out grey areas. Based on these findings the study recommends that teachers should endeavour to incorporate the conceptual change model as one of the teaching approaches to be adopted in schools since it increases the learners' interest and learning in Science, especially in Physics

Les transformations de supersymétrie (ou de Darboux) sont appliquées à l'étude du problème inverse, c'est à dire à la construction d'un potentiel d'interaction à partir de données de collisions, en mécanique quantique. En effet, ces transformations permettent de construire de nouveaux potentiels à partir d'un potentiel donné. Leur formalisme est étudié en détail, ainsi que celui correspondant à l'itération de deux telles transformations (paires de transformations).

La présence d'états liés rend le problème inverse ambigu :plusieurs potentiels ayant des spectres liés différents peuvent avoir les mêmes propriétés pour la description des collisions; de tels potentiels sont dits équivalents en phase. Une décomposition originale du problème inverse est proposée pour gérer efficacement cette ambiguïté :dans un premier temps, un potentiel est construit à partir des données de collision (ce qui constitue le problème inverse proprement dit); dans un second temps, tous les potentiels équivalents en phase au potentiel ainsi obtenu sont construits. Avant ce travail, il était connu que ces deux aspects du problème inverse pouvaient être traités à l'aide de paires de transformations de supersymétrie.

En ce qui concerne la construction de potentiels équivalents, nous étendons les méthodes existantes à des catégories de potentiels très utilisées en physique nucléaire, à savoir les potentiels optiques (ou complexes), les potentiels en voies couplées et les potentiels dépendant linéairement de l'énergie. En utilisant une paire de transformations permettant d'enlever un état lié, nous comparons les propriétés physiques des potentiels nucléaires profonds (c'est à dire possédant des états liés interdits par le principe de Pauli) et peu profonds. Des calculs dans des modèles à trois corps du noyau à halo d'6He et de la collision 16O+17O à basse énergie n'ont pas révélé d'importantes différences entre ces familles de potentiels. D'autres types de transformations permettent d'ajouter des états liés à énergie et normalisation arbitraires. Cependant, dans le cas à plusieurs voies, leur utilisation est compliquée par la possibilité d'avoir des états liés dégénérés et non dégénérés. Une étude préliminaire à deux voies montre que ces deux types d'états peuvent être traités par supersymétrie.

En ce qui concerne le problème inverse proprement dit, nous montrons que l'utilisation de transformations simples (plutôt que de paires) permet une meilleure compréhension des méthodes existantes, tant pour l'inversion à moment cinétique orbital fixe que pour l'inversion à énergie fixe. De plus, l'utilisation de transformations simples mène dans certains cas à de nouvelles catégories de potentiels. Ainsi, nous construisons un nouveau potentiel d'interaction nucléon nucléon pour l'onde 1S; ce potentiel possède une singularité en r 2 à l'origine. La possibilité de construire des potentiels profonds par inversion est brièvement discutée. Pour les voies couplées, une étude bibliographique révèle certaines propriétés contradictoires des méthodes existantes, mais une analyse complète reste à faire.

Doctorat en sciences appliquées
info:eu-repo/semantics/nonPublished

In response to the increasing international competitiveness, many manufacturing businesses are rethinking their management strategies and philosophies towards achieving a computer integrated environment. The explosive growth in Advanced Manufacturing Technology (AMI) has resulted in the formation of functional "Islands of Automation" such as Computer Aided Design (CAD), Computer Aided Manufacturing (CAM), Computer Aided Process Planning (CAPP) and Manufacturing Resources Planning (MRPII). This has resulted in an environment which has focussed areas of excellence and poor overall efficiency, co-ordination and control. The main role of Computer Integrated Manufacturing (CIM) is to integrate these islands of automation and develop a totally integrated and controlled environment. However, the various perceptions of CIM, although developing, remain focussed on a very narrow integration scope and have consequently resulted in mere linked islands of automation with little improvement in overall co-ordination and control. This thesis, that is the research described within, develops and examines a more holistic view of CIM, which is based on the integration of various business elements. One particular business element, namely control, has been shown to have a multi-facetted and underpinning relationship with the CIM philosophy. This relationship impacts various CIM system design aspects including the CIM business analysis and modelling technique, the specification of systems integration requirements, the CIM system architectural form and the degree of business redesign. The research findings show that fundamental changes to CIM system design are required; these are incorporated in a generic CIM design methodology. The affect and influence of this holistic view of CIM on a manufacturing business has been evaluated through various industrial case study applications. Based on the evidence obtained, it has been concluded that this holistic, control based approach to CIM can provide a greatly improved means of achieving a totally integrated and controlled business environment. This generic CIM methodology will therefore make a significant contribution to the planning, modelling, design and development of future CIM systems.

It is not reliable to depend on a persons inference on dense data of high dimensionality on a daily basis. A person will grow tired or become distracted and make mistakes over time. Therefore it is desirable to study the feasibility of replacing a persons inference with that of Machine Learning in order to improve reliability. One-Class Support Vector Machines (SVM) with three different kernels (linear, Gaussian and polynomial) are implemented and tested for Anomaly Detection. Principal Component Analysis is used for dimensionality reduction and autoencoders are used with the intention to increase performance. Standard soft-margin SVMs were used for multi-class classification by utilizing the 1vsAll and 1vs1 approaches with the same kernels as for the one-class SVMs. The results for the one-class SVMs and the multi-class SVM methods are compared against each other within their respective applications but also against the performance of Back-Propagation Neural Networks of varying sizes. One-Class SVMs proved very effective in detecting anomalous samples once both Principal Component Analysis and autoencoders had been applied. Standard SVMs with Principal Component Analysis produced promising classification results. Twin SVMs were researched as an alternative to standard SVMs.

Bulk metallic glasses and multi-principal element alloys represent relatively new classes of multi-component engineering materials designed for satisfying multiple functionalities simultaneously. Correlating the microstructure with mechanical behavior (at the microstructural length-scales) in these materials is key to understanding their performance. In this study, the structure evolution and nano-mechanical behavior of these two classes of materials was investigated with the objective of fundamental scientific understanding of their properties. The structure evolution, high temperature nano-mechanical behavior, and creep of two Zr-based alloys was studied: Zr41.2Ti13.8Cu12.5Ni10.0Be22 (Vitreloy1) and Zr52.5Ti5Cu17.9Ni14.6All0 (Vitreloy105). Devitrification was found to proceed via the formation of a metastable icosahedral phase with five-fold symmetry. The deformation mechanism changes from inhomogeneous or serrated flow to homogenous flow near 0.9Tg, where Tg is the glass transition temperature. The creep activation energy for Vitreloy1 and Vitreloy105 were 144 kJ/mol and 125 kJ/mol, respectively in the range of room temperature to 0.75Tg. The apparent activation energy increased drastically to 192 kJ/mol for Vitreloy1 and 215 kJ/mol for Vitreloy105 in the range of 0.9Tg to Tg, indicating a change in creep mechanism. Structure evolution in catalytic amorphous alloys, Pt57.5Cu14.7Ni5.3P22.5 and Pd43Cu27Ni10P20, was studied using 3D atom probe tomography and elemental segregation between different phases and the interface characteristics were identified. The structure evolution of three multi-principal element alloys were investigated namely CoCrNi, CoCrFeMnNi, and Al0.1CoCrFeNi. All three alloys formed a single-phase FCC structure in as-cast, cold worked and recrystallized state. No secondary phases precipitated after prolonged heat treatment or mechanical working. The multi-principal element alloys showed less strain gradient plasticity compared to pure metals like Ni during nano-indentation. This was attributed to the highly distorted lattice which resulted in lesser density of geometrically necessary dislocations (GNDs). Dislocation nucleation was studied by low load indentation along with the evaluation of activation volume and activation energy. This was done using a statistical approach of analyzing the "pop-in" load marking incipient plasticity. The strain rate sensitivity of nanocrystalline Al0.1CoCrFeNi alloy was determined by in situ compression of nano-pillars in a Pico-indenter. The nanocrystalline alloy demonstrated a yield strength of ~ 2.4 GPa, ten times greater than its coarse grained counterpart. The nanocrystalline alloy exhibited high strain rate sensitivity index of 0.043 and activation volume of 5b3 suggesting grain boundary dislocation nucleation.

Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references (page 40).
The consumer market currently offers no options for a low-cost, personal ascending device. The purpose of this project is to propose a powered ascender, actuated by common power tool components and operating on the principle of a capstan winch, as a candidate to fill that void. The first objective was to design and construct a working prototype. The second was to explore the feasibility of manufacturing a low cost consumer version of the product. Safety, functionality, and cost drove the design process. The ascender was designed and built around the motor and gearbox from a Dewalt 36v hammerdrill. Individual components were machined in undergraduate machine shops on the MIT campus and in the MIT Hobby Shop. Testing of the ascender was carried out using standard gym equipment and weights. The completed unit can lift 100 kg at 0.4 meters per second with an overall efficiency of 8.5%. This result was 57% lower than the predicted speed of 0.7 meters per second with an expected 14.7% efficiency. Analysis revealed a design flaw which can account for most of the discrepancy in the predicted and observed performance and which can easily be remedied. Powered ascenders within the same speed and load range are sold for several thousand dollars, demonstrating the feasibility of a low cost powered ascender as a viable product.
by Daniel P. Gillund.
S.B.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.
Includes bibliographical references.
A new type of sub-Kelvin refrigerator, the superfluid Joule-Thomson refrigerator, has been developed and its performance has been experimentally verified. This refrigerator uses a liquid superfluid mixture of He and 4He as the working fluid and depends on the non-ideal-gas-like behavior of the 3He component in this mixture to provide cooling when the mixture is throttled. This work included the design and development of low dissipation valves and a low temperature compressor that were successfully operated at 1.2 K. Analytical and numerical models were developed to predict the performance of the refrigerator and to provide insight to improve and further develop this new technology. The refrigerator achieved an ultimate temperature of 0.68 K when rejecting heat at 1.2 K.
by Franklin k. Miller.
Ph.D.

Syftet med examensarbetet är att undersöka om en småskalig variant av vattenkraftverk baserat på Arkimedes skruv kan vara lönsam för att driva elljusspår eller gatubelysning. Ett teoretiskt lösningsförslag på hur Arkimedes skruv kan fungera som vattenkraftverk togs fram via design thinking och brainstorming samt en sållningsmetod av lösningsförslag genom morfologisk matris. I denna rapport ingår även ett förslag avseende lämpliga delar till en framtida prototyp, prisförslag och årlig energiproduktion. Vattenkraftverket var tänkt att användas för att producera energi för att driva 4 km elljusspår eller 6 km gatubelysning. För att ta reda på om vattenkraftverket är ekonomiskt lönsamt jämfördes vattenkraftverket med vindkraft, där vattenkraftverket ansågs vara lönsamt ifall det kunde motsvara vindkraftverkets återbetalningstid. Arbetet resulterade i en teoretisk modell av ett fungerande småskaligt vattenkraftverk som klarar att driva upp till 4 km elljusspår eller gatubelysning upp till 6 km. Lösningsförslaget klarar däremot inte att konkurrera med ett fullskaligt vindkraftverks återbetalningstid. Däremot är inte vattenkraft i allmänhet sämre än vindkraft då Sveriges vattenkraftverk producerar nästan fyra gånger så mycket energi jämfört med Sveriges vindkraftverk. [1]
The purpose of this master thesis is to examine if a small-scale hydro power plant based on Archimedes screw could be a profitable way to power an illuminated outdoor exercise track or corresponding streetlights. A theoretical solution of how the Archimedes screw could work as a hydro power plant was decided on by using a morphological matrix as a by a screening method. Suggestions of parts for the prototype, price calculations and annual energy production of the design. The hydro screw was designed to produce energy that can supply an illuminated exercise track of 4 km or streetlights up to 6 km. To figure out if the hydro screw is economically profitable, the solution was compared to a land-based windmill, were the hydro screw was considered to be profitable if it could match a windmills payback time.  The work resulted in a theoretical design of a small-scale hydro power plant that could work for powering illuminated exercise tracks up to 4 km or streetlights up to 6 km. Results include that the solution cannot match a windmills payback time. On the other hand, hydropower is generally not worse than wind power since Sweden´s hydro powerplants produce almost four times as much energy compered to Sweden´s wind power production. [1]

The present thesis is devoted to the study of path probability of random motion on the basis of an extension of Hamiltonian/Lagrangian mechanics to stochastic dynamics. The path probability is first investigated by numerical simulation for Gaussian stochastic motion of non dissipative systems. This ideal dynamical model implies that, apart from the Gaussian random forces, the system is only subject to conservative forces. This model can be applied to underdamped real random motion in the presence of friction force when the dissipated energy is negligible with respect to the variation of the potential energy. We find that the path probability decreases exponentially with increasing action, i.e., P(A) ~ eˉγA, where γ is a constant characterizing the sensitivity of the action dependence of the path probability, the action is given by A = ∫T0 Ldt, a time integral of the Lagrangian L = K-V over a fixed time period T, K is the kinetic energy and V is the potential energy. This result is a confirmation of the existence of a classical analogue of the Feynman factor eiA/ħ for the path integral formalism of quantum mechanics of Hamiltonian systems. The above result is then extended to real random motion with dissipation. For this purpose, the least action principle has to be generalized to damped motion of mechanical systems with a unique well defined Lagrangian function which must have the usual simple connection to Hamiltonian. This has been done with the help of the following Lagrangian L = K - V - Ed, where Ed is the dissipated energy. By variational calculus and numerical simulation, we proved that the action A = ∫T0 Ldt is stationary for the optimal paths determined by Newtonian equation. More precisely, the stationarity is a minimum for underdamped motion, a maximum for overdamped motion and an inflexion for the intermediate case. On this basis, we studied the path probability of Gaussian stochastic motion of dissipative systems. It is found that the path probability still depends exponentially on Lagrangian action for the underdamped motion, but depends exponentially on kinetic action A = ∫T0 Kdt for the overdamped motion.

Ce travail présente et valide une théorie nonlocale nouvelle et généralisée, de la propagation acoustique dans les milieux poreux à structure rigide, saturés par un fluide viscothermique. Cette théorie linéaire permet de dépasser les limites de la théorie classique basée sur la théorie de l'homogénéisation. Elle prend en compte non seulement les phénomènes de dispersion temporelle, mais aussi ceux de dispersion spatiale. Dans le cadre de la nouvelle approche, une nouvelle procédure d'homogénéisation est proposée, qui permet de trouver les propriétés acoustiques à l'échelle macroscopique, en résolvant deux problèmes d'action-réponse indépendants, posés à l'échelle microscopique de Navier-Stokes-Fourier. Contrairement à la méthode classique d'homogénéisation, aucune contrainte de séparation d'échelle n'est introduite. En l'absence de structure solide, la procédure redonne l'équation de dispersion de Kirchhoff-Langevin, qui décrit la propagation des ondes longitudinales dans les fluides viscothermiques. La nouvelle théorie et procédure d'homogénéisation nonlocale sont validées dans trois cas, portant sur des microgéométries significativement différentes. Dans le cas simple d'un tube circulaire rempli par un fluide viscothermique, on montre que les nombres d'ondes et les impédances prédits par la théorie nonlocale, coïncident avec ceux de la solution exacte de Kirchhoff, connue depuis longtemps. Au contraire, les résultats issus de la théorie locale (celle de Zwikker et Kosten, découlant de la théorie classique d'homogénéisation) ne donnent que le mode le plus attenué, et encore, seulement avec le petit désaccord existant entre la solution simplifiée de Zwikker et Kosten et celle exacte de Kirchhoff. Dans le cas où le milieu poreux est constitué d'un réseau carré de cylindres rigides parallèles, plongés dans le fluide, la propagation étant regardée dans une direction transverse, la vitesse de phase du mode le plus atténué peut être calculée en fonction de la fréquence en suivant les approches locale et nonlocale, résolues au moyen de simulations numériques par la méthode des Eléments Finis. Elle peut être calculée d'autre part par une méthode complètement différente et quasi-exacte, de diffusion multiple prenant en compte les effets viscothermiques. Ce dernier résultat quasi-exact montre un accord remarquable avec celui obtenu par la théorie nonlocale, sans restriction de longueur d'onde. Avec celui de la théorie locale, l'accord ne se produit que tant que la longueur d'onde reste assez grande.

Courses in analytical mechanics for undergraduate students are often limited to treatment of holonomic constraints, which are constraints on coordinates. The concept of nonholonomic constraints, constraints on velocities, is usually only mentioned briefly and it is easy to get a wrongful idea of what they are and how to treat them. This text explains and compares the methods of deriving the Euler-Lagrange equations and the consequences when imposing different kinds of constraints. One way to properly treat both holonomic and nonholonomic constraints is given, pinpointing the difficulties and common errors. Along the way, the treatment in local coordinates is also put in more modern terms, in the language of differential geometry, which is the language most commonly used in modern texts on the subject.

