Programa de Pós-Graduação em Engenharia Industrial - PPGEI/ITEC
URI Permanente desta comunidadehttps://repositorio.ufpa.br/handle/2011/10050
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Navegando Programa de Pós-Graduação em Engenharia Industrial - PPGEI/ITEC por Orientadores "MACHADO, Paulo Cordeiro"
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Item Acesso aberto (Open Access) Análise do estado plano de tensões em chapas de aço ASTM A131 por métodos ultrassônicos(Universidade Federal do Pará, 2023-08-17) ALBUQUERQUE, Lucas Gabriel de Sousa; MACHADO, Paