EM - Escola de Minas
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/6
Notícias
A Escola de Minas de Ouro Preto foi fundada pelo cientista Claude Henri Gorceix e inaugurada em 12 de outubro de 1876.
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7 resultados
Resultados da Pesquisa
Item Characterization of flotation tailings from Samarco and other varieties of sand for use in sand molding in the foundry industry.(2019) Figueiredo, Ricardo Augusto Martins; Oliveira, Sávio José de; Silva, Guilherme Francisco de Sales; Vieira, Cláudio Batista; Pinto, Maria Aparecida; Carneiro, Leandro Moreira; Seshadri, Varadarajan; Araújo, Denilson Rodrigues de; Vilela Neto, Gil RibeiroFoundry sand used for molding should have specific properties so that molds with adequate strength, porosity, etc to produce defect free castings. Thus, characterization of two types of flotation tailings from the mineral processing of itabirites and three types of base sand for molding have been carried out. The resulting properties have been compared to evaluate the suitability of use of typical flotation tailing for the molding process. The main properties determined are the grain shape and structure, chemical composition, grain size distribution, fineness modulus, fines content, moisture content and loss on ignition. Furthermore other properties of these sands prepared with binders have been compared like compactability, permeability and green compressive strength for green sand. For cold set and sodium silicate/CO2 processes properties like tensile strength and bending strength have been evaluated. The results show that the flotation tailing SA2 presented a good potential of use in the foundry.Item Fracture toughness, fatigue crack resistance and wear resistance of two railroad steels.(2020) Godefroid, Leonardo Barbosa; Souza, Andrew T.; Pinto, Maria AparecidaThis research evaluated the microstructure and compared important mechanical properties of two steels for use in the railway sector. The main objective of the work was to verify the possibility of replacing a traditional C-Mn-Si pearlitic steel widely used in the world for application on rails, here called CS (common steel), by an also pearlitic steel with Nb and V micro-additions, rarely applied on rails, here called MS (microalloyed steel). The microstructures were characterized by means of pearlite colony size and pearlitic interlamellar spacing measurements, using light optical microscopy (LOM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The mechanical properties were evaluated by tensile tests, hardness tests, fracture toughness tests, force controlled axial fatigue tests, fatigue crack growth rate tests and microabrasion wear tests. CS presented a more refined microstructure than MS, due to differences in the thermomechanical industrial procedures. However, hardness, yield and tensile strength, and fracture toughness were similar for both steels. The main differences in the mechanical behavior were verified in the tensile ductility, fatigue crack growth resistance and wear resistance; the value for these three properties was higher for MS. Considering the main metallurgical requirements for an adequate selection of materials to be applied in the railway sector, these results show that the use of a Nb-V microalloyed steel is therefore a good option to ensure the best performance in service of the rail.Item Aferição de parâmetros de labirinto hidráulico em turbinas Francis: proposta de uma bancada de teste.(2020) Castro, Ana Leticia Pilz de; Serrano, Rodrigo Otávio Peréa; Sampaio, Mila Correa; Coelho, Stenio Augusto; Pinto, Maria Aparecida; Mancilla Rico, Edwin Andres; Viana, Edna Maria de Faria; Martinez, Carlos BarreiraA geração de energia elétrica no Brasil é fortemente dependente da hidroeletricidade. As turbinas hidráulicas são máquinas responsáveis em transformar a maior parte da energia do escoamento contínuo da água que a atravessa a usina hidrelétrica em trabalho mecânico. Os principais componentes das turbinas do tipo Francis são: o rotor, o distribuidor e a caixa espiral, e é no rotor onde estão localizados os anéis de desgaste superior e inferior, e entre os anéis de desgaste os labirintos inferior e superior. Contudo, a fuga de fluido que ocorre nos labirintos das turbinas hidráulicas um dos responsáveis pelas perdas de geração de energia elétrica, vislumbrou-se a necessidade de se desenvolver um aparato que permita simular um labirinto de uma turbina Francis, afim de obter parâmetros que poderão auxiliar na tomada de decisões de projetos nesse segmento.Item Case study : abrasive capacity of Limnoperna fortunei (golden mussel) shells on the wear of 3 different steel types.(2019) Castro, Ana Leticia Pilz de; Serrano, Rodrigo Otávio Peréa; Pinto, Maria Aparecida; Silva, Gilberto Henrique Tavares Álvares da; Ribeiro, Livia de Andrade; Viana, Edna Maria de Faria; Martinez, Carlos BarreiraThe impact of particles suspended in the water is responsible for the wear of mechanical surfaces in hydraulic systems. The characteristics and concentrations of these particles in the flow directly influence the intensity of the abrasion processes. Within this context, knowledge of the abrasive power of a particle is of great importance. It is known that an invasive species, known as golden mussel shell, has become embedded in several hydroelectric plants of the South and Southeast of Brazil, provoking an increase of the wear caused by shells that pass through the hydraulic system. In this context, the abrasive capacity of ground golden mussel shells on the three metallic materials used in the labyrinth component of the hydraulic turbines was analyzed. To determine the wear pattern and the relationship of the specific wear coefficient of the material (k), due to the increased concentration of golden mussel shell, micro-scale abrasive wear tests were performed on three different steel plates using abrasive suspensions at different concentrations of ground golden mussel shell in distilled water. The abrasivity of the golden mussel shell was also compared with the abrasivity of silicon carbide (SiC), commonly used as standard material in microabrasion tests. The analyses showed that the golden mussel shell is around 16 times less abrasive than the silicon carbide, taking into account the average obtained for the three different materials tested. In addition, the wear mechanisms acting on the SiC tests and those with the golden mussel shell were the same.Item Abrasive effects of sediments on impellers of pumps used for catching raw water.(2018) Serrano, Rodrigo Otávio Peréa; Castro, Ana Leticia Pilz de; Mancilla Rico, Edwin Andres; Pinto, Maria Aparecida; Viana, Edna Maria de Faria; Martinez, Carlos BarreiraThis study presents an analysis of the abrasive effects of sediments from the bed of the Acre River, Brazil, on the wear of three different ferrous materials employed in the manufacture of impellers of centrifuge pumps used to catch raw water. In order to evaluate the abrasive wear and specific wear coefficient (k) as a function of sediment concentration, tests were conducted in samples of SAE 8620 steel, nodular cast iron and gray cast iron by using a rotary-ball abrasion meter. These tests employed abrasive slurry with concentration of 1, 2, 3, 5 and 10 g L-1 of sediments in distilled water. The volume of worn material as a function of the relative velocity of water flow in relation to the impeller blades was mathematically estimated. The experimental results showed that: i) The semi-angular and semi-rounded shapes of the sediments from the Acre River produced evidence of micro-grooving and plastic deformation in the three metallic alloys; ii) SAE 8620 steel showed higher resistance to abrasive wear than samples of gray and nodular cast iron; iii) the increase in the volume of worn material due to increment in sediment concentration and the relative velocity of the mixture (water + sediment) to the rotor pads.Item The use of rapid prototyping in the joining of fractured historical silver object.(2017) Silva, Maria Luiza Seixas de Souza e; Assis, Paulo Santos; Figueiredo Junior, João Cura D'Ars; Pinto, Maria Aparecida; Paula, Daniella Gualberto CaldeiraPurpose – This paper aims to present a proposal for the restoration of a silver crown by means of fitting pieces produced by the process of 3D modelling and rapid prototyping. It also analyses the benefits of this procedure in restoration of objects weakened by corrosive processes. Design/methodology/approach – Elemental chemical analysis was carried out in the alloy used in the manufacture of the crown and the constructive and corrosive processes present were studied. Three fitting pieces were modelled and prototyped in wax casting by the stereolithography apparatus system aiming to restore the part and protect the original metal against impacts and external tensions which could speed up some deterioration processes. Findings – The procedure presented in this paper has shown that formal and dimensional accuracy, only achieved by means of 3D technologies, made the restoration and mechanical stability of the crown possible without the use of adhesives or welding. Originality/value – The proposed procedure is a new restoration alternative which causes minimal impact to the object and abides by the main standards for modern conservation. It is made with metal which is compatible with the original piece, retractable and easily identifiable.Item Effect of high-energy milling and sintering temperature on the structure of a hardmetal.(2018) Batista, Adriano Corrêa; Oliveira, Hellen Cristine Prata de; Filgueira, Marcello; Pinto, Maria Aparecida; Faria, Geraldo Lúcio de; Perpétuo, Genivaldo JulioThis paper evaluated the effect of high-energy milling and sintering temperature on the structural characteristics of WC- 10%Co. These samples were sintered at temperatures of 1350°C, 1400°C and 1450°C. The cooling rate of 100°C/h was used within the temperature range of 1000°C and 800°C to relieve residual stress from the sintering process. The samples were submitted to X-ray diffraction analysis with Rietveld refinement in order to characterize, at the atomic level, the effects of each processing stage on the material structure. The high-energy milling process may have accelerated the dissolution process of a large part of the WC particles during sintering, contributing to the formation of n phases. The characterization techniques were effective to evaluate the effects of high-energy milling, sintering temperature and residual stress on the structural characteristics of the composites investigated and the formation of amounts above 34% by weight of the Co W C and Co W C phases.