Les contraintes économiques et environnementales toujours plus exigeantes tendent à réduire la quantité de lubrifiant utilisée dans les systèmes mécaniques. Il en résulte des épaisseurs de film de l’ordre du nanomètre dans les zones de contact, laissant seulement quelques couches de molécules de lubrifiant pour assurer la séparation des surfaces. Pour relever ce défi, de nouveaux fluides sont à l’étude tels que les liquides ioniques qui présentent un formidable potentiel en tant que lubrifiants. Grâce à la Dynamique Moléculaire, la réponse rhéologique d’un liquide ionique à différentes sollicitations de température, pression et cisaillement est tout d’abord caractérisée en détail. Avec l’appui d’essais expérimentaux, l’aptitude du liquide ionique à lubrifier des films minces est confirmée. Cette étude a également permis de jeter un nouveau regard sur les modèles analytiques classiques utilisés en rhéologie. Le liquide ionique en situation de nano-confinement entre deux surfaces représentatives d’un contact acier-acier est ensuite étudié. Les effets combinés du glissement à la paroi, de la rhéofluidification et de l’élévation de température apportent des éléments de réponse pour expliquer la saturation de la contrainte de cisaillement aux fortes sollicitations. Enfin, l’influence de différents revêtements de surface limitant grandement le frottement est analysée. Selon le matériau utilisé, des régimes de lubrification très différents surviennent avec un glissement du fluide à la paroi parfois prédominant. L’utilisation de surfaces polaires impacte également fortement la réponse des contacts lubrifiés par un liquide ionique. / Increasing economic and environmental constraints tend to reduce the amount of lubricant used in mechanical systems. This results in nanometric film thicknesses in the contact areas, leaving only a few layers of lubricant molecules to ensure the separation of the surfaces. To meet this challenge, new fluids are being considered such as ionic liquids which feature a great potential as lubricants. Through Molecular Dynamics simulations, the rheological response of an ionic liquid to different conditions of temperature, shear and pressure is first characterized in detail. The ability of the ionic liquid to lubricate thin films is confirmed. Besides, this study goes back over the classic analytical models used in rheology. The ionic liquid is then nanoconfined between two representative surfaces of a steel-steel contact. The combined effects of wall slip, shear-thinning and temperature rise provide answers to explain the saturation of the shear stress. Finally, the influence of different low friction surface coatings is analyzed. According to the material used, very different dynamical behaviors occur. Moreover, it is shown that the use of polar surfaces significantly impacts the response of ionic liquid lubricated contacts.

Ce travail de thèse est centré sur la compréhension des mécanismes mis en jeu lors de l’impression d’encres à base de nanoparticules d’argent en jet d’encre dans le but d’optimiser la production de fines (<100 µm) pistes conductrices performantes et homogènes. L’impression jet d’encre se décompose en plusieurs étapes : l’éjection de gouttelettes picovolumétriques, l’impact sur le support, l’étalement et le séchage. La phase de séchage est une phase complexe sujette aux phénomènes de transfert de matière comme l’effet coffee ring. Cet effet, dû au flux capillaire qui induit un mouvement du centre vers les bords de la goutte, conduit la majorité des particules en suspension sur les bords du motif imprimé. L’objectif de ce travail est de décrire et de comprendre précisément les mécanismes qui opèrent et qui conduisent à ces effets de transfert de matière pour les limiter, voire les annuler et ainsi garantir la production de pistes conductrices fines et homogènes aux performances élevées. Pour atteindre cet objectif, trois axes de travail ont été développés: (i) Une première étude s’est concentrée sur l’analyse des différentes phases régissant la vie d’une goutte éjectée en jet d’encre. L’identification et l’optimisation des paramètres clés influençant la morphologie des gouttes jet d’encre après séchage ont été réalisées avec un focus particulier sur l’influence de la température du support. Quatre indices géométriques sont proposés pour caractériser quantitativement l’homogénéité du profil des gouttes produites. (ii) Une seconde partie du travail s’est spécifiquement concentrée sur la phase de séchage des gouttes picovolumétriques pour comprendre les phénomènes engagés. Une modélisation du séchage des gouttes est notamment proposée pour permettre une meilleure compréhension des phénomènes de transfert de matière observés. (iii) Enfin, une dernière partie s’intéresse à la production par jet d’encre de fines lignes conductrices (cas de gouttelettes juxtaposées). Des corrélations entre la morphologie des lignes, celle des gouttes individuelles et les performances électriques seront établies afin de produire des systèmes optimisés. / This thesis focuses on the understanding of the mechanisms involved in the inkjet printing of silver nanoparticles-based inks in order to optimize the manufacturing of thin (width <100 µm) conductive tracks with high and homogeneous performances. Inkjet printing can be divided into several phases: the ejection of picovolumetric droplets, the impact on the substrate, the spreading and the drying. The drying phase is a complex phase prone to particle migration phenomena such as coffee ring effect. This phenomenon, due to the capillary flow which implies a movement from the center to the edges of the drop, drives most of the suspended particles towards the edges of the printed patterns. The aim of this work is to describe precisely and understand the mechanisms which operate and lead to the transfer effects in order to limit or even eliminate them and guarantee the production of performing and homogenous fine conductive lines. To achieve this objective, three paths of investigation were developed: (i) a first axis deals with the study of the different phases of the droplet generation process. Parameters impacting the dried droplet morphology are identified and optimized with a focus on substrate temperature. Four geometrical indexes are designed to characterize quantitatively the dried droplet profile homogeneity. (ii) A second axis specifically studies the drying phase of picovolumetric droplet in order to understand the phenomena occurring during this phase. A modelling of droplet drying is set up in order to understand the forces influencing the matter transport. (iii) Finally, a last axis studies the print of thin conductive lines composed of several printed droplets partially superimposed. Correlations between line morphology, droplet morphology and electrical conductivity are established in order to produce optimized systems.

