Made available in DSpace on 2014-12-17T15:42:30Z (GMT). No. of bitstreams: 1 KeilaRS_TESE.pdf: 2025404 bytes, checksum: f62ed0f0a6e3ff3ceed81829e8165b40 (MD5) Previous issue date: 2014-05-16 / Petr?leo Brasileiro SA - PETROBRAS / The role of carboxymethylcellulose (CMC) in association to calcium carbonate particles (CaCO3) in most water-based drilling fluids is to reduce the fluid loss to the surrounding formation. Another essential function is to provide rheological properties capable of maintaining in suspension the cuttings during drilling operation. Therefore, it is absolutely essential to correlate the polymer chemical structure (degree of substitution, molecular weight and distribution of substituent) with the physical-chemical properties of CaCO3, in order to obtain the better result at lower cost. Another important aspect refers to the clay hydration inhibitive properties of carboxymethylcellulose (CMC) in drilling fluids systems. The clay swelling promotes an undesirable damage that reduces the formation permeability and causes serious problems during the drilling operation. In this context, this thesis consists of two main parts. The first part refers to understanding of interactions CMC-CaCO3, as well as the corresponding effects on the fluid properties. The second part is related to understanding of mechanisms by which CMC adsorption occurs onto the clay surface, where, certainly, polymer chemical structure, ionic strength, molecular weight and its solvency in the medium are responsible to affect intrinsically the clay layers stabilization. Three samples of carboximetilcellulose with different molecular weight and degree of substitution (CMC A (9 x 104 gmol DS 0.7), CMC B (2.5 x 105 gmol DS 0.7) e CMC C (2.5 x 105 gmol DS 1.2)) and three samples of calcite with different average particle diameter and particle size distribution were used. The increase of CMC degree of substitution contributed to increase of polymer charge density and therefore, reduced its stability in brine, promoting the aggregation with the increase of filtrate volume. On the other hand, the increase of molecular weight promoted an increase of rheological properties with reduction of filtrate volume. Both effects are directly associated to hydrodynamic volume of polymer molecule in the medium. The granulometry of CaCO3 particles influenced not only the rheological properties, due to adsorption of polymers, but also the filtration properties. It was observed that the lower filtrate volume was obtained by using a CaCO3 sample of a low average size particle with wide dispersion in size. With regards to inhibition of clay swelling, the CMC performance was compared to other products often used (sodium chloride (NaCl), potassium chloride (KCl) and quaternary amine-based commercial inhibitor). The low molecular weight CMC (9 x 104 g/mol) showed slightly lower swelling degree compared to the high molecular weight (2.5 x 105 g/mol) along to 180 minutes. In parallel, it can be visualized by Scanning Electron Microscopy (SEM) that the high molecular weight CMC (2.5 x 105 g/mol e DS 0.7) promoted a reduction in pores formation and size of clay compared to low molecular weight CMC (9.0 x 104 g/mol e DS 0.7), after 1000 minutes in aqueous medium. This behavior was attributed to dynamic of interactions between clay and the hydrodynamic volume of CMC along the time, which is result of strong contribution of electrostatic interactions and hydrogen bounds between carboxylate groups and hydroxyls located along the polymer backbone and ionic and polar groups of clay surface. CMC adsorbs on clay surface promoting the skin formation , which is responsible to minimize the migration of water to porous medium. With the increase of degree of substitution, it was observed an increase of pores onto clay, suggesting that the higher charge density on polymer is responsible to decrease its flexibility and adsorption onto clay surface. The joint evaluation of these results indicate that high molecular weight is responsible to better results on control of rheological, filtration and clay swelling properties, however, the contrary effect is observed with the increase of degree of substitution. On its turn, the calcite presents better results of rheological and filtration properties with the decrease of average viii particle diameter and increase of particle size distribution. According to all properties evaluated, it has been obvious the interaction of CMC with the minerals (CaCO3 and clay) in the aqueous medium / O papel da carboximetilcelulose (CMC) em associa??o com o carbonato de c?lcio (CaCO3) na maioria dos fluidos de perfura??o base ?gua ? reduzir a perda de fluido para a forma??o. Outra fun??o essencial ? promover propriedades reol?gicas