Made available in DSpace on 2014-10-09T12:55:24Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:07:13Z (GMT). No. of bitstreams: 0 / Este trabalho trata da avaliação da compressibilidade de misturas de pós de nióbio e alumínio, previamente ativadas por moagem de bolas de alta energia. Foram variados o tempo de moagem e a quantidade de ácido esteárico, adicionado como agente controlador de processo (ACP), assim como o tamanho médio de partícula do pó de alumínio. Os pós de partida e as misturas moídas foram caracterizados por microscopia eletrônica de varredura (forma das partículas) e por difração de raios laser (distribuição granulométrica). Uma máquina universal de ensaios foi utilizada nos testes de compressibilidade mediante compactação das amostras numa matriz cilíndrica de aço-ferramenta. Os dados de compressibilidade foram comparados graficamente segundo curvas de densidade (relativa) versus pressão. As diferenças de comportamento na compactação das amostras foram correlacionadas com as diferentes condições de moagem. Houve um decréscimo da compressibilidade com o aumento do tempo de moagem e da quantidade de ACP. Menos compressíveis foram também as misturas provenientes do pó de alumínio com maior tamanho de partícula. Uma nova equação de compactação foi ainda proposta, cujo ajuste aos dados deste trabalho foi superior aos verificados nas equações de modelos anteriormente publicados. / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2014-11-10T11:55:57Z No. of bitstreams: 0 / Made available in DSpace on 2014-11-10T11:55:57Z (GMT). No. of bitstreams: 0 / Os moinhos de bolas são equipamentos presentes em plantas de mineração, sendo uma máquina importante no circuito de cominuição de minérios. Em função de inúmeros fatores como, por exemplo, projeto, fabricação, sobrecarga no equipamento, falta de manutenção e procedimentos de operação inadequados, são desenvolvidas descontinuidades nos componentes estruturais desse equipamento. Os componentes estruturais dos moinhos, basicamente, corpo, tampas e munhões, além do custo elevado, possuem prazos de fabricação que podem variar de dois a três anos dependendo da demanda do mercado. Portanto é cada vez mais necessário que as descontinuidades detectadas nesses componentes sejam corretamente avaliadas. Neste trabalho analisaram-se pela mecânica da fratura a criticalidade de descontinuidades, tais como trincas constatadas em um munhão de um moinho de bolas e compararam-se os valores teóricos de taxa de propagação (crescimento) dessas descontinuidades com valores reais obtidos por meio de inspeções periódicas realizadas neste componente. A nucleação das trincas foi causada por falta de lubrificação nos mancais do moinho, gerando esforços térmicos circunferenciais no munhão, em que a temperatura estimada do contato munhão e bucha atingiu a faixa de 100 °C a 150 °C. No período analisado, os resultados obtidos por meio da norma BS7910 mostraram-se mais próximos dos valores reais do que a norma ASME Seção XI, Apêndice A. O tamanho da trinca mais crítica foi aceito pelos critérios da norma BS7910 e aprovado apenas na condição de emergência da norma ASME Seção XI, Apêndice A. / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Orientador: Anselmo Eduardo Diniz / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-25T10:42:27Z (GMT). No. of bitstreams: 1 Lacerda_RafaelSegantin_M.pdf: 5082934 bytes, checksum: 9288c8f97c6d45416ba8bc96895fc01d (MD5) Previous issue date: 2014 / Resumo: A fabricação de pás de turbinas hidráulicas representa uma das atividades mais importantes no processo de fabricação do rotor de uma usina hidrelétrica e corresponde a uma parcela considerável do custo de produção do mesmo. Devido às características geométricas e requisitos hidráulicos destes componentes, as operações de fresamento em cinco eixos são altamente solicitadas e se destacam pela versatilidade e rapidez que proporcionam para o processo produtivo. Todavia, o fresamento de pás de turbinas hidráulicas apresenta alguns pontos críticos relacionados com a qualidade superficial, qualidade dimensional e os custos da operação de usinagem. A taxa de remoção de material, a variação das condições de fresamento diretamente relacionada com os parâmetros de corte e a necessidade de se reduzir os ciclos de produção são itens que fazem o estudo detalhado desta operação ter importância fundamental para a utilização das modernas tecnologias de usinagem. O objetivo deste trabalho é identificar as condições de corte mais adequadas para o processo de fresamento em cinco eixos de pás de turbinas hidráulicas. Para isto, o processo de fabricação foi monitorado e ensaios foram realizados para comparação entre diferentes estratégias de fresamento e parâmetros de corte. Durante estes ensaios observaram-se os parâmetros elétricos do motor da máquina e também a coloração dos cavacos, para estabelecer uma relação entre estes parâmetros e o real desgaste sofrido pela ferramenta, a fim de se ter um método direto e prático para definição de seu fim de vida. As principais