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Simulation and Optimization of Mechanical Alloying Using the Event-Driven MethodBarahona, Javier 30 November 2011 (has links)
Mechanical Alloying is a manufacturing process that produces alloys by cold welding of powders. Usually, a vial containing both the powder and steel balls is agitated. Due to impact between the balls and balls and the vial, the powder is mechanically deformed, crushed, and mixed at nano-scales. In this thesis, a numerical model is developed to simulate the dynamics of the vial and the grinding balls of the SPEX 8000 ball milling device, a standardized equipment in both industrial and academic investigations of ball milling. The numerical model is based on the Event Driven Method, typically used to model granular flows. The method implemented is more efficient than the discrete element method used previously to study ball milling dynamics. The numerical tool obtained is useful for scale-up and optimization of mechanical alloying of various materials. An optimization study is presented for the SPEX 8000.
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Simulation and Optimization of Mechanical Alloying Using the Event-Driven MethodBarahona, Javier 30 November 2011 (has links)
Mechanical Alloying is a manufacturing process that produces alloys by cold welding of powders. Usually, a vial containing both the powder and steel balls is agitated. Due to impact between the balls and balls and the vial, the powder is mechanically deformed, crushed, and mixed at nano-scales. In this thesis, a numerical model is developed to simulate the dynamics of the vial and the grinding balls of the SPEX 8000 ball milling device, a standardized equipment in both industrial and academic investigations of ball milling. The numerical model is based on the Event Driven Method, typically used to model granular flows. The method implemented is more efficient than the discrete element method used previously to study ball milling dynamics. The numerical tool obtained is useful for scale-up and optimization of mechanical alloying of various materials. An optimization study is presented for the SPEX 8000.
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Simulation and Optimization of Mechanical Alloying Using the Event-Driven MethodBarahona, Javier 30 November 2011 (has links)
Mechanical Alloying is a manufacturing process that produces alloys by cold welding of powders. Usually, a vial containing both the powder and steel balls is agitated. Due to impact between the balls and balls and the vial, the powder is mechanically deformed, crushed, and mixed at nano-scales. In this thesis, a numerical model is developed to simulate the dynamics of the vial and the grinding balls of the SPEX 8000 ball milling device, a standardized equipment in both industrial and academic investigations of ball milling. The numerical model is based on the Event Driven Method, typically used to model granular flows. The method implemented is more efficient than the discrete element method used previously to study ball milling dynamics. The numerical tool obtained is useful for scale-up and optimization of mechanical alloying of various materials. An optimization study is presented for the SPEX 8000.
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Simulation and Optimization of Mechanical Alloying Using the Event-Driven MethodBarahona, Javier January 2011 (has links)
Mechanical Alloying is a manufacturing process that produces alloys by cold welding of powders. Usually, a vial containing both the powder and steel balls is agitated. Due to impact between the balls and balls and the vial, the powder is mechanically deformed, crushed, and mixed at nano-scales. In this thesis, a numerical model is developed to simulate the dynamics of the vial and the grinding balls of the SPEX 8000 ball milling device, a standardized equipment in both industrial and academic investigations of ball milling. The numerical model is based on the Event Driven Method, typically used to model granular flows. The method implemented is more efficient than the discrete element method used previously to study ball milling dynamics. The numerical tool obtained is useful for scale-up and optimization of mechanical alloying of various materials. An optimization study is presented for the SPEX 8000.