capazes de manter em suspens?o os cascalhos durante a opera??o de perfura??o. Dessa forma, ? absolutamente essencial correlacionar a estrutura qu?mica do pol?mero (grau de substitui??o, massa molar e distribui??o do substituinte) com as propriedades f?sicoqu?micas do CaCO3, de forma a obter o melhor resultado a mais baixo custo. Outro importante aspecto refere-se ?s propriedades de inibi??o da CMC em rela??o ? hidrata??o de argilas presentes na forma??o rochosa. O inchamento de argilas promove um dano indesej?vel que reduz a permeabilidade da forma??o e causa s?rios problemas durante a perfura??o. Nesse contexto, essa Tese consiste de duas partes principais. A primeira parte refere-se ao entendimento das intera??es CaCO3-CMC, assim como os efeitos correspondentes ?s propriedades do fluido. A segunda parte est? relacionada ao entendimento dos mecanismos pelos quais a adsor??o da CMC ocorre na aresta da argila, onde, certamente, a estrutura qu?mica do pol?mero, for?a i?nica, massa molar e sua solubilidade no meio s?o respons?veis por afetar intrinsecamente a estabiliza??o das camadas da argila. Foram utilizadas no estudo tr?s amostras de carboximetilcelulose com diferentes massas molares e graus de substitui??o: CMC A (9 x 104 gmol DS 0.7), CMC B (2.5 x 105 gmol DS 0.7) e CMC C (2.5 x 105 gmol DS 1.2)) e tr?s amostras de calcita (CaCO3), com diferentes di?metros m?dios de part?culas e curvas de distribui??o em tamanho. O aumento do grau de substitui??o da CMC contribuiu para o aumento da densidade de carga do pol?mero e dessa forma, reduziu sua estabilidade em salmoura, promovendo agrega??o e o aumento do volume de filtrado. Por sua vez, o aumento da massa molar promoveu um aumento das propriedades reol?gicas com a redu??o do volume de filtrado. Ambos os efeitos est?o diretamente ligados ao volume hidrodin?mico da mol?cula do pol?mero no meio. A granulometria das part?culas do CaCO3 influenciou n?o somente as propriedades reol?gicas, devido ? adsor??o de pol?meros em sua superf?cie, mas tamb?m as propriedades de filtra??o. Foi observado que o menor volume de filtrado foi obtido pelo uso da amostra de CaCO3 de menor tamanho de part?cula com a faixa mais ampla de dispers?o em tamanho. Com rela??o ? inibi??o de inchamento de argilas, a efici?ncia da CMC foi comparada a outros produtos comumente empregados (cloreto de s?dio (NaCl), cloreto de pot?ssio (KCl) e um inibidor comercial ? base de amina quatern?ria). A CMC de baixa massa molar (9 x 104 g/mol) propiciou grau de inchamento da bentonita ligeiramente mais baixo que a CMC de alta massa molar (2.5 x 105 g/mol), no decorrer de 180 minutos. Por outro lado, p?de ser visualizado por microscopia eletr?nica de varredura que a CMC de maior massa molar (2.5 x 105 g/mol e DS 0.7) promoveu uma redu??o na forma??o e no tamanho dos poros da argila comparada ? CMC de menor massa molar (9.0 x 104 g/mol e DS 0.7), ap?s 1000 minutos em meio aquoso. Esse comportamento foi atribu?do ? din?mica das intera??es entre a argila e a cadeia polim?rica da CMC ao longo do tempo, que ? resultado da forte contribui??o das intera??es eletrost?ticas e liga??es de hidrog?nio entre os grupos carboxilato e hidroxila localizados ao longo da cadeia polim?rica e os s?tios i?nicos e polares da superf?cie da argila. A CMC adsorve na superf?cie da matriz de argila promovendo a forma??o de uma pel?cula , a qual ? respons?vel por minimizar a migra??o da ?gua para o meio poroso. Com o aumento do grau de substitui??o, foi observado aumento de poros na matriz de argila, sugerindo que a maior densidade de cargas no pol?mero diminui a sua flexibilidade e a adsor??o sobre a matriz argilosa. A an?lise conjunta dos resultados vi indica que altas massas molares da CMC propiciam melhores resultados no controle das propriedades reol?gicas, de filtra??o e de inchamento de argilas, entretanto, efeito contr?rio ? observado com o aumento do grau de substitui??o. Por sua vez, o CaCO3 apresenta melhores resultados de propriedades reol?gicas e de filtra??o com a diminui??o do di?metro m?dio das part?culas e aumento da distribui??o em tamanho. Em todas as propriedades analisadas, foram evidentes os sinais de intera??o da CMC com os minerais (carbonato de c?lcio e argila) presentes no meio aquoso