L’objectif de cette thèse est de proposer une stratégie simplifiée et précise pour caractériser et modéliser le comportement mécanique des polymères amorphes de l'état quasi-fluide à l'état solide.L'étude a été réalisée sur des PMMA de masses molaires et de degré de réticulations différentes.D’abord, le comportement mécanique dans le domaine viscoélastique linéaire est étudié à l'aide de tests DMTA et rhéologiques. Il ressort de l’étude que l'augmentation de la masse molaire et du degré de réticulation augmentait les modules de stockage et de perte en tant que la transition α. En parallèle, l'utilisation du principe de superposition temps-température a permis de déterminer «des vitesses de déformation équivalentes à la température de référence».Ensuite, le comportement mécanique à grande déformation est étudié par essais cycliques en traction uni-axial et de cisaillement à haute température et couplés à la DIC. De plus, les effets de la vitesse de déformation et de la température ont été couplés grâce à "vitesse de déformation équivalent à la température de référence" extrait des observations dans le domaine linéaire. Les résultats ont montré que cibler la même vitesse de déformation équivalente conduira aux mêmes courbes contrainte-déformation, c'est-à-dire la même réponse mécanique. Ceci permet de réduire le nombre de tests expérimentaux nécessaires pour caractériser le comportement mécanique des polymères amorphes.Enfin, un modèle basée dans un cadre thermodynamique a été utilisée pour reproduire la réponse mécanique des PMMAs à grande déformation. Le modèle présentait un bon accord avec les données expérimentales, étant capable de reproduire des comportements visco-élasto-plastiques, viscoélastiques, hyperélastiques et visco-hyperelastiques pour la traction cyclique
The present PhD thesis proposes a simplified and accurate strategy for characterising and modelling the mechanical behaviour of amorphous polymers from the quasi-fluid state up to the solid state.The study was carried out on PMMAs with different molar masses and crosslinking degree.First, we addressed the mechanical behaviour in the linear viscoelastic domain using DMTA and rheological tests. Results showed that increasing the molar mas and crosslinking degree increased the elastic and loss moduli as the α-transition. In parallel, using the time-temperature superposition principle allowed determining “equivalent strain rates at reference temperature”.Then, we performed uniaxial tensile and shear uploading-unloading tests at high temperature and coupled with DIC, to characterise the mechanical behaviour at large strain. Additionally, strain rate and temperature effects were coupled by means of the “equivalent strain rate at reference temperature” extracted from observations in the linear domain. Results showed that targeting the same equivalent strain rate lead to the same stress-strain curves, i.e. same mechanical response. This allows reducing the number of experimental tests needed to characterise the mechanical behaviour of amorphous polymers.Finally, a constitutive modelling based in a thermodynamics framework, was used to reproduce the mechanical response of the PMMAs at large deformation. The model presented a good agreement with the experimental data, being able to reproduce viscoelastoplastic, viscoelastic, hyperelastic and viscohyperelastic behaviours for cyclic loading tensile

This Master's thesis relates to continuum mechanics and its connection with selected directions of modern differential geometry, which deal with geometric structures and objects. These are mainly tensors, bundles, varieties and jets. The first part is devoted to the mechanics of the continuum itself and its description in several areas, others deal with mathematical concepts and their possible application in mechanics.

Soil behaviors are quite complex under dynamic loadings, such as wave loading, earthquake loading, etc, but they share common characteristics that the soil is subjected to considerable principal stress rotations (PSR). PSR can generate plastic deformation even without a change of principal stress magnitudes. Continuous PSR can also generate excess pore water pressures and cumulative shear strains in undrained condition. Therefore, the PSR from the dynamic loadings can accelerate undrained soil liquefaction because it can cause cumulative plastic volumetric deformations. Ignoring PSR induced deformation may lead to unsafe design. It is therefore important to understand the soil behaviors under cyclic loadings with the PSR and take account of this PSR impact in the numerical simulations of corresponding geotechnical problems. Although researchers have recognized the importance of the PSR in real geotechnical problems under diverse loading conditions and conducted extensive experimental studies, there are limited considerations of the PSR impact on numerical simulations of boundary value problems. Moreover, most of the constitutive models widely-used in the numerical investigations at present cannot simulate this PSR behavior properly. Therefore, a new kinematic hardening soil model (PSR model) developed on the basis of a well-established model with bounding surface concept is used to simulate the PSR behavior in this research. It can take account of the PSR impact by treating the stress rate generating the PSR independently. To investigate the impacts of PSR in numerical simulations of geotechnical problems, the PSR model is implemented into both the single element and finite element analysis of a series of geotechnical problems by a constitutive model subroutine written in Fortran. In this subroutine, an explicit substepping integration algorithm with automatic error controls is used to perform the constitutive formulations. The imposed strain increment can be automatically divided and the sizes of the sub-increments are also automatically determined based on the prescribed error tolerance in this numerical integration scheme. The single element analyses include the simulations of the triaxial and hollow cylinder tests with monotonic, rotational and torsional loading paths, while the finite element analyses consist of the simulations of the centrifuge experimental tests under wave loadings and earthquake loadings. The predicted results by using the soil model with and without considering the PSR impact, as well as the experimental results will be compared. From these single element and finite element analyses, it is evident that the rotational, torsional and dynamic loadings such as wave and earthquake loadings can produce the PSR and non-coaxiality in the soil. The comparisons between the predicted results from the modified PSR model, the original model, and the laboratory results from these experimental tests all show that although the original model can reflect some non-coaxiality, it can produce very limited build-up of pore water pressure and cumulative shear strain under cyclic loading path. However, due to consideration of the PSR impact, the modified PSR model can generate higher pore water pressure and shear strain than the original model, thus bringing the soil to the liquefaction and agrees better with the experimental results. Therefore, it is important to consider the PSR effect in the simulation of geotechnical problems such as wave-seabed interactions and the earthquake induced liquefactions, and the PSR model presented in this research has a great ability and plays an important role in these numerical simulations.

L'intégration des expertises métiers constitue un enjeu primordial des nouvelles générations des systèmes de gestion globale du cycle de vie du produit. La maîtrise d'ouvrage de telles intégrations est rendue difficile par la complexité de la gestion de la connaissance proportionnelle à celle croissante du produit, la diversité des acteurs de tels projets et le manque de retour au cours ou à l'issue de déploiements de tels projets passés et présents. Ces travaux de thèse ont été menés en parallèle d'un cas d'étude sur le projet USIQUICK, visant à l'automatisation de la génération de gamme d'usinage. Cette expérience a également été confrontée à des projets dans d'autres secteurs de l'industrie ou des services. La contribution de cette thèse propose un ensemble d'outils conceptuels utilisables en préparation ou au cours d'un projet d'intégration d'expertise. En phase amont cet ensemble d'outils peut être utilisé pour consolider les expériences précédentes et constituer des grilles d'analyses pour la prise de décision des méthodologies à déployer. Au cours du projet, cette base méthodologique d'outils donne à la maîtrise d'ouvrage des critères d'analyse pour évaluer la dynamique de projet. Elle permet de faire émerger les problèmes liés à la modélisation de l'expertise, de préparer les phases de programmation et de faire ressortir dans ces deux cas des lieux de représentations propices à l'émergence d'indicateurs de performance relatifs à la spécificité du projet étudié. L'apport méthodologique pour la maîtrise d'ouvrage est constitué de la proposition et de l'analyse des quatre « piliers » de ressources à la modélisation et à l'intégration d'expertise (réseaux de concepts, listes de spécifications, corpus de document, outils de gestion). Ces piliers permettent de justifier une série de phases décrivant les enjeux de la modélisation (phases d'identification, d'extraction, de structuration et de formalisation) et de l'intégration (phases de raffinement, de spécification des développements, de diffusion et de maintenance). Grâce à une analyse des niveaux de maturité de la gestion initiale et attendue de l'expertise, ces « piliers » et ces phases permettent de cadrer le contexte d'un retour d'expérience ou d'un projet à déployer. En parallèle, trois couples de concepts, syntaxe / sémantique, infrastructure / architecture, domaine / projet, permettent un questionnement pour identifier les zones potentielles de problèmes dans les représentations et envisager des axes de résolution. Il est ainsi permis de contribuer au rapprochement du systématisme épistémologique de la gestion des connaissances avec la pratique empirique et pragmatique contenue dans les savoirs. La consolidation des liens entre ces aspects de l'expertise permet un pilotage de projet par des éléments réels de connaissances et d'expertise.

Thesis (M.S.)--University of Akron, Dept. of Mechanical Engineering, 2008.
"December, 2008." Title from electronic thesis title page (viewed 12/9/2009) Advisor, Jiang John Zhe; Faculty Readers, Joan Carletta, Dane Quinn; Department Chair, Celal Batur; Dean of the College, George K. Haritos; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.

Etablissement du principe des puissances virtuelles pour les milieux continus presentant des discontinuites, des surfaces singulieres et des interfaces. Application aux milieux deformables usuels, puis extension a l'electromagnetodynamique et aux semiconducteurs piezoelectriques. Par combinaison de cette formulation avec les principes de la thermodynamique et par construction de lois de comportement, obtention de systemes differentiels et de conditions aux limites necessaires a l'etude des ondes en volume et a l'interface. Application a l'analyse de la propagation des ondes dans les solides anisotropes purement elastiques, electroelastiques et semiconducteurs en vue de la realisation de dispositifs acoustoelectroniques associant les caracteres acoustique et electronique dans le meme milieu

The paper treats the question of feasibility of measuring intrinsic thin film stresses due to nanoindentation. A variety of different methods is proposed and analysed with respect to their applicability. As this accuracy-estimation results in boundary conditions for the measurements which can not be fulfilled yet, the whole topic is considered from a purely academic point of few. With the help of a special software package [25] the following methods are considered: 1. Taking the moment of beginning plastic flow within the substrate as indictor, 2. Taking the moment of beginning plastic flow within the film as indictor, 3. Applying mixed loads (normal and lateral forces), 4. Applying the concept of the effectively shaped indenter. While the methods 2 to 4 appear to be in principle feasible, method 1 can completely be ruled out as being of no practical use. The mentioned software package (FilmDoctor prototype) is part of the supplemental material of this study.

Durant els darrers quaranta anys la geometria diferencial ha estat una eina fonamental per entendre la teoria de control òptim. Habitualment la millor estratègia per resoldre un problema és transformar-lo en un altre problema que sigui més tractable. El Principi del Màxim de Pontryagin proporciona al problema de control òptim d’una estructura Hamiltoniana. Les solucions del problema Hamiltonià que satisfan unes determinades propietats són candidates a ésser solucions del problema de control òptim. Aquestes corbes candidates reben el nom d’extremals. Per tant, el Principi del Màxim de Pontryagin aixeca el problema original a l’espai cotangent. En aquesta tesi desenvolupem una demostració completa i geomètrica del Principi del Màxim de Pontryagin. Investiguem cuidadosament els punts més delicats de la demostració, que per exemple inclouen les perturbacions del controls, l’aproximació lineal del conjunt de punts accessibles i la condició de separació. Entre totes les solucions d’un problema de control òptim, existeixen les corbes anormals. Aquestes corbes no depenen de la funció de cost que es vol minimitzar, sinó que només depenen de la geometria del sistema de control. En la literatura de control òptim, existeixen estudis sobre l’anormalitat, tot i que només per a sistemes lineals o afins en el controls i sobretot amb funcions de cost quadràtiques en els controls. Nosaltres descrivim un mètode geomètric nou per caracteritzar tots els diferents tipus d’extremals (no només les anormals) de problemes de control òptim genèrics. Aquest mètode s’obté com una adaptació d’un algoritme de lligadures presimplèctic. El nostre interès en les corbes anormals es degut a les corbes òptimes estrictament anormals, les quals també queden caracteritzades mitjançant l’algoritme descrit en aquesta tesi. Com aplicació del mètode mencionat, caracteritzem les extremals d’un problema de control òptim lliure, aquell on el domini de definició no està donat. En concret, els problemes de temps mínim són problemes de control òptim lliures. A més a més, som capaços de donar una corba extremal estrictament anormal aplicant el mètode descrit per a un sistema mecànic. Un cop la noció d’anormalitat ha estat estudiada en general, ens concentrem en l’estudi de l’anormalitat per a sistemes de control mecànics, perquè no existeixen resultats sobre l’existència de corbes òptimes estrictament anormals per a problemes de control òptim associats a aquests sistemes. En aquesta tesi es donen resultats sobre les extremals anormals quan la funció de cost és quadràtica en els controls o si el funcional a minimitzar és el temps. A més a més, la caracterització d’anormals en casos particulars és descrita mitjançant elements geomètrics com les formes quadràtiques vector valorades. Aquests elements geomètrics apareixen com a resultat d’aplicar el mètode descrit en aquesta tesi. També tractem un altre enfocament de l’estudi de l’anormalitat de sistemes de control mecànics, que consisteix a aprofitar l’equivalència que existeix entre els sistemes de control noholònoms i els sistemes de control cinemàtics. Provem l’equivalència entre els problemes de control òptim associats a ambdós sistemes de control i això permet establir relacions entre les corbes extremals del problema nonholònom i del cinemàtic. Aquestes relacions permeten donar un example d’una corba òptima estrictament anormal en un problema de temps mínim per a sistemes de control mecànics. Finalment, i deixant de banda per un moment l’anormalitat, donem una formulació geomètrica dels problemes de control òptim no autònoms mitjançant la formulació unificada de Skinner-Rusk. La formulació descrita en aquesta tesis és fins i tot aplicable a sistemes de control implícits que apareixen en un gran nombre de problemes de control òptim dins de l’àmbit de l’enginyeria, com per exemple els sistemes Lagrangians controlats i els sistemes descriptors.
Durante los últimos cuarenta años la geometría diferencial ha sido una herramienta para entender la teoría de control óptimo. Habitualmente la mejor estrategia para resolver un problema es transformarlo en otro problema que sea más tratable. El Principio del Máximo de Pontryagin dota al problema de control óptimo de una estructura Hamiltoniana. Las soluciones del problema Hamiltoniano que satisfagan determinadas propiedades son candidatas a ser soluciones del problema de control óptimo. Estas curvas candidatas se llaman extremales. Por lo tanto, el Principio del Máximo de Pontryagin levanta el problema original al espacio cotangente. En esta tesis doctoral, desarrollamos una demostración completa y geométrica del Principio del Máximo de Pontryagin. Investigamos minuciosamente los puntos delicados de la demostración, como son las perturbaciones de los controles, la aproximación lineal del conjunto de puntos alcanzables y la condición de separación. Entre todas las soluciones de un problema de control óptimo, existen las curvas anormales. Estas curvas no dependen de la función de coste que se quiere minimizar, sino que sólo dependen de la geometría del sistema de control. En la literatura de control óptimo existen estudios sobre la anormalidad, aunque sólo para sistemas lineales o afines en los controles y fundamentalmente con funciones de costes cuadráticas en los controles. Nosotros presentamos un método geométrico nuevo para caracterizar todos los distintos tipos de extremales (no sólo las anormales) de problemas de control óptimo genéricos. Este método es resultado de adaptar un algoritmo de ligaduras presimpléctico. Nuestro interés en las extremales anormales es debido a las curvas óptimas estrictamente anormales, las cuales también pueden ser caracterizadas mediante el algoritmo descrito en esta tesis. Como aplicación del método mencionado en el párrafo anterior, caracterizamos las extremales de un problema de control óptimo libre, aquél donde el dominio de definición de las curvas no está dado. En particular, los problemas de tiempo óptimo son problemas de control óptimo libre. Además, somos capaces de dar un ejemplo de una curva extremal estrictamente anormal aplicando el método descrito. Una vez la noción de anormalidad en general ha sido estudiada, nos centramos en el estudio de la anormalidad para sistemas de control mecánicos, ya que no existen resultados sobre la existencia de curvas óptimales estrictamente anormales para problemas de control óptimo asociados a estos sistemas. En esta tesis, se dan resultados sobre las extremales anormales cuando la función de coste es cuadrática en los controles o el funcional a minimizar es el tiempo. Además, la caracterización de las anormales en casos particulares es descrita por medio de elementos geométricos como las formas cuadráticas vector valoradas. Dichos elementos geométricos aparecen como consecuencia del método descrito para caracterizar las extremales. También se considera otro enfoque para el estudio de la anormalidad de sistemas de control mecánicos, que consiste en aprovechar la equivalencia que existe entre sistemas de control noholónomos y sistemas de control cinemáticos. Se prueba la equivalencia entre problemas de control óptimo asociados a ambos sistemas de control, lo que permite establecer relaciones entre las extremales del problema noholónomo y las extremales del problema cinemático. Estas relaciones permiten dar un ejemplo de una curva optimal estrictamente anormal en un problema de tiempo óptimo para sistemas de control mecánicos. Por último, olvidándonos por un momento de la anormalidad, se describe una formulación geométrica de los problemas de control óptimo no autónomos aprovechando la formulación unificada de Skinner-Rusk. Esta formulación es incluso válida para sistemas de control implícitos que aparecen en numerosos problemas de control óptimo de ámbito ingenieril, como por ejemplo, los sistemas Lagrangianos controlados y los sistemas descriptores.
For the last forty years, differential geometry has provided a means of understanding optimal control theory. Usually the best strategy to solve a difficult problem is to transform it into a different problem that can be dealt with more easily. Pontryagin's Maximum Principle provides the optimal control problem with a Hamiltonian structure. The solutions to the Hamiltonian problem, satisfying particular conditions, are candidates to be solutions to the optimal control problem. These candidates are called extremals. Thus, Pontryagin's Maximum Principle lifts the original problem to the cotangent bundle. In this thesis, we develop a complete geometric proof of Pontryagin's Maximum Principle. We investigate carefully the crucial points in the proof such as the perturbations of the controls, the linear approximation of the reachable set and the separation condition. Among all the solutions to an optimal control problem, there exist the abnormal curves. These do not depend on the cost function we want to minimize, but only on the geometry of the control system. Some work has been done in the study of abnormality, although only for control-linear and control-affine systems with mainly control-quadratic cost functions. Here we present a novel geometric method to characterize all the different kinds of extremals (not only the abnormal ones) in general optimal control problems. This method is an adaptation of the presymplectic constraint algorithm. Our interest in the abnormal curves is with the strict abnormal minimizers. These last minimizers can be characterized by the geometric algorithm presented in this thesis. As an application of the above-mentioned method, we characterize the extremals for the free optimal control problems that include, in particular, the time-optimal control problem. Moreover, an example of an strict abnormal extremal for a control-affine system is found using the geometric method. Furthermore, we focus on the description of abnormality for optimal control problems for mechanical control systems, because no results about the existence of strict abnormal minimizers are known for these problems. Results about the abnormal extremals are given when the cost function is control-quadratic or the time must be minimized. In this dissertation, the abnormality is characterized in particular cases through geometric constructions such as vectorvalued quadratic forms that appear as a result of applying the previous geometric procedure. The optimal control problems for mechanical control systems are also tackled taking advantage of the equivalence between nonholonomic control systems and kinematic control systems. In this thesis, it is found an equivalence between time-optimal control problems for both control systems. The results allow us to give an example of a local strict abnormal minimizer in a time-optimal control problem for a mechanical control system. Finally, setting aside the abnormality, the non-autonomous optimal control problem is described geometrically using the Skinner-Rusk unified formalism. This approach is valid for implicit control systems that arise in optimal control problems for the controlled Lagrangian systems and for descriptor systems. Both systems are common in engineering problems.