conclusões deste trabalho são que a variável de entrada mais influente na vida da ferramenta dentre as testadas foi a estratégia de corte (concordante ou concordante / discordante) e para estas ferramentas, o desgaste de flanco (VB) foi o principal determinante para o fim de vida da aresta de corte. Em adicional, a observação da potência consumida e da coloração do cavaco realizada pelo operador, mostrou-se adequada para determinar o momento de troca da ferramenta neste tipo de fresamento em desbaste. Palavras chave: fresamento em cinco eixos, pás, turbinas hidráulicas e desgaste de flanco / Abstract: The manufacturing process of blades for hydraulic turbines is one of the most important activities to fabricate a runner for a hydraulic power plant and is responsible for a considerable portion of the production cost thereof. Due to the geometric characteristics and hydraulic requirements in these components, the milling operations in five axis is highly appreciated and offer the versatility and speed for the production process. However, the milling process for blades of hydraulic turbines present some critical issues related to the surface quality, dimensional quality and machining costs. The rate of material removal, the variation of milling conditions directly related with cutting parameters and the need to reduce production cycles are items that make a detailed study of this operation has high importance on the application of the most modern machining technologies. The objective of this work is to identify the most suitable cutting conditions for five axis milling in blades of hydraulic turbines. For this, the manufacturing process was monitored and tests were performed in order to compare different milling strategies and cutting parameters. During these tests was observed the electrical parameters of the machine motor and also the colors of the chips to establish a relationship between these parameters and the actual wear suffered by the tool in order to have a derictly and practical method to define the end of the tool life. The main conclusions are that the most influential variable in the tool life among those tested was the cutting strategy (Up Milling or Up Milling / Down Milling) and for these tools, the main determinant for the end of life is the flank wear (VB) of the cutting edge. In additional, the observation of the power consumption and the colors of the chips performed by the operator, with the goal of determining the exactly time to exchange the tool was adequate for this type of rough milling. Keywords: five axis milling, blades, hydraulic turbines and flank wear / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica

Orientador: Amauri Hassui / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-21T02:15:20Z (GMT). No. of bitstreams: 1 Zanuto_RodolfodeSouza_M.pdf: 2395857 bytes, checksum: 8416f382a0b6fea6d86adb4d90e04b73 (MD5) Previous issue date: 2012 / Resumo: Com o rápido avanço tecnológico que o mundo vem passando desde a revolução industrial, novos materiais vão sendo desenvolvidos a todo momento, sendo o aço inoxidável aeronáutico 15-5 PH um destes exemplos contemporâneos, com grande potencial de aplicações, no entanto, ainda com poucas informações de como processá-lo. Com este cenário em mente, este trabalho tem por objetivo contribuir para a compreensão do fresamento de faceamento desse material. Para isso foram feitos ensaios de vida da ferramenta com três diferentes estratégias de entrada na peça (direta, reduzida e rolagem) para os cortes predominantemente concordante e discordante. Foram avaliadas também duas geometrias (positiva e neutra) e duas classes de ferramentas (M 40 e M 25), bem como duas velocidades de corte (170 m/min e 195 m/min) e dois avanços por dente (0,15 mm/dente e 0,25 mm/dente). Por fim, foram medidos os esforços de corte e realizada a caracterização microestrutural da ferramenta (MEV e EDS) para as três estratégias de entrada. A rugosidade também foi acompanhada ao longo de todos os ensaios. Os melhores resultados foram obtidos para a estratégia de entrada por rolagem no corte discordante, já no corte concordante não houve uma melhora quando utilizada esta estratégia. Avanços maiores também propiciaram melhores vidas, mesmo com velocidades de corte mais altas. A geometria da ferramenta neutra apresentou melhor resultado quando combinado a uma classe mais tenaz, porém se a classe da ferramenta for mais dura, uma geometria mais positiva, que propicia um corte menos severo, teve desempenho melhor / Abstract: The world has passing through a fast technological advance since the Industrial Revolution, so new materials have been developed every moment. The 15-5 PH stainless steel is an example of one of these new materials, with great potential of applications, nevertheless with fill information about the way of processing it. With this scenario in mind the present work has the goal of contribute to the comprehension of the face milling of this material. To achieve this several tool life tests were carried out with three