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Multilayers provide an ideal tool to study thermodynamics of heterogeneous systems far from equilibrium. In this study, synthesis, characterization, thermal stability and phase equilibrium of multilayers are investigated based on Au-Pt system. Au-50%Pt multilayers were first formed by repeated rolling and folding. The microstructure was investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). These methods revealed that the process reduced layer thicknesses to below 30nm. However, delaminating and non-uniform spacings were also observed in some regions. To get well- welded and regular multilayers, the experiment was redesigned. The improved approach, involving repeated cutting, stacking, annealing and cold rolling, has yielded uniform multilayers with interlamellar spacings as low as 6nm. XRD demonstrated the formation of a homogeneous solid solution during cold rolling at room temperature. TEM suggested that the multilayers were discontinuously homogenized via steady state motion of boundaries. The reason for the solid solution formation is that the stored interface energy is higher than the energy barrier for solid solution formation. The solid solution is unstable. It decomposes into Au and Pt after heating to 500°C at 50°C/min by differential scanning calorimetry (DSC). The phase diagram is strongly modified in the nanometer range when we take into account of interface energy. The grain size dependent phase diagram model of Au-Pt system shows that the melting points of Au and Pt can be lowered more than 300K if the average grain size is reduced to 10nm. The melting temperature of Au/Pt multilayers has been studied with theoretical and experimental approaches. High speed laser heating was used to minimize any modification of the multilayer structure prior to melting. The qualitative experimental results are shown to be in agreement with expectations. / Thesis / Master of Applied Science (MASc)

AC main drives, such as cycloconverters, offer the possibility of higher speed and torque response over their DC counterparts. The price to be paid, however, is torque ripple which is a function of the operating frequency. Even a small value of ripple, at an underdamped plant resonant frequency, may be multiplied by the plant "Q" to a large enough value to cause trouble. Typical classical approaches used in the rolling mill industry to deal with mechanical resonance tend to fall apart with large values of time lag. We investigate a modified LQR/LQE approach using a torque sensor as the feedback element. The result is a low order SISO filter that suppresses the effects of the torque ripple on the underdamped plant. / Master of Science

The low frequency (0-500 Hz) automotive noise and vibration behavior is influenced by the rolling dynamics of the tire. Driven by pressing environmental concerns, the automotive industry has strived to innovate fuel-efficient and quieter powertrain systems over the last decade. This has eventually led to the prevalence of hybrid and electric vehicles. With the noise masking effect of the engine orders being absent, the interior structure-borne noise is dominated by the tire pavement interaction under 500 Hz. This necessitates an accurate estimation of rolling tire dynamics. To this date, there is no direct procedure available for modal analysis of rolling tires with tread patterns under realistic operating conditions. The present start-of-art laser vibrometer based non-contact measurements are limited to tread vibration measurement of smooth tires only in a lab environment. This study focuses on devising an innovative strategy to use a wireless Tire Cavity Accelerometer (TCA) and two optical sensors in a tire on drum setup with cleat excitation to characterize dynamics of tread vibration in an appreciably easier, time and cost-effective approach. In this approach, First, the TCA vibration signal in a single test run is clustered into several groups representing an array of virtual sensor position at different circumferential positions. Then modal identification has been performed using both parametric and non-parametric operational modal identification procedures. Furthermore, relevant conclusions are drawn about the observed modal properties of the tire under rolling including the limitations of the proposed method. The method proposed here, as is, can be applied to a treaded tire and can also be implemented in an on-road test setup. / Master of Science / The low frequency(0-500 Hz) interior noise and vibration of an automobile is primarily influenced by the dynamics of the rolling tire. In recent studies, the laser vibrometer with moving mirrors for measurement of vibration on the tread of a rotating tire has been used. However, these are limited to tires without tread pattern. In this study, an innovative experimental way of performing operational modal analysis using the Tire cavity Accelerometer (TCA) and optical sensors is presented. The proposed method is simpler in terms of instrumentation and cost and time-effective. This method, as is, can also be implemented in case of a treaded tire

O objetivo deste trabalho é comparar diferentes formas de estimação de modelos de apreçamento de ativos. Além dos métodos tradicionais, que utilizam toda a amostra no processo de estimação dos parâmetros do modelo, será utilizado o método rolling, que estima os parâmetros através da utilização de janelas móveis de tamanho fixo. Com isso, utilizando a técnica de backtesting, procura-se averiguar se o método rolling proporciona um ganho na qualidade de ajuste em modelos de apreçamento de ativos. / The aim of this project is to compare methods of estimating asset pricing models. In addition to using traditional methods, which estimate the models parameters by using the entire sample at once, the rolling method will be used. This method estimates the models parameters by using a rolling window of fixed size through the sample. By using backtesting, we seek to investigate whether the rolling approach provides an improvement in the goodness of fit in asset pricing models.

L'adhésion cellulaire est un phénomène important en biologie. Le but de ce travail est le développement d'un modèle mécanique décrivant des phénomènes d'adhésion cellulaire à différentes échelles. La première échelle, microscopique, a pour objet la description des phénomènes cinétiques moléculaires durant le rolling. La seconde échelle, mésoscopique, est relative à la modélisation des déformations actives de la cellule durant la motilité. La troisième échelle, dite macroscopique, concerne la description de l'évolution dans le temps de l'adhésion d'une population de cellules. Les simulations réalisées mettent en évidence le rolling, et la déformation active de la cellule / Cell adhesion is an important phenomenon in biology, especially in the immune defence and tissue growth.We focus in this work on the development of a mechanical model for the description of the cell adhesion in a multiscal context. The first one is microscopic scale, which describes the molecular rupture and adhesion kinetics.At the mesoscopic scale, we model the active deformation of the cell during the motility phenomenon. At the macroscopic scale, we model the time evolution of the adhesion of cell population, under the action of the fluid. Numerical simulations emphasize the rolling phenomenon and the active deformation of a cell

Este trabalho visa analisar a influência das taxas de resfriamento e temperatura no último passe de laminação a quente de fio máquina de um aço DIN 41Cr4 sobre a microestrutura obtida após a laminação e a sua correlação com aquela resultante do tratamento térmico de esferoidização. Foi avaliado a influência da microestrutura prévia de laminação nos tempos e taxa de resfriamento do tratamento térmico necessários para garantir adequada microestrutura do aço DIN 41Cr4. Foram aplicados conceitos de laminação termomecânica através da variação dos parâmetros: temperatura no último passe de laminação (acabador) e após o último passe de laminação (formador de espiras); velocidade das esteiras do “cooling conveyor” e consequente tempo de permanência das espiras sobre a região de ventiladores e alguns parâmetros no ciclo de tratamento térmico: tempo em patamar e taxa de resfriamento durante a produção de fio máquina redondo de bitolas entre 15,88mm e 16,15mm. A avaliação da resposta às variações impostas ao processo foi realizada através de análises metalográficas de microestrutura no material laminado e no material esferoidizado (grau de esferoidização), descarbonetação e de ensaios de propriedades mecânicas como dureza e tração. A partir dos resultados buscou-se determinar a influência dos parâmetros de laminação na microestrutura do material laminado e a influência desta na resposta ao tratamento térmico de esferoidização. Foram analisadas oito diferentes condições e os resultados mostraram que maiores taxas de resfriamento resultam em microestruturas mais refinadas proporcionando uma simplificação no tratamento térmico, atendendo as propriedades desejáveis no produto final (fio máquina redondo esferoidizado). / This work aims to analyze the influence of the cooling rate, the temperature of the finishing pass and at the coil-forming during hot rolling of DIN 41Cr4 steel wire rod on the microstructure and its influence on plateau times and cooling rate during the spheroidizing heat treatment. For this study thermomechanical rolling concepts were applied through the variation of some hot rolling parameters such as: temperature at the finishing pass and at the coils-former, the cooling conveyor belts velocity and some parameters in the heat treatment cycle: soak temperature and cooling rate during the production of round wire rod with 15,88 mm and 16,15 mm diameter. The evaluation response to changes imposed on the process was evaluated by metallographic analysis of microstructure in hot rolled and spheroidized material (spheroidizing degree), hardness, decarburization and tensile test. Eight rolling conditions and cooling rates were analyzed and results showed that higher cooling rates result in finer microstructures allowing a reduction in heat treatment time to achieve the desirable properties in the final product (spheroidized round wire rod).

In this study, a novel incremental ring rolling process used in production of rings with various cross sections is examined. A basic type of this process is investigated numerically, using commercial finite element programs / MSC Superform, MSC Marc. The user defined subroutines are also utilized for flexibility in modeling. The aim of modeling is to determine the material flow for geometrical analysis, strain/stress distribution for tool force analysis and residual stresses, in a cost effective way. The process has instabilities and requires large number of incremental stages to complete a full finite element simulation. The full models are reliable but costly hence the numerical studies are focused on reliable simplified models with lower computation time. Different approaches are developed: three-dimensional segment model, improved segment model, velocity coupling model. The results of these models are compared with experimentally verified full models. Numerical parameters such as mesh type, step size, convergence ratio are examined. After verification of the model different applications to of the process is developed and physical parameters affecting the process are discussed / such as the tool path .