Using the generative processes developed over two stages of creative development and the performance of The Physics Project at the Loft at the Creative Industries Precinct at the Queensland University of Technology (QUT) from 5th – 8th April 2006 as a case study, this exegesis considers how the principles of contemporary physics can be reframed as aesthetic principles in the creation of contemporary performance. The Physics Project is an original performance work that melds live performance, video and web-casting and overlaps an exploration of personal identity with the physics of space, time, light and complementarity. It considers the acts of translation between the language of physics and the language of contemporary performance that occur via process and form. This exegesis also examines the devices in contemporary performance making and contemporary performance that extend the reach of the performance, including the integration of the live and the mediated and the use of metanarratives.

Polymeric adhesives play an increasingly critical role in today's engineering designs. When used, adhesively bonded components reduce or eliminate the need for bolted or welded connections. In many cases, this can reduce stress concentrations and weight. With energy dissipating adhesives, noise and vibration reduction are possible, as is the use of unique or complicated designs that could not otherwise be constructed. Adhesive properties however, can vary greatly with time, temperature, and environmental exposure conditions such as moisture. It is therefore critical, to understand the behavior of adhesives over the range of conditions that a bonded component might experience. In this work, the behavior of a urethane-based adhesive was characterized and long-term durability predictions were developed as a result of the data collected. The popular T-peel sample geometry has been used extensively in this study to explore the mechanics of a bonded system and the resulting impact on adhesive durability. The T-peel specimens used, consist of two aluminum sheets or adherends bonded together, with tabs bent back in the shape of a "T" for gripping in a universal load frame. Unlike some other test geometries, T-peel samples are often made with relatively thin adherends that may experience significant plastic deformation during testing. This extraneous energy dissipation greatly complicates the analysis to extract meaningful fracture properties of the adhesive. During testing, the load required to propagate a crack in the adhesive layer is measured at fixed displacement rates. The total system energy can then be partitioned into the energy dissipated within the adhesive (fracture energy), and the energy dissipated through plastic work in bending of the adherends. By performing these tests at different temperatures and rates, the calculated fracture energies span a wide range of possible material behavior. Using the principles of Time Temperature Superposition (TTS), the collected data can be shifted to different times or temperatures. This behavior is well understood in polymer physics, and is made possible with material specific "shift factors". By using the principles of TTS, data collected in in a relatively short experimental window, can be used to accurately predict the behavior of the adhesive in years or even decades. In this work, nearly 200 T-peel samples were tested in four different studies. A preliminary set of unaged specimens was used to develop testing and data analysis methodologies. A second set of unaged samples was tested over a wide range of temperatures and rates, in addition to a third group, subjected to constant moisture and cyclically varying temperature. The final set of specimens, was exposed to 20 separate isothermal aging conditions. The experimental data showed that the 400+ cycles, were insufficient to statistically distinguish these samples from their unaged counterparts. Additionally, samples aged for up to 2000 hours in a dry environment, or 500 hours in a wet environment, showed no reduction in fracture energies in comparison with unaged samples. Specimens aged for more than 500 hours however, were observed to have a significant decrease in fracture energy values. Strong correlations between the thickness of the adhesive layer and estimated fracture energy values were found in this study. As adhesive thickness varied substantially due to manufacturing differences in the specimens tested, new analysis techniques were developed to deal with the variations in adhesive thickness. A MATLAB code based on the ICPeel program, was written to provide a spatial variation of parameters such as adhesive thickness, peel load, and fracture energy. This provided additional insights into the behavior of these T-peel coupons, and prompted the investigation of the Universal Peel Diagram concept. While this diagram was not found to be applicable to the adhesive tested in this study, the analysis indicated that T-peel coupons could be multivalued. That is, a single measured load value does not always describe an adhesive's fracture energy (as is widely believed). Depending on the sample's geometry and material properties, several measured loads could cause debonding. This has potentially far reaching implications on the selection of appropriate T-peel test geometries, as a single measured load is often assumed to correlate to an adhesive's true fracture energy. In this work, both aged and unaged T-peel specimens were tested and the basis of the Universal Peel Diagram investigated. Given sufficient exposure times to moisture, elevated temperatures were found to significantly reduce the amount of energy dissipated in the urethane-based adhesive. Additionally, the Universal Peel Diagram indicated that for some systems, the load required for debond is in fact, multivalued. Therefore, care should be taken when designing a T-peel test configuration to avoid the multivalued regions.
Master of Science
Polymeric adhesives play an increasingly critical role in today's engineering designs. When used, adhesively bonded components reduce or eliminate the need for bolted or welded connections, reducing their weight in the process. With adhesives, noise and vibration reduction are possible, as is the use of unique or complicated designs that could not otherwise be constructed. Adhesive properties, however, can vary greatly with time, temperature, and other environmental exposure conditions such as moisture. It is therefore critical to understand the behavior of adhesives over the range of conditions that a bonded component might experience. In this work, the behavior of a urethane-based adhesive was characterized in order to develop long-term durability predictions. Numerous test methods have been developed to characterize the behavior of adhesively bonded joints. In this work, T-peel specimens were used consisting of two aluminum sheets (the adherends), bonded together with tabs bent back in the shape of a "T" for gripping in a universal load frame. During testing, the load required to propagate a crack in the adhesive layer is measured. An outcome of this measurement and subsequent data analysis is the fracture energy—a measure of the effectiveness of the adhesive in transferring loads. If we perform these tests at different temperatures and loading rates, we can determine fracture energy values which span a wide range of possible material behavior. Using principles from basic polymer physics, the collected data can be shifted to different times or temperatures enabling us to accurately predict the behavior of the adhesive over years or even decades. In this work, nearly 200 T-peel samples were tested in four different studies. A preliminary set of unaged specimens was used to develop testing and data analysis methodologies. Unaged and cyclically (temperature) aged samples were tested over a wide range of temperatures and rates. The fourth set of specimens was subjected to 20 separate isothermal aging conditions and also tested at different temperatures and rates. The experimental data showed that the 400+ temperature cycles were insufficient to damage these samples significantly. Additionally, samples aged for up to 2000 hours in a dry environment, or 500 hours in a wet environment showed no reduction in performance in comparison with unaged samples. Specimens aged for more than 500 hours in a wet environment however, demonstrated a significant decreases in fracture energy values. Strong correlations between the thickness of the adhesive layer and estimated fracture energy values were found in this study, and new analysis techniques were developed to analyze the effect of these thickness variations on the joint performance.

