Pendant la dernière décennie, il y a eu un incrément de la résolution spatiale des observations satellitaires. Cela est notamment dû aux avancées technologiques implémentées sur les satellites. La quantité d'information observée est vaste, et il faut donc identifier des techniques efficaces pour la traiter et pour produire de cartes précises de la dynamique en surface. La mission future SWOT collectera de données d'élévation de surface (SSH) à très haute résolution spatiale : une partie de la dynamique à petites longueurs d'onde, c'est-à-dire, de la sousméso-échelle, sera représentée dans ces observations. Les observations satellitaires servent à réaliser la reconstruction spatiale en surface et aussi à la projeter vers l'intérieur de l'océan et vers des autres variables. La question posée est donc quelles méthodes peuvent fournir ces estimés 3D et multivariés avec une bonne précision à des échelles proches de la sousméso-échelle.Nous nous situons dans ce travail de thèse dans un cadre d'assimilation de données et d'images : l'objectif du travail étant la reconstruction de façon précise de la dynamique dans la couche de surface de l'océan (~500 m) à partir d'observations satellitaires. Pour ce faire, nous implémentons une méthode qui utilise différentes observations en surface à deux étapes d'analyse séparées. Elle consiste d'abord d'une première étape d'assimilation de données qui réalise une correction linéaire de l'écoulement. La deuxième étape se base dans une méthode d'assimilation d'images (Gaultier et al, 2012) dont l'objectif est de bien localiser les structures lagrangiennes obtenues par le calcul des exposants de Lyapunov. Dans le but de fournir des incertitudes associées aux estimés, nous disposons d'une distribution de probabilité d'ébauche qui sera corrigé par notre méthode : (i) la première étape effectue une analyse SEEK pour corriger cette distribution d'ébauche en utilisant une observation d’élévation de SSH; (ii) la deuxième étape minimise une fonction coût en utilisant l'observation d'une image structure et nous obtenons ainsi une distribution de probabilité finale. Les estimés sont projetés dans la dimension verticale en utilisant des EOFs (Empirical Orthogonal Functions) 3D multivariées, de cette sorte nous avons des estimés de variables observées et des variables non-observées (Duran-Moro et al, 2017).La méthode est testée en utilisant des données synthétiques produites par un modèle numérique à haute résolution (~3 km) dans la Mer de Salomon (SOSMOD36). La méthode fournit des résultats positifs : les estimés sont bien reconstruites sur la vertical et aussi concernant les variables non-observées. Dans ce cadre, nous réalisons une évaluation de l'impact de diverses pseudo-observations altimétriques dans la performance de la méthode. Ceci est réalisé par l'implémentation des traces Jason et Envisat sur l'observation de SSH ainsi qu'à partir du simulateur SWOT développé au JPL. Ce dernier est utilisé pour générer des pseudo-observations SWOT ainsi que des erreurs et du bruit prévus pour cette mission. La corrélation significative de ces erreurs a motivé l'application de la technique dans Ruggiero et al, 2016 dans notre analyse. Des simulations à plus haute résolution spatiale (~1 km) récemment produites à partir du modèle numérique NATL60 en Atlantique Nord sont aussi utilisées pour tester la méthode. Cette étude permet d'évaluer la dépendance des résultats avec la variabilité saisonnière de la dynamique aux moyennes latitudes. / During the last decade, high resolution observations have significantly increased mainly due to the strong innovations of satellite technology. The amount of observed information from satellites is large, and it is necessary to identify effective techniques to treat and to generate surface maps of the ocean dynamics. The future SWOT mission will collect sea surface height (SSH) measurements with a high spatial resolution : some dynamics at small wavelengths, which is known as submeso-scale, will be present in these new observations. Satellite observations could be used to carry out a vertical projection into the deeper ocean and to other variables. The question that rises is which methods can be used to carry out a 3D multivariate analysis with a significant precision, especially at meso and submeso-scale.We work here in a data/image assimilation framework : our objective if to reconstruction with good precision the dynamics in the upper oceanic layer (~500 m) using satellite observations. To do so, we implement a two-step method that uses different observations of the sea surface. The first step consist on the SEEK filter which is a data assimilation technique to carry out a first linear correction of the flow. The second step uses an image assimilation method (Gaultier et al , 2012) to correct the location of the main dynamical structure. This main dynamical structure is obtained by the computation of the Lyapunov exponents. A probability approach is applied to provide uncertainties on the estimates at each step. A first probability distribution of a background state is supposed to be known : the two-step method corrects this probability distribution at each step in order to converge towards the real ocean state. The SEEK filter corrects the background probability distribution using a SSH observation. The second step continues this correction towards smaller scales by using