Cette étude s’inscrit dans une problématique d’économie d’énergie à travers l’augmentation des rendements des turbines à gaz. L’objectif est alors de mettre au point un procédé permettant la croissance et la mise en forme de céramiques d’oxydes à la composition eutectique pour l’élaboration d’aubes de turbine. En conservant leurs propriétés mécaniques jusqu’à 1700°C et en présentant une densité plus faible que les superalliages actuellement utilisés dans les aubes, ces nouveaux matériaux seraient une solution potentielle pour augmenter notablement le rendement global des turboréacteurs. Dans ce contexte, le procédé EFG utilisé pour la production de saphir a été identifié comme le procédé d’élaboration le plus prometteur, et la céramique Al2O3/YAG/ZrO2 comme la composition présentant les meilleurs propriétés mécaniques.Dans un premier temps une étude approfondie du procédé EFG utilisé par RSA le Rubis, l’entreprise dans laquelle s’est déroulé ce travail, a été menée. Nous avons alors réalisé un modèle analytique de résolution du point de fonctionnement du procédé. Ce modèle est basé sur nos connaissances dans la cristallisation de saphir et nécessite des ajustements pour convenir à la cristallisation de la céramique.Nous avons donc mesuré les propriétés de mouillage du matériau. La densité liquide et la tension de surface ont été mesurées à l’aide d’une méthode dérivée de la méthode de Wilhelmy. En outre, une simulation numérique du procédé, accompagnée de mesures de températures par thermocouple, a permis de connaitre plus précisément la distribution thermique à proximité de la zone de cristallisation. Cette étude complète les résultats du modèle.Ainsi, nous avons pu solidifier des plaques en céramique eutectique avec le procédé EFG. Plusieurs essais ont été nécessaires au dimensionnement d’une zone chaude assurant le maintien géométrique des plaques, puis de nombreux essais d’optimisation ont permis de prolonger les tirages et ainsi produire des plaques de plus grandes dimensions.Enfin, nous nous sommes intéressés à la caractérisation des céramiques. L’analyse des microstructures définit la vitesse de cristallisation maximale admissible pour réaliser des cristaux sans colonie, qui sont les défauts principaux dans ce type de microstructure. Une campagne d’essais mécaniques a également été effectuée, révélant des problématiques d’usinage nouvelles et particulièrement importantes. / This study is a part of an energy saving issues through an increase of gas turbine yields. The objective is to adapt a process for the growth of oxide ceramics with eutectic composition for the manufacture of turbine blades. Sustaining their mechanical properties up to 1700 ° C and with a lower density than superalloys which are currently used in the blades, these new materials are a potential solution to significantly increase the overall efficiency of jet engines. In this context, the EFG process used for the production of sapphire has been identified as the most promising process, and the eutectic composition Al2O3/YAG/ZrO2 as the ceramic with the best mechanical properties.First, a thorough study of the EFG process used by RSA le Ruby, the company where this work was conducted, was done. An analytic model to resolve the setting point of the process was realized. This model is based on the RSA le Rubis’s knowledge in the sapphire crystallization.The wetting properties of the material were measured to fit the model. The liquid density and surface tension were measured using a method derived from the Wilhelmy method. In addition, a numerical simulation of the process, accompanied by temperature measurement by thermocouple, was done. It allows to know the temperature distribution close to the crystallization zone with a better accuracy.Thus, eutectic ceramic plates were solidified with the EFG process. Several tests were necessary in order to design a process ensuring the solidification of net shaped plates. Then lot of optimization pulls have been done to extend the plate’s dimensions.Finally, some characterizations were achieved on the plates. Analysis of the microstructure defines the maximum rate of crystallization to produce crystals without colonies, which are the main defect in these kinds of microstructures. A campaign of mechanical testing was also performed, revealing new machining problems which are particularly important.

Es precisamente a partir de la discusión con Nietzsche sobre el poder durante 1930-40 que Heidegger compromete explícitamente su pensamiento con la cuestión de la técnica. Si bien, la técnica no piensa, sí está abierta al destino del mundo, y, por lo tanto, da mucho que pensar, lo cual, supone replantear el problema en torno a los límites de la tecnología. En este sentido, el llamado a rememorar el ser no sería sino una respuesta a la amenaza de la especialización técnica que se cierne sobre la realidad del mundo. En estas líneas, nos proponemos llevar a cabo una exploración del mundo de la tecnología como una apertura a la experiencia de la realidad humana bajo el signo del nihilismo y la metafísica consumada en la perspectiva del pensamiento de Martín Heidegger. Por lo tanto, no sólo como fragmentación y empobrecimiento cognitivo de la imaginación crítica, sino, también como epifanía o claridad del ser. La imposición (Ge-stell) objetivante y separadora de la naturaleza constituye en un sentido esencial la permanente negación de la finitud de la vida donde el verdadero peligro no radica sino en la completa objetivación del mundo, cuyo correlato es la reducción de la subjetividad a una función de ese engranaje. Para Heidegger la pregunta por sentido del ser está en la base de aquella sobre el sentido de la existencia, y, por lo tanto, constituye necesariamente apertura al mundo de las valoraciones y acciones humanas. El trazado de una ontología fundamental encuentra su piedra angular en una ontología regional de la “existencia” en tanto que la idea de ente se mueve en la línea de una precomprensión del ser que finalmente remite al ahí del ser que es el hombre. Las preguntas esenciales que surgen y se agitan dando vida a estos análisis son: ¿Estamos realmente ante un empobrecimiento sin retorno de la capacidad de comprender nuestro entorno y darle un sentido unitario a la realidad? ¿El despliegue de la tecnología planetaria como voluntad de poder introduce secretamente una “pérdida” de la realidad y el sentido? O bien, el reverso necesario de las anteriores; ¿Es posible experimentar esta caída (o destitución de las coordenadas metafísicas esenciales) como un pensamiento de la promesa por-venir.

Este trabalho visa propor uma metodologia de análise da variabilidade do tempo de atraso de propagação no FPGA. Para alcançar esse objetivo são utilizados três circuitos diferentes: o circuito 1 mede a diferença de atrasos de dois circuitos, o circuito 2 identifica o atraso menor de dois circuitos e, por fim, o terceiro circuito que consiste do oscilador em anel. Cada circuito foi avaliado individualmente numa estrutura BIST, implementada nos FPGA XC3S200-FT256 e EP2C35F672C6. Os métodos utilizados para análise dos dados foram a média móvel, o plano de mínimos quadrados e o teste t-student. A metodologia permitiu mostrar a variabilidade within-die e suas componentes sistêmica e randômica. / This work aims to propose a methodology of analysis of variability of propagation-delay time in FPGA. To achieve this goal three different circuits are implemented: the circuit 1 measures the delay difference of two logic paths, the circuit 2 identifies smallest delay of two logic paths, and finally the third circuit consists of a ring oscillator. Each circuit has been assessed individually in a BIST structure, implemented in FPGAs XC3S200-FT256 and EP2C35F672C6. The methods used for data analysis were the moving average, least-squares plane and the t-student test. The methodology has allowed to evaluate the within-die variability and its systemic and random components.

No forjamento em matriz aberta o tempo gasto com retrabalhos e descarte de material não conforme gera custos e atraso no atendimento ao cliente. A fim de minimizar estas perdas, realizou-se uma revisão dos principais conceitos e fundamentos do processo de forjamento a quente em matriz aberta que influenciam na qualidade interna do produto. Com o intuito de desenvolver o processo de forjamento a quente em matriz aberta de chapas do aço W.NR. 1.2714 com espessura de 311 mm, largura de 634 mm e comprimento de 6000 mm, avaliou-se as descontinuidades internas deste produto. Através de análises preliminares realizadas, foi possível observar que a descontinuidade interna típica tratava-se de vazio. Com este resultado, desenhou-se um projeto experimental com corpos de prova quadrados com defeitos falsos de 30 mm de diâmetro e forjados para simular uma das etapas do forjamento de chapas. Foram selecionadas três combinações de matrizes e dois tempos de encharque. Todos os corpos de prova foram aquecidos no mesmo forno sob mesmas condições e forjados com duas reduções de 50 mm cada (33% - deformação relativa total), com giro de 180 graus entre elas. Após o resfriamento ao ar, as amostras sofreram alívio de tensões e foram cortadas em serra a 150 mm da extremidade do furo. As variáveis respostas do plano experimental foram a área do furo, o alargamento e o alongamento. A amostra forjada com a combinação de matriz AC, composta pela matriz funil na parte superior e mesa de forjamento na parte inferior e tempo de encharque de 7h teve o furo caldeado. Com todas as combinações de matrizes, o tempo de encharque de 7h levou a menor área do furo, maior alargamento e maior alongamento que o tempo de 11h. / In open die forging the time spent on rework, and disposal of non-compliant material, generates costs and delays in customer service. To minimize these losses, a review of key concepts and fundamentals of the process of open die forging was carried out emphasizing the internal quality of the product. In order to develop the process of open die hot forging in plate steel W.NR 1.2714 with a thickness of 311 mm, width 634 mm and a length of 6000 mm, internal discontinuities of this product were evaluated. Through preliminary analysis was possible to observe that the typical internal discontinuity were voids. With this result, experiments were designed for square specimens with false defects of 30 mm in diameter, which were forged in order to simulate one of the steps in the forging of plates. Three combinations of dies and two soak times were selected. All samples were heated in the same furnace on the same conditions and forged with two reductions of 50 mm each (33% - total relative deformation) with 180 degrees among them. After air cooling, the samples were heated up to promote a stress relief and were cut at a position 150 mm from the edge of the hole. Output variables were the area of the hole, widening and lengthening. The sample forged with the combination of die AC, with funnel die at the top and forging table at the bottom and the soaking time of 7 hours had the hole closed. For all combinations of dies, the soaking time of 7 hours led to a lower area of the hole, higher widening and lengthening than for 11hours soak time.

O presente trabalho estuda o processo de estampagem incremental em chapas de alumínio puro, descrevendo as ferramentas e um suporte prensa chapas. Estuda e pesquisa bibliograficamente e experimentalmente o processo de estampagem incremental. O trabalho apresenta os procedimentos de caracterização utilizados para determinar os limites do processo, aplicáveis para chapas de 0,5 mm de espessura em alumínio puro. A caracterização da chapa, juntamente com o ensaio mecânico de tração e os testes práticos de estampagem fornecerão um panorama da estampagem incremental, para algumas situações diversas sobre o tema. Para a execução dos testes práticos foi fabricado um dispositivo prensa chapas e um punção, matriz incremental e ferramenta de estampagem incremental, também foram feitas adaptações na máquina CNC, centro de usinagem CNC com três eixos. / This paper studies the process of incremental sheet forming, in plates the aluminum pure, describing the tools and support a press plates. Studies and literature search and experimentally the process of stamping incremental. The work presents the characterization of procedures used to determine the limits of the process, applicable to plates of 0.5 mm thick pure aluminum. The characterization of the plate, along with mechanical traction test and practical tests of printing provide an overview of incremental printing, for some different situations on the subject. For the practical implementation of the tests was a device manufactured press plates and a puncture, matrix and incremental tool for stamping incremental, were also made adjustments in the CNC machine, CNC machining center with three axles.

Esse trabalho propõe a investigação da geometria dos contornos internos de eixos vazados para aerogeradores quando aplicados mandris com diferentes diâmetros ao longo de seu comprimento no forjamento incremental em matriz aberta. Tem-se por finalidade a fabricação de um mandril que proporcione à peça forjada formato mais perto do formato final proposto. Foram estudados através do uso de simulações numéricas computacionais com o software Simufact.forming 12 e ensaios com o material modelo plasticina possíveis geometrias de mandris, variando a angulação na região de troca de diâmetros ao longo do comprimento entre 0˚, 30˚ e 60˚, e analisados o comportamento do escoamento do material na região. Com o processo simulatório concluído, foi produzido o mandril que apresentou melhor desempenho e foram realizados testes práticos. No total, duas peças foram forjadas e analisados seus resultados. A geometria proposta da peça foi alcançada, confirmando a escolha da cinemática do processo. A temperatura do mandril foi aferida e comparada com a temperatura durante a simulação, onde no último passe, a medida foi 720°C e a simulada em torno de 620°C. As forças de forjamento apresentaram diferença entre a simulação e forjado na média de 7,6%. / This work proposes the investigation of the internal contour of hollow shafts for wind turbines when applied mandrels with different diameters along its length in incremental open-die forging. It is intended to manufacture a mandrel to provide a forged part closer to the final proposed geometry. Studies were conducted using the numerical computer simulations software Simufact.forming 12 and models of plasticine aiming possible mandrel geometries, varying the angle of the different-diameters region along the length between 0˚, 30˚ and 60˚ and analyzed the behavior of the material flow in the region. As the simulation process was concluded, the mandrel with the best performance was produced and practical tests were performed. In total, two workpieces were forged and analyzed its results. The proposed geometry was achieved, confirming the choice of process kinematics. The temperature of the mandrel was measured and compared with the temperature during the simulation at the last pass, the measurement resulted in 720°C and the simulated around 620°C. The forging forces showed differences between simulation and forging of an average of 7.6%.