À la différence des liquides simples, les solides amorphes, une vaste catégorie de matériaux allant des verres métalliques aux émulsions concentrées, ne se mettent à s'écouler qu'au-delà d'une contrainte finie. Notre thèse a pour objet la modélisation de cet écoulement, dans un cadre général et avec un accent mis sur les hétérogénéités. En premier lieu, notre travail a porté sur l'inclusion d'inhomogénéités dans le cadre de la théorie de couplage de modes appliquée à la rhéologie et nous avons notamment obtenu une équation générale d'évolution des inhomogénéités de densité. À basse température, l'écoulement est en effet fortement hétérogène : des phases de déformation élastique sont entrecoupées de réarrangements de particules, brusques et localisés, qui interagissent par le biais des déformations élastiques qu'ils génèrent. En second lieu, nous avons donc considéré un modèle calqué sur ce scénario et affiné ses éléments constitutifs pour rendre compte de la compétition entre cisaillement appliqué et réarrangements locaux, à l'origine de la courbe d'écoulement des matériaux athermiques. Cette dernière a été reproduite de manière satisfaisante. Pour ce qui est des corrélations spatiales dans l'écoulement, nous avons montré qu'il n'existe pas de loi d'échelle universelle dans les modèles élasto-plastiques, malgré la présence d'une classe de longueurs de corrélation décroissant comme dot{gamma}^{ icefrac{-1}{d}} en d dimensions, dans le régime dominé par le cisaillement. Par ailleurs, dans diverses variantes du modèle, le cisaillement se trouve localisé dans une région du matériau. Ce phénomène apparaît dès lors que les blocs élasto-plastiques sont durablement fragilisés à la suite d'un événement plastique. Enfin, les prédictions du modèle ont été directement mises en regard avec des expériences sur l'écoulement en microcanal d'émulsions concentrées et des simulations de dynamique moléculaire à température nulle. Les écarts observés nous ont poussé à développer et implémenter un code plus flexible, qui s'appuie sur une routine simplifiée d'Éléments Finis et rend mieux compte du désordre structurel et des effets inertiels. / Contrary to the case of simple fluids, a finite stress is required to initiate the flow of amorphous solids, a broad class of materials ranging from bulk metallic glasses to dense emulsions. The objective of this thesis is to model the flow of these materials in a general framework, with an emphasis on heterogeneities. In a first approach, using the liquid regime as a starting point, I have investigated to what extent inhomogeneities can be accommodated in the framework of the mode-coupling theory of rheology. A generic equation for the evolution of density inhomogeneities has been derived. At low temperatures, the flow is indeed quite heterogeneous: it consists of periods of elastic deformation interspersed with swift localised rearrangements of particles, that induce long-range elastic deformations and can thereby spark off new rearrangements. In a second approach, a model rooted in this scenario has been refined so as to reflect the interplay between the external drive and the localised rearrangements, which is at the origin of the flow curve of athermal solids. The latter has been reproduced satisfactorily. Turning to spatial correlations in the flow, we have shown that there exists no universal scaling for these correlations in elastoplastic models, although a broad class of correlation lengths scale with dot{gamma}^{ icefrac{-1}{d}} in the shear-dominated regime in d dimensions. Besides, shear localisation has been observed in diverse variants of the model, whenever blocks are durably weakened following a plastic event. Finally, we have directly compared model predictions to experimental results on the flow of dense emulsions through microchannels and to athermal molecular dynamics simulations. Spurred on by the observation of some discrepancies, we have developed and implemented a more flexible code, based on a simplified Finite Element routine, which notably provides a better account of structural disorder and inertial effects.

Au cours de la dernière décennie, l'utilisation croissante de nombreuses nouvelles technologies comme des systèmes de livraison contrôlée a incité un développement empirique coûteux de systèmes nouveaux et efficaces. Pour faciliter une conception plus raisonnable et une optimisation, faisant face à l'ensemble de possibilités existantes, n'importe quelle solution qui pourrait semi-automatiser le développement de produits apporteraient l'aide précieuse aux utilisateurs (des scientifiques de formulation et des éducateurs). Ceci faciliterait l'importance essentielle de choisir les matériels justes pour l'application correcte. Dans cette thèse, un projet à long terme concernant une génie inverse est proposé, commençant d'une propriété d'utilisation finale (libération contrôlée), la cible mondiale est de développer une méthodologie de conception de produit qui nous permet de déterminer les caractéristiques optimales d'une formulation à préparer: les phases, la composition, le type d'interface, la taille et la distribution d'objets actuels, l'équilibre de phase, la diffusion dans des phases et le caractère évolutionnaire du matériel. Dans la considération d'un exemple de commodité de système structuré et dispersé: des émulsions fortement concentrées, le problème de design a été décomposé dans un ordre hiérachique de sous-problèmes ou des boîtes, combinant les modèles constitutifs qui évaluent le transport de masse de principe actif comme une fonction de paramètres de formulation et des techniques assistées par ordinateur comme la modélisation moléculaire pour le volume/surface de molécules, ou des modèles d'UNIFAC pour des prédictions d'équilibre aussi bien que pour des évaluations de viscosités de mélange. Un ultérieur design de factoriel d'expériences virtuelles a permis d'obtenir une description quantitative de la sortie selon les paramètres modèles et une analyse composante principale a évalué l'importance des variables. En utilisant une cartographie basée sur trois tensio-actifs (pour SPAN 80, PGPR et BRIJ 93), quatre huiles (dodecane, hexadecane, isopropyl myristate et isopropyl palmitate) et l'acide mandelic comme le principe actif, le modèle ab initio physicochimique a été expérimentalement validé. Les résultats montrent que le modèle mécaniste systématiquement prévoit la diffusion du principe actif d'émulsions à un moyen récepteur dans des parfaites 'sink' conditions. Cette approche de génie inverse a montré pour être d'intérêt très élevé dans le domaine de formulation en permettant des études préliminaires examinantes rapides et robustes sur une large gamme de composants aussi bien que des outils de prédiction précis et rigoureux optimiser la sortie contrôlée d'un système identifié. Il est souhaitable de mettre en œuvre ces extensions à d'autre systèmes semblables / In the past decade, the growing use of numerous novel technologies as controlled-delivery systems has prompted a costly trial-and-error development of new and effective systems. In order to facilitate a more rational design and optimization, facing the set of existing possibilities, any solution that could semiautomate the product development would bring precious help to the users (formulation scientists and educators). This would facilitate the essential importance of choosing the right materials for the correct application. In this thesis, a long-term project concerning a reverse engineering is proposed, starting from a final usage property (controlled release), the global target is to develop a product design methodology which allows us to determine the optimal features of a formulation to prepare: phases in presence, composition, interface type, size and distribution of current objects, phase equilibrium, diffusion within phases and evolutionary character of the material. Considering a convenience example of structured-dispersed system: highly concentrated emulsions, the design problem has been decomposed into a hierarchical sequence of subproblems or boxes, combining constitutive models that estimate the active ingredient mass transport as a function of formulation parameters and computer-aided techniques such as molecular modeling for volume/area of molecules, or UNIFAC models for equilibria predictions as well as for mixture viscosities estimations. A subsequent full factorial design of virtual experiments has allowed to obtain a quantitative description of the release depending on the model parameters, and a principal component analysis has assessed the importance of the variables. Using a cartography focused on three surfactants (SPAN 80, PGPR and BRIJ 93), four oils (dodecane, hexadecane, isopropyl myristate and isopropyl palmitate) and mandelic acid as an active ingredient, the ab-initio physicochemical model has been experimentally validated. Results show that the mechanistic model consistently predicts the diffusion of the active ingredient from emulsions to a release medium in perfect sink conditions. This reverse engineering approach is showing to be of very high interest in the domain of formulation by allowing fast and robust screening preliminary studies on a broad range of components as well as precise and rigorous prediction tools to optimize controlled release from an identified system. It is fully recommended to implement its extensions to other similar disperse systems

A falta de controle tecnológico e conhecimento técnico na produção de argamassas resultam muitas vezes no aparecimento de manifestações patológicas, o que compromete o adequado cumprimento de suas principais funções: proteção, estanqueidade e acabamento estético das edificações. Buscando-se um melhor entendimento dos parâmetros que influenciam na resistência de aderência à tração e ao cisalhamento dos revestimentos argamassados aos substratos de concreto, o principal objetivo desta pesquisa consiste em verificar a influência da interação entre a área potencial de contato do substrato e a reologia das argamassas de revestimento no desempenho quanto a estas propriedades. Ainda, verificou-se a influência das propriedades reológicas das argamassas afetadas pelo teor de aditivo incorporador de ar na resistência de aderência à tração e ao cisalhamento de revestimentos argamassados, bem como o controle da rugosidade durante a confecção de substratos de concreto, proporcionando um aumento da área potencial de contato da argamassa de revestimento assentada sobre ele, visando melhorar o desempenho do revestimento quanto à resistência de aderência à tração e ao cisalhamento. Para que fosse possível alcançar estes objetivos foram realizados procedimentos laboratoriais que compreenderam a moldagem de prismas de concreto, com resistência à compressão de 35MPa, de 25x35x5cm, sobre placas de borracha que estamparam três diferentes tipos de rugosidades em suas superfícies. Sobre estes prismas, foram assentadas três diferentes tipos de argamassas de proporcionamento 1:1:4 (cimento:cal hidratada:areia, em volume, material seco), variando-se o comportamento reológico destas através de diferentes adições de aditivo incorporador de ar. Este assentamento ocorreu com o uso de caixa de queda, visando uma maior uniformidade da energia de aplicação. Para analisar as diferentes características reológicas das argamassas foram realizados ensaios de caracterização no estado fresco e endurecido conforme as normas vigentes. Os substratos de concreto foram caracterizados quanto à sua rugosidade com Scanner 3D a laser, além de ensaios de controle tecnológico. Ao final desta pesquisa pode-se concluir que nem sempre um acréscimo da área de contato proporcionado pela rugosidade do substrato é sinônimo de aumento da extensão de aderência e consequentemente da resistência de aderência. A reologia da argamassa possui grande influência sobre estes fatores, sendo essencial uma compatibilidade entre rugosidade do substrato e reologia das argamassas para que se tenha um incremento na resistência de aderência dos revestimentos ao substrato. / and the shear bond strength of mortar rendering applied to concrete surfaces, this work intended to verify the influence of the interaction between surface potential contact area and mortar renderings’ rheology on these performance properties. Moreover, this work has the objective to verify the influence of the mortar’s rheology affected by the air-entraining agents in bond strength and the concrete surface roughness control in this property. In this study, three different pre-defined surface roughnesses were stamped with rubber plates (25x35x5cm) in a concrete mold then concrete prisms were molded. The surface concrete has a fix compressive strength of 35MPa. Three mortars with the 1:1:4 (cement: hydrated lime:sand, in volume, dry material) mix proportion, changing the air-entraining proportion to modify the rheology behavior were placed on these concrete surfaces, using a drop box for mortars. Tests of tensile bond strength (Ra), according to the requirements of Brazilian Standard - NBR 13528 (2010) and shear bond strength (Rc) had been carried out with these samples. Additionally characterization tests in fresh and hardened mortars had been done. The surfaces roughnesses were characterized by a 3D laser scanner and by technologic tests control. The results indicated that the increasing of the surface contact area is not an indicative that the bond strength will also increase. The mortar’s rheology has a very important influence in these factors, and it is essential the compatibility of the system to rise the contact area and consequently the bond strength.

Submitted by Daniel Fialho Madureira (daniel.fialho01@gmail.com) on 2015-03-06T22:35:06Z No. of bitstreams: 1 viscosidade_emulsoes.pdf: 1828480 bytes, checksum: 77a4926687a6e5e766bedf0f444d191b (MD5) / Approved for entry into archive by Janete de Oliveira Feitosa (janete.feitosa@fgv.br) on 2015-06-16T14:06:31Z (GMT) No. of bitstreams: 1 viscosidade_emulsoes.pdf: 1828480 bytes, checksum: 77a4926687a6e5e766bedf0f444d191b (MD5) / Approved for entry into archive by Marcia Bacha (marcia.bacha@fgv.br) on 2015-06-19T11:59:55Z (GMT) No. of bitstreams: 1 viscosidade_emulsoes.pdf: 1828480 bytes, checksum: 77a4926687a6e5e766bedf0f444d191b (MD5) / Made available in DSpace on 2015-06-19T12:00:12Z (GMT). No. of bitstreams: 1 viscosidade_emulsoes.pdf: 1828480 bytes, checksum: 77a4926687a6e5e766bedf0f444d191b (MD5) Previous issue date: 2014-12-17 / A formação de emulsão de água-em-óleo gera um significativo incremento na viscosidade, o que afeta diretamente a produção do poço, pois aumenta a perda de carga ao longo da linha de produção, dificultando o escoamento e diminuindo a produção de óleo. A presença e natureza da emulsão, e seu impacto na reologia do petróleo, podem determinar a viabilidade econômica e técnica dos processos envolvidos. A medida que a fração de água aumenta e a temperatura é reduzida, o comportamento das emulsões se torna cada vez mais não-Newtoniano. A decorrência disso, é que a temperatura e a taxa de cisalhamento passam a ter maior impacto na variação da viscosidade das emulsões. Nesse estudo são propostos novos métodos que levam em conta essas variáveis. Os dados reológicos experimentais de 15 petróleos leves foram utilizados para avaliar o desempenho dos modelos existentes na literatura e compará-los com os novos métodos propostos nesse estudo. / The formation of water-in-oil emulsion produces a significant increase in viscosity, which directly affects the production from the well as it increases the pressure drop along the production line, thus hindering the flow and reducing oil production. The presence and nature of the emulsion, and its impact on oil rheology, can determine the economic and technical feasibility of the processes involved. As the water fraction rises and the temperature is reduced, the behavior of the emulsions becomes increasingly non-Newtonian. The result of this is that the temperature and shear rate have more impact on the variation in the viscosity of emulsions. In this study are proposed new methods that take into account these variables. The experimental rheological data of 15 light oil were used to evaluate the performance of existing models in the literature and compare them with the new methods proposed in this study.

A importância do aprofundamento dos estudos sobre argamassas de revestimento justifica-se por este ser um material muito utilizado internamente e externamente em edificações brasileiras, no entanto, ainda apresentar grande quantidade de manifestações patológicas. Estudos sobre os mecanismos envolvidos no desenvolvimento da aderência das mesmas vêm sendo realizados por pesquisadores nacional e internacionalmente, com o intuito de compreender as interações que ocorrem entre a argamassa e os substratos. Neste contexto, o principal objetivo desta pesquisa consiste em determinar a influência dos parâmetros reológicos de argamassas, da energia de aplicação e da tensão superficial dos substratos na área de contato na interface argamassa/substrato. Os objetivos secundários consistem em caracterizar diferentes argamassas através do squeeze-flow e reometria rotacional, verificar a influência da distribuição granulométrica nos parâmetros reológicos, verificar a influência da energia de aplicação no desenvolvimento da área de contato da interface argamassa/substrato e desenvolver metodologia para a quantificação da área de contato da interface argamassa/substrato. Para atingir estes objetivos, foi montada uma matriz experimental com argamassas de três diferentes proporcionamentos, quais sejam: 1:0:3 (A3), 1:1:6 (A6), e 1:2:9 (A9) (cimento:cal:areia, materiais secos, em volume). Estes proporcionamentos foram confeccionados com cimento Portland CPIV, cal hidratada CHI e três composições granulométricas (CG) de agregado miúdo. As areias passantes nas peneiras, 1,2, 0,6, 0,3 e 0,15mm foram compostas com 25% de cada uma das frações para a CG1, 10% das frações extremas e 40% das frações intermediárias para a CG2 e 40% das frações extremas e 10% das frações intermediárias para a CG3. Por fim, cada uma das argamassas proporcionadas com as diferentes CG foram dosadas para o índice de consistência de 240 mm. Depois de caracterizadas quanto as suas propriedades no estado fresco e endurecido, as argamassas foram submetidas a ensaios reológicos de squeeze-flow (NBR 15839/2010) e reometria rotacional. Para a avaliação da área de contato das argamassas sobre os substratos, foram escolhidos três substratos com acabamento superficial liso e sem absorção significativa e com diferentes ângulos de contato: o vidro, o acrílico e o polietileno. Cada uma das argamassas dosadas foi lançada sobre estes substratos, dispostos em gabaritos de madeira, a alturas de queda de 30 e 100 cm, através da caixa de queda. Por fim, as argamassas foram descoladas dos substratos e foi realizada a digitalização tridimensional a laser, através de scanner 3D, onde as áreas sem contato das argamassas foram quantificadas com a utilização dos softwares Geomagic Studio e Photoshop. Os resultados mostraram que o uso do scanner 3D associado à análise de imagens através de softwares de fácil manuseio e interpretação mostra-se como uma boa técnica de análise da área de contato. Quanto aos proporcionamentos de argamassas propostos, a alteração da faixa granulométrica da areia demonstrou-se uma boa estratégia no sentido de alterar a reologia das argamassas. A seleção dos substratos mostrou-se eficaz no sentido de reproduzir superfícies com ângulos de contato distintos, potencialmente