Les capteurs résonants de type M/NEMS sont largement utilisés dans l’environnement biologique pour la mesure de masse de biomolécules en raison de leur grande précision combinée à une taille réduite. Classiquement, la détection et la quantification se basent sur le décalage fréquentiel induit par la masse ajoutée. Toutefois, ce décalage devient très faible et difficile à distinguer du bruit de mesure lorsque les masses considérées sont très petites. Il est théoriquement possible de gagner encore un ou plusieurs ordres de grandeur en résolution avec ces méthodes fréquentielles en diminuant encore les tailles et/ou en augmentant le rapport signal sur bruit, c’est-à-dire en actionnant de manière plus importante les résonateurs. Mais, dans ces conditions, les nanorésonateurs ont un comportement très fortement non-linéaire, source d’instabilités et de mixage de bruit basses et hautes fréquences susceptibles de dégrader la fiabilité et la précision des mesures. C’est pourquoi cette thèse a pour objectif de définir des principes de détection alternatifs basés sur l’exploitation des phénomènes non-linéaires, tels que les comportements hystérétiques et les bifurcations des courbes de réponse en fréquence. Pour cela, un modèle réduit de micro/nano-poutre résonante avec actionnement électrostatique est considéré. Les résultats numériques montrent que les brusques sauts d’amplitude à proximité des points de bifurcation permettent la détection de masses très faibles. Contrairement à la détection fréquentielle, ces sauts sont d’autant plus grands que la masse additionnelle est petite, ce qui rend cette technique particulièrement intéressante. De plus, le seuil de détection peut être ajusté avec la valeur de la fréquence de fonctionnement. Un mécanisme de réinitialisation est toutefois indispensable pour rendre la détection à nouveau possible après un saut d’amplitude. Afin d’automatiser la réinitialisation et ainsi permettre la détection en temps réel, un concept totalement innovant de détection de masse par balayage en fréquence des cycles d’hystérésis est proposé, qui permet de détecter, quantifier et localiser la masse ajoutée sur la poutre résonante. La mise en réseau de plusieurs poutres résonantes est également traitée et constitue un premier pas vers la mise en oeuvre de réseaux de milliers de capteurs. Pour cela, des architectures efficaces sont proposées et les modèles numériques sont adaptés en conséquence. Sur des configurations symétriques, l’exploitation des bifurcations de type brisure de symétrie permet là-encore d’améliorer la détection de masse
Resonant M/NEMS mass sensors are widely used in biological environment for measuring the mass of biomolecules due to their high accuracy combined with a reduced size. Usually, the detection and the quantification are based on the frequency shift induced by an added mass. However, this shift becomes very small and difficult to distinguish from the noise of measurement as the considered masses are tiny. It is theoretically possible to increase further one or several orders of magnitude in resolution with these frequency methods by further reducing size and/or by increasing the signal-to-noise ratio, that is to say by operating more importantly the resonators. But in these conditions, the nanoresonators have a strongly nonlinear behavior, a source of instability and noise mix of low and high frequencies likely to degrade the reliability and the accuracy of measurements. Therefore, the thesis’s objective is to define alternative principles of detection based on exploiting the nonlinear phenomena, such as the hysteretic behavior and the bifurcations of frequency-response curves. To this end, a reduced model of resonant micro/nano-beam with electrostatic actuation is considered. The numerical results show that the sudden jumps in amplitude close to bifurcation points allow the detection of very small masses. Unlike the frequency detection, the smaller the added mass, the larger the increase of the jump, which makes this technique particularly interesting. In addition, the detection threshold can be adjusted with the value of the operating frequency. However, a mechanism of reinitialization is mandatory to make the detection possible again after a jump in amplitude. In order to automate the reinitialization and allow the detection in real-time, a completely innovative concept of mass detection by the frequency sweep of the hysteretic cycles is proposed to detect, quantify and locate the added mass on the resonant beam. An array of several resonant beams is also considered and constitutes a first step toward the implementation of arrays of thousands of sensors. Efficient architectures are proposed for this purpose and the numerical models are adapted accordingly. On symmetric configurations, exploiting the bifurcations of symmetry-breaking type allows here again to improve the mass detection

I defend three general claims concerning inter-theoretic reduction in physics. First, the popular notion that a superseded theory in physics is generally a simple limit of the theory that supersedes it paints an oversimplified picture of reductive relations in physics. Second, where reduction specifically between two dynamical systems models of a single system is concerned, reduction requires the existence of a particular sort of function from the state space of the low-level (purportedly more accurate and encompassing) model to that of the high-level (purportedly less accurate and encompassing) model that approximately commutes, in a specific sense, with the rules of dynamical evolution prescribed by the models. The third point addresses a tension between, on the one hand, the frequent need to take into account system-specific details in providing a full derivation of the high-level theory’s success in a particular context, and, on the other hand, a desire to understand the general mechanisms and results that under- write reduction between two theories across a wide and disparate range of different systems; I suggest a reconciliation based on the use of partial proofs of reduction, designed to reveal these general mechanisms of reduction at work across a range of systems, while leaving certain gaps to be filled in on the basis of system-specific details. After discussing these points of general methodology, I go on to demonstrate their application to a number of particular inter-theory reductions in physics involving quantum theory. I consider three reductions: first, connecting classical mechanics and non-relativistic quantum mechanics; second,connecting classical electrodynamics and quantum electrodynamics; and third, connecting non-relativistic quantum mechanics and quantum electrodynamics. I approach these reductions from a realist perspective, and for this reason consider two realist interpretations of quantum theory - the Everett and Bohm theories - as potential bases for these reductions. Nevertheless, many of the technical results concerning these reductions pertain also more generally to the bare, uninterpreted formalism of quantum theory. Throughout my analysis, I make the application of the general methodological claims of the thesis explicit, so as to provide concrete illustration of their validity.

Texture evolution is a vital component of many computational tools that link structure, properties and processes of polycrystalline materials. By definition, this evolution process involves the manipulation, via rotation, of points in orientation space. The computational requirements of the current methods being used to rotate crystalline orientations are a significant limiting factor in the drive to merge the texture information of materials into the engineering design process. The goal of this research is to find and implement a practical rotation algorithm that can significantly decrease the computation time required to rotate macroscopic and microscopic crystallographic textures. Three possible algorithms are considered in an effort to improve the computational efficiency and speed of the rotation process. The first method, which will be referred to as the Gel'fand method, is based on a paper, [1], that suggests a practical application of some of Gel'fand's theories for rotations [2]. The second method, which will be known as the streamline method, is a variation on the Gel'fand method. The third method will be known as the principal orientation method. In this method, orientations in Fourier space are written as linear combinations of points on the convex surface of the microstructure hull to reduce the number of points that must be rotated during each step in the texture evolution process. This thesis will discuss each of these methods, their strengths and weaknesses, and the accuracy of the computational results obtained from their implementation.

Dans le cadre du design des assemblages combustibles, les écoulements turbulents induits par les grilles de maintien provoquent de fortes fluctuations de pression dues aux niveaux de vitesses du fluide induisant la vibration des crayons combustibles. Or ces vibrations sont une source de vieillissement accéléré et d’usure prématurée des assemblages combustibles dont l’origine convient d’être mieux analysée.Dans cette l'optique, des simulations numériques ont été utilisées pour prédire les niveaux de vitesses transverses ainsi que le niveau de turbulence en aval de la grille. Cependant, les codes CFD doivent être validés avec des mesures expérimentales conduisant ainsi à une meilleure compréhension des structures mis en jeu dans le processus de mélange. Or la caractéristique de ce type d'écoulement repose sur son caractère tridimensionnel entre les faisceaux de crayons où l'accès optique est limité et à l'heure actuelle, aucune mesure de vitesse 3D n'a été réalisée. C'est pourquoi nous nous proposons de présenter dans cette étude l'application d'une technique de mesure 3D résolue en temps dans une boucle hydraulique transparente. L’approche consiste à utiliser une stratégie de suivi, dans lequel des particules traceuses individuelles sont d'abord détectées dans l’écoulement et ensuite suivies dans le temps – PTV 3D.Cette thèse présente les résultats obtenus dans une veine d’essais hydraulique en utilisant une approche de suivi à l’aide de deux caméras. Dans un premier temps, une nouvelle extension de la technique de défocalisation permettant de récupérer les positions des particules dans le temps avec une caméra est présentée et la méthodologie pour récupérer les déplacements individuels est décrite. Des cas d’application et de validation de la technique sont présentés afin de mieux quantifier les erreurs de mesures. Ensuite, la boucle hydraulique est introduite et son écoulement caractérisé par des techniques établies de mesure de vitesse. Finalement, les mesures 3D à deux caméras sont réalisées et discutées
In order to validate the numerical simulation of the mixing phenomena downstream a spacer grid in the reactor core, reaching the 3rd velocity component through experimental studies is of major importance since mechanical structures responses are linked to transverse velocities. Nevertheless the main difficulty relies on applying a non-intrusive velocimetry technique around obstacles composed of a vertical set of rods. So far only 1D and 2D temporal studies have been performed.Hence, numerical methods have been widely used to predict correctly those transverse velocities and the turbulence level downstream the grid. However, CFD codes are to be validated with experimental measurements leading to a better understanding of the detailed flow structure in the mixing process. Therefore we propose to present in this study the application of a 3D time resolved velocity measurement technique to a hydraulic test facility. The approach is to use a tracking strategy, in which individual particles are first detected then followed in time - 3D time resolved Particle Tracking Velocimetry.This PhD Thesis presents results obtained in a hydraulic test section using a tracking based approach with two cameras. At first, a new extension of the defocussing technique to recover particles location in time with one camera is presented and the methodology o get individual velocity vector is then described. Applications and validations of the technique in dedicated flows allow to determinate and quantify measurement uncertainties. Then the hydraulic test section is introduced together with preliminary flow characterization using Laser Doppler Velocimetry or 2D time resolved PIV analysis. Finally, two cameras measurements are reported and post-processing techniques are discussed

