Thesis (Ph. D.)--University of Wisconsin--Madison, 1958. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 240-244).

Neste trabalho realizaram-se varias nitretações e nitrocarbonetações a plasma em um aço AISI 4140 temperado e revenido, com o objetivo de avaliar a magnitude do parâmetro “composição gasosa” nas propriedades metalúrgicas das camadas formadas após a nitretação. Para a realização deste trabalho foram necessárias adaptações do forno e experimentos prévios para verificar a influência do posicionamento das peças na câmara. Todas as superfícies nitretadas para o estudo das misturas gasosas, foram caracterizadas quanto aos seguintes parâmetros: dureza superficial, perfis de dureza e de composição química, fases formadas nas primeiras regiões da superfície, espessura da camada branca, tenacidade superficial, rugosidade e morfologia topográfica. As amostras provenientes do estudo das variáveis térmicas da câmara foram estudadas quanto à espessura da camada branca e perfis de dureza e composição química. Encontrou-se que as variáveis térmicas são determinantes em termos de alterações no processo e que, cuidados com simetria, devem ser levados em consideração em estudos similares em equipamentos sem aquecimento auxiliar nas paredes. Verificou-se também amplas variações nas propriedades microestruturais das amostras tratadas sob as diferentes misturas gasosas postas em uso e, foi possível sugerir com base nos resultados e na literatura, aplicações para alguns dos casos estudados. / In this work various plasma nitriding and plasma nitrocarburizing treatments with hardened and tempered AISI 4140 steel were carried out. The main aim was evaluating the gas mixture influence on metallurgical properties of plasma nitriding and nitrocarburizing layers. For the realization of this study, furnace adaptations and previous experiments in order to verify the parts position influence on final treatments results were necessary. The samples that were nitrided in previous experiments were characterized concerning of compound layer, hardness and chemical composition profiles. All nitride surfaces, were characterized with the parameters: surface hardness, hardness and chemical composition profiles, phases composition on surface, thickness of compound layer, surface toughness, surface roughness and topographical morphology. It was found that thermal parameters are determinants in order to modify the process. Care must be taken about symmetry with this kind of equipment that have no auxiliary heating wall. Later, large variations on microstructural properties in samples under different gas conditions were verified and applications to some cases were proposed.

Neste trabalho realizaram-se varias nitretações e nitrocarbonetações a plasma em um aço AISI 4140 temperado e revenido, com o objetivo de avaliar a magnitude do parâmetro “composição gasosa” nas propriedades metalúrgicas das camadas formadas após a nitretação. Para a realização deste trabalho foram necessárias adaptações do forno e experimentos prévios para verificar a influência do posicionamento das peças na câmara. Todas as superfícies nitretadas para o estudo das misturas gasosas, foram caracterizadas quanto aos seguintes parâmetros: dureza superficial, perfis de dureza e de composição química, fases formadas nas primeiras regiões da superfície, espessura da camada branca, tenacidade superficial, rugosidade e morfologia topográfica. As amostras provenientes do estudo das variáveis térmicas da câmara foram estudadas quanto à espessura da camada branca e perfis de dureza e composição química. Encontrou-se que as variáveis térmicas são determinantes em termos de alterações no processo e que, cuidados com simetria, devem ser levados em consideração em estudos similares em equipamentos sem aquecimento auxiliar nas paredes. Verificou-se também amplas variações nas propriedades microestruturais das amostras tratadas sob as diferentes misturas gasosas postas em uso e, foi possível sugerir com base nos resultados e na literatura, aplicações para alguns dos casos estudados. / In this work various plasma nitriding and plasma nitrocarburizing treatments with hardened and tempered AISI 4140 steel were carried out. The main aim was evaluating the gas mixture influence on metallurgical properties of plasma nitriding and nitrocarburizing layers. For the realization of this study, furnace adaptations and previous experiments in order to verify the parts position influence on final treatments results were necessary. The samples that were nitrided in previous experiments were characterized concerning of compound layer, hardness and chemical composition profiles. All nitride surfaces, were characterized with the parameters: surface hardness, hardness and chemical composition profiles, phases composition on surface, thickness of compound layer, surface toughness, surface roughness and topographical morphology. It was found that thermal parameters are determinants in order to modify the process. Care must be taken about symmetry with this kind of equipment that have no auxiliary heating wall. Later, large variations on microstructural properties in samples under different gas conditions were verified and applications to some cases were proposed.

Neste trabalho realizaram-se varias nitretações e nitrocarbonetações a plasma em um aço AISI 4140 temperado e revenido, com o objetivo de avaliar a magnitude do parâmetro “composição gasosa” nas propriedades metalúrgicas das camadas formadas após a nitretação. Para a realização deste trabalho foram necessárias adaptações do forno e experimentos prévios para verificar a influência do posicionamento das peças na câmara. Todas as superfícies nitretadas para o estudo das misturas gasosas, foram caracterizadas quanto aos seguintes parâmetros: dureza superficial, perfis de dureza e de composição química, fases formadas nas primeiras regiões da superfície, espessura da camada branca, tenacidade superficial, rugosidade e morfologia topográfica. As amostras provenientes do estudo das variáveis térmicas da câmara foram estudadas quanto à espessura da camada branca e perfis de dureza e composição química. Encontrou-se que as variáveis térmicas são determinantes em termos de alterações no processo e que, cuidados com simetria, devem ser levados em consideração em estudos similares em equipamentos sem aquecimento auxiliar nas paredes. Verificou-se também amplas variações nas propriedades microestruturais das amostras tratadas sob as diferentes misturas gasosas postas em uso e, foi possível sugerir com base nos resultados e na literatura, aplicações para alguns dos casos estudados. / In this work various plasma nitriding and plasma nitrocarburizing treatments with hardened and tempered AISI 4140 steel were carried out. The main aim was evaluating the gas mixture influence on metallurgical properties of plasma nitriding and nitrocarburizing layers. For the realization of this study, furnace adaptations and previous experiments in order to verify the parts position influence on final treatments results were necessary. The samples that were nitrided in previous experiments were characterized concerning of compound layer, hardness and chemical composition profiles. All nitride surfaces, were characterized with the parameters: surface hardness, hardness and chemical composition profiles, phases composition on surface, thickness of compound layer, surface toughness, surface roughness and topographical morphology. It was found that thermal parameters are determinants in order to modify the process. Care must be taken about symmetry with this kind of equipment that have no auxiliary heating wall. Later, large variations on microstructural properties in samples under different gas conditions were verified and applications to some cases were proposed.

