A ciência na qual se estuda a deformação de um fluido no qual é aplicada uma tensão de cisalhamento é conhecida como reologia e o equipamento utilizado para a realização dos ensaios é chamado de reômetro. Devido a impraticabilidade de uso de reômetros comerciais, diversos pesquisadores desenvolveram reômetros capazes de analisar suspensões de macropartículas, baseados nos mesmos princípios de funcionamento dos equipamentos já existentes. Em alguns casos, a medição do torque do motor é realizada pela aquisição da tensão, uma vez que esta é proporcional ao torque. Entretanto, para melhor compreensão do resultado e para evitar a possibilidade de conclusões precipitadas, vê-se necessária correta interpretação do sinal elétrico, precisando avaliar qual frequência do sinal é relevante para o ensaio e, também, qual a melhor taxa de amostragem. Além da aquisição, para que o ensaio reológico seja realizado com precisão, é indispensável ótimo controle da taxa ou tensão do motor e uma alternativa é a utilização de um servomotor e um servoconversor. No caso desse ser comercial é essencial saber configurá-lo. Para facilitar o usuário leigo, alguns pesquisadores desenvolveram softwares para controle do equipamento e análise dos dados. Assim, o presente trabalho tem como objetivo propor uma metodologia para compreender o sinal aquisitado de um reômetro servo controlado e desenvolvimento do software de análise para o tratamento dos dados obtidos a partir de ensaios reológicos. Verificou-se a melhor configuração do servocontrolador, a melhor taxa de amostragem, de no mínimo 20 amostras/segundo, e, também, desenvolveu-se um filtro digital passa-baixa do tipo FIR para remover a frequência indesejada. Além disso, foi desenvolvido um software utilizando uma rotina em Matlab e uma interface gráfica do usuário (Graphical User Interface - GUI), para o pós-processamento dos dados para auxiliar o usuário leigo no tratamento e interpretação do resultado, que se mostrou eficaz. / Rheology is the study of the behavior of material in fluid state. Rheometer is the equipment used to perform rheological measurements. Because of the impracticability of commercial rheometer, many researchers have developed rheometer able to analyze macro particles suspension, based on the principle of operation of the existing equipment. In some cases, measurement of the motor torque is performed by acquiring voltage signal, since is proportional to torque. However, for better understanding of the rheological results, it is necessary to understand the electrical signal, evaluating which signal frequency is relevant and what is the best sample rate. In addition, for an accurate rheological testing, it is essential a precise control of the shear rate or shear stress of the motor and a good alternative is the use of a servomotor and a drive. In the case of the drive being commercial, it is essential to know how to configure it. To turn rheometer user-friendly, some researchers have developed software to control the equipment and to analyze data. Thus, this dissertation propose a methodology to understand the electrical signal of a servo controlled rheometer and development of analysis software to process the data obtained from rheological tests. It has been found the best configuration of the servo drive, minimum sampling rate of 20 samples/second, and development of a low pass digital filter to remove unwanted frequency. In addition, was developed a software using a Matlab routine and a Graphical User Interface (GUI) to assist the user in the processing and interpretation of the result.

Self-compacting concrete (SCC) offers rational and fast casting process since it merely has to be poured, or pumped, into the formwork without any compaction work needed. But this can be at the cost of high form pressure. However, reported results show that SCC can act thixotropically, i.e., build up a structure at rest, and this can reduce the form pressure considerably. Thus, in order to utilise the favourable possibilities to increase effectiveness without risking form collapses, the need arises for deeper and broader understanding of the mechanisms behind this thixotropic behaviour. Methodologies have been developed for the characterisation and measurement of the structural build-up at rest, both for the fluid (micro mortar) phase and the concrete itself. Hypotheses state that thixotropic mechanisms originate within the colloidal domain and, thus, motivate studies on the fluid phase comprising this domain. The stress-strain methodology is based on the hypothesis stating that the magnitude of the structure is represented by the maximum elastic stress the fresh material can withstand before the structure breaks. An instrumented steel tube is used to simulate various casting heights and rates. Results show that both micro mortar and SCC are thixotropic and this behaviour is influenced by every measure taken influencing the interparticle colloidal forces. The time-dependent structural build-up of SCC is a function of an irreversible structure (slump-loss) and a reversible, thixotropic structure. There is apparently a threshold value of the structural build-up necessary to reach before obtaining any significant form pressure reduction. Housing SCC´s, with W/C = 0.58, show low degree of structural build-up and pressure decrease while civil engineering SCC´s can show the opposite, but this often at the cost of slump-loss. Recommendations are presented and for the nearest future, suggesting a conservatism regarding design of formwork systems when SCC is used. If the behaviour of a SCC is known it should be used to optimise the formwork. If not, calculating with hydrostatic pressure should be done or the knowledge missing should be gained by using this methodology. A third option is given and this is to monitor the form pressure in real time using sensors. / QC 20100812