Orientador: Maria da Consolação Fonseca de Albuquerque / Resumo: A inserção de resíduos de borracha de pneu no concreto, embora traga melhoras em propriedades acústicas, térmicas e redução da fadiga e da vibração no concreto, tem como consequência negativa a queda da resistência à tração e à compressão. Tendo em vista tal problema, admitiu-se uma mistura de Concreto de Alto Desempenho (CAD) como referência e a partir desta, substituíram-se diferentes granulometrias de areia por resíduos de borracha, em volume. Ao encontrar a melhor resistência respectiva ao tamanho dos grãos de resíduos, aumentaram-se as proporções de substituição do material, a fim de encontrar a viabilidade do uso. Com os dados obtidos, observou-se que até 10% de substituição de areia pelo resíduo (na granulometria e traço adotado) a interferência na resistência é mínima, ou praticamente nula. Com 15% de substituição, ocorre queda drástica na resistência à compressão axial. Neste ponto, portanto, decide-se realizar adições na mistura, a fim de diminuir a queda na resistência, ocasionada pelo resíduo. Pôde-se ainda comparar os comportamentos relacionados aos diferentes processos de curas no concreto e tratamentos superficiais nos corpos de prova para ensaios de resistência (com e sem resíduos). As substituições de areia por resíduos em até 10% ocasionaram pequena queda na resistência à compressão axial. A utilização de partículas de borracha separadas na faixa granulométrica de 0,6 mm até 1,19 mm foi a melhor solução para a diminuição da queda na resistência, quando compa... (Resumo completo, clicar acesso eletrônico abaixo) / Mestre

Este trabalho apresenta uma proposta para o controle da suspensão veicular utilizando o amortecedor magneto-reológico, sendo o controle proposto composto pela associação de duas estratégias de controle, o controle ótimo e o controle fuzzy. O Controle ótimo é utilizado para determinar a força a ser utilizada pelo amortecedor magneto-reológico, e o controle fuzzy é utilizado para determinar a corrente elétrica, a ser utilizada no amortecedor magento-reológico e é obtido considerando o modelo de Mandani. Para o controle fuzzy, são consideradas duas entradas, a velocidade de deslocamento do pistão do amortecedor e a força prevista pelo controle ótimo, e uma saída, a corrente elétrica [A]. Para demonstrar a eficiência do controle proposto são consideradas simulações computacionais, utilizando um modelo matemático não-linear de um quarto de veículo. A análise do desempenho do controle é realizada, considerando excitações provocadas por irregularidades na pista, as irregularidades são representadas por entradas tipo degrau, impulso e senoidal. As simulações computacionais são realizadas, utilizando o Matlab® e o Simulink. Os resultados das simulações demonstram que o controle proposto aumenta a segurança do veículo e melhora sua dirigibilidade, reduzindo o deslocamento vertical do conjunto eixo e roda e o espaço de trabalho do amortecedor, quando comparado como o sistema passivo. Também contribui com o conforto dos passageiros, reduzindo as oscilações da carroceria, mantendo os níveis de aceleração abaixo dos considerados desconfortáveis pela norma BS 6841, 1987. Para verificar o comportamento do controle proposto, diante de incertezas, são realizadas simulações computacionais, considerando a possibilidade de erros paramétricos. As simulações, considerando os erros paramétricos, demonstram que o controle ótimo, mesmo quando sujeito a incertezas, permanece sendo estável e ótimo. / This work presents a proposal for control of vehicular suspension using the magneto-rheological damper, the proposed control is composed by association of two control strategy, the optimal control and the fuzzy control. The optimal control is used to determine the power to be applied by the magneto-rheological damper, and the fuzzy control is used to determine the electric current to be used in the magneto-rheological damper and is obtained considering the Mandani's model. For the fuzzy control two inputs are considered, the velocity of the piston's damper and the force provided by the optimal control, and one output, the electric current [A]. To demonstrate the efficiency of the proposed control, computational simulations are considered using a nonlinear mathematical model for a quarter-car. The performance of the control is analyzed considering excitements provoked by irregularities in the track, the irregularities are represented by entrances step type, pulse and sinusoidal. The computational simulations are performed using the Matlab® and the Simulink. The results of simulations show that the proposed control increases the vehicle security and improves the drive ability by reducing the vertical wheel displacement and the workspace to be used by the damper when compared to the passive system. It also helps with the comfort of passengers, reducing the bodywork oscillations, maintaining levels of accelerating below considered uncomfortable by standard BS 6841, 1987. To verify the behavior of the proposed control, in the face of uncertainty, computational simulations are carried out, considering the possibility of parametric errors. The simulations, show that the Optimal Control, even when subject to uncertainties, remains stable and optimal.