Law / LL.M.

O presente trabalho estuda o processo de estampagem incremental em chapas de alumínio puro, descrevendo as ferramentas e um suporte prensa chapas. Estuda e pesquisa bibliograficamente e experimentalmente o processo de estampagem incremental. O trabalho apresenta os procedimentos de caracterização utilizados para determinar os limites do processo, aplicáveis para chapas de 0,5 mm de espessura em alumínio puro. A caracterização da chapa, juntamente com o ensaio mecânico de tração e os testes práticos de estampagem fornecerão um panorama da estampagem incremental, para algumas situações diversas sobre o tema. Para a execução dos testes práticos foi fabricado um dispositivo prensa chapas e um punção, matriz incremental e ferramenta de estampagem incremental, também foram feitas adaptações na máquina CNC, centro de usinagem CNC com três eixos. / This paper studies the process of incremental sheet forming, in plates the aluminum pure, describing the tools and support a press plates. Studies and literature search and experimentally the process of stamping incremental. The work presents the characterization of procedures used to determine the limits of the process, applicable to plates of 0.5 mm thick pure aluminum. The characterization of the plate, along with mechanical traction test and practical tests of printing provide an overview of incremental printing, for some different situations on the subject. For the practical implementation of the tests was a device manufactured press plates and a puncture, matrix and incremental tool for stamping incremental, were also made adjustments in the CNC machine, CNC machining center with three axles.

Este trabalho visa propor uma metodologia de análise da variabilidade do tempo de atraso de propagação no FPGA. Para alcançar esse objetivo são utilizados três circuitos diferentes: o circuito 1 mede a diferença de atrasos de dois circuitos, o circuito 2 identifica o atraso menor de dois circuitos e, por fim, o terceiro circuito que consiste do oscilador em anel. Cada circuito foi avaliado individualmente numa estrutura BIST, implementada nos FPGA XC3S200-FT256 e EP2C35F672C6. Os métodos utilizados para análise dos dados foram a média móvel, o plano de mínimos quadrados e o teste t-student. A metodologia permitiu mostrar a variabilidade within-die e suas componentes sistêmica e randômica. / This work aims to propose a methodology of analysis of variability of propagation-delay time in FPGA. To achieve this goal three different circuits are implemented: the circuit 1 measures the delay difference of two logic paths, the circuit 2 identifies smallest delay of two logic paths, and finally the third circuit consists of a ring oscillator. Each circuit has been assessed individually in a BIST structure, implemented in FPGAs XC3S200-FT256 and EP2C35F672C6. The methods used for data analysis were the moving average, least-squares plane and the t-student test. The methodology has allowed to evaluate the within-die variability and its systemic and random components.

abstract: Die-off of screwbean mesquite (Prosopis pubescens), a species native to the American Southwest, has been documented regionally within the last decade. Historical causes for episodic mortality of the more widely distributed velvet mesquite (Prosopis velutina) and honey mesquite (Prosopis glandulosa) include water table declines and flood scour. Causes of the recent die-offs of P. pubescens have received little study. Numerous riparian restoration projects have been implemented regionally that include screwbean mesquite. Restoration propagules from foreign sources can introduce diseases, and low genetic diversity plantings may allow for disease irruptions. I asked: 1) Are die-offs associated with a particular age class, 2) Is die-off suggestive of a pathogen or related to specific environmental stressors, 3) Are mortality influences and outcomes the same between restoration and local populations, 4) Are particular land uses and management associated with die-off, and 5) Are populations rebounding or keeping pace with mortality? I documented the screwbean mesquite population status at rivers and wetlands in Arizona with varying levels of restoration. I used logistic regression and Pearson correlation analysis to explore mortality response to site factors and disease related variables. I compared mortality response and disease severity between local and restoration populations. Biotic damage surfaced as the most important factor in statistical analyses, suggesting that mortality was caused by a pathogen. Mortality was greatest for young size classes (3 to 14 cm), and biotic damage was higher for individuals at infrequently flooded areas. Strong differences were not found between local and restoration populations – however restoration populations were less stressed and had lower biotic damage. Novel urban and restored sites may provide refuge as site conditions at other locations deteriorate. A culmination of past water diversion, development and land use may be surfacing, rendering riparian species vulnerable to diseases and triggering such events as region-wide die-off. / Dissertation/Thesis / Masters Thesis Plant Biology 2016