In this study, we were particularly interested in looking at the possibility that cross metathesis of olefins in melt phase could be used to produce polydimethylsiloxane (PDMS) modified polypropylene (PP). The intention of this project was also to study and quantify relationships among the main experimental factors in the reaction: temperature, catalyst concentration and molar ratio of PP to PDMS, through a 2-level factorial statistical design. In order to examine if PP-PDMS copolymers were synthesized in the melt phase, measurement of the chemical, physical and viscoelastic properties of the synthesized copolymers was necessary. Techniques including proton (¹H)-nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), rheometry and scanning electron microscopy (SEM), were all used to characterize the synthesized copolymers. ¹H NMR measurements confirmed the presence of PDMS in the copolymers. They also provided a quantitative measurement of PP to PDMS molar ratio in copolymers by determining the integration of PP PDMS repeating unit signals in NMR spectra. Compared to virgin PP, a lower melting enthalpy of the PP phase in the copolymer was observed from DSC results. This implied that the PDMS component influenced the thermal behavior of the PP crystalline phase in the copolymers. Moreover, TGA measurements indicated that a higher thermal stability was obtained for PP-PDMS copolymers than that for virgin PP wax and this was expected since PDMS is known for its excellent stability at high temperature. Rheological analysis showed that the presence of PDMS in the copolymers gave lower complex viscosities and loss moduli, but higher storage moduli than those for virgin PP. Furthermore, the morphology of copolymers was examined by SEM and elemental analysis at the surface using an energy dispersive X-ray (EDX) analyzer on the SEM. It was found that micrographs of copolymers showed round domains on the surface, which were not observed in virgin PP wax and those round segments were confirmed to contain silicon. Torque values used in a batch mixer for polymerizations and the remaining weight % of copolymers at 350°C were used to conduct statistical analysis, through which models used to describe the relationships between experimental factors and these physical responses were determined.

