Les aciers de construction au carbone manganèse (C-Mn) sont largement utilisés pour diverses applications mécaniques, et en particulier pour les tuyauteries de circuit secondaire des centrales nucléaires de type Réacteurs à Eau sous Pression (REP). La robustesse des composants des circuits sous pression des REP vis-à-vis de la fissuration doit être démontrée, tant au niveau de la conception que de l’exploitation. Les aciers au C-Mn sont sensibles au vieillissement sous déformation qui entraîne une chute importante de ductilité et de ténacité entre 150 et 350°C,températures de service des tuyauteries du circuit secondaire. Ce phénomène est dû à une interaction entre les atomes de solutés et les dislocations, et peut se traduire entre autres par une sensibilité négative de la contrainte à la vitesse de déformation, et des localisations de la déformation plastique (Lüders, Portevin – Le Chatelier). L’origine physique du vieillissement sous déformation a été beaucoup étudiée, surtout dans les métaux purs, en relation avec le phénomène Portevin-Le Chatelier (PLC), mais son influence sur les propriétés mécaniques et notamment la rupture reste très controversée. L’objectif de la thèse est de modéliser le comportement et la rupture d’un acier au C-Mn dans un large domaine de température compris entre 20 et 350°C, en tenant compte des phénomènes de vieillissement sous déformation, et en particulier des localisations de déformation. Le comportement et la rupture de l’acier au C-Mn étudié ont été caractérisés expérimentalement dans le domaine 20-350°C à l’aide d’essais de traction sur éprouvettes lisses, sur éprouvettes axisymétriques entaillées, et d’essais de déchirure sur éprouvettes CT. Le modèle d’Estrin Kubin McCormick, prenant en compte le vieillissement sous déformation, a été identifié dans cette même gamme de température et la plupart des effets du vieillissement sous déformation ont pu être simulés numériquement : sensibilité négative de la contrainte d’écoulement à la vitesse de déformation, bandes de Lüders, effet PLC, modification des propriétés mécaniques de traction… Le modèle ainsi identifié a été appliqué à l’étude de la rupture d’éprouvettes lisses, entaillées et CT. La baisse de l’allongement réparti est bien décrite en traction sur éprouvettes lisses. Pour prévoir la rupture des éprouvettes entaillées, l’approche locale de la rupture a été appliquée (modèle de Rice et Tracey). Cette étude a donc permis de disposer d’un modèle prenant en compte le vieillissement sous déformation de 20°C à 350°C et décrivant les localisations de déformation plastique de type Lüdersou PLC, pour différentes géométries d’éprouvettes. Ce modèle a été utilisé pour simuler la rupture des aciers au C-Mn, suscitant ainsi une vision nouvelle pour comprendre la baisse de ductilité associée au vieillissement dynamique. / Pas de résumé en anglais disponible.