an image structure observation. To carry out the vertical projection, an ensemble of 3D multivariate EOFs (Empirical Orthogonal Functions) is used (Duran-Moro et al, 2017).The method is tested using synthetic data generated by a numerical model in the Solomon Sea region (SOSMOD36). The spatial resolution of these simulations is of ~3 km. We evaluate the response of our method in an idealized case study by using pseudo-observations generated from the simulations. The method provides good results and the estimates are corrected also in the vertical and in terms of other variables. A more detailed exploration of the altimetric observation is realized, especially related to future SWOT observations. Errors of SWOT observations have strong spatial correlations and another technique needs to be used in our method : this modification is carried out following work done in Ruggiero et al, 2016. Simulations from another NEMO configuration in the North Atlantic region (NATL60) are also used to evaluate the method. This second test allows us to explore the method in a different latitude of the globe.

Customized cellular material is a relatively new area made possible by advancements in rapid manufacturing technologies. Rapid manufacturing is ideal for the production of customized cellular structure, especially on the meso scale, due to the size and complexity of the design. The means to produce this type of structure now exist, but the processes to design the structure are not well developed. The manual design of customized cellular material is not realistic due to the large number of features. Currently there are few tools available that aid in the design of this type of material. In this thesis, an automated tool to design customized cellular structure is presented.

Rapid prototyping (RP) can be used to make complex shapes with very little or even no constraint on the form of the parts. New design methods are needed for parts that can take advantage of the unique capabilities of RP. Although current synthesis methods can successfully solve simple design problems, practical applications with thousands to millions elements are prohibitive to generate solution for. Two factors are considered. One is the number of design variables; the other is the optimization method. To reduce the number of design variables, parametric approach is introduced. Control diameters are used to control all strut size across the entire structure by utilizing a concept similar to control vertices and Bezier surface. This operation allows the number of design variables to change from the number of elements to a small set of coefficients. In lattice structure design, global optimization methods are popular and widely used. These methods use heuristic strategies to search the design space and thus perform, as oppose to traditional mathematical programming (MP) methods, a better global search. This work propose that although traditional MP methods find local optimum near starting point, given a quick convergence rate, it will be more efficient to perform such method multiple times to integrate global search than using a global optimization method. Particle Swarm Optimization and Levenburg-Marquardt are chosen to perform the experiments.

The advent of rapid manufacturing has enabled the realization of countless products that have heretofore been infeasible. From customized clear braces to jet fighter ducts and one-off dental implants, rapid manufacturing allows for increased design complexity and decreased manufacturing costs. The manufacturing capabilities of this process have evolved to the point that they have surpassed current design capabilities. Meso-scale lattice structures can now be built that contain more lattice struts than it is reasonable to efficiently define. This work has attempted to create a method for designing such lattice structures that is efficient enough to allow for the design of large or complex problems. The main hindrance to the design of complex meso-scale lattice problems is essentially the need to define the strut diameters. While it is obvious that a large design would contain more struts than can be specified by hand, designs also quickly surpass the current capabilities of computational optimization routines. To overcome this problem, a design method has been developed that uses a unit-cell library correlated to finite element analysis of the bounding geometry to tailor the structure to the anticipated loading conditions. The unit-cell library is a collection of base lattice primitives, or unit-cells, that have been specialized for certain applications. In this case, primitives have been created that perform best under the types of stress analyzed by finite element analysis. The effectiveness of this process has been demonstrated through several example problems. In all cases, the unit-cell library approach was able to create structures in less time than current methods. The resulting structures had structural performance slightly lower than similar models created through optimization methods, although the extent of this degradation was slight. The method developed in this work performs extremely well, and is able to create designs for even the most complex lattice structures. There is room for future development, however, in the streamlining of the design process and consideration of higher-order affects within unit-cells.