different tool entry strategies in workpiece (direct, reduced and rolling) to the mainly up milling and mainly down milling. They were evaluated two cutting tool geometries (positive and neutral) and two grades (M 40 and M 25), as well as two cutting speeds (170 m/min and 195 m/min) and two feed per tooth (0.15 mm/tooth and 0.25 mm/tooth). Finally, we measured the cutting forces and did the tool microstructural characterization (SEM and EDS) for the three entry strategies. The surface roughness was also monitored throughout all experiments. The best results were obtained for the rolling entry strategy in the down milling, on the other hand, no cutting improvement when utilizing this strategy for up milling. Higher feed per tooth also resulted in longer tool lives, even with higher cutting speeds. The neutral cutting tool geometry presented better result when combined with a tougher grade, but if the tool grade is harder, then a positive geometry, that generate a less severe cut, presented better performance / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica

A rapid non-destructive Image Analysis (IA) technique was developed for the determination of maize kernel endosperm vitreousness. Kernels were analysed using a Leica Q-Win Q500 IW-DX Image Analyser fitted with Leica Q-Win software and connected to a Sony XC-75 CCD camera. Kernel translucency measurements were optimised by using a light system that involved positioning whole kernels on top of a mask containing round illuminated areas (circles), smaller than the projected areas of the kernels, allowing light to shine through the kernels only. Correction factors allowing for constant illumination of kernels were developed to adjust for kernel size variation in relation to constant light area. Similarly, a correction factor for the effect of kernel thickness on detected translucency values were developed. Significant correlations were found between corrected translucency values and vitreous and opaque endosperm yields as determined by hand dissection. These were: translucency as a percentage of the whole kernel and vitreous endosperm (mass%) (Translucency 1), r = 0.77, p<0.00001, and Translucency 1 and opaque endosperm (mass%), r = -0.72, p<0.00001 for white maize. Similar correlations were found for translucency as a percentage of endosperm (Translucency 2). Correlation coefficients increased significantly after kernel thickness corrections. Significant negative correlations were also found between corrected translucency values and Floating Number. For yellow maize, Translucency 1 correlation coefficients was r = 0.78, p<0.00001 and r = -0.71, p<0.00001 respectively with similar correlations for Translucency 2. Correlations were obtained after applying both correction factors for exposure and thickness. The IA technique was evaluated for predicting the yield of vitreous endosperm products during dry maiz~ milling in laboratory and industrial-scale milling trials. Significant positive correlations were found between corrected translucency values and yields of milling products from vitreous endosperm. Experiments using a laboratory-scale experimental roller milling test without a degerming stage produced the following correlations: between Translucency 1 and semolina yield (mass%), 0.74, p<0.001 and Translucency 2 and semolina yield (mass%), 0.70, p<0.001. For industrial-scale milling, a Bühler industrial-scale maize mill (3 tons per hour) was used. The correlation between Translucency 1 and extraction at degermer (degermer overtail yield) was 0.93, p<0.0001. There was a similar correlation for Translucency 2. Yellow maize was degermed using a pilot-scale Beall-type degermer and the correlation between Translucency 1 and flaking grits> 3.9 mm was 0.67, p< 0.001. The IA technique permits the non-destructive analysis of maize endosperm translucency on large samples of single kernels. It is suitable for rapid quantification of maize endosperm contents and predicting dry maize milling performance, as kernel translucency was significantly correlated with vitreousness in all instances. With further development of specific hardware and software, the technique has potential as an on¬line maize kernel classification system in industrial mills. As the method is non¬destructive, it is also suitable for classification of maize seed breeding material. It is also a potential method for the measurement of maize opacity as used by the wet milling industry, where opacity (the opposite of vitreousness) is related to maize starch yield. / Thesis (PhD(Food Science))--University of Pretoria, 2006. / Food Science / unrestricted

The particle size distribution produced from first break roller milling of wheat determines the flows through the rest of the mill and hence the quality of the final flour, and is affected by debranning and by the operation of the roller mill. The Double Normalised Kumaraswamy Breakage function (DNKBF) gives a quantitative basis to describe breakage during first break milling of wheat and to interpret effects. Previous work developed and extended the breakage equation in order to understand and predict wheat breakage based on distributions of the grain characteristics and the operating parameters of the mill. However, broken particles vary in composition as well as size; therefore the primary objective of the current work was to extend the DNKBF during first break milling to include particle composition, using fingerprints of pericarp, aleurone, endosperm and germ. Meanwhile, debranning is a technology that has enhanced flour milling in recent years, leading to improvements in quality that are not well understood but that start with the effect on milling. A second objective of the current work was therefore to apply the DNKBF to describe and interpret the effects of debranning on wheat breakage and, in so doing, to clarify the physical significance of the DNKBF parameters. Samples of Mallacca (hard wheat) and Consort (soft wheat) were debranned for nine different times, at three roll gaps and under S-S and D-D dispositions. The DNKBF successfully described the normalised particle size distribution at different debranning times. The DNKBF describes wheat breakage in terms of Type 1 and Type 2 breakage, where Type 1 describes a relatively narrow distribution of mid-sized particles, whilst Type 2 describes a wide size range of predominantly small particles extending to very large particles. The proportion of Type 1 breakage increased at longer debranning times, while Type 2 breakage decreased, for both wheats under both dispositions. S-S milling tended to produce more Type 1 breakage than D-D. A mechanism of wheat breakage is proposed to explain the co-production of very large and small particles via Type 2 breakage, and hence the effect of debranning. The proposed mechanism is that small particles of endosperm arise from scraping of large flat particles of wheat bran under the differential action of the rolls; removal of the bran reduces the production of the large bran particles and thus reduces the opportunity for the scraping mechanism that produces the very small particles. The composition of broken particles can be characterised considering the four major wheat components, pericarp, aleurone, endosperm and germ. Kernels of Mallacca and Consort wheats were manually dissected to isolate these components. FTIR spectroscopy was able to distinguish the different components in milled fractions. However, attempts to quantify the relative contribution of each wheat component in milled fractions (by measuring specific peak heights and by Partial Least Squares, PLS) were compromised by technical limitations. An alternative approach aimed to fingerprint the components using sugar analysis by HPLC, with some success; however the technique was too complex and limited by the detection limit of HPLC, in particular for arabinose and xylose. Instead, the botanical distributions within eight milled fractions of Mallacca and Consort wheats milled under S-S and D-D dispositions were analyzed by PLS models developed by Barron (2011). The concentration functions were then found by applying the DNKBF to the particle size distributions and to the compositional distributions, the ratio of the DNKBFs giving the concentration function. The DNKBF was able to describe the data well for the four botanical components studied in both wheats: pericarp, aleurone, intermediate layer and starchy endosperm. The analysis clarified the nature of the particles produced on breakage, showing that for Mallacca wheat, the pericarp and aleurone layer compositions mostly varied with particle size in similar ways. Intermediate layer showed broadly similar results to those for pericarp and aleurone in the Mallacca wheat despite being the least accurate component predicted. However, for Consort wheat, the intermediate layer behaved differently from pericarp and aleurone, suggesting a different breakage mechanism, perhaps associated with how the wheat hardness affects breakage of the bran and the production of large flat bran particles. Creation of pericarp/intermediate layer/aleurone dust during milling was notable, in particular for Mallacca wheat. The relative uniformity of the Mallacca compositions in relation to pericarp, intermediate layer and aleurone, which varied in consistent ways with particle size, was also notable. By contrast, for Consort wheat, the relative proportions of these three components appear to vary substantially in particles of different size, pointing to very different breakage origins. It seems that in the hard wheat, the breakage patterns are dominated by the endosperm physical properties, while for the soft wheat, the behaviour of the large bran particles produced is dictated much more by the properties and structure of the bran layers than by the hardness of the endosperm. The approach presented is practical to describe, quantify and interpret the effects of breakage on component distributions, in order to understand the fate of kernel components during milling and hence the origins of flour quality.