Spray models are increasingly becoming the principal tools in the design and development of gas turbine combustors. Spray modeling requires a knowledge of the liquid atomization process, and the sizes and velocities of subsequently formed droplets as initial conditions. In order to have a better understanding of the liquid atomization process,the breakup characteristics of plane liquid sheets in co-flowing gas streams are investigated by means of linear and nonlinear hydrodynamic instability analyses. The liquid sheet breakup process is studied for initial sinuous and varicose modes of disturbance. It is observed that the sheet breakup occurs at half-wavelength intervals for an initial sinuous disturbance and at full-wavelength intervals for an initial varicose disturbance. It is also found that under certain operating conditions, the breakup process is dictated by the initial varicose disturbance compare to its sinuous counterpart. Further, the breakup process is studied for the combined mode and it is found that the sheet breakup occurs at half- or full-wavelength intervals depending on the proportion of the individual sinuous and varicose disturbances. In general, the breakup length decreases with the increase in the Weber number, gas-to-liquid velocity and density ratios. A predictive model of the initial droplet size and velocity distributions for the subsequently formed spray is also formulated here. The present model incorporates the deterministic aspect of spray formation by calculating the breakup length and the mass-mean diameter and the stochastic aspect by statistical means through the maximum entropy principle based on Bayesian entropy. The two sub-models are coupled together by the various source terms signifying the liquid-gas interaction and a prior distribution based on instability analysis, which provides information regarding the unstable wave elements on the two liquid-gas interfaces. Experimental investigation of the breakup characteristics of the liquid sheet is performed by a high speed CCD camera and the measurement of the initial droplet size and distributions is conducted by phase-Doppler interferometry. Good agreement of the theoretical breakup length with the experiment is obtained for a planar, an annular and a gas turbine nozzle. The predicted initial droplet size and velocity distributions show reasonably satisfactory agreement with experimental data for all the three types of nozzles. Hence this spray model can be utilized to predict the initial droplet size and velocity distributions in sprays, which can then be implemented as a front-end subroutine to the existing computer codes.

Yes
Cementitious composites are generally brittle and develop considerable tension cracks, resulting in corrosion of steel reinforcement and compromising structural durability. With careful selection and treatment, some kinds of bacteria are able to precipitate calcium carbonate and ‘heal’ cracks in cementitious composites through their metabolism, namely bacterial activity. It is envisioned that the bacterial technology-enabled cementitious composites could have great potential for engineering applications such as surface treatment, crack repair and self-healing construction material. This paper presents the state-of-the-art development of bacterial technology-enabled cementitious composites from the following aspects: mechanisms of bacterial induced calcium carbonate precipitation; methods of applying bacteria into cementitious composites; mechanical properties, durability and their influencing factors; various applications; cost effective analysis and prospect. The paper concludes with an outline of some future opportunities and challenges in the application of bacterial technology-enabled cementitious composites in construction.
National Science Foundation of China (51578110) and the Fundamental Research Funds for the Central Universities in China (DUT18GJ203).

The object of this work is to explore the influence superhydrophobic (SH) surfaces exert in laminar jet impingement and when they are combined with riblets in turbulent channel flow. A SH surface generates an apparent slip due to the combination of micropatterning and chemical hydrophobicity. Because of surface tension, water does not enter the cavities between the features, increasing the contact angle of a water droplet on the surface and reducing the liquid-solid contact area. An analysis based on the integral momentum approach of Karman and Pohlhausen is presented that predicts jet impingement behavior on SH surfaces. The model is first applied to the scenario where the slip at the surface is isotropic and a downstream depth is imposed such that a circular hydraulic jump occurs. The model predicts the thin film parameters downstream of the jet and the radial location of the hydraulic jump. An increase in the hydraulic jump radius occurs as slip increases, momentum of the jet increases, or the downstream depth decreases. Modifications to the model are made for the scenario where the slip at the surface varies azimuthally, as would be the case for a surface patterned with microribs. The average behavior is similar, although now an elliptically shaped jump forms with the major axis aligned parallel to the rib/cavity structures. The ellipse eccentricity increases as the slip increases, the jet momentum increases, or the downstream depth decreases. Where there is no downstream depth imposed on SH surfaces, the thin film breaks up into droplets instead of forming a hydraulic jump. Further changes are made to the model to incorporate this behavior for isotropic and anisotropic surfaces resulting in circular and elliptically shaped breakups respectively. This work also explores SH surfaces with riblets in turbulent channel flow. Pressure drop measurements across surfaces exhibiting superhydrophobicity, riblets, and surfaces with both drag reducing mechanisms are presented. The SH surface reduces drag because the effective surface area is reduced and riblets are able to reduce drag by dampening the spanwise turbulence. Photolithography was used to fabricate all surface types. An aluminum channel with a control and a test section was used for testing. Pressure transducers recorded the pressure drop across smooth silicon wafers and patterned test surfaces simultaneously allowing for computation of the friction factors.

Dampening systems are important in heavy vehicles utilized in rough terrains, with purpose to reduce shocks and vibrations with negative influences on the vehicle and, more importantly, on the operator of the vehicle. During the years the heavy vehicles require sturdier construction parts, due to demands on higher load capacity, where the easy solution to scale up the construction parts is not always applicable for dampening systems with nonlinear behavior. Hence, the sturdiness in the design of these dampening systems requires improvement. In this thesis the design of the rubber spring used as rubber spring in Volvo’s articulated hauler A40G is treated. The aim of this thesis is to find alternative design solutions on the rubber spring, improving its lifetime. The usual failure of these rubber springs is crack propagation in the rubber body. In the method of this thesis, alternative design solution are generated in concepts though brain storming, which are adjusted to achieve the desired behavior of the rubber spring through calculations and tested in performance through simulations in Abaqus. From analyzing the generated data, it is concluded that among the tested design solutions, a combination of fewer plates and shaping the plates as thin bowls, results in highest potential increase in lifetime.

Cette thèse traite de la modélisation dynamique des systèmes non-holonomes intermittents et de son application à la bicyclette 3D de Whipple. Pour cela, nous nous sommes appuyés sur un ensemble d'outils en mécanique géométrique (réduction Lagrangienne et projection dans le noyau des contraintes cinématiques essentiellement). Dans un premier temps, nous avons traité le cas de la bicyclette persistante. En définissant l'espace des configurations du vélo comme un fibré principal de groupe structural SE(3), nous avons obtenu un modèle des points de contact et des contraintes exempt de toute non-linéarité associée à un paramétrage de type coordonnées généralisées. Cette formulation nous a permis d'obtenir le noyau des contraintes sous une forme symbolique sans singularité. Nous avons alors produit un modèle symbolique de la dynamique de la bicyclette persistante en utilisant la méthode de réduction par projection de sa dynamique libre dans le sous espace de ses vitesses admissibles. Cette approche étend le cadre général mis au point ces dernières années pour la locomotion bio-inspirée. Profitant de la structure de SE(3), un modèle de la bicyclette intermittente a été proposé dans le cadre d'une approche événementielle. L'adoption du modèle physique de l'impact plastique, nous a permis d'étendre la méthode de réduction par projection au cas intermittent. Nous avons alors comparé notre approche "réduite" à l'approche classiquement utilisée et avons montré qu'elles partageaient une interprétation géométrique commune. Ces outils ont finalement été appliqués à la simulation de la bicyclette intermittente afin d'illustrer la richesse de sa dynamique
This thesis deals with the dynamic modelling of intermittent non-holonomic systems andits application to the Whipple 3D bicycle. To that end, we relied on a set of tools in geometric mechanics (mainly Lagrangian reduction and the projection in the kernel of the kinematic constraints). In the first instance, we have addressed the case of the bicycle subjected to persistent contacts. By defining the space of the bicycle configurations as a principal fibre bundle with SE(3) as structural group, we obtained a model of the contact points and of the constraints free of any non-linearities associated with a generalized coordinate type configuration. This formulation allowed us to obtain the kernel of the constraints in a symbolic form without singularity. We then produced a symbolic model of the dynamics ofthe bicycle subjected to persistent contacts using the projection reduction method of its free dynamics in the subspace of its permissible speeds. This approach extends the general framework developed in recent years for bio-inspired locomotion. Taking advantage of the structure of SE(3), a model of the intermittent bicycle was proposed as part of an event-driven approach. Moreover, the adoption ofthe physical model of plastic impact has allowed us to extend the projection reduction method to the intermittent case. We then compared our "reduced" approach to the conventional approach and showed that they shared a common geometric interpretation. These tools were finally applied to the simulation of the intermittent bicycle to illustrate its rich dynamics