In the process of crushing concrete waste, significant amounts of fine by-products, the so called fine recycled concrete aggregates (FRCA), are generated and excluded from potential use. Limited research has thoroughly investigated the performance of concrete mixes with FRCA, very likely due to the complexity in analysing non-negligible amounts of adhered residual cement paste (RCP). Although some studies have proposed promising sustainable mix-design procedures accounting for the different microstructure when using coarse recycled concrete aggregates (CRCA), no similar approach exists for FRCA concrete. In this work, two promising procedures for mix-designing eco-efficient concrete with 100% FRCA are proposed accounting for the presence of RCP to reduce cement content in new mixtures. First, built on top of the existing procedure for CRCA mix-design, modifications to the Equivalent Volume (EV) method were introduced toconsider full replacement of fine natural sand by FRCA. Second, based on the concept of continuous Particle Packing Models (PPM), an optimized procedure was proposed to allow maximum packing density of FRCA mix linked to a given level of measured RCP content. Results verified the feasibility of producing eco-efficient concrete mixes with 100% FRCA, emphasizing the PPM mixes to report superior rheological and mechanical performance along with suitable durability-related properties. Yet, results also indicated the influence of simple or multistage crushed FRCA on the overall performance of mixes.

Ballistic fabrics made from high performance polymeric fibers such as Kevlar®, Twaron® and Spectra® fibers and composites utilizing these fabrics are among the leading materials for modern body armor systems. Polymeric fibers used to produce ballistic fabrics often behave viscoelastically and exhibit time- and rate-dependent stress-strain relations. This necessitates the study of the constitutive behavior of composites filled by ballistic fabrics. Rheological models based on discrete rheological components (including spring and dashpot) have been widely used to study the viscoelastic behavior of polymeric fabrics. Such rheological (or viscoelasticity) models are qualitatively useful in understanding the effects of various micro-mechanisms and molecular features on the macroscopic responses of ballistic fabrics. In the present work, the constitutive behavior of Twaron CT709® fabric/natural rubber (Twaron®/NR) composite is studied using three viscoelasticity models (i.e., a four-parameter Burgers model, a three-parameter generalized Maxwell (GMn=1) model, a five-parameter generalized Maxwell (GMn=2) model) and a newly developed para-rheological model. The new model utilizes a three-parameter element to represent the Twaron® fabric and the affine network based molecular theory of rubber elasticity to account for the deformation mechanisms of the NR constituent. The uniaxial stress-strain relation of the Twaron®/NR composite at two constant strain rates is experimentally determined. The values of the parameters involved in all the models are extracted from the experimental data obtained in this study. The stress-relaxation response (under a uniaxial constant strain) and the creep deformation (under a uniaxial constant stress) of the composite are also experimentally measured. The three viscoelasticity models considered here are capable of predicting the viscoelastic constitutive behavior of the composite with different levels of accuracy. The stress-strain relation at each strain rate predicted by the newly developed para-rheological model is seen to be in good agreement with the measured stress-strain curve over the entire strain range studied. It is shown that the new model also predicts the elastic moduli and ultimate stress of the Twaron®/NR composite well. All the four models are found to predict the initial relaxation response of the composite fairly well, while the long-term stress relaxation is more accurately represented by the para-rheological model. An implicit solution provided by the para-rheological model is shown to predict the creep response of the composite more accurately than all the other models at both the primary and secondary stages. The mathematical complexity that arises from including an additional Maxwell element to the GMn=1 model to obtain the GMn=2 model with enhanced predictability is traded with the use of simple characteristic time functions in the para-rheological model. These functions are found to greatly improve the predictability of the newly developed model for the stress relaxation modulus and creep compliance. This study also explores the utility of the para-rheological model as a tool to probe the micromechanisms and molecular features that are causally related to the macroscopically observed viscoelastic behavior of the composite. The relaxation and creep trends predicted by the para-rheological model indicate that the long time viscoelastic response of the composite lies between that of a crosslinked polymer and a semi-crystalline thermoplastic.