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Caracterização microestrutural do aço inoxidável superdúplex UNS S32520 (UR 52N+) processado por moagem de alta energiaYonekubo, Ariane Emi 10 September 2010 (has links)
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Previous issue date: 2010-09-10 / Fundação Araucária de Apoio ao Desenvolvimento Científico e Tecnológico do Paraná / Superduplex stainless steels are often used in applications where is necessary high mechanical strength combined with corrosion resistance. They are formed by a ferrite (a) BCC and austenite (g) FCC mixture, have a yield stress about of the double of the
austenitic and ferritic stainless steels, larger plasticity that the one of the martensitic and precipitation hardening, high resistance to the intergranular corrosion, pitting and the stress-corrosion cracking. However, during hot deformation, these steels
recrystallize forming a lamellar microstructure with anisotropic properties. Through the high energy milling, accomplished with Spex, Attritor and Planetary ball mills, it was aimed to obtain a homogeneous and with fine grains superduplex stainless
steel. Initially, in this work, chips were made by machining of a UR 52N+ (UNS S32520) commercial superduplex stainless steel rolled sheet, without previous heat treatment, which will be submitted to the high energy milling adjusting the milling
parameters and subsequently it was accomplished the heat treatment at temperatures of 1200 °C e 1250 °C for 1 hour in argon atmosphere and 1200 °C for 1 hour in argon with 2% of hydrogen. The obtained powders were analyzed by scanning electron microscopy, observing that the smaller and more homogeneous particles were obtained by Spex milling for 16 and 32 hour; the compressibility curve showed that after a long time milling, the material can present compaction difficulty
and this way, great final porosity. The x ray diffraction presented peaks with a bottom widening due to the small size of the obtained particles. The porosity percentage determined by optical microscopy, reduced after heat treatment at 1200 °C in argon atmosphere with 2% hydrogen, however the scanning electron microscopy showed a fine porosity that could not be observed only in the optical microscopy analysis. The
differential scanning calorimetry and the differential thermal analysis showed formation and revertion of strain induced martensite peaks and using atomic force microscopy, magnetic ferrite and paramagnetic austenite phases were observed by a
non destructive test. The milling of the chips in Spex milling for 16 hours provided a refined microstructure with equiaxial grains and size of 11 μm after heat treatment at 1200 °C for 1 hour in argon atmosphere. / Aços inoxidáveis dúplex são frequentemente utilizados em aplicações onde é necessária elevada resistência mecânica combinada a resistência à corrosão. São formados por uma mistura de ferrita (a) CCC e austenita (g) CFC, apresentam limite
de escoamento cerca de o dobro dos aços inoxidáveis austeníticos e ferríticos, maior plasticidade que a dos martensíticos e dos endurecíveis por precipitação, elevada
resistência à corrosão intergranular, à corrosão localizada e à corrosão sob tensão. Porém, durante a deformação a quente, estes aços recristalizam-se formando uma microestrutura lamelar com propriedades anisotrópicas. Através da moagem de alta
energia, realizada com moinhos de bolas dos tipos Spex, Attritor e Planetário, objetivou-se obter um aço inoxidável superdúplex de grãos homogêneos equiaxiais e finos. Inicialmente, neste trabalho, foram feitos cavacos por usinagem da chapa
laminada de um aço inoxidável superdúplex comercial UNS S32520 (UR 52N+), sem tratamento térmico prévio, os quais foram submetidos à moagem de alta energia acertando-se os parâmetros de moagem e posteriormente realizou-se o tratamento
térmico em temperaturas de 1200 °C e 1250 °C, por tempo de 1 hora em atmosfera de argônio, e a 1200 °C por 1 hora em atmosfera de argônio com 2% de hidrogênio. Analisaram-se os pós obtidos por microscopia eletrônica de varredura, observando
que as partículas menores e mais homogêneas foram obtidas após as moagens no Spex por 16 e 32 horas; a curva de compressibilidade mostrou que após um tempo muito grande de moagem, o material pode apresentar dificuldade de compactação e desta maneira, maior porosidade final. A difração de raios x apresentou picos com alargamento na base devido ao tamanho pequeno de partículas obtidas. A porcentagem de porosidade, determinada por micrografia óptica, diminuiu após tratamento térmico a 1200 °C em atmosfera de argônio com 2% de hidrogênio,porém a microscopia eletrônica de varredura mostrou uma porosidade fina que não pôde ser observada somente através da microscopia óptica. As análises térmicas
por calorimetria exploratória diferencial e por análise térmica diferencial mostraram picos de formação e reversão de martensita induzida por deformação e pela microscopia de força atômica, foram observadas as fases ferrita magnética e
austenita paramagnética por ensaio não destrutivo. A moagem dos cavacos em moinho do tipo Spex por 16 horas forneceu uma microestrutura refinada com grãos equiaxiais e tamanho de 11 μm após tratamento térmico a 1200 °C por 1 hora em atmosfera de argônio.
