Influencia da Carga no Comportamento quanto ao Desgaste de um Aco ABNT-1020 Bifasico Revenido a 450°C

The wear rate of the dual-phase steel ABNT-1020 tempered at 450°C sliding against cemented steel ABNT-1020 in function of load value is investigated in wide load range. The alteration in behavior of this function at intermediate load level, like in the case of low hardness steel sliding against high hardness steel, is observed. The analysis by scanning electronic microscope before and after this alteration showed a change of wear mechanism from plastic displacement to embrittlement.

Friction and wear properties of functionally graded aluminum matrix composites

Aluminum matrix composites are currently considered as promising materials for tribological applications in the automotive, aircraft and aerospace industries due to their great advantage of a high strength-to-weight ratio. A superior combination of surface and bulk mechanical properties can be attained if these composites are processed as functionally graded materials (FGM's). In this work, homogeneous aluminum based matrix composite, cast by gravity, and aluminum composites with functionally graded properties, obtained by centrifugal cast, are tested against nodular cast iron in a pin-on-disc tribometer. Three different volume fractions of SiC reinforcing particles in each FGM were considered in order to evaluate their friction and wear properties. The sliding experiments were conducted without lubrication, at room temperature, under a normal load of 5 N and constant sliding speed of 0.5 ms-1. The worn surfaces as well as the wear debris were characterized by SEM/EDS and by atomic force microscopy (AFM). The friction coefficient revealed a slightly decrease (from 0.60 to 0.50) when FGM's are involved in the contact instead of the homogeneous composite. Relatively low values of the wear coefficient were obtained for functionally graded aluminum matrix composites (≈10-6 mm3N-1 m-1), which exhibited superior wear resistance than the homogeneous composite and the opposing cast iron surface. Characterization of worn surfaces indicated that the combined effect of reinforcing particles as load bearing elements and the formation of protective adherent iron-rich tribolayers has a decisive role on the friction and wear properties of aluminum matrix composites.

Production of Ti-35Nb alloy by powder metallurgy for aerospace application

Titanium and its alloys provide high strength-to-weight ratios, good fatigue strength and increased corrosion resistance compared with others materials. Its acceptance in aerospace has been limited by costs considerations such as high cost of raw material, high buy-to-fly ratios and expensive machining operations. Significant cost reductions can be obtained by vacuum sintering and powder metallurgy (P/M) techniques by producing near net shapes and consequently minimizing material waste and machining time. The Ti 35Nb alloy exhibit a low modulus of elasticity. Stemming from the unique combination of high strength, low modulus of elasticity and low density, this alloy is intrinsically more resistant to shock and explosion damages than most other engineering materials. Samples were produced by mixing of initial metallic powders followed by uniaxial and cold isostatic pressing with subsequent densification by sintering between 900 and 1600 °C, in vacuum. Sintering behavior was studied by means of dilatometry. Sintered samples were characterized for phase composition, microstructure and microhardness by X-ray diffraction, scanning electron microscopy and Vickers indentation, respectively. Density was measured by Archimedes method. Copyright © 2004 Society of Automotive Engineers, Inc.

Comparative study on turning CI and CGI using silicon nitride cutting tools

There has been a great interest for improving the machining of cast iron materials in the automotive and other industries. Comparative studies for tool used to machine grey cast iron (CI) and compacted graphite iron (CGI) on dry machining were also performed in order to find out why in this case the tool lifetime is not significantly higher. However the machining these materials while considering turning with the traditional high-speed steel and carbide cutting tools present any disadvantages. One of these disadvantages is that all the traditional machining processes involve the cooling fluid to remove the heat generated on workpiece due to friction during cutting. This paper present a new generation of ceramic cutting tool exhibiting improved properties and important advances in machining CI and CGI. The tool performance was analyzed in function of flank wear, temperature and roughness, while can be observed that main effects were found for tool wear, were abrasion to CI and inter-diffusion of constituting elements between tool and CGI, causing crater. However the difference in tool lifetime can be explained by the formation of a MnS layer on the tool surface in the case of grey CI. This layer is missing in the case of CGI.

Estimate of concrete block texture using image analysis

The texture of concrete blocks is very important and is often the decisive factor when choosing a product, particularly if the building specifications call for high-strength blocks allied to low-cost finish, in which case exposed blocks with a closer texture are often preferred. Furthermore, a closer texture, especially for exteriors, may be a vital factor in ensuring the building's durability. At present, however, there is no standard to quantify the texture of a structural block. Further, when studying masonry blocks compressive strength should never be overlooked. This article discusses a procedure to produce concrete block textures with and without the addition of lime, but still to achieve the required compressive strength. The method used in this study, to evaluate texture, proved to be simpler and cheaper than methods reported by other authors in the literature. The addition of small quantities of lime proved beneficial for both texture and compressive strength. Increasing the amount of lime further, however, only improved texture.

Concreto de alto desempenho com adição de resíduos de borracha de pneu

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Avaliação dos parâmetros de soldagem para compósitos de PPS/fibras contínuas com aplicações aeronáuticas

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Propriedades físico-mecânicas de painéis particulados de Eucalyptus saligna e casca de noz macadâmia

Pós-graduação em Engenharia Mecânica - FEG

Investigação do potencial dos ensaios APULOT e pull-out para estimativa da resistência a compressão do concreto

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Análise de variáveis dinâmicas na fundição centrifugada de cilindros de laminação

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Caracterização microestrutural e mecânica de aços bifásicos de ultra-alta resistência como médio teor de carbono

Pós-graduação em Engenharia Mecânica - FEG

Estudos dos efeitos no comportamento em fadiga das camadas de níquel eletrolítico, processo sulfamato, em aços de alta resistência

Pós-graduação em Engenharia Mecânica - FEG

Análise experimental de lajes lisas unidirecionais de concreto armado de alta resistência com metacaulim apoiadas em pilares retangulares e armadas à punção

Foram analisadas experimentalmente 10 (dez) lajes lisas de concreto dosado com metacaulim e concreto de alta resistência (fcc =60 MPa). submetidas a carregamento simétrico. objetivando analisar a influência da variação do índice de retangularidade dos pilares (CIII;{. mm = 1. 3 e 5) e de armaduras de cisa1harnento na resistência ao puncionamento das mesmas. As armaduras de cisalhamento foram constituídas por estribos abertos inclinados. As lajes tinham dimensões de (1.800 x 1.800 x 110) mm e as principais variáveis foram à variação do índice de retangularidade dos pilares e distribuição dos estribos inclinados em tomo dos mesmos. Analisou-se os resultados de cargas de ruptura. flechas. mapa de fissuração. ductilidade. deformações no concreto e nas armaduras de ftexão e cisalhamento, e os modos de ruptura atingidos. Os resultados experimentais foram comparados com os resultados estimados por diversas normas. São também apresentados os resultados obridos numericamente para as lajes ensaiadas e comparados com os resultados experimentais. Os resultados experimentais mostraram que o aumento do índice de retangularidade faz com que as forças cortantes se concentrem nas extremidades do pilar, o que sugere que nessa região as armaduras de combate ao pmtcionamento são mais solicitadas. Os estribos inclinados foram eficientes no aumento das cargas de ruptura e alteraram inclusive o modo de ruptura de algumas lajes. Observou-se ganhos de até 32% quando os estribos foram distribuídos em tomo das extremidades dos pilares. A baixa capacidade resistente à flexão limitou a resistência última.

Proposição de um novo método de medição do desgaste em ferramentas de corte empregadas em operações de fresamento da madeira

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Obtenção e caracterização de compósitos de fibras de carbono/PEKK com aplicações aeronaúticas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)