Sorghum is a drought resistant indigenous African cereal and traditional food crop. Unfortunately. milling sorghum. as is normally done using a Prairie Research Laboratory (PRL)-type abrasive dehuller is not effective. Because in sorghum the germ is integral in the grain. the process of removing the outer bran layers by abrasion leads to high losses, up to as much as 40% if a flour of less than I% fat is to be produced. The pericarp of sorghum is rich in cellulose and hemicelluloses, and the germ, lipids. Specific hydrolytic enzymes should degrade these chemical components and thus remove the bran and germ with minimal loss of grain material. In this work. four industrial enzymes. endo-β-glucanase. xylanase. pectinase and lipase were applied either singly or in combination to two different commercial batches of sorghum to determine whether hydrolytic enzymes could be used to decorticate sorghum grain. Sorghum grain was either de-waxed with hexane or scraped to remove the waxy material on the pericarp and seed coats. The grain was then soaked in a 10% (w/w) solution of either single or combined enzymes in flasks which were then incubated at 50°C in a water bath and left overnight with shaking. SEM showed that endo-β-glucanase caused decortication of the sorghum grain at the seed coat/aleurone layer interface with both the hexane de-waxed grain and the scraped one. The germ was not removed. The results suggested that endo-β-glucanase hydrolysed the exposedpericarp cell wall material and thus loosened the pericarp, and hence its removal. The germ could not be removed perhaps due to the fact that, in sorghum grain the germ/endosperm interface is at right angles to the surface of the grain, thus enzymes have only a small area to act on and all the underlying interface is not accessible. Different endo-β-glucanase concentrations were applied to partially decorticated sorghum grain to establish the optimum concentration to be used to remove the pericarp material to an acceptable level. The lowest level when there was a good decortication effect, as indicated by grain ash content and colour, was at 0.01% endo-β-glucanase concentration (ml/l00 g grain). The effectiveness of enzymic and mechanical decortication was compared in terms of the relationships between decortication yield and grain ash content, and between decortication yield and grain colour. To reduce the grain ash to an acceptable level (about 1.1%), enzyme decortication resulted in about 10% saving in grain material relative to the mechanical process. However. at the same decortication yield. the mechanical process gave a lighter product than the enzymIc process. It appears that endo-β-glucanase can remove the pencarp from sorghum grain at an economically feasible concentration (0.01%). and that there is significant reduction of grain material loss relative to the mechanical process. However, more work needs to be done to improve the colour of the product. and to find a way to remove the germ. / Dissertation (MSc (Food Science))--University of Pretoria, 2006. / Food Science / unrestricted

Current manufacturing research aims at increasing productivity by optimal selection of process parameters. This is accomplished by understanding the fundamental physics of individual manufacturing processes. In this thesis, peripheral milling of very flexible cantilevered plates is studied. The static and dynamic deflections of the plate under periodic milling forces are modelled. A new dynamic cutting force model is developed which considers five discrete zones of relative motion between the tool and the workpiece. The kinematics of both milling and vibratory motions are modelled, which is an original research contribution in this area. It is shown that the penetration of the tool into the workpiece during vibratory cutting has a strong influence on the damping and stiffness characteristics of the milling process. A structural model of a discontinuous cantilevered plate is determined using the finite element method. A reduced order structural model at the tool-workpiece contact zone is implemented for discrete time response analysis of the plate under cutting force excitations during milling. The closed loop dynamic behaviour of the system is modelled and taken into account in the analysis. Simulations of plate machining are compared with experimental results. A model of the surface finish generation mechanism is deduced from the analysis and experimental results. Applications of this research include peripheral milling of integral jet engine impellers, computer disk drives and other flexible mechanical components. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

