Regelflächen, das sind durch die Bewegung von Geraden erzeugte Flächen, haben für den Betonleichtbau unter den Gesichtspunkten Statik und Herstellung herausragende Eigenschaften: Auch wenn sie doppelt gekrümmt sind, können sie geradlinig bewehrt oder vorgespannt werden. Außerdem kann die Schalung beispielsweise durch Heißdrahtschneiden aus Polystyrol-Hartschaum gewonnen werden. In gängigen CAD-Systemen ist die Klasse der Regelflächen bislang nicht angemessen repräsentiert und steht deshalb für die Bauteilgestaltung nur eingeschränkt zur Verfügung. Liniengeometrie für den Leichtbau liefert nun ein mathematisches Modell, das Regelflächen und auf sie wirkende Kräfte abbildet, und entwickelt daraus Formfindungswerkzeuge, die in einer vertrauten Entwurfsumgebung das Prinzip form follows force unterstützen. [Aus. Einführung] / Ruled surfaces, which are surfaces created by the movement of straight lines, have outstanding properties for lightweight concrete construction from the viewpoints of statics and production: even if they are double-curved, they can be reinforced or prestressed in a rectilinear fashion. In addition, the formwork can be obtained ef ciently from rigid polystyrene foam by hot wire cutting, for example. In current CAD systems, the class of ruled surfaces has not yet been adequately implemented and is therefore only available to a limited extent for component design. This project Line Geometry for Lightweight Structures provides a mathematical model that represents ruled surfaces and the forces acting on them, and uses this to develop form finding tools that support the principle of form follows force in a familiar design environment. [Off: Introduction]

This thesis contributes to the theoretical work on decision and game theory when decision makers or players perceive ambiguity. The first article introduces a new axiomatic framework for ambiguity aversion and provides axiomatic characterizations for important preference classes that thus far had lacked characterizations. The second article introduces a new axiom called Weak Monotonicity which is shown to play a crucial role in the multiple prior model. It is shown that for many important preference classes, the assumption of monotonic preferences is a consequence of the other axioms and does not have to be assumed. The third article introduces an intuitive definition of perceived ambiguity in the multiple prior model. It is shown that the approach allows an application to games where players perceive strategic ambiguity. A very general equilibrium existence result is given. The modelling capabilities of the approach are highlighted through the analysis of examples. The fourth article applies the model from the previous article to a specific class of games with a lattice-structure. We perform comparative statics on perceived ambiguity and ambiguity attitude. We show that more optimism does not necessarily lead to higher equilibria when players have Alpha-Maxmin preferences. We present necessary and sufficient conditions on the structure of the prior sets for this comparative statics result to hold. The introductory chapter provides the basis of the four articles in this thesis. An overview of axiomatic decision theory, decision-making under ambiguity and ambiguous games is given. It introduces and discusses the most relevant results from the literature.

Orientador: Renato Pavanello / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia mecanica / Made available in DSpace on 2018-08-04T08:49:46Z (GMT). No. of bitstreams: 1 PoelFilho_CornelisJoannesvander_D.pdf: 8296875 bytes, checksum: 048da8ba9cfe029f98229ac0b593f989 (MD5) Previous issue date: 2005 / Resumo: Microsistemas eletromecânicos geralmente têm seu princípio de funcionamento baseado na interação entre dois ou mais campos físicos. Para seu projeto são necessárias ferramentas de simulação multi-domínios. Este trabalho visa estudar o fenômeno de acoplamento eletromecânico em microsistemas e construir uma ferramenta de simulação numérica para este tipo de problema. São apresentados métodos de análise estática, modal e transiente baseados em modelos de elementos finitos e de ordem reduzida. Na análise estática cada domínio é resolvido separadamente. Foi mostrado um método de transferência das forças eletrostáticas para o domínio mecânico e proposto e testado um esquema de atualização da malha elétrica. Para a análise dinâmica transiente foi implementado um método de Newmark adaptado de forma a considerar os efeitos do acoplamento eletromecânico. Outro método de análise dinâmica apresentado é baseado numa estratégia de perturbação do sistema em equilíbrio em conjunto com a resolução de um problema de autovalor / autovetor. O método de perturbação fornece diretamente as freqüências naturais de vibração do sistema acoplado. A técnica de redução de ordem apresentada é baseada numa projeção de Galerkin da equação diferencial governante utilizando como funções de base os modos empíricos do sistema dinâmico. Um programa computacional para modelagem numérica multi-domínios com solução particionada para o acoplamento eletromecânico foi proposto e implementado. O código computacional, denominado MefLab, onde os métodos numéricos foram programados, usa o paradigma de orientação a objetos e a linguagem C++. Resultados com as diversas metodologias são mostrados e analisados / Abstract: Microelectromechanical systems have their working principIes based on the interaction between two or more physical fields. To design them, multi-physics simulation tools are needed. This work aims to study the coupled field effects in microsystems and build a computer code for numerical simulation of this problem. Static, dynamic modal and transient methods are introduced. They are based on finite elements and reduced order models. The static analysis is done by a staggered treatment. A method for transfering electrostatic pressures to the mechanical domain was shown and a mesh updating scheme was proposed and tested. For the transient analysis, in order to consider the electromechanical coupling effects, an adaptation was inserted in the classical Newmark direct integration method. A dynamical modal method based in a perturbation strategy was presented. It involves the staggered static algorithm and the solution of an eigenvalue/eigenvector problem. This method is able to give the natural coupled frequencies of the system with low computational costs. A reduced order modeI was constructed by using a Galekin projection of the governing differential equations in an empirical basis. This basis was obtained through results of transient finite element analysis. A multi-domain project with staggered procedures for the electromechanical coupling was proposed and implemented. It refers to the software MefLab++, a computer code written in C++ where numerical strategies are programmed according to the oriented object paradigm. Numerical results for the static, dynamic modal and transient methodologies are shown / Doutorado / Mecanica dos Sólidos e Projeto Mecanico / Doutor em Engenharia Mecânica