The main objective in this work was to learn how the instrument, the Interfacial Shear Rheometer (ISR400), worked and to investigate how the rheological properties, storage modulus (elasticity), G' and loss modulus (viscous), G'', changes when the surface pressure at the air-liquid interphase changes. The second objective were to examine the different kind of magnetic needles used in the experiments and to conclude which type of needle is best for its specific field of analysis. It was concluded that the relative heavy needle with mass 70.6 mg and length 50 mm was best for systems where the viscous and elastic components are significantly large, where the inertia of the needle is not dominant. It also worked of using the heavier needle for a system of phospholipids. For the hydroxystearic acid (HSA) experiment that were tested on NaCl sub-phase there was a clear improvement after switching from the heavy needle (mass 41.5 mg; length 51 mm) to the relative lighter needle (mass 6.94 mg; length 34.7 mm). The values for the dynamic modulus therefore had a better agreement with reference literature. A spread layer of class II hydrophobins (HFBII) could be compressed to a surface pressure of 46 mNm-1. The G' and G'' values from the frequency sweep were discarded because the monolayer turned into a very viscous-like liquid, and the oscillating needle, after compression, was kind of stuck in the sub-phase and moved very staggering during a frequency sweep. The needle comparison experiment with silica particles 10 wt% Bindzil CC30 (BCC30), at pH 3.5 was done to see if there was any difference in the sensitivity for the needles at the interface which consisted of a pure 10 mM NaCl solution or a 10 mM NaCl solution with BCC30 added to it. The differences were negligible in terms of surface tension but there was a clear difference between the heavy needle and the light needle, when oscillating at higher frequencies (>≈6 rad/s). With this study, the understanding of ISR400 has increased largely. Several issues have been addressed and the results provide a good basis for further studies within the many areas the instrument can be used for. Despite the project's time limit, and the fact that the instrument was new and untested where the project was carried out, focus areas were prioritized so good results could be achieved within reasonable goals. / Huvudmålet med detta arbete var att lära sig hur instrumentet ytskiktsreometern (ISR400) fungerade och undersöka hur de reologiska egenskaperna, elasticitetsmodulen G' och viskositetsmodulen G'', kommer att förändras när det sker en förändring för yttrycket vid gränsskiktet mellan luft och vätska. Det sekundära målet var att undersöka vilken typ av magnetiska nålar som är bäst att använda för respektive gränsskiktssystem. Av att använda den tyngre nålen med massan 70.6 mg och längden 50 mm kunde man dra slutsatsen att den är bäst att använda för system där de viskösa och elastiska komponenterna är signifikant stora, där nålens tröghet inte är dominant. Den fungerade även att mäta med i ett fosfolipidsystem. I experimentet med 12-hydroxy-stearinsyra (HSA) som utfördes på en subfas av NaCl, syntes en klar förbättring efter att byta från en tyngre nål (massa 41.5 mg; längd 51 mm) till en lättare (massa 6.94 mg; längd 34.7 mm). Värdena för dynamiska modulen stämde därför bättre överens med referenslitteraturen. Det utspridda lagret av klass II hydrophobins (HFBII) kunde komprimeras upp till yttrycket 46 mNm-1. Värdena för G' och G'' förkastades därför att monolagret förvandlades till en väldigt viskösliknande vätska, och den oscillerande nålen, efter kompressionen, satt fast i denna tröga vätska och rörde sig väldigt hackigt och oregelbundet under tiden ett frekvenssvep utfördes. Då en jämförelse av olika typer av nålar genomfördes med kiseldioxidpartiklar (10 % (viktsprocent) Bindzil CC30 med pH 3.5), för att se om det är någon skillnad i känslighet för nålarna vid gränssnittet, som bestod av en ren 10 mM NaCl-lösning eller en 10 mM NaCl-lösning med tillsatt BCC30. Skillnaderna var försumbara gällande ytspänningen, men det var en klar skillnad mellan den tunga nålen och den lätta nålen vid oscillering vid höga frekvenser (>≈6 rad/s). I och med detta arbete så har förståelsen för hur ISR400 fungerar förbättrats mycket sedan starten. Flera frågeställningar har behandlats och resultaten ger en bra grund för fortsatta studier inom de många områden som utrustningen kan användas till. Trots projektets tidsbegränsning, och det faktum att instrumentet var nytt och oprövat på platsen där detta arbete utfördes, så prioriterades fokusområden så att goda resultat kunde uppnås inom rimliga mål.

Asphalt mixtures are complex composites that comprise aggregate, asphalt binder, and air. Several research studies have shown that the mechanical behavior of the asphalt mixture is strongly influenced by the matrix, i.e. the asphalt binder. Therefore, accurate constitutive models for the asphalt binders are critical to ensure accurate performance predictions at a material and structural level. However, researchers who use computational methods to model the micromechanics of asphalt mixtures typically assume that (i) asphalt binders behave linearly in shear, and (ii) either bulk modulus or Poisson’s ratio of asphalt binders is not time dependent. This research develops an approach to measure and model the shear and bulk behavior of asphalt binders at intermediate temperatures. First, this research presents the findings from a systematic investigation into the nature of the linear and nonlinear response of asphalt binders subjected to shear using a Dynamic Shear Rheometer (DSR). The DSR test results showed that under certain conditions a compressive normal force was generated in an axially constrained specimen subjected to cyclic torque histories. This normal force could not be solely attributed to the Poynting effect and was also related to the tendency of the asphalt binder to dilate when subjected to shear loads. The generated normal force changed the state of stress and interacted with the shear behavior of asphalt binder. This effect was considered to be an “interaction nonlinearity” or “three dimensional effect”. A constitutive model was identified to accommodate this effect. The model was successfully validated for several different loading histories. Finally, this study investigated the time-dependence of the bulk modulus of asphalt binders. To this end, poker-chip geometries with high aspect ratios were used. The boundary value problem for the poker-chip geometry under step displacement loading was solved to determine the bulk modulus and Poisson’s ratio of asphalt binders as a function of time. The findings from this research not only improve the understanding of asphaltic materials behavior, but also provide tools required to accurately predict pavement performance. / text

In this study, we were particularly interested in looking at the possibility that cross metathesis of olefins in melt phase could be used to produce polydimethylsiloxane (PDMS) modified polypropylene (PP). The intention of this project was also to study and quantify relationships among the main experimental factors in the reaction: temperature, catalyst concentration and molar ratio of PP to PDMS, through a 2-level factorial statistical design. In order to examine if PP-PDMS copolymers were synthesized in the melt phase, measurement of the chemical, physical and viscoelastic properties of the synthesized copolymers was necessary. Techniques including proton (¹H)-nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), rheometry and scanning electron microscopy (SEM), were all used to characterize the synthesized copolymers. ¹H NMR measurements confirmed the presence of PDMS in the copolymers. They also provided a quantitative measurement of PP to PDMS molar ratio in copolymers by determining the integration of PP PDMS repeating unit signals in NMR spectra. Compared to virgin PP, a lower melting enthalpy of the PP phase in the copolymer was observed from DSC results. This implied that the PDMS component influenced the thermal behavior of the PP crystalline phase in the copolymers. Moreover, TGA measurements indicated that a higher thermal stability was obtained for PP-PDMS copolymers than that for virgin PP wax and this was expected since PDMS is known for its excellent stability at high temperature. Rheological analysis showed that the presence of PDMS in the copolymers gave lower complex viscosities and loss moduli, but higher storage moduli than those for virgin PP. Furthermore, the morphology of copolymers was examined by SEM and elemental analysis at the surface using an energy dispersive X-ray (EDX) analyzer on the SEM. It was found that micrographs of copolymers showed round domains on the surface, which were not observed in virgin PP wax and those round segments were confirmed to contain silicon. Torque values used in a batch mixer for polymerizations and the remaining weight % of copolymers at 350°C were used to conduct statistical analysis, through which models used to describe the relationships between experimental factors and these physical responses were determined.

A ciência na qual se estuda a deformação de um fluido no qual é aplicada uma tensão de cisalhamento é conhecida como reologia e o equipamento utilizado para a realização dos ensaios é chamado de reômetro. Devido a impraticabilidade de uso de reômetros comerciais, diversos pesquisadores desenvolveram reômetros capazes de analisar suspensões de macropartículas, baseados nos mesmos princípios de funcionamento dos equipamentos já existentes. Em alguns casos, a medição do torque do motor é realizada pela aquisição da tensão, uma vez que esta é proporcional ao torque. Entretanto, para melhor compreensão do resultado e para evitar a possibilidade de conclusões precipitadas, vê-se necessária correta interpretação do sinal elétrico, precisando avaliar qual frequência do sinal é relevante para o ensaio e, também, qual a melhor taxa de amostragem. Além da aquisição, para que o ensaio reológico seja realizado com precisão, é indispensável ótimo controle da taxa ou tensão do motor e uma alternativa é a utilização de um servomotor e um servoconversor. No caso desse ser comercial é essencial saber configurá-lo. Para facilitar o usuário leigo, alguns pesquisadores desenvolveram softwares para controle do equipamento e análise dos dados. Assim, o presente trabalho tem como objetivo propor uma metodologia para compreender o sinal aquisitado de um reômetro servo controlado e desenvolvimento do software de análise para o tratamento dos dados obtidos a partir de ensaios reológicos. Verificou-se a melhor configuração do servocontrolador, a melhor taxa de amostragem, de no mínimo 20 amostras/segundo, e, também, desenvolveu-se um filtro digital passa-baixa do tipo FIR para remover a frequência indesejada. Além disso, foi desenvolvido um software utilizando uma rotina em Matlab e uma interface gráfica do usuário (Graphical User Interface - GUI), para o pós-processamento dos dados para auxiliar o usuário leigo no tratamento e interpretação do resultado, que se mostrou eficaz. / Rheology is the study of the behavior of material in fluid state. Rheometer is the equipment used to perform rheological measurements. Because of the impracticability of commercial rheometer, many researchers have developed rheometer able to analyze macro particles suspension, based on the principle of operation of the existing equipment. In some cases, measurement of the motor torque is performed by acquiring voltage signal, since is proportional to torque. However, for better understanding of the rheological results, it is necessary to understand the electrical signal, evaluating which signal frequency is relevant and what is the best sample rate. In addition, for an accurate rheological testing, it is essential a precise control of the shear rate or shear stress of the motor and a good alternative is the use of a servomotor and a drive. In the case of the drive being commercial, it is essential to know how to configure it. To turn rheometer user-friendly, some researchers have developed software to control the equipment and to analyze data. Thus, this dissertation propose a methodology to understand the electrical signal of a servo controlled rheometer and development of analysis software to process the data obtained from rheological tests. It has been found the best configuration of the servo drive, minimum sampling rate of 20 samples/second, and development of a low pass digital filter to remove unwanted frequency. In addition, was developed a software using a Matlab routine and a Graphical User Interface (GUI) to assist the user in the processing and interpretation of the result.

No description available.

This diploma thesis is focused on the study of the behaviour of carbon fibers in the hydrogel, especially the viscoelastic modules od these gels ort he coefficient of color transmission through the gel. The main goals were to optimize the samples and measure their viscoelastic modules on a rheometer, in several different modes. This was followed by simulation of physiological conditions for selected samples and their measurement on the rheometer. There was also an experiment of continuous diffusion in cuvettes, in which the penetration of the dye through the gel with the addition of fibers and for comparison also without them. Last but not least diffusion pairs were prepared.

[pt] O sucesso da operação de perfuração de poços de petróleo provém da incessante pesquisa científica que busca soluções e melhorias às diversas etapas deste processo. A correta formulação dos fluidos de perfuração e suas medições reológicas são parte fundamental neste cenário. O objetivo deste estudo é investigar o funcionamento de um viscosímetro Fann 35A e a metodologia utilizada para caracterização reológica de fluidos de perfuração, mediante comparação com um reômetro rotacional. Por conseguinte, diferentes fluidos, tais como soluções poliméricas e fluidos de perfuração, foram analisados com a finalidade de propor novas recomendações e aprimorar o uso do equipamento, comumente utilizado pelas companhias de petróleo. Curvas de escoamento e testes de força gel foram executados e, os resultados mostraram que as equações API são responsáveis pela determinação errônea dos parâmetros reológicos destes fluidos. Além disso, foi realizado um estudo teórico da relação entre a pressão e vazão em escoamento em tubo e espaço anular. Observou-se que a escolha precisa da função de viscosidade é imprescindível para o correto dimensionamento de bomba. Ademais, uma geometria ranhurada foi projetada e desenvolvida a fim de evitar os efeitos do deslizamento aparente em baixas taxas de cisalhamento. A força gel, medida importante para avaliar o reinício do escoamento em poços de petróleo, também foi avaliada e apresentou resultados bastante divergentes dos obtidos no reômetro. O gel adicional exibiu respostas significativas e assim, sua utilização é indicada. Por fim, as melhorias e metodologias propostas mostraram-se promissoras, embora em alguns casos não possua valia pelo custo benefício. A incorporação das recomendações obtidas no presente estudo garante aquisição com maior acurácia da reologia de fluidos de perfuração e, consequentemente, desempenho correto de algumas funções atribuídas ao mesmo, evitando assim ocorrência de sérios problemas operacionais, ambientais e financeiros. / [en] The success of a drilling operation in an oil well emerges from the unrelenting scientific research for solutions and improvements to the various stages of this process. The correct formulations of drilling fluids and their rheological measurements are essential to this scenario. This study aims to investigate the functionality of a rotational viscometer 35A and the methodology used to characterize the fluids’ rheology through the comparison with a rotational rheometer. Hence, different fluids, such as polymeric solutions and drilling fluids, were analyzed to propose new standards and improve the equipment operation, generally used by the oil companies. The results show that API equations are responsible for the inaccurate determination of these fluids rheological parameters. Besides, a theoretical study of the relationship between pressure and flow rate in a tube and annular flow was performed. It was observed that the choice of viscosity function is extremely important to determine the correct pump size. Also, a roughed geometry was designed and developed for the viscometer to avoid wall slip at low shear rates. The gel strength, an important parameter to analyze restart of flows in oil wells, was analyzed and presented expressively divergent results from those obtained with a rheometer. The additional gel strength showed interesting results that indicate its use. Finally, the improvements and proposed methodology were found to be promising, although in some cases, it is not worth the cost-benefit analysis. The use of this present study s recommendations guarantees the accuracy of drilling fluids rheology and, consequently, a good performance of some of its functions, avoiding the occurrence of serious operational, environmental and financial problems.