hidrofóbicas e potencialmente hidrofílicas e pode-se notar através das alturas de queda escolhidas influenciam nos demais parâmetros de avaliação em função desta alteração da energia de lançamento. Todos as variáveis controláveis foram significativamente influentes na área de contato na interface argamassa/substrato, sendo que a mais significativa foi o proporcionamento das argamassas. Além disso, constatou-se que maiores energias de aplicação resultam em maiores áreas de contato desde que o substrato aonde a argamassa for aplicada seja favorável ao espalhamento, por fim, foi possível concluir que o empacotamento das partículas e o coeficiente de uniformidade exercem grande influência na viscosidade das argamassas, sendo que área de contato da interface mostrou ser inversamente proporcional à viscosidade. / This study assesses the influence of the granulometric composition of sand, application energy and the superficial tension of substrates on the contact area of rendering mortars. Three substrates with distinct wetting behaviors were selected through preliminary analysis, three non-absorbent substrates with different wettability ratings were chosen: glass, acrylic, and polypropylene. Mortars were prepared with different proportioning and sand compositions. The compositions of 1:0:3 (A3), 1:1:6 (A6) and 1:2:9 (A9) (cement: hydrated lime: dry sand) were produced according to the Brazilian Standard NBR 13276/2005, for a 240 mm consistence index, all of them, with grains retained in sieves #1.2; 0.6; 0.3 and 0.15 mm. The first composition (CG1, unitary mass 1.51 g/cm³) consists of equal fractions of each sieve, 25% for each. The second (CG2, unitary mass 1.48 g/cm³), with 10%, 40%, 40% and 10% from sieve respectively, and third (CG3, unitary mass 1.54 g/cm³) with 40%, 10%, 10% and 40% from sieve, respectively. Characterization tests were performed on fresh and hardened mortars, as well as a rheological characterization. Mortars were applied on substrates with two different energies. The interfacial area was then digitized with a 3D scanner. Results show that 3D scanning proved to be an appropriate method for real contact area measurement. Additionally, all variables have interfacial contact influence, in terms of the contact area development, among which the most significant was mortar proportioning. Furthermore, it was found that higher applying energy results in larger interfacial contact areas since substrate where the mortar is applied has favorable wettability. Finally, it was concluded that the particles packing and uniformity coefficient greatly influence the mortar viscosity, and interface contact area was found to be inversely proportional to viscosity.

Le travail de thèse s'inscrit dans la modélisation numérique de l'écoulement des matériaux cimentaires à l'état frais couplée à un outil d'identification des paramètres. Il traite en particulier l'étape de mise en place de l'identification par analyse inverse. D'abord, une analyse de la littérature fait ressortir l'existence d'outils rhéométriques dédiés aux suspensions cimentaires ; le passage des grandeurs macroscopiques à celles locales est faite, soit par le biais de l'utilisation de géométries conventionnelles, soit au moyen de méthodes de calibration. Néanmoins, ces outils ne permettent pas de trouver une signature rhéologique unique pour une même suspension. De plus, les stratégies d'identification des paramètres relatifs aux matériaux cimentaires frais sont peu nombreuses et limitées aux données locales. Ensuite, une stratégie qui consiste à identifier les paramètres d'une loi supposée, directement à partir des mesures macroscopiques simulées (couples, vitesses de rotation imposées au mobile de cisaillement) a été développée et validée en 2D, en discutant notamment de l'efficacité des algorithmes d'optimisation testés (méthode du simplexe et algorithmes génétiques), en fonction du degré de connaissances que l'utilisateur a du matériau. Enfin, la méthode a été appliquée en 3D sur des fluides modèles supposés homogènes. Elle apparaît efficace en fluide pseudo-plastique, notamment par combinaison des algorithmes d'optimisation. Mais il reste des obstacles à lever en fluide visco-plastique, vraisemblablement liés aux outils expérimentaux plutôt qu'à la procédure d'identification elle-même. / The thesis work is part of the numerical modeling of the flow of cementitious materials in the fresh state coupled with an identification procedure of the parameters. It deals in particular with the step of the development of the identification by inverse analysis. First,the literature review reveals the existence of rheometric tools dedicated to cementitious suspensions; The passage from the macroscopic quantities to the local ones is made either by the use of conventional geometries or by means of calibration methods. Nevertheless, these tools do not make it possible to find the expected single rheological signature for a given suspension. In addition, there are few studies reporting strategies for identifying constitutive parameters in the case of fresh cement-based materials and they are limited to local data. Then, a strategy consisting in identifying the parameters of a supposed law, directly on the basis of the simulated macroscopic measurements (torques, rotational speeds imposed on the shearing tool) was developed and validated in 2D, discussing in particular the efficiency Of the optimization algorithms tested (simplex method and genetic algorithms), according to the degree of knowledge that the user has of the material. Finally, the method has been applied in 3D on model fluids, assuming that they are homogeneous. The method appears effective in the case of pseudo-plastic fluid, in particular by combining both optimization algorithms used. But there remain obstacles to overcome in the case of visco-plastic fluids, probably related to the experimental tools rather than to the procedure of identification itself.