Le procédé de thermo-estampage est une voie intéressante pour la production en grande série de pièces composites. Cependant ce procédé est complexe à maitriser et simuler, en raison des phénomènes multi-physiques mis en jeu (déformation textiles, choc thermique, frottements...) ce qui engendre des campagnes par essai-erreurs qui peuvent être très coûteuses. Cette étude s'intéresse à la mesure et à la caractérisation du procédé d'estampage et des matériaux utilisés afin de simuler le refroidissement de la matrice et la mise en forme du textile. Des défauts récurrents sont évoqués ainsi que des solutions industrielles afin de les résoudre. La simulation thermique permet de déterminer le temps de consolidation nécessaire afin d'optimiser les temps de production en fonction des matériaux et de leur épaisseur. La simulation de la mise en forme textile permet de prédire la faisabilité d'une pièce et l'orientation des fibres afin de définir au mieux les pièces suivant les cas de charges statiques et dynamiques. Les apports de ce travail sont les suivants : la réalisation de mesures thermiques du flan durant un estampage et du choc thermique en surface du stratifié, la réalisation d'une méthodologie efficiente pour analyser la faisabilité d'une pièce complexe dans un contexte industriel grâce à des simulations de mise en forme couplées à des essais expérimentaux. Enfin une méthode d'analyse du comportement en cisaillement plan, pour des renforts dont les fils de chaîne et de trames ne sont pas orthogonaux est proposée. / The thermo-stamping process is a promising way for the mass production of the composite parts. However this process is complex to master and simulate due to the multi-physics background (textile deformation, thermal shock, rubbing...) and trial and error tests campaigns can be expensive. This study focuses on the measurement and assessment of the process and materials behaviour, to simulate the cooling down of the matrix and the forming of the woven. Typical defects are mentioned as well as associated industrial solutions to solve them. The simulation makes it possible to determine the consolidation time necessary in order to optimize the manufacturing time as a function of the material used and of its thickness. Furthermore the forming simulation shows the feasibility of the part and the fibre orientation to design the product for the static and crash cases. The contributions of this work are the following: thermal measurements of the pre-consolidated plate during the stamping phase and the thermal chock at the surface of the composites, an efficient method to analyse the feasibility of a complex shape in an industrial context is proposed through forming simulations compared to the experiment. Finally, a methodology for the analysis of the in-plane shearing behaviour of a woven fabric with non-orthogonal warp and weft yarn is proposed.