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Caracterização do polietileno de ultra alta massa molar processado por moagem de alta energiaMendes, Luciana Biagini 05 August 2010 (has links)
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Previous issue date: 2010-08-05 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This research was an exploratory study of the changes that high energy mechanical milling can induce in ultra high molecular weight polyethylene (UHMWPE), using the
mills Spex, Attritor and Planetary, and several times and reasons for grinding. The milling products were characterized using scanning electron microscopy (SEM), optical microscopy (OM), differential scanning calorimeter (DSC), x-ray diffraction
(XRD), x-ray fluorescence (XRF), and intrinsic viscosity for calculate the viscosity average molecular weight. For the analysis of micrographs observed the morphological change of particles with the grinding, the particles are initially rounded
and the milling time increases the aspect ratio, acquire the form of flakes. Changing the shape in Spex mill occurs in less time, because it is a mill more energetic that Attritor and Planetary. By analysis of DSC was possible to observe the influence of high energy mechanical milling on melting and crystallization temperatures, and the percentage of crystalline phase of UHMWPE. Was used deconvolution of peaks in xray
diffraction patterns for better identification of the peaks of monoclinic and orthorhombic crystalline structures. Observed the formation of monoclinic phase in the UHMWPE processed in high energy mills, to a greater percentage in the mill
Attritor, possibly because it has a temperature control and avoiding a reversal of the monoclinic crystalline structure in orthorhombic crystalline structure. / Este trabalho foi realizado para um estudo exploratório das modificações que a moagem de alta energia pode provocar no polietileno de ultra alta massa molar (PEUAMM), utilizando os moinhos Spex, Attritor e Planetário, e variando tempo e poder de moagem. Os produtos de moagem foram caracterizados utilizando microscopia eletrônica de varredura (MEV), microscopia ótica (MO), calorimetria exploratória diferencial (DSC), difração de raios x (DRX), fluorescência de raios x
(FRX), e medidas de viscosidade intrínseca para o cálculo da massa molar viscosimétrica média. Pelas análises das micrografias observou-se a mudança morfológica das partículas com a moagem, inicialmente as partículas são
arredondadas e com o tempo de moagem aumentam a razão de aspecto, adquirem a forma de flakes. Para o moinho Spex a mudança da forma das partículas ocorre em menor tempo, por este ser um moinho mais energético que o Attritor e Planetário. Pela análise do DSC foi possível observar a influência da moagem de alta energia nas temperaturas de fusão e cristalização, e na porcentagem de fase
cristalina do PEUAMM. Foi utilizada a deconvolução de picos nos difratogramas de raios x para melhor identificação dos picos das estruturas cristalinas ortorrômbica e monoclínica. Com a moagem de alta energia ocorreu a formação da estrutura cristalina metaestável monoclínica, em maior porcentagem no moinho Attritor, possivelmente por este possuir um controle de temperatura e evitando uma reversão
da estrutura cristalina monoclínica em ortorrômbica.
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O, quae mutatio rerum : Antikreception och antikbruk hos studentföreningar vid Stockholms universitetWibacke, Elis January 2020 (has links)
The aim of this thesis is to analyse the meaning of instances of classical reception and uses of Antiquity within student clubs and societies at Stockholm University. The analysis is structured around a variety of factors, concerning the names and symbols of local student associations, as well as their social events and theatrical projects. There are notable differences to be found between societies targeting Classics students and those aimed at other student groups. Even though instances of classical reception are present in many different types of student associations, they take on a particular meaning for Classics students, who are more invested in the accuracy of the references than others. The theoretical framework of Swedish scholar Peter Aronsson is used to explain these differences. Furthermore, the study indicates that all student organisations are somewhat dependent on the classical tradition existent within academia.
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