Orientadores: Elizabete Jordão, Moysés Alberto Navarro / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-20T11:58:32Z (GMT). No. of bitstreams: 1 Rezende_HugoCesar_D.pdf: 10614958 bytes, checksum: aa2b2ce9d9ec481bd44e74cc217832a2 (MD5) Previous issue date: 2012 / Resumo: O escoamento monofásico termicamente estratificado ocorre em tubulações horizontais onde duas camadas diferentes de um mesmo líquido escoam separadamente, sem que ocorra mistura significativa entre as camadas, devido às baixas velocidades e à diferença de densidade (e temperatura). As consequências desse fenômeno não foram consideradas no projeto da maioria das centrais nucleares atualmente em operação. Entretanto, em alguns componentes de centrais nucleares, as diferenças de temperatura podem atingir cerca de 200 °C em uma região bastante estreita nas proximidades da interface entre as camadas de água fria e quente. Nesta condição, as fortes tensões geradas pelas diferenças de dilatação podem comprometer a integridade estrutural e a vida útil de tubulações relacionadas aos sistemas de segurança dessas centrais nucleares. Com o objetivo de estudar o fenômeno da estratificação foi projetada e construída a Instalação de Testes de Estratificação Térmica (ITET), tendo sido realizada uma série de experimentos simulando o bocal de injeção do gerador de vapor de uma central nuclear tipo PWR. Foram estudadas a evolução e as configurações de escoamento em regime de estratificação térmica, assim como a influência do número de Froude nos gradientes de temperatura, na posição da interface entre as camadas de água fria e de água quente e no aparecimento de oscilações desta interface. Os experimentos foram realizados com número de Froude variando de 0,02 a 0,4...Observação: O resumo, na íntegra, poderá ser visualizado no texto completo da tese digital / Abstract: One phase thermally stratified flows occur when two different layers of the same liquid at different temperatures flow separately in horizontal pipes without appreciable mixing due to the low velocities and difference in density (and temperature). The phenomenon was not considered in the design stage of most of the operating nuclear power plants. However, temperature differences of about 200 °C have been found in a narrow band around the hot and cold water interface in components under stratified flows. Loadings due to this phenomenon affected the integrity of safety related piping systems. The Thermal Stratification Test Facility (ITET), built to allow the experimental simulation of the thermal stratification, is presented so as the results of some experiments simulating one phase thermally stratified flows in geometry and flow condition similar to a nuclear reactor steam generator nozzle. They have the objective of studying the flow configurations and understanding the evolution of the of thermal stratification process. The driving parameter considered to characterize flow under stratified regime due to difference in specific masses is the Froude number. Different Froude numbers, from 0.02 to 0.4, were obtained in different testes by setting injection cold water flow rates and hot water initial temperatures as planned in the test matrix. Results are presented showing the influence of Froude number on the hot and cold water interface position, temperature gradients and striping phenomenon...Note: The complete abstract is available with the full electronic document / Doutorado / Sistemas de Processos Quimicos e Informatica / Doutor em Engenharia Química

Buried pipeline networks play a vital role in the transportation of oil and natural gas from centers of production to centers of consumption. A common manufacturing technique for such pipes is the UOE process, where a flat steel plate is first formed into a U shape, then into an O shape, welded at the seam, and mechanically expanded before being shipped on site. The UOE forming process deforms the pipe material plastically and induces residual strains in the pipe. Such pipes are commonly buried on side and then are pressurized under the high head of the fluids they convey which induce hoop stresses as high as 80% of the pipe yield strength. When buried pipelines cross the regions of discontinuous permafrost, they undergo differential frost heaving, inducing significant bending deformations, which potentially induce local buckling in the pipe wall. To control local buckling, design standards impose threshold limits on buckling strains. Such threshold values are primarily based on costly full-scale experimental results. Past nonlinear finite element analysis attempts aiming at determining the threshold buckling strains have neglected the presence of residual stresses induced by the UOE forming and were thus found to grossly overestimate the buckling strains compared to those based experiments. Within the above context, the present study focuses on developing a numerical technique to predict the residual stresses induced during UOE forming, and incorporating the induced residual stresses in 3D nonlinear FEA modeling to more reliably predict buckling strain limits. Comparisons with conventional analysis techniques that omit residual stresses reveal the importance of incorporating residual stresses induced in forming when quantifying buckling strains.