Thermodynamic and thermoeconomic aspects of 12.5 kW residential solar-thermal power generating systems suitable for distributed, decentralized power generation paradigm are presented in this thesis. The design of a meso-scale power system greatly differs from centralized power generation. As a result, this thesis provides guidance in the selection of the power cycle and operating parameters suitable for meso-scale power generation. Development of standard thermodynamic power cycle computer simulations provides means for evaluation of the feasibility of meso-scale solar-thermal power generation. The thermodynamic power cycles considered in this study are the Rankine cycle, the organic Rankine cycle with toluene, R123, and ethylbenzene as working fluids, the Kalina cycle, and the Maloney-Robertson cycle. From a strictly thermodynamic perspective, the cycles are evaluated based on first- and second-law efficiencies. Additionally, the study includes economic feasibility through thermoeconomic characterization that encompasses a meso-scale cost model for solar-thermal power generation systems. Key results from this study indicate that a R123 organic Rankine cycle is the most cost-effective cycle implementation for operating conditions in which the maximum temperature is limited below 240C. For temperatures greater than 240C and less than 375C, the toluene and ethylbenzne organic Rankine cycles outperform the other cycles. The highest first law efficiency of 28% of the Kalina cycle exceeds all other cycles at temperatures between 375C and 500C. However, when considering cycle cost and overall feasibility, including thermodynamic and thermoeconomic performance, the Maloney-Robertson and Kalina cycles have poor performance on a cost-to-efficiency basis.

Le brouillard est un phénomène météorologique dangereux car les fines gouttelettes d'eau en suspension dans l'atmosphère réduisent considérablement la visibilité. Bien que les avancées scientifiques et informatiques permettent d'utiliser des modèles de prévision numérique du temps de plus en plus détaillés, la prévision du brouillard reste encore un challenge dû à la multitude et la complexité des processus mis en jeu lors du cycle de vie du brouillard (dynamique, microphysique, turbulent et radiatif). Dans cette thèse, des simulations sont réalisées sur l'aéroport Paris Charles-de-Gaulle avec le modèle à échelle kilométrique AROME afin d'étudier l'impact de la résolution verticale sur la prévision du brouillard. L'étude détaillée d'un cas de brouillard a permis de mettre en évidence le fort impact de la résolution verticale sur la formation du brouillard. La résolution verticale a un impact sur l'heure de formation, le développement spatial et même sur les processus physiques liés à l'apparition du brouillard. L'impact de la résolution verticale a été évalué statistiquement sur l'hiver 2011-2012 et a permis de confirmer les résultats obtenus lors de l'étude de cas. Il a été mis en évidence qu'une résolution verticale fine permet de simuler davantage de brouillards locaux qu'une résolution verticale lâche. De plus, ces simulations ont souligné que le modèle surestime la hauteur de la base du nuage quelle que soit la résolution verticale. Bien que le nombre de bonnes détections augmente avec une résolution verticale fine, la qualité de la prévision reste inchangée à cause d'un nombre de fausses alarmes plus important ce qui peut être expliqué par l'hétérogénéité spatiale des brouillards simulés. Utiliser une résolution fine sur un grand domaine entraîne un surcoût numérique qui n'est pas envisageable en opérationnel. Dans cette thèse, deux méthodes numériques de représentation de la couche limite de surface permettant d'associer une résolution fine près du sol et un temps de calcul modeste ont été évaluées pour une étude de cas et durant une saison hivernale. La meilleure des méthodes basée sur le schéma Canopy permet de bien représenter le comportement physique du modèle à résolution verticale fine lors de l'apparition de brouillards purement radiatifs. Cependant, la méthode atteint ses limites lorsque l'apparition du brouillard est impactée par des circulations locales car l'advection n'est pas prise en compte par cette méthode. Le diagnostique de brouillard par Canopy permet de corriger le biais sur la fréquence d'occurrence de brouillard mais n'améliore pas significativement la qualité de la prévision. / The fog is a hazardous meteorological phenomenon because of the visibility decrease due to water droplets present in the atmosphere. Despite scientific and numerical improvements allowing the use of very detailed numerical weather prediction models, fog forecasting is still a challenge to address. Indeed, several complex processes are involved during the fog life cycle (dynamic, micro-physic, turbulence and radiation). In this thesis, simulations are performed at the Paris Charles-de-Gaulle airport with the kilo-metric scale model AROME in order to study the impact of the vertical resolution on the fog forecasting. A detailed study case highlights the strong impact of vertical resolution on the fog formation. Vertical resolution impacts both the onset time, the spatial development and also the physical processes involved at the fog onset. The impact of vertical resolution has been evaluated statistically over the winter season 2011-2012 and has confirmed the results obtained with the