Les suspensions concentrées sont des fluides qui présentent des propriétés rhéologiques complexes. Ces propriétés sont modélisées par des équations structurelles qui considèrent à la fois les phases liquide et solide, mais avec un manque de lien avec les paramètres granulaires (en particulier la compacité des suspensions non modèles). L'objectif global de ce travail est d'étudier la dépendance de la viscosité de suspensions concentrées énergétiques aux propriétés physico-chimiques de leurs composants. Les propriétés ayant l'impact le plus significatif sur la viscosité sont choisies en utilisant la méthodologie des plans d’expériences. Le modèle résultant représente le diamètre médian D50 en volume de petites et grandes particules, la densité des grosses particules d, la surface spécifique des particules, la contrainte de cisaillement γ ̇ appliquée à la suspension, la viscosité du fluide de suspension ηf et une constante valeur pour la fraction volumique en solide φ≃0.51. De plus, ce modèle permet de prédire la viscosité des suspensions étudiées pour une fraction volumique en solide allant de 0 à 0,51 %. / Concentrated suspensions are fluids which display complex rheological properties. These properties are modelled through structural equations which consider both the liquid and solid phases, but with a lack of consistency for the granular parameters (in particular the maximum packing fraction of non-model suspensions). The overall objective of this paper is to investigate the dependence of the viscosity of energetic concentrated suspensions on the physicochemical properties of their components. The properties with the most significant impact on the viscosity are chosen using the Design of Experiments methodology. The resulting model accounts for the mass median diameter D50 in small and large particles, the large particles density d, the specific surface area of small particles, the shear stress γ ̇ applied to the suspension, the viscosity of the suspending fluid η_f and a constant value for the volume fraction in solid ϕ≃0.51. Moreover, this model allows predicting the viscosity of the studied suspensions for a volume fraction in solid from 0 to 0.51 %

O Smallanthus sonchifollius também conhecido como Yacon é uma planta de origem andina que armazena em suas raízes tuberosas os carboidratos frutose, glicose, e, principalmente frutooligossacarídeos e inulina. Os frutooligossacarídeos e a inulina têm sido designados como prebióticos e fibras alimentares solúveis por sua não digestibilidade pelas enzimas do trato digestivo humano, estímulo seletivo do crescimento e atividade de bactérias intestinais promotoras de saúde. Neste trabalho foram estudados propriedades físico - químicas do suco de yacon concentrado e da polpa de yacon. As raízes foram descascadas, cortadas em rodelas de 0,5+0,2cm, branqueadas mediante vapor por 4 minutos seguido por resfriamento em banho de gelo por 3 minutos e posteriormente passadas em um processador de frutas para extração do suco que foi concentrado na faixa de 10 a 50ºBrix em rotavapor a vácuo. Foi estudado o comportamento reológico, composição química e atividade de água e o ponto de inicio de congelamento do suco de yacon em função da concentração de sólidos solúveis. Para as medidas reológicas foi empregado um viscosímetro rotacional, as medidas da atividade de água foram realizadas através de leitura direta em medidor eletrônico e a determinação do ponto de início de congelamento dos sucos foi obtida a partir das curvas de congelamento. O teor de açucares foi quantificado através de HPLC. Os resultados indicaram que o teor de inulina manteve-se constante, enquanto a concentração dos açucares redutores glicose e frutose aumentaram com o aumento da concentração. O suco de yacon comportouse como um fluido newtoniano, observando-se que a viscosidade manteve-se constante para cada concentração independente da taxa de deformação aplicada. Para os sucos com concentrações de 10, 15, 20, 25 e 30ºBrix os valores de viscosidade não apresentaram diferenças significativas entre si e para as concentrações maiores que 30ºBrix, a viscosidade aumentou significativamente. No caso do ponto de início congelamento, este diminuiu à medida que o suco de yacon foi concentrado não existindo diferenças significativas entre os valores que correspondem às concentrações de 10º com 15º Brix, de 20º com 25ºBrix e de 40º com 45ºBrix. A atividade de água diminuiu significativamente apenas na concentração de 50ºBrix. A seguir foi estudado o comportamento da secagem do suco de yacon concentrado sem branqueamento a 40ºBrix, empregando amido de milho como encapsulante, e da polpa de yacon. Os ensaios experimentais foram conduzidos em um secador de ar forçado, nas temperaturas de 50, 60 e 70°C por um tempo de 5 horas. Foi observado que com o aumento da temperatura do ar de