Orientadores: Maria Angela de Almeida Meireles Petenate, Tânia Forster Carneiro / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-27T17:37:35Z (GMT). No. of bitstreams: 1 CardenasToro_FiorellaPatricia_D.pdf: 20104541 bytes, checksum: 3c5867a10520478debcff56ff3a375e4 (MD5) Previous issue date: 2015 / Resumo: A fibra de palma prensada (Elaes guineensis) é um resíduo procedente da indústria de extração de óleo de palma que possui na sua composição compostos bioativos tais como alfa- e beta-caroteno, assim como os polissacarídeos (celulose e hemicelulose). Estes compostos podem ser recuperados mediante processos de extração e hidrólise com a finalidade de produzir de forma sustentável, extratos enriquecidos com carotenoides e produtos hidrolisados com aplicação na indústria química, de alimentos e farmacêutica. Entre as tecnologias que utilizam solventes limpos a altas e baixas pressões, temos a extração por Soxhlet (LPSE-SOX), extração por percolação (LPSE-PE), extração por líquido pressurizado (PLE), extração com fluído supercrítico (SFE) e hidrólise subcrítica com água (SubWH). Neste trabalho, um processo integrado utilizando SFE e SubWH foi proposto como modelo de aproveitamento integral da fibra de palma prensada. O estudo incluiu a avaliação dos efeitos dos parâmetros operacionais de extração: temperatura e pressão empregando uma razão mássica de solvente por massa de matéria-prima (S/F) de 30 na obtenção de um extrato rico em carotenoides; e dos parâmetros operacionais de hidrólise: temperatura, pressão, S/F e tempo de residência na produção de monossacarídeos e oligossacarídeos nos produtos hidrolisados. Após esse primeiro estudo, um segundo estudo dos processos de extração LPSE-SOX, LPSE-PE e PLE utilizando etanol como solvente limpo foi realizado com o objetivo de explorar as condições de operação: temperatura, pressão e vazão na razão S/F de 20, que favorecessem a produção de um extrato rico em carotenoides (alfa e beta-caroteno) incluindo a avaliação econômica de cada processo. Os resultados do primeiro estudo para o SFE utilizando dióxido de carbono como solvente indicaram que o maior rendimento de carotenoides totais no extrato foi 800 ± 200 ug beta-caroteno/g extrato na condição de 318 K (45°C) e 15 MPa. Posteriormente, os experimentos de hidrólise subcrítica da fibra de palma desengordurada obtiveram uma mistura de produtos hidrolisados e produtos de degradação de açúcares, sendo a condição de 523 K (250°C), 15 MPa, tempo de residência de 2,5 min e S/F de 120 aquela com maiores rendimentos de açúcares redutores totais (22,9 g glicose/100 g carboidrato). Este estudo mostrou a viabilidade de integração de processos para o melhor aproveitamento da fibra de palma prensada. Na segunda parte do estudo, os processos de extração com etanol à baixa e alta pressão com melhores rendimentos de carotenoides foram: 305 ± 18 ug alfa-caroteno/g extrato e 713 ± 46 ug beta-caroteno/g extrato para o processo PLE na condição de 308 K (35°C), 4 MPa, 2,4 g/min e 37 min; 142 ± 13 ug alfa-caroteno/g extrato e 317 ± 46 ug beta-caroteno/g extrato para o processo LPSE-SOX num tempo de 6 h; 79 ± 9 ug alfa-caroteno/g extrato e 195 ± 20 ug beta-caroteno/g extrato para o processo LPSE-PE na condição de 308 K (35°C), 2,4 g/min e 37 min. Os custos de manufatura (COM) na escala industrial de 0,5 m3 utilizando 2 extratores em modo contínuo foram de US$98,1/g carotenoide para o processo LPSE-SOX; US$48,9/g carotenoide para o processo LPSE-PE e US$28,7/g carotenoide para o processo PLE. Diante dos resultados obtidos no primeiro e segundo estudo, um estudo cinético dos processos de extração a altas pressões PLE e SFE foi realizado nas condições operacionais que obtiveram altos rendimentos de carotenoides no extrato. O rendimento de extração na razão S/F de 7 e 10 resultou em 90% do total do extrato obtido no final da extração para o processo PLE e SFE, respectivamente. Para o processo PLE e SFE os menores valores de COM foram encontrados para as capacidades de extratores industriais de 0,05 m3 e 0,5 m3. Para o processo PLE, na razão S/F de 8 obtiveram-se os menores valores de COM e COM* específico: US$30,4/kg extrato e US$0,02/g carotenoide para 0,5 m3. Uma tendência similar foi observada para o processo SFE com valores de COM de US$30,8/kg extrato e US$0.08/g carotenoide para 0,5 m3. Baseados nestes resultados, o processo PLE apresenta uma melhor vantagem econômica que o processo SFE e pode ser considerado como a primeira etapa do processo integrado de obtenção de extrato rico em carotenoides seguido do processo SubWH para a obtenção de produtos hidrolisados / Abstract: Pressed palm fiber (Elaes guineensis) is a residue obtained from the palm oil extraction industry that is a source of bioactive compounds such as alpha- and beta-carotene present in the residual oil and polysaccharides (cellulose and hemicellulose), which can be recovered by extraction and hydrolysis processes in order to produce in a sustainable manner extracts enriched with carotenoid for direct application in food industry as additives and/or formation of hydrolysate products with high yields of monosaccharides and oligosaccharides with application in the chemical food and pharmaceutical industry. Technologies that use clean solvents at high and low pressures include Soxhlet extraction (LPSE-SOX), extraction by percolation (LPSE-PE), pressurized liquid extraction (PLE), supercritical fluid extraction (SFE) and subcritical hydrolysis (SubWH). In this work, an integrated process using SFE and SubWH was proposed as the model of completely utilization of pressed palm fiber. The study included the evaluation of the effects of operating parameters of extraction: temperature and pressure at the ratio of solvent mass to feed mass (S/F) of 30 in the obtaining of extracts rich in carotenoids and the study of operational parameters of hydrolysis: temperature, pressure, S/F and residence time on the production of monosaccharides and oligosaccharides in the hydrolyzed products. After this first study, a second study of the extraction processes LPSE-SOX, LPSE-PE and PLE using ethanol as a clean solvent was conducted in order to explore the operational conditions: temperature, pressure and flow rate at S/F ratio of 20, which promotes the production of an extract rich in carotenoids (alpha- and beta-carotene) including the economic evaluation of each process. Results of the first study for SFE using carbon dioxide as a solvent indicated that the highest yield of total carotenoids in the extract was 800 ± 200 ug alpha-carotene/g extract at the condition of 318 K (45°C) and 15 MPa. Thereafter, the experiments of subcritical hydrolysis of defatted pressed palm fiber resulted in a mixture of hydrolysate products and sugar degradation products, where the condition of 523 K (250°C), 15 MPa, residence time of 2.5 min and S/F 120 presented the highest yield of total reducing sugars (glucose 22.9 g/100 g carbohydrate). In the second part of this study, the extraction processes with ethanol at low and high pressure with highest yields of carotenoids in extracts were: 305 ± 18 ug alpha-carotene/g extract and 713 ± 46 ug beta-carotene/g extract for the PLE process at the condition of 308 K (35°C), 4 MPa, 2.4 g/min and 37 min; 142 ± 13 ug alpha-carotene/g extract and 317 ± 46 ug beta-carotene/g extract for LPSE-SOX process at 6 h; and 79 ± 9 ug alpha-carotene/g extract and 195 ± 20 ug beta-carotene/g extract for LPSE-PE process at condition of 308 K (35°C), 2.4 g/min and 37 min. The cost of manufacturing (COM) for the industrial scale of 2 extractors in continuous mode with capacity of 0.5 m3 were US$98.1/g carotenoid for the LPSE-SOX process, US$48.9/g carotenoid for the LPSE-PE process and US$28.7/g carotenoid for the PLE process. From the results obtained in the first and second study, a kinetic study of the PLE and SFE processes at the operating conditions which obtained the highest carotenoid yields from pressed palm fiber was carried out in order to find the adequate processing time and manufacturing cost. The results showed that the extraction at the S/F ratio of 7 and 10 resulted in extract yields higher than 90% for the PLE and SFE process. On the other hand, the carotenoid yield of carotenoids in the extract increased with the S/F ratio. For PLE and SFE processes, the lowest COM values were found for the industrial scale of extractors of 0.05 and 0.5 m3. For PLE process, the S/F ratio of 8 resulted in the lowest COM and specific COM* value: US$30.4/kg extract and US$0.02/g carotenoid for 0.5 m3. A similar trend was observed for the SFE process with values of US$30.8/kg extract and US$0.08/g carotenoid for capacity of 0.5 m3. Based on these results, the PLE process is economically more advantageous than the SFE process and PLE can be considered as the first step of the integrated process for obtaining of extract rich in carotenoids followed by SubWH for obtaining of hydrolysate products / Doutorado / Engenharia de Alimentos / Doutora em Engenharia de Alimentos