Orientador: Anselmo Eduardo Diniz / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-28T09:40:41Z (GMT). No. of bitstreams: 1 Castanhera_IsabeladaCosta_M.pdf: 4815385 bytes, checksum: a3fe6159dcb93e0e05191d8e898977e9 (MD5) Previous issue date: 2015 / Resumo: Na década de 1970, o fresamento de materiais, sobretudo aços, endurecidos a mais de 45 HRC era desaconselhado, visto que a usinabilidade de aços tende a diminuir com o aumento de dureza. Com investimentos em máquinas-ferramenta e materiais de ferramenta, o fresamento de aços endurecidos tornou-se aconselhável, tanto para formas geométricas mais simples quanto para formas geométricas complexas, pois os centros de usinagem alcançam maiores rotações e eixos de posicionamento e usinagem. Para tanto, toda a estrutura destas máquinas-ferramentas é reforçada. As ferramentas apresentam materiais mais nobres e coberturas mais resistentes e tenazes. O fresamento do tipo high speed machining é utilizado principalmente para a usinagem de moldes e matrizes, tanto para abertura das cavidades, quanto para usinagem em acabamento fino, substituindo, quando possível, o processo de eletroerosão. Para a usinagem de uma superfície curva de aço ferramenta para trabalho a frio AISI D6, as estratégias de trajetória de ferramenta escolhidas podem afetar de modo significativo o acabamento da peça e a vida de ferramenta alcançada, sendo a estratégia descendente, que trabalha com menores diâmetros efetivos de corte, a estratégia que proporcionou as melhores vidas de ferramenta. A inclinação de ferramenta, para que se evite o contato do centro da fresa do tipo ball nose, pode apresentar grande influência no acabamento superficial, com rugosidade baixa ou rugosidade alta, sem garantia de que a simples inclinação da ferramenta apresenta contribuição positiva à rugosidade. A inclinação da ferramenta apresenta contribuição na forma de manifestação da vibração durante o corte. A vibração que resulta em diferentes forças com que cada dente corte o cavaco apresenta a maior influência na rugosidade / Abstract: In 1970 decade, milling harder than 45 HRC steels was inadvisable because of the low machinability. The investments in machining centers enabled the hardened steels milling for simple geometries or complex geometries workpieces, because the spindle speed and the extra axis for positioning and machining. The machine structure is enhanced. Tool materials are advanced, sub micrometric grain size cemented carbide and resistant tool coating. High speed machining is utilized principally in molds and dies machining for cavities opening or super finishing, reducing production time, costs reduction and EDM process substitution. In a tool steel AISI D6 hardened at 60 HRC curve surface milling, the chosen tool path strategy may affect surface finish and tool life. Downward cut, which works in lower effective diameters than upward cut, improved tool life. Tool inclination, utilized to avoid tool center in cut of tool type ball nose, may influence significantly the surface finish. Tool vibration influences surface finish because of tool bend, which promotes different cut force for each tool tooth. Tool inclination does not guarantee a good surface finish or a good vibration behavior. Tool inclination might change the manner the vibration presents itself. The vibration responsible by different cut forces in each tooth is the most influential vibration in roughness in presented cut / Mestrado / Materiais e Processos de Fabricação / Mestra em Engenharia Mecânica

This thesis deals with a creation of a control system of 3-axis milling machine. The beginning of the thesis is dedicated to the general description of the problematic of the numerically controlled machines and the technologies used in this branch. The next chapter describes mechanical and electronical adjustments of the machine. Following chapters are dedicated to the creation of PLC program and HMI using the TwinCAT software. In conclusion, this thesis deals with commissioning of the machine, measuring its geometrical accuracy and testing.