study case. It has been shown that a finer vertical resolution leads to the simulation of more local fog events than a coarser vertical resolution. Furthermore, these simulations emphasize that the model overestimates the cloud base height whatever the vertical resolution. In spite of the increase of good detections with a finer vertical resolution, the overall forecast quality does not change because of more frequent false alarms. These false alarms can be explained by enhanced spatial heterogeneities of simulated fogs at finer vertical resolution. Using a finer vertical resolution on a large domain increase the numerical cost, which is not affordable for operational forecasting. In this thesis, two numerical methods representing the surface boundary layer and allowing a finer vertical resolution at a low computational cost have been tested for the case study and during the winter season. The best method is based on the surface boundary layer scheme Canopy, which improves the physical behavior of the model during the onset of radiation fogs. However, the limits of the method are reached when the onset is impacted by local circulations, which they are not taken into account with this method. The fog diagnostic by Canopy reduces the frequency bias fog forecast but it does not significantly improve the overall forecast quality because of more frequent false alarms.

Multiple studies on the microstructures of advanced high-strength steels are presented here that seek to add to the already substantial body of knowledge on martensite in steel. These studies seek to gain additional insight into the role that the martensite transformation has on the observed mechanical properties of modern steels. Crystallographic Reconstruction of Parent Austenite Twin Boundaries in a Lath Martensitic Steel The study of post-transformation microstructures and their properties can be greatly enhanced by studying their dependence on the grain boundary content of parent microstructures. Recent work has extended the crystallographic reconstruction of parent austenite in steels to include the reconstruction of special boundaries, such as annealing twins. These reconstructions present unique challenges, as twinned austenite grains share a subset of possible daughter variant orientations. This gives rise to regions of ambiguity in a reconstruction. A technique for the reconstruction of twin boundaries is presented here that is capable of reconstructing 60 degree twins, even in the case where twin regions are comprised entirely of variants that are common between the twin and the parent. This technique is demonstrated in the reconstruction of lath martensitic steels. The reconstruction method utilizes a delayed decision-making approach, where a chosen orientation relationship is used to define all possible groupings of daughter grains into possible parents before divisive decisions are made. These overlapping, inclusive groupings (called clusters) are compared to each other individually using their calculated parent austenite orientations and the topographical nature of the overlapping region. These comparisons are used to uncover possible locations of twin boundaries present in the parent austenite. This technique can be applied to future studies on the dependence of post-transformation microstructures on the special grain boundary content of parent microstructures. Coupling Kinetic Monte Carlo and Implicit Finite Element Methods for Predicting the Strain Path Sensitivity of the Mechanically Induced Martensite Transformation The kinetic Monte Carlo method is coupled with a finite-element solver to simulate the nucleation of martensite inside the retained austenite regions of a TRIP (transformation induced plasticity) assisted steel. Nucleation kinetics are expressed as a function of load path and kinematic coupling between retained austenite regions. The model for martensite nucleation incorporates known elements of the kinetics and crystallography of martensite. The dependence of martensite transformation on load path is simulated and compared to published experimental results. The differences in transformation rates of retained austenite are shown to depend on load path through the Magee effect. The effects of average nearest neighbor distance between austenite grains is shown to affect the rate at which martensite nucleates differently depending on load path. Ductility and Strain Localization of Advanced High-Strength Steel in the Presence of a Sheared Edge The localization of strain in the microstructures of DP 980 and TBF 980 is quantified and compared. Of particular interest is the difference in final elongation observed for both materials in the presence of a sheared edge. Scanning electron micrographs of etched microstructures near the sheared edge are gathered for both materials at varying amounts of macroscopic strain. These micrographs are used to generate strain maps using digital image correlation. A two point statistical measure for strain localization is developed that utilizes strain map data to quantify the degree to which strain localizes around the hard phase of both materials. The DP steel exhibits higher strain localization around the martensite phase. Reasons for differences in strain localization and shear banding between the two materials are suggested, and the role played by the mechanically induced martensite transformation is speculated.

Mangotes de transferência têm sido utilizados em grande quantidade em operações de descarga de óleo, principalmente em águas profundas, onde existem cargas estáticas e cíclicas variáveis devido ao ambiente de trabalho. Apesar da grande demanda dessas estruturas, seu comportamento é pouco conhecido e discutido na literatura devido a sua complexidade. Além disso, os materiais utilizados nesse equipamento podem ocasionar um elevado número de falhas, sendo muitas vezes superestimados, deixando o mangote com peso excessivo. Este trabalho objetiva o desenvolvimento de uma metodologia de análise de materiais poliméricos avançados, especificamente fibras de poliaramida e materiais compósitos à base de fibra de carbono, em substituição a materiais tradicionais, utilizando modelos numéricos capazes de prever o comportamento da pressão de ruptura das carcaças e resistência a compressão radial do mangote, além da avaliação em fadiga dos cordonéis à base de poliaramida dessas novas estruturas. Modelos em meso-escala foram desenvolvidos utilizando conceitos de hiperelasticidade e de critérios de falha de materiais compósitos para previsão das tensões e deformações locais em regiões críticas do mangote. Análises numéricas foram realizadas via elementos finitos com o software comercial para auxiliar a elaboração dos modelos e a realização dos cálculos numéricos. Foram realizados ensaios experimentais para validação desses modelos numéricos, bem como para a previsão do comportamento estático e em fadiga dos materiais envolvidos. Foram desenvolvidos dois modelos. Em um modelo foi aplicado pressão interna no mangote para previsão de ruptura das carcaças no qual tem o objetivo de avaliar o desempenho dos novos reforços de poliaramida. No outro modelo foi aplicada uma carga radial na seção central do mangote para prever a resistência ao esmagamento, no qual tem o objetivo de avaliar o desempenho do componente de sustentação em material compósito de fibra de carbono. Os resultados dos modelos numéricos apresentaram boa concordância com os resultados experimentais em grande parte das análises. Também se observou que os novos materiais apresentam um grande potencial de substituição dos materiais tradicionais, bem como um excelente comportamento frente a carregamentos estáticos e dinâmicos envolvidos na aplicação, sendo verificada diminuição significativa de peso e aumento do desempenho. / Offloading hoses have been extensively used at offloading oil operations, especially in deep water, where there are variable static and cyclic loads due to the working environment. Despite the great demand for these structures, their behavior is little known and discussed in the literature due to the complexity. In addition, the materials used in this equipment may lead to a high number of failures, being often overestimated, leading to excessive weight. This work aims to develop a methodology for analysis of advanced polymeric materials, specifically polyaramide fibers and carbon fiber composite materials, in the substitution of traditional materials, using numerical models able to predict the static behavior of the burst pressure of the carcasses and radial compression strength of the hose. In addition, fatigue tests were performed to evaluate the polyaramide cords of these new structures. Meso-scale models were developed using advanced hyperplastic and composite failure criteria concepts to predict local stresses and strains in critical regions of the hose. Numerical analyses were performed using finite elements with commercial software to aid the development of models and to carry out numerical calculations. Several experimental tests were performed to validate numerical models, as well as to forecast the static and fatigue behavior of the materials used. Two models were developed. A model is used to predict the burst pressure of the hose in order to evaluate the performance of the new polyaramide reinforcements cords. In the other model, a radial load was applied in the central section of the hose to predict the crushing strength, in which it has the aim of evaluating the performance of the load-bearing component made with carbon fiber composite material. The results of the computer models showed good agreement with the experimental results in most analyses. It was also found that the studied materials offered considerable potential for the substitution of traditional materials, as well as an excellent behavior under static and dynamic loads related to this application, with a significant weight reduction and increased performance of the new configurations over traditional hoses.

