ABSTRACT. In spite of technological importance of solidification of metallic alloys under radial heat flow, relatively few studies have been carried out in this area. In this work the solidification of Al 4.5 wt% Cu cylinders against a steel massive mold is analyzed and compared with unidirectional solidification against a cooled mold. Initially temperature variations at different positions in the casting and in the mold were measured during solidification using a data acquisition system. These temperature variations were introduced in a numerical method in order to determine the variation of heat transfer coefficient at metal/mold interface by inverse method. The primary and secondary dendrite arm spacing variations were measured through optical microscopy. Comparisons carried out between experimental and numerical data showed that the numerical method describes well the solidification processes under radial heat flux.Keywords: unidirectional solidification, radial heat flow, heat transfer coefficient, aluminum alloy.Estudo comparativo da solidificação da liga Al-Cu sob fluxo de calor radial cilíndrico e unidirecional ascendente RESUMO. A despeito da importância tecnológica da solidificação de ligas metálicas sob fluxo de calor radial, relativamente poucos estudos estão sendo realizados nessa área. Neste trabalho, a solidificação da liga Al-4,5%Cu em molde de aço radial cilíndrico é analisada e comparada com a solidificação unidirecional em molde resfriado. Inicialmente, a variação de temperatura em diferentes posições no metal e no molde foram medidas durante a solidificação usando um sistema de aquisição de dados. Essas variações de temperatura foram introduzidas num método numérico para determinar a variação do coeficiente de transferência de calor na interface metal/molde pelo método inverso. Os espaçamentos interdendríticos são determinados a partir das micrografias. Comparações entre variações e temperaturas calculadas numéricas e experimentalmente comprovaram que o método numérico descreve satisfatoriamente o processo de solidificação.Palavras-chave: solidificação unidirecional, fluxo de calor radial, coeficiente de transferência de calor, ligas alumínio.
Experimental evaluations based on statistical and scientific criteria play fundamental role in identification of optimal performance parameters in manufacturing engineering. Based on this premise, the Doehlert's experimental planning method was applied to external cylindrical turning process of ABNT 1045 steel, with the purpose of determining the roughness correlation as a function of the cutting speed (Vc) and feed rate (f). The Doehlert's matrix was defined with five levels for feed rate and three levels for cutting speed, according to coded variables. From these experiments the correlation between input and output variables was determined. The best model is in agreement with the analysis of variance and Fischer's test. Graphs were obtained for both response and contour surfaces. In addition, the optimal point for the best model was determined by the Lagrange criterion, which corresponds to a feed rate (f) of 0.0880 mm rev-1 and the cutting speed (Vc) of 155 mm min.-1 , resulting in a minimum roughness average value (Ra) equals to 0.8916 μm.
ABSTRACT. The cutting fluids in machining, when chosen and applied adequately can contemplate in benefits during the manufacturing processes. The selected method should allow the cutting fluid to reach the closest possible of the cutting edge lubricating the chip-tool interface. The properties of the fluid are fundamental so that the same facilitates the machining process. However the fluid can represent a great problem for the environment and health of the operator. For that reason, several scientific and technological studies are constantly developed to investigate the performance and alternative applications of cutting fluids in machining operations. This work studies the effect of sunflower oil in the cutting forces for the drilling process of 1045 ABNT steel. The fluid was applied in the form MQL -Minimum Quantity Lubrication for different cutting conditions. The cutting speed, feed rate and the length of the hole were varied. Each one of the cutting variables two levels were used. The results suggest a good acting sunflower oil in the work accomplished. Estudo da aplicação do óleo de girassol no processo de furação do aço ABNT 1045 RESUMO. Na usinagem os fluidos de corte, quando escolhidos e aplicados apropriadamente, podem refletir em benefícios durante os processos de fabricação. O método selecionado deve permitir que o fluido de corte atinja o mais próximo possível da aresta de corte lubrificando a interface cavaco/ferramenta. As propriedades do fluido são fundamentais para que o mesmo facilite o processo de usinagem. No entanto o fluido pode representar um grande problema para o meio ambiente e saúde do operador. Por esse motivo, vários estudos de cunho científico e tecnológico são constantemente desenvolvidos para investigar o desempenho e alternativas de aplicações dos fluidos de corte nas perações de usinagem. Este trabalho estuda o efeito do óleo vegetal de girassol nas forças de corte para o processo de furação do aço ABNT 1045, o fluido é aplicado na forma MQL -Minimum Quantity Lubrication (mínima quantidade de fluido) para diferentes condições de corte. São variados a velocidade de corte o avanço e o comprimento do furo. São utilizados dois níveis, para cada uma das variáveis de corte. Os resultados sugerem bom desempenho do óleo de girassol na pesquisa realizada.Palavras-chave: fluidos de corte, furação, aço ABNT 1045, técnica MQL.
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