Les systèmes de transmission par engrenages sont largement utilisés pour transmettre de la puissance et adapter les vitesses de rotation entre organes moteurs et récepteurs. Dans ce contexte, les engrenages sont fréquemment les organes parmi les plus sensibles de la chaîne cinématique et peuvent être soumis à un grand nombre d’avaries (fatigue de contact, fatigue de flexion, usure…etc.) apparaissant lors du fonctionnement et dont les causes sont multiples. L’objectif de ce travail est, d’une part, de simuler l’usure abrasive et la fatigue de contact conduisant à de l’écaillage (pitting) et, d’autre part, d’analyser les interactions entre ces avaries et le comportement statique et dynamique de transmission par engrenages. A cette fin, un modèle dynamique tridimensionnel d’engrenages de fortes largeurs est couplé à des modèles d’usure et d’avaries de contact. L’usure est simulée en s’appuyant sur le modèle d’Archard modifié afin de tenir compte de l’influence du régime de lubrification. Les usures obtenues après un certain nombre de cycles de chargement sont considérées comme des écarts initiaux additionnels par rapport à la géométrie idéale du flanc de denture. Les phénomènes de fatigue de contact par pitting sont analysés en deux étapes; a) une période d’initiation de fissure simulée en s’appuyant sur plusieurs critères de fatigue multiaxiaux et b) une phase de propagation de fissure traitée par la mécanique linéaire élastique de la rupture. Les sollicitations dynamiques fournies par le modèle dynamique d’engrenages sont utilisées comme données d’entrée pour la simulation des périodes d’initiation puis de propagation. Un grand nombre d’exemples d’application sont présentés et les interactions entre comportement dynamique, usure et fatigue sur des engrenages cylindriques sont analysées. / Gear transmissions have high power-to-weight ratios, can be made very compact and match the speeds and torques of one machine to another with high efficiency. However, gears are one of the weakest links in a transmission and can develop a number of failures (wear, contact fatigue, bending fatigue, etc.) which downgrade the overall transmission performance. The objective of this work is twofold; on the one hand, simulate abrasive wear on tooth flanks and contact fatigue leading to pitting, on the other hand, analyse the interactions between these damages and the dynamic and static behaviour of geared transmissions. To this end, a three dimensional gear dynamic model is used and coupled with several wear and fatigue models. The wear on tooth flanks is simulated based on a modified Archard’s law which includes the influence of the lubrication regime. Wear is accounted for via time- and position-varying distributions of normal deviations with respect to ideal flank geometry which are superimposed on profile and lead modifications. The occurrence of pitting is divided into two periods: a) a crack initiation period simulated by using several multi-axial fatigue criteria and, b) a crack propagation phase which is tackled using the theory of linear elastic rupture mechanics. The dynamic tooth loads delivered by the gear dynamic model are used as input data for the simulations of crack initiation and then crack propagation. A number of results are presented and the interactions between wear, contact fatigue and dynamic behaviour are investigated and commented upon.

This diploma thesis deals with the numerical modeling of the nail joint of the timber roof structure and it is based on the already realized physical experiment. Totally twelve various solutions, where the isotropic and ortotropic characteristics of the spruce timber and steel components change, have been created. The final values of the joint shift obtained by using of the numerical modeling are compared with results of physical experiment. Program system ANSYS is used.

Le projet consacré à la statique graphique étudie un aspect jusqu'ici peu exploré de l'histoire technique tchèque de la seconde moitié du XIXème au début du XXe siècle, lorsque les pays tchèques ont joué un rôle de premier plan en matière de technologie dans l'ancienne monarchie autrichienne. Une part du projet a permis de révéler le transfert de cette méthode de calcul en pratique d'ingénierie depuis son lieu d'origine, France et Suisse, vers les pays tchèques, et la contribution originale du milieu tchèque dans ce domaine. Le transfert de la statique graphique vers les pays tchèques fut effectué après sa formation dans la seconde moitié des années 1860. Le transfert culturel a prospéré grâce à la diffusion de la presse et des livres publiés principalement en allemand et, bien sûr, grâce aux contacts personnels étroits entre les conférenciers des écoles polytechniques européennes, en particulier des langues allemandes. La thèse contient également des exemples d'importants bâtiments historiques tchèques, pour lesquels la statique graphique a été utilisée pour calculer la structure. Ces calculs sont illustrés par la documentation archivistique, qui n'a pas encore été publiée. Une part de la thèse est également consacrée à la comparaison de deux méthodes de calcul de déformation des treillis (système triangulés). La première est la méthode du français V.-J. Williot, qui a été publiée en août 1878. La seconde est la méthode du professeur tchèque V. Bukovsky de janvier 1879. Comme il n'existe à l'heure actuelle aucune étude détaillée portant sur Victor-Joseph Williott ( 1843-1907), certains documents d'archives jamais publiés ont été recherchés pour illustrer sa vie. / The project of graphic statics is studying a heretofore little explored part of the Czech technical history of the second half of the 19th, and beginning of the 20th centuries, when the Czech lands held a leading role in technology in the former Austrian Monarchy. A part of the project is to reveal the transfer of this computational method in engineering practice from the place of its origin, France and Switzerland, to the Czech lands, as well as original contribution of the Czech millieu to this field. The transfer of graphic statics to the Czech lands came very soon after its formation in the second half of the 1860' s. Cultural transfer prospered thanks to the distribution of press and books published mainly in German, and, of course, thanks to the close persona) contacts among lecturers at European, especially German-speaking, polytechnic high school! The thesis also contains examples of significant Czech historical buildings, for which graphic statics was used to calculate the structure. These calculations are illustrated by archival documentation, which has not yet been published. A special part of the thesis is a comparison of two calculation methods of deformation of trusses. The first one is the method of French V.-J. Williot, which was published in August 1878. The second one is the Czech professor V. Bukovsky's method of January 1879. As no more detailed information was known about Victor-Joseph Williott ( 1843- 1907), some never published archival documents were searched to illustrate his life.

The diploma thesis deals with a structural and technical survey of the surviving cellar of the German House in Brno. The first part of the thesis is devoted to the theoretical description of the constructions, methods performed and their evaluation concerning the investigated space. The aim of the survey is to determine the strength characteristics of the masonry and on their basis to propose appropriate rehabilitation and structural protection.