Pour déterminer la vulnérabilité des systèmes de production viticole au changement et variabilité climatique, il faut connaître l’exposition physique d’une région, la sensibilité de la vigne et la capacité adaptative, apporté par le viticulteur par son « savoir-faire ». Ainsi, les mesures d’adaptation comme réponses au changement climatique (CC), résultent de la conjonction de ces trois composantes, analysées dans une perspective locale. L’objectif de cette étude a été définir la variabilité du climat dans la région viticole côtière du sud de l’Uruguay, évaluer les possibles impacts sur la vigne, et d’apporter des réponses sur l’adaptation de la vigne dans un contexte de CC. Dans dix vignobles commerciaux de Tannat situés dans les départements de Montevideo et Canelones, des capteurs de température ont été installés, répartis en fonction de la distance au Río de la Plata. La variabilité spatiale et temporelle de la température des vignobles a été mesurée par une analyse à méso-échelle. À une échelle plus fine, le phénomène de la pénétration de la brise de mer et leur effet sur l’évolution thermique diurne a été ainsi étudié. Le Río de la Plata à travers l’effet de l brise, est une des composants principaux du climat de la région viticole. La réponse de la vigne à la température sur la composition est expliquée par des conditions climatiques générales pendant la maturation (thermiques et hydriques). Les principaux acteurs de la filière (viticulteurs et conseillers) connaissent la variabilité locale du climat et ils ont identifié les aspects défavorables pour la production du raisin de qualité. Cependant, le climat ne semble pas avoir un rôle important dans la prise de décisions, mais d’une manière sous-jacente, il joue un rôle fondamental en la gestion du vignoble. Finalement, ils ont été identifiés des mesures d’adaptation à la variabilité locale du climat, en proposant stratégies à partir de la connaissance locale. / To determine the vulnerability of viticulture farming system to climate change (CC) and variability, the knowledge of climate exposure over the region, sensitivity and adaptive capacity provided by the winegrowers through their “savoir-faire” is primordial to contribute to adaptation issues to CC. The aim of this study was to define climate variability of the southern coastal wine region of Uruguay, evaluate its possible impacts in vinegrape and to provide adaptative responses in the context of CC. Ten plots were installed in commercial vineyards of Tannat over Canelones and Montevideo region at different distances to the Río de la Plata. Spatial and temporal variability of temperature was defined over the coastal region at meso-scale. At a fine scale, it was studied the sea breeze penetration and its impacts in the diurnal thermal evolution. The Río de la Plata through the sea breeze effect is one of the principal climate components in the southern wine region. Temperature grapevine sensitivity on berry composition at harvest is explained by climate general conditions during ripening (thermal and hydric conditions). The principal actors (winegrowers and advisors) know the local climate variability and have well identified unfavorable climate conditions to produce high quality grapes. However, climate seemed to be not relevant in producers’ decision making, but in an underlined way, its plays a fundamental role in vineyard management. Adaptation measures to local climate variability were identified by strategies proposed from the local knowledge / Para determinar la vulnerabilidad de los sistemas de producción vitícola al cambio y la variabilidad climática, se requiere conocer la exposición física de una región, su sensibilidad y la capacidad adaptativa aportada por el viticultor por su savoir-faire. Las medidas de adaptación en respuesta al cambio climático (CC), resultan de la conjunción de estos componentes, analizados desde una perspectiva local. El objetivo del estudio fue definir la variabilidad del clima actual de la región costera Sur de Uruguay, evaluar los posibles impactos en la vid, y aportar respuestas para su adaptación en el contexto de CC. En diez viñedos comerciales de Tannat ubicados en Canelones y Montevideo se instalaron sensores de temperatura según un diseño que contempló la distancia del Río de la Plata. Se precisó la variabilidad espacial y temporal de la temperatura de estos viñedos mediante un análisis a meso-escala. A una escala más fina, se estudió el fenómeno de la penetración de la brisa marina y su efecto en la evolución térmica diurna. El Río de la Plata a través del efecto de la brisa, es uno de los componentes principales del clima de la región vitícola sur. La sensibilidad de la vid a la temperatura sobre la composición es explicada por las condiciones climáticas generales durante la maduración (térmicas e hídricas). Los principales actores del sector (viticultores y asesores) conocen la variabilidad local del clima y tienen identificados los aspectos que son desfavorables para producir uvas de calidad. Sin embargo el clima no parece tener un rol preponderante en la toma de decisiones, pero de manera subyacente, este juega un rol fundamental en la gestión del viñedo. Por último, se identificaron medidas de adaptación a la variabilidad local del clima, proponiendo estrategias a partir del conocimiento local