Pages A58-A66 are missing from original but content appears complete. / This project investigates the time-dependent rheological behaviour of fresh and reconstituted milk concentrates. New experimental protocols, including sampling and measurement techniques, as well as equipment calibration and data analysis procedures were developed for both the industrial surveys and controlled rheology experiments. The controlled rheology experiments were mainly carried out on reconstituted milk concentrates to minimise the variation in composition of fresh milk. A new recombination rig was built which could minmise the age thickening process by mixing at 35°C and recirculating at 40,000 s-1 to break down the structure completely. This is the essence of this project, where age thickening is studied from a starting point of a filly broken down structure in contrast to past research. Using this method, the replicate milk concentrate samples had reproducible rheological behaviour, with a maximum reproducible error of 10%. Age thickening involves two stages, a slow initial increase in apparent viscosity with storage time, followed by a sudden sharp rise which marks the onset of gelation. The age thickening behaviour of milk concentrates is dependent on the processing variables prior to rheological measurement. These include solids content, shear rate and temperature during recombination, shear rate and residence time in the plate heat exchanger, and most importantly the raw material. The viscosity at the gelling point is an important characteristic of the age thickening process, and seems to depend mainly on the powder used, rather than the process treatments applied. Industrial surveys exhibited similar trends, even under varying conditions that could not be completely controlled. It is proposed that two types of age thickening phenomena can be distinguished: type I occurs below the temperature at minimum viscosity (65°C in this case), where weak interactions take place between the casein micelles; type II occurs above the temperature at minimum viscosity, where additional stronger covalent bonds are formed, primarily due to the denaturation of whey proteins. No mathematical model for the time-dependent rheology was developed. However, some important issues that must be taken into account during modelling were discussed. The results showed that the age thickening process is more complex than had previously been envisaged. The knowledge of the interactions between the operating conditions, rheology of fresh concentrates and powder properties should be invaluable in the improvement of plant efficiency and quality control.

Resumo: Exopolissacarídeos (EPS) são polímeros produzidos por uma grande variedade de microrganismos e possuem diferentes propriedades estruturais, físicas e químicas. A investigação das propriedades reológicas de suas soluções é importante devido ao crescente interesse na aplicação comercial de polissacarídeos, principalmente na indústria de alimentos. Assim, o objetivo deste trabalho foi investigar as características reológicas dos exopolissacarídeos R1, R2, R3 e R4 produzidos por diferentes linhagens de Rhizobium e Mesorhizobium. Análises quantitativas mostraram que o teor de ácido urônico encontrado em R3 (8,4 %) foi maior que em R1 (2,4 %), R2 (1,7 %) e R4 (0,8 %). A cromatografia de filtração em gel mostrou que R2 e R3 são mais homogêneos e menos polidispersos. Hidrólise ácida total e análise por HPAEC/PAD mostrou glucose como constituinte básico majoritário dos EPS, além de galactose e manose. Todos os polissacarídeos apresentaram comportamento não-Newtoniano, com características de soluções pseudoplásticas nas concentrações de 2, 5 e 10 g/L. O modelo reológico de Ostwald-de-Waele (Lei da Potência) foi utilizado para representar os dados experimentais de tensão de cisalhamento versus taxa de deformação. Os EPS R1, R2 e R4 demonstraram pequeno aumento na viscosidade em presença de NaCl, e apresentaram comportamento viscoelástico de gel, sendo R1 o que apresenta características de gel mais forte. O EPS R3 manteve-se como o menos viscoso, tanto em meio aquoso quanto em solução salina, provavelmente devido ao maior percentual de ácidos urônicos em sua estrutura. Além disso, R3 exibiu comportamento de solução diluída a baixas concentrações, e viscoelástico de gel fraco em concentrações mais elevadas. A análise da influência da temperatura sobre o comportamento viscoelástico das soluções polissacarídicas mostrou... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Exopolysaccharides (EPS) are polymers produced by a great variety of microorganisms and possess different structural, physical and chemical properties. Investigation of rheological properties of these solutions is important due to an increasing interest in polysaccharides commercial applications, mainly in food sectors. The objective of this work was investigate rheological characteristics of exopolysaccharides R1, R2, R3 and R4 produced by different Rhizobium and Mesorhizobium strains. Quantitative analysis showed that uronic acid component found in R3 (8,4 %) was higher than R1 (2,4 %), R2 (1,7 %) and R4 (0,8 %). Gel filtration chromatography indicated that EPS R2 and R3 are more homogeneous and less polidisperse. Acid hydrolysis and HPAEC/PAD analysis revealed that glucose was the main monosaccharide, beyond galactose and mannose. All exopolysaccharides had non-Newtonian behavior, with pseudoplastic characteristics at concentrations of 2, 5 and 10 g/L. The Ostwald-de-Waele (Power Law) was the rheological model used to represent the experimental data of the shear stress versus shear rate. EPS R1, R2 and R4 demonstrated a slight increase in viscosity in presence of NaCl, and viscoelastic behavior, R1 had strong gelling characteristics. The EPS R3 was less viscous, in water solutions and presence of salt, probably due to a high percentual of uronic acids on its structure. Moreover, R3 exhibited diluted solution behavior at low concentration, and viscoelastic weak gelling at high concentrations. Analysis of temperature influence over polysaccharide solutions viscoelastic behavior showed that EPS R1, R2 e R4 had strong gelling characteristics, at concentrations of 5 g/L. / Orientador: Maria de Lourdes Corradi Custódio da Silva / Coorientador: Ana Lúcia Barretto Penna / Banca: Eliana Gertrudes de Macedo Lemos / Banca: Javier Telis Romero / Mestre

Este trabalho apresenta uma proposta para o controle da suspensão veicular utilizando o amortecedor magneto-reológico, sendo o controle proposto composto pela associação de duas estratégias de controle, o controle ótimo e o controle fuzzy. O Controle ótimo é utilizado para determinar a força a ser utilizada pelo amortecedor magneto-reológico, e o controle fuzzy é utilizado para determinar a corrente elétrica, a ser utilizada no amortecedor magento-reológico e é obtido considerando o modelo de Mandani. Para o controle fuzzy, são consideradas duas entradas, a velocidade de deslocamento do pistão do amortecedor e a força prevista pelo controle ótimo, e uma saída, a corrente elétrica [A]. Para demonstrar a eficiência do controle proposto são consideradas simulações computacionais, utilizando um modelo matemático não-linear de um quarto de veículo. A análise do desempenho do controle é realizada, considerando excitações provocadas por irregularidades na pista, as irregularidades são representadas por entradas tipo degrau, impulso e senoidal. As simulações computacionais são realizadas, utilizando o Matlab® e o Simulink. Os resultados das simulações demonstram que o controle proposto aumenta a segurança do veículo e melhora sua dirigibilidade, reduzindo o deslocamento vertical do conjunto eixo e roda e o espaço de trabalho do amortecedor, quando comparado como o sistema passivo. Também contribui com o conforto dos passageiros, reduzindo as oscilações da carroceria, mantendo os níveis de aceleração abaixo dos considerados desconfortáveis pela norma BS 6841, 1987. Para verificar o comportamento do controle proposto, diante de incertezas, são realizadas simulações computacionais, considerando a possibilidade de erros paramétricos. As simulações, considerando os erros paramétricos, demonstram que o controle ótimo, mesmo quando sujeito a incertezas, permanece sendo estável e ótimo. / This work presents a proposal for control of vehicular suspension using the magneto-rheological damper, the proposed control is composed by association of two control strategy, the optimal control and the fuzzy control. The optimal control is used to determine the power to be applied by the magneto-rheological damper, and the fuzzy control is used to determine the electric current to be used in the magneto-rheological damper and is obtained considering the Mandani's model. For the fuzzy control two inputs are considered, the velocity of the piston's damper and the force provided by the optimal control, and one output, the electric current [A]. To demonstrate the efficiency of the proposed control, computational simulations are considered using a nonlinear mathematical model for a quarter-car. The performance of the control is analyzed considering excitements provoked by irregularities in the track, the irregularities are represented by entrances step type, pulse and sinusoidal. The computational simulations are performed using the Matlab® and the Simulink. The results of simulations show that the proposed control increases the vehicle security and improves the drive ability by reducing the vertical wheel displacement and the workspace to be used by the damper when compared to the passive system. It also helps with the comfort of passengers, reducing the bodywork oscillations, maintaining levels of accelerating below considered uncomfortable by standard BS 6841, 1987. To verify the behavior of the proposed control, in the face of uncertainty, computational simulations are carried out, considering the possibility of parametric errors. The simulations, show that the Optimal Control, even when subject to uncertainties, remains stable and optimal.