Este estudo visou à utilização da tecnologia que emprega CO2 em estado supercrítico (SFE) para estudar a bioatividade dos diterpenos presentes no óleo de café verde, cafestol (C) e caveol (K), contudo propondo também a otimização de extração com líquido pressurizado (PLE) em batelada, utilizando para isto um Delineamento Composto Central Rotacional (DCCR2). O referido tema tem caráter inovador e inédito, já que a tecnologia de extração com líquido pressurizado, até então empregada para extração de analitos, passa a ser estudada em processos de extração de óleos vegetais tais como, óleo de pequi, óleo de café verde, extrato de sementes de pitanga no LTAPPN. Esta técnica utiliza solventes orgânicos e emprega elevada temperatura de extração, o que aumenta a capacidade de solubilização do solvente, e o emprego de altas pressões que acelera a difusão nos poros da matriz já que a viscosidade do solvente é diminuída. Este comportamento ocasiona maior penetração do solvente na matriz, aumentando sua capacidade de extração. A extração supercrítica (SFE) é uma tecnologia limpa, pois não emprega solventes orgânicos sendo promissora na obtenção de extratos enriquecidos com compostos bioativos que possam desempenhar alguma atividade. O estudo da atividade aguda dos diterpenos presentes no óleo de grãos de café verdes obtidos via SFE e PLE demonstrou que o óleo extraído com CO2 supercrítico, na dose de 2.000 mg/Kg no estudo de toxicidade aguda e nas doses de 25, 50 e 75 mg/Kg no estudo de toxicidade de doses repetidas, não apresentou letalidade aos animais, porém parâmetros bioquímicos, hematológicos e histológicos, apresentaram alterações. Todavia para aplicações do óleo de café verde em produtos desenvolvidos pelas indústrias farmacêuticas, alimentícias e/ou cosméticas, mais estudos de avaliação dos efeitos do óleo de café verde in vivo são necessários. Igualmente, o estudo de inovação tecnológica para obtenção de óleo de café verde visa obter extratos enriquecidos em diterpenos, evitando a degradação e tornando-os mais estáveis. Os resultados obtidos indicam que o óleo dos grãos de café verde extraídos via SFE e PLE (em batelada) possuem altas concentrações dos compostos ativos cafestol e caveol, sendo a condição de melhor rendimento a condição 4 (70º C e 8 min. ) a de maior rendimento de óleo 9,78%. / This study aimed to evaluate the bioactivity of the diterpenes in green coffee oil, cafestol (C), and kahweol (K) using supercritical fluid extraction (SFE- CO2), and to optimize the extraction with pressurized liquid extraction (PLE) in batch by using a rotatable central composite design (RCCD2). This issue has innovative and novel character, since the pressurized liquid extraction technology available until now for analyte extraction has been studied in vegetable oil extraction processes such as Pequi oil, green coffee oil, and Pitanga seeds extracts, at LTAPPN. This technique uses organic solvents and high extraction temperature, which increases the solvent solubilization capacity. The use of high pressure accelerates the diffusion rates into the pores of the matrix, due to the lower solvent viscosity. This behavior provides greater penetration of the solvent into the matrix, increasing solvent extraction capacity. The supercritical fluid extraction (SFE) is a clean technology as it does not employ organic solvents, besides being a promising alternative to obtain extracts enriched with bioactive compounds. The results of the acute activity of diterpenes in green coffee oil extracted by SFE and PLE showed that although no lethality was observed in the animals using the oil extracted by SFE at a dose of 2,000 mg / kg in an acute toxicity study, and 25, 50, and 75 mg / kg in a repeated dose toxicity study, changes were observed in biochemical, hematological, and histological parameters. However, more in vivo studies about the effects of green coffee oil are required for pharmaceutical, food, and cosmetic applications. Similarly, the technological innovation to obtain the green coffee oil aims at obtaining extracts enriched in diterpenes, preventing degradation and increasing stability. The results indicate that green coffee oil extracted by SFE and PLE (in batch) have high concentrations of the active compounds cafestol and kahweol, and the best extraction condition was the trial 4 (70 º C, and 8 min), and the highest oil yield was 9.78%.