Submitted by Cássia Santos (cassia.bcufg@gmail.com) on 2017-01-30T09:49:46Z No. of bitstreams: 2 Dissertação - Wanessa Mesquita Godoi Quaresma - 2016.pdf: 2901974 bytes, checksum: fcac435f9dfd087f8402d916a36a5f05 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-01-30T10:04:13Z (GMT) No. of bitstreams: 2 Dissertação - Wanessa Mesquita Godoi Quaresma - 2016.pdf: 2901974 bytes, checksum: fcac435f9dfd087f8402d916a36a5f05 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-01-30T10:04:13Z (GMT). No. of bitstreams: 2 Dissertação - Wanessa Mesquita Godoi Quaresma - 2016.pdf: 2901974 bytes, checksum: fcac435f9dfd087f8402d916a36a5f05 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-07-06 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / This work deals with the study of the concrete mechanical behavior using a two-dimensional numerical modeling in mesoscopic scale. The material is considered to be composed of three phases consisting of the interface zone matrix and inclusions, where each constituent is modeled properly. In the representative volume element (RVE) inclusions of as various shapes and randomly arranged are considered. The interface zone is modeled by finite elements where a model of fracture and contact recently proposed is incorporated. On the other hand, the transition zone is modeled by triangular finite elements where the Mohr-Coulomb model with lower strength characteristics compared to the mortar, is used. Inclusion is modeled as a linear elastic material and the matrix is considered as elastoplastic materials governed by the Mohr-Coulomb model. Our main goal is to show that a formulation based on computational homogenization is an alternative to complex macroscopic constitutive models for the mechanical behavior of brittle materials using a procedure based on the Finite Element Method and a multiscale theory. Examples changing the form of aggregate, their volume fraction and distribution in RVE, as well as various strategies for modeling the transition zone are shown to illustrate the performance of the proposed model. The results evidence that the proposed modeling leads to are promising results for employment in a multiscale modeling. Also, this work shows the importance of parametric identification of fracture and contact model in the microstructural analysis of concrete. / Este trabalho trata do estudo do comportamento mecânico do concreto utilizando uma proposta de modelagem numérica bidimensional em escala mesoscópica. O material é considerado como composto por três fases consistindo de zona de interface, matriz e inclusões, onde cada constituinte é modelado adequadamente. O Elemento de Volume Representativo (EVR) consiste de inclusões idealizadas como de várias formas e aleatoriamente dispostas no EVR. Uma das abordagens permite que a zona de interface seja modelada por meio de elementos finitos coesivos de contato, onde um modelo de fratura e contato recentemente proposto é incorporado ao elemento. Por outro lado, a zona de transição pode ser modelada por elementos finitos triangulares onde o modelo de Mohr- Coulomb com características de menor resistência em relação à argamassa, é utilizado. A inclusão é modelada como sendo um material elástico linear, já a matriz é considerada como material elastoplástico obedecendo ao modelo de Mohr-Coulomb. O principal objetivo é mostrar que uma formulação baseada na homogeneização computacional é uma alternativa aos modelos constitutivos macroscópicos complexos para o comportamento mecânico de matérias frágeis usando um procedimento baseado no Método dos Elementos Finitos no âmbito de uma teoria multiescala. Uma série de exemplos envolvendo a mudança de forma de agregados, sua fração volumétrica e sua distribuição no EVR, assim como diferentes estratégias de modelagem da zona de transição, é apresentada de modo a ilustrar a performance da modelagem proposta. Os resultados encontrados evidenciam que as modelagens propostas apresentam resultados promissores para o emprego numa modelagem multiescala. Também, este trabalho mostra a importância da identificação paramétrica do modelo de fratura e contato na análise microestrutural do concreto.