Orientador: Amarildo Tabone Paschoalini / Resumo: O presente trabalho apresenta um estudo de uma classe de materiais chamado de Elastômeros Magneto-Reológicos (MRE – Magneto-Rheological Elastomers, da sigla em inglês), com foco principal em sua resposta mecânico-magnética, onde as propriedades das micropartículas de Ferro Carbonila funcionalizaram a borracha de silicone. As amostras foram preparadas a partir da dispersão de partículas de Ferro Carbonila em borracha de silicone, sendo que, a vulcanização do material aconteceu por meio de um catalisador, e foram realizados ensaios do tipo de cisalhamento. Foram realizados ensaios experimentais de cisalhamento em que as amostras foram organizadas na forma de “sanduiche” formado por Latão/MRE/Latão/MRE/Latão e acopladas à máquina de ensaio universal entre imãs permanentes, no qual se analisou a relação tensão-deformação de várias amostras com concentrações de 18%, 33% e 48% em volume de Ferro Carbonila, com e sem campo magnético. Considerando a caracterização do MRE, são apresentados também resultados utilizando a técnica de Espectroscopia Infravermelha por Transformada de Fourier visando construir uma compreensão da relação entre as propriedades das amostras mediante sua concentração e a técnica de Microscopia Eletrônica de Varredura com o objetivo de se observar a caracterização morfológica das partículas dispersas no silicone. Os resultados apontam para a possibilidade de utilização do MRE em sistemas como absorvedores dinâmicos de vibrações sintonizáveis uma vez que os resul... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This dissertation presents a study of a class of materials called Magneto-Rheological Elastomers (MRE) with main focus on its mechanical and magnetic response, where the properties of the iron carbonyl micro particles functionalize rubber silicone. Samples were prepared from the dispersion of iron carbonyl particles in silicone rubber, and that vulcanization of the material took place by means of a catalyst, and the type of shear tests were performed. We carried out experimental shear tests in which the samples were arranged in the form of "sandwich" formed by Brass / MRE / Brass / MRE / brass and attached to the universal test machine between permanent magnets, which examined the relationship tension strain samples with different concentrations of 18%, 33% and 48% by volume iron carbonyl with and without magnetic field. Considering the characterization of the MRE, they are also displayed results using the Infrared Spectroscopy technique of Fourier Transform aimed at building an understanding of the relationship between the properties of the samples by concentration and scanning electron microscopy technique in order to observe the characterization morphological particles dispersed in the silicone. The results point to the possibility of use of the MRE system as Dynamic Vibration Absorbers tunable since the results obtained are within 50% variation of the stiffness of the system with and without magnetic field. / Mestre

Concrete, the major construction material used in the civil industry worldwide, displays remarkable performance and economic benefits. Yet, it also presents a huge environmental impact producing about 7% of the global carbon dioxide (CO2). Given the rise of global warming concerns, studies have been focusing on alternatives to reduce the amount of Portland cement (PC), which is the least sustainable ingredient of the mixture, for example by adopting particle packing model (PPM) techniques. Although a promising alternative, there is currently a lack of studies regarding the efficiently use of PPMs to reduce PC without compromising the fresh and hardened properties of the material. This work appraises the influence of PPMs and advanced mix-design techniques on the fresh (rheological behaviour) and hardened (compressive strength, modulus of elasticity, porosity, and permeability) state behaviours of systems with reduced amount of PC, the so-called low cement content (LCC) concrete. Results show that is possible to produce eco-efficient concrete maintaining and/or enhancing fresh and hardened properties of the material. Nevertheless, further durability and long-term behaviour must be performed on LCC systems.