Es wurde ein Modell zur realistischen Beschreibung der Kühlmittelvermischung innerhalb des Reaktordruckbehälters von Druckwasserreaktoren in den gekoppelten Programmkomplex DYN3D/ATHLET implementiert. Diese Modell basiert auf dem Prinzip der linearen Superposition Dirac-Impuls-ähnlicher Störungen und kann für die Modellierung der Vermischung von Kühlmittel unterschiedlicher Temperatur und/oder unterschiedlicher Borsäurekonzentration eingesetzt werden. Der um das Vermischungsmodell erweiterte Programmkomplex DYN3D/ATHLET wurde für Analyse von Borverdünnungsstörfällen und Frischdampflecks angewandt. Für den Fall "Start der ersten Hauptkühlmittelpumpe bei Vorhandensein eines minderborierten Pfropfens im kalten Strang" zeigten die Ergebnisse der durchgeführten Parameterstudie, dass es selbst bei Annahme des maximal möglichen Pfropfenvolumens nicht zu einer Schädigung des Brennstoffes kommt. Mit den Analysen zu einem generischen Frischdampfleckszenario wurde die Anwendbarkeit des Programmkomplexes DYN3D/ATHLET auf die zweite Störfallklasse, in der die Kühlmittelvermischung eine wichtige Rollen spielt, demonstriert. Im Rahmen der Arbeiten zum Projekt wurde außerdem gezeigt, dass der Einfluss der turbulenten Schwankungen des Geschwindigkeitsfeldes innerhalb des Reaktordruckbehälters auf neutronenkinetische Parameter im Nominalbetrieb und unter Störfallbedingungen nicht zu vernachlässigen ist. A model for the realistic description of the coolant mixing inside the pressure vessel of pressurized water reactors was implemented into the coupled code complex DYN3D/ATHLET. This model is based on the linear superposition Dirac-pulse-like perturbations. The model can be applied to the mixing of coolant of different temperature and/or boron concentration. The coupled code complex DYN3D/ATHLET with the newly implemented model was applied to the analysis of boron dilution and steam line break accidents. The results of a parameter study for the case "Start-up of the first main coolant pump with a slug of lower borated water in the cold leg" have shown, that even under the conditions of the maximum slug volume there is no fuel damage. The applicability to the second class of accidents, where the coolant mixing has to be considered, was demonstrated by the analysis of a generic main steam line break scenario. Further it was shown, that the influence of turbulent fluctuations of the velocity inside the reactor pressure vessel during nominal and accident conditions on neutron-kinetic parameters cannot be neglected.