secagem diminuiu o tempo necessário para as amostras atingirem o equilíbrio. Os valores de umidade no equilíbrio foram de 0,0071; 0,0052 e 0,0050 para a polpa de yacon e de 0,0075; 0,0030 e 0,0030 para o suco encapsulado nas temperaturas de 50, 60 e 70ºC respectivamente, resultando em valores de atividade de água menores que 0,25. O suco de yacon encapsulado e da polpa de yacon em pó obtidos a temperatura de 70ºC foram visualizados em microscópico eletrônico de varredura. O pó de suco de yacon demonstrou um bom encapsulamento pelo amido de milho e na polpa de yacon em pó verificou-se a presença de estruturas microscópicas com formato alongado características do açúcar inulina. A temperatura de transição vítrea do suco encapsulado obtido à temperatura de 50, 60 e 70ºC e da polpa de yacon em pó obtida à temperatura de 70ºC foi determinada pela técnica de calorimetria diferencial de varredura. As temperaturas de transição vítrea para o pó de suco concentrado encapsulado foram de 44,74; 45,14 e 49,72ºC para valores de atividade de água de 0,15; 0,07 e 0,03 respectivamente e para o pó da polpa de yacon foi de 48,78ºC em atividade de água de 0,13. / The Smallanthus sonchifollius also known as Yacon is a plant of Andean origin which stores the carbohydrates fructose, glucose, and mainly fructooligosaccharides and inulin. The fructooligosaccharides and the inulin have been designed as pre-biotic and alimentary fibers soluble for their no digestibility by enzymes from human digestive tract, selective stimulus of growth and activity of intestinal bacteria promoters of health. In this work, the yacon juice concentrated and the yacon pulp physicochemical properties were studied. The roots were peeled, cut and sliced in 0.5 +0.2cm, bleached by steam for 4 minutes followed by ice bath for 3 minutes and later passed into fruit processor in order to extract the juice which was concentrated in a range from 10 to 50°Brix in a vacuum Rota-stea m. The rheologic behavior, chemical composition and water activity and the initial freezing point of yacon juice according to the soluble solid concentration. A rotational viscosimeter was employed for the rheologic measures, the water activity measurements were carried out through the direct reading in an electronic measurer and the determination of the initial freezing point of juice was obtained from the freezing curves. The sugar content was quantified through HPLC. The results indicated that the inulin content remained constant, while the concentration of the reducer sugars glucose and fructose increased with the increase of the concentration. The yacon juice behaved as a Newtonian fluid, it was observed that the viscosity kept itself constant for each concentration independent from the applied deformation rate. For the juices with concentrations of 10, 15, 20, 25 and 30°Brix the vi scosity values didn’t present significant differences among themselves and for concentrations higher than 30°Brix, the viscosity increased significantly. In the case of the initial freezing point, this decreased as the yacon juice was concentrated. There weren’t significant differences among the values which correspond to concentrations of 10° with 15°Brix, of 20° with 25°Brix and of 40° with 45°Brix. The water activity decreases significantly only in the concentration of 50°Brix. Next the behavior of the drying of the juice of yacon concentrated without bleaching at 40°Brix, using co rn starch as encapsulant, and yacon pulp. The experimental essays were conducted in a forced air dryer, at the temperatures of 50, 60 and 70° C during 5 hours. It was observed that with the increasing of the drying air temperature, the period of time necessary for the samples reach the balance decreases. The moisture values in the balance were of 0.0071; 0.0052 and 0.0050 for the yacon pulp and of 0.0075; 0.0030 and 0.0030 for the encapsulated juice at temperatures of 50, 60 and 70° C respectively, resulting in values of water activity lower than 0.25. The yacon juice encapsulated and yacon pulp in powder obtained at a temperature of 70° C w ere visualized in the scanning electron microscope. The powder of yacon juice demonstrated a good encapsulation by corn starch. And in the powdered yacon pulp one verifies the presence of microscopic structures with elongated shape features of inulin sugar. The glass transition temperature of the encapsulated juice obtained at the temperature of 50, 60 and 70° C and of the yacon pulp in powder obtain ed at the temperature of 70° C was determined by the differential scanning calorimetry technique. The glass transition temperatures for the powder of encapsulated concentrated juice were of 44.74; 45.14 and 49.72° C for the values of water a ctivity of 0.15; 0.07 and 0.03 respectively, and for the yacon pulp powder was of 48.78° C in water activity of 0.13.