Orientador: Adalberto Bono Maurizio Sacchi Bassi
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química
Made available in DSpace on 2018-08-25T02:48:09Z (GMT). No. of bitstreams: 1 Reis_MartinaCosta_D.pdf: 1200753 bytes, checksum: 9318dbbd02e3d4660c4a6806e68dad7d (MD5) Previous issue date: 2014
Resumo: Este trabalho descreve a termodinâmica de sistemas eletroquímicos. Explorando os princípios da teoria constitutiva, algumas hipóteses ad hoc e, em especial, o princípio de entropia Müller-Liu, modelos termo-eletroquímicos são propostos para soluções eletrolíticas e para as regiões de bulk e dupla camada de um sistema eletroquímico. A influência das interações íon-íon e íon-solvente sobre a dinâmica da mistura é considerada através da termodinâmica de contínuos polares e as equações de balanço são apropriadamente postuladas. Além disso, equações fenomenológicas são apresentadas para uma solução eletrolítica diluída e isotrópica e as condições para o equilíbrio termodinâmico local do bulk e da dupla camada são investigadas. Comparando-se as desigualdades residuais de entropia obtidas para cada região, foi demonstrado que alguns processos, tais como os fenômenos de difusão térmica, termoeletricidade e eletroforese, desenvolvem-se somente na dupla camada. Consequentemente, o estado de equilíbrio termodinâmico local na dupla camada requer condições termodinâmicas mais severas do que no bulk. Apesar das equações constitutivas serem as mais simples possíveis, os modelos constitutivos propostos para as regiões de dupla camada e bulk são fisicamente consistentes e mais abrangentes do que os modelos eletroquímicos usuais, visto que as equações e relações termodinâmicas obtidas não se limitam às condições limites e nem de equilíbrio. Portanto, a descrição termodinâmica mostrada neste trabalho pode estimular químicos e engenheiros químicos a usar a abordagem contínua no estudo da mobilidade iônica em meios bio e geológicos, fluxos de íons e de outras espécies químicas através de membranas e processos cujas transferências de calor e massa são intensificadas por campos eletromagnéticos
Abstract: This work concerns the thermodynamics of electrochemical systems. Exploiting the principles of constitutive theory, few expedient assumptions, and, in special, the Müller-Liu entropy principle, a thermo-electrochemical continuum model is proposed for electrolyte solutions as well as for the bulk and double layer regions of an electrochemical system. The influence of ion-ion and ion-solvent interactions on the mixture dynamics is taken into account through the thermodynamics of polar materials and balance laws for an electrochemical system are accordingly stated. In addition, phenomenological equations are schemed for a dilute and isotropic electrolyte solution, and the conditions for local thermodynamic equilibrium of bulk and double layer regions are investigated. Comparing the residual entropy inequalities obtained for each region of an electrochemical system, it is shown that some mechanisms develop only in the double layer, such as the thermal diffusion, thermoelectricity and electrophoresis phenomena. As a consequence, the local thermodynamic equilibrium state in the double layer requires stricter conditions than in the bulk. Although the constitutive equations are the simplest possible, the constitutive models proposed for the double layer and bulk regions are physically consistent and more comprehensive than the usual models since the emerging equations do not constrain themselves to equilibrium neither limiting conditions. Therefore, the thermodynamic description provided in this work may stimulate chemists and chemical engineers to take advantage of it to study the flow of ions and other chemical species across cell membranes, ionic mobility in bio and geological media, and processes whose heat and mass transfers are enhanced by electromagnetic fields
Doutorado
Físico-Química
Doutora em Ciências

Lors de la modélisation du comportement mécanique de structures comme des avions, ou des lanceurs spatiaux, il subsiste des incertitudes parfois fortes, notamment en ce qui concerne l'évaluation des efforts extérieurs ou la rigidité des liaisons. Jusqu'à présent, des coefficients de sécurité, souvent forfaitaires, sont employés, de manière à assurer le bonne tenue des structures, en se basant sur les résultats de modèles simplifiés de la réalité. Cette thèse s'inscrit dans la problématique de validation des modèles numériques utilisés, et tente d'apporter des outils pratiques pour le dimensionnement de toute structure réelle, en présence d'incertitudes, tout en limitant les sur-dimensionnements liés à l'éventuel emploi de coefficients de sécurité. Dans cette optique, les travaux présentés ici s'appuient sur la théorie des méconnaissances, qui vise à remplacer les politiques de marges par une approche un peu plus scientifique. Développée au LMTCachan depuis 2002, son objet est de fournir, moyennant une modélisation originale des incertitudes en présence, les bornes de l'intervalle qui, pour une famille de structures donnée, a une certaine probabilité de contenir la quantité d'intérêt recherchée. Nous proposons des extensions permettant de modéliser les incertitudes portant sur les efforts appliqués aux structures étudiées, ou sur des rigidités anisotropes. Un autre aspect du travail présenté concerne la propagation des méconnaissances introduites à des quantités d'intérêt statiques, de type contraintes ou déplacements locaux. Une fois ceci défini, il est alors possible de définir une approche permettant d'estimer la probabilité de défaillance d'une structure à partir d'un modèle avec méconnaissances, et d'obtenir des indicateurs de la marge disponible par l'amélioration de telle ou telle méconnaissance. Cette approche permet d'inscrire la théorie des méconnaissances dans une optique de conception robuste.

Dans un contexte où l'utilisation de structures déployables s'est généralisée, le département Recherche de la société Thales Alenia Space étudie un nouveau concept de télescope spatial dont le miroir secondaire est déployé grâce au déroulement de six mètres rubans. Des études antérieures ont permis la mise au point d'un prototype constitué de rubans métalliques dont le déploiement s'est avéré trop violent. Dans ce travail de thèse nous proposons d'une part un nouveau type de ruban à la vitesse de déroulement maîtrisable et d'autre part un modèle original décrivant le comportement dynamique de tels rubans, permettant de mieux appréhender les phénomènes complexes pouvant intervenir lors de scénarios de pliage, de déploiement ou de déroulement. La solution envisagée pour contrôler la vitesse de déroulement repose sur l'exploitation des propriétés mécaniques d'une couche de matériau viscoélastique collée à la surface du ruban. Ces propriétés variant avec la température permettent de garantir un maintien de la position enroulée à froid et assurent un déroulement régulé grâce à un réchauffage localisé. Ces phénomènes ont été mis en évidence expérimentalement et numériquement. La lourdeur des méthodes classiques de modélisation et le manque de richesse des méthodes simplifiées nous ont conduit à développer un modèle de poutre à section fortement déformable permettant de décrire le comportement dynamique des rubans en grands déplacements. Partant d'un modèle de coque, l'originalité de la méthode repose essentiellement sur l'introduction d'une cinématique de type elastica pour décrire les grandes variations de forme de la section. Un modèle énergétique 1D est obtenu en intégrant dans la section et le problème est résolu à l'aide du logiciel de modélisation par éléments finis COMSOL. On propose finalement un modèle continu 1D à 4 paramètres cinématiques qui permet de rendre compte d'une large gamme de phénomènes intervenant dans des scénarios complexes de pliage, de déroulement et de déploiement dynamique
The research department of Thales Alenia Space is studying new concepts of space telescopes whose secondary mirror is deployed thanks to the unreeling of six tape-springs. A breadboard using metallic tape-springs has been built during preliminary studies and has exhibited a deployment that is too energetic and induce too important shocks.In this thesis a new kind of tape-spring with a controlled uncoiling speed is introduced. Secondly a rod model with highly deformable thin-walled cross-sections describing the dynamic behaviour of tape-springs is derived.In order to over come the deployment speed of a tape spring, a viscoelastic layer is stuck on its sides. Thanks to its properties varying with the temperature, the viscoelastic layer is used to maintain the tape-spring in a coiled configuration at low temperature whereas a local heating leads to a controlled uncoiling. These phenomenons have been underlined experimentally and numerically.Because of the high complexity of classical shell models and the lack of details of simplified models, smart modelling methods need to be developed to describe the highly non linear behaviour of a tape-spring. A planar rod model with highly deformable thin-walled cross-sections that accounts for large displacements and large rotations in dynamics is proposed. Starting from a classical shellmodel, the main additional assumption consists in introducing an elastica kinematics to describe thelarge changes of the cross-section shape with very few parameters. The expressions of the strain andkinetic energies are derived by performing an analytical integration over the section. The Hamilton principle is directly introduced in a suitable finite element software to solve the problem. Several examples (folding, coiling and deployment of a tape spring) are studied through the FEM software COMSOL to demonstrate the ability of the 4-parameter model to account for several phenomena: creation of a single fold and associated snap-through behaviour, splitting of a fold into two, motion of a fold along the tape during a dynamic deployment, scenarios of coiling and uncoiling of a bistable tape-spring