Innerhalb des Vorhabens wurde ein ATHLET-CD-Eingabedatensatz für einen generischen deutschen DWR vom Typ KONVOI entwickelt. Das ATHLET-CD-Modell wurde für die Simulation schwerer Störfälle aus den Störfallkategorien Station Blackout (SBO) und Kühlmittelverluststörfällen mit kleinen Lecks (SBLOCA) eingesetzt. Dabei ist die vollständige Störfalltransiente für den Zeitbereich zwischen dem einleitenden Ereignis bis zum Versagen des Reaktordruckbehälters (RDB) abgedeckt und alle wesentli-chen Phänomene schwerer Störfällen werden abgebildet: Beginn der Kernaufheizung, Spaltproduktfrei-setzung, Aufschmelzen von Brennstoff- und Absorbermaterialien, Oxidationsprozesse mit Freisetzung von Wasserstoff, Verlagerung von geschmolzenem Material, Verlagerung in das untere Plenum, Schä-digung und Versagen des RDB. Das Modell wurde für die Analyse möglicher präventiver und mitigativer Notfallmaßnahmen für SBO und SBLOCA angewandt. Dafür wurden die Notfallmaßnahmen primärseitige Druckentlastung (PDE), primärseitiges Einspeisen mit mobilen Pumpensystemen sowie für SBLOCA das verzögerte Einspeisen der kaltseitigen Druckspeicher untersucht und die Eigenschaften und Einleitekriterien der Maßnahmen variiert. Es wurden die Zeitverläufe der Unfallszenarien analysiert und die verbleibenden Zeitspannen für die Einleitung zusätzlicher Maßnahmen ermittelt. Für ein SBO-Szenario mit PDE wurde für die Frühphase der Transiente (bis zum Beginn der Kernschmelze) eine Unsicherheits- und Sensititvitätsanalyse durchgeführt. Zusätzlich wurde für ein SBLOCA-Szenario ein Code-zu-Code-Vergleich zwischen ATHLET-CD und dem Störfallcode MELCOR erarbeitet.

In this Master Thesis work, the effect of pressure on sintering of cemented carbides is investigated. Special focus hasbeen given to the residual porosity after sintering. It is well known that sintering shrinkage depends on binder phasecontent, grain size, temperature and pressure. Thus 4 different cemented carbides grades were selected. The gradeswere pressed into standard products and TRS (Tensile Rupture Strength) rods with two different shrinkage factors.These were then sintered at different pressures and temperatures. Thereafter the impact of pressure on propertiessuch as Density, Coercivity, Porosity and TRS were analyzed. The observations were further supported with Weibullprobability analysis and fracture surface analysis in SEM.It has been shown that there exists a distinct threshold pressure at which significant reduction in porosity occurs forgiven compacted densities. For 3 out of 4 cemented carbide grades it has been observed that P2 sintering pressure issufficient to meet desired product characteristics. The fourth grade required a minimum sintering pressure of P4 toachieve desired quality criteria. Moreover it has been concluded that an increased sintering pressure increasesmaterial strength, as compared to vacuum sintering, thereby reducing the amount of early failures caused by poresduring TRS test.                                    Keywords: Cemented Carbides, Pressurized Sintering, Tungsten carbide, Porosity, Vacuum sintering, TensileRupture Strength, Weibull analysis, Fracture surface analysis.

Hot isostatic pressing (HIP) is a thermal treatment method that is used to consolidate, densify or bondcomponents and materials. Argon gas is commonly used as the pressure medium and is isostaticallyapplied to the material with an excess pressure of 500-2000 bar and a temperature of 500-2200oC. WithHIP treatment being a well-established technology for the last decades, one is now striving to obtain anincreased understanding of local details in the internal gas flow and heat flux inside the HIP apparatus.The main objective of this work is to assess the potential of using computational fluid dynamics (CFD) asa reliable tool for future HIP development. Two simulations are being performed of which the first one isa steady-state analysis of a phase in the HIP-cycle called sustained state. The second simulation is atransient analysis, aiming to describe the cooling phase in the HIP-cycle. The most suitable modelingapproaches are determined through testing and evaluation of methods, models, discretization schemes andother solver parameters. To validate the sustained state simulation, the solution is compared tomeasurements of operating pressure, heat dissipation rate out through the HIP vessel and localtemperature by the vessel wall. However, no validation of the cooling simulations has been conducted. Asensitivity analysis was also performed, from which it could be established that a mesh refinement ofstrong temperature gradients resulted in an increase of wall heat dissipation rate by 1.8%. Both of thesimulation models have shown to yield satisfactory solutions that are consistent with the reality. With theachieved results, CFD has now been introduced into the HIP field and the presented modeling methodsmay serve as guidelines for future simulations.

Thesis. 1978. Nucl.E.--Massachusetts Institute of Technology. Dept. of Nuclear Engineering. / MICOFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Includes bibliographical references. / Nucl.E.