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Yes / Three equations of state with a group contribution model for binary interaction parameters were employed to calculate the vapor-liquid equilibria of synthetic and real natural gas mixtures with heavy fractions. In order to estimate the binary interaction parameters, critical temperatures, critical pressures and acentric factors of binary constituents of the mixture are required. The binary interaction parameter model also accounts for temperature. To perform phase equilibrium calculations, the heavy fractions were first discretized into 12 Single Carbon Numbers (SCN) using generalized molecular weights. Then, using the generalized molecular weights and specific gravities, the SCN were characterized. Afterwards, phase equilibrium calculations were performed employing a set of (nc + 1) equations where nc stands for the number of known components plus 12 SCN. The equations were solved iteratively using Newton's method. Predictions indicate that the use of binary interaction parameters for highly sour natural gas mixtures is quite important and must not be avoided. For sweet natural gas mixtures, the use of binary interaction parameters is less remarkable, however.

Unlike the conventional "lock-and-key" sensor design in which one sensor is finely tuned to respond to one analyte, the sensor array approach employs multiple sensors in which one sensor responds to many analytes. Consequently, signal processing algorithms must be used to identify the analyte present from the array's response. The analyte identification process becomes significantly more complicated when a mixture of analytes is presented to the sensor array. Conventional methods that are employed in gas mixture identification are plagued by several design issues like: complexity, scalability, and flexibility. This thesis derives and develops a novel method, fingerprint-based ICA (FICA), to extract and identify individual analytes from a sensor array's response to a gas mixture of the analytes. FICA is a simple, flexible, and scalable signal processing system that employs independent components analysis (ICA) to extract and identify individual analytes present in a gas mixture; separation and identification of gas mixtures using ICA has not been investigated previously. FICA takes a fundamentally different approach that reflects the underlying property of gas mixtures: gas mixtures are composed of individual analyte responses. Conventional signal processing methods that identify gas mixtures have been developed and implemented in this work; this helps us understand the drawbacks in the conventional approach. FICA's performance is compared to the performance of conventional methods using metric like error rate and false positives rate. Properties like flexibility, scalability, and the data requirements for both conventional methods and FICA are examined. Results obtained in this work indicates that FICA results in lower error rates, and it's performance is better than conventional methods like multi-stage multi-stage support vector machines, and PCR. Furthermore, FICA provides the most simple, scalable, and flexible signal processing system. / Master of Science

<p>This thesis focuses on the numerical and theoretical studies of gas quenching in industrial furnaces. Gas quenching is the rapid cooling of metal pieces, aiming at forcing a phase transformation of the metal structure to improve its mechanical properties. The numerical methodology has been evaluated with respect to the desired accuracy and different aspects of the flow with importance for achieving an optimized process have been investigated. Initially, attention was paid to the flow and heat transfer fields both in an empty furnace and in a furnace loaded with different charges with the objective to study the influence of the charge configuration on the flow and heat transfer uniformity. This study led to the identification of several possible improvements, which are currently being implemented by the industrial partners of this project. As earlier studies had shown the importance of flow uniformity on the quality of the heat treatment, the subsequent work focused substantially on the flow uniformity upstream of the quenching zone resulting in design recommendations for the particular type of furnace under consideration. The dependence of the performance of the coolant medium on its composition was investigated theoretically and an analysis of most important parameters was carried out. Improved knowledge of the effect of gas mixture composition on heat transfer was added to the body of knowledge already available.</p>

This thesis focuses on the numerical and theoretical studies of gas quenching in industrial furnaces. Gas quenching is the rapid cooling of metal pieces, aiming at forcing a phase transformation of the metal structure to improve its mechanical properties. The numerical methodology has been evaluated with respect to the desired accuracy and different aspects of the flow with importance for achieving an optimized process have been investigated. Initially, attention was paid to the flow and heat transfer fields both in an empty furnace and in a furnace loaded with different charges with the objective to study the influence of the charge configuration on the flow and heat transfer uniformity. This study led to the identification of several possible improvements, which are currently being implemented by the industrial partners of this project. As earlier studies had shown the importance of flow uniformity on the quality of the heat treatment, the subsequent work focused substantially on the flow uniformity upstream of the quenching zone resulting in design recommendations for the particular type of furnace under consideration. The dependence of the performance of the coolant medium on its composition was investigated theoretically and an analysis of most important parameters was carried out. Improved knowledge of the effect of gas mixture composition on heat transfer was added to the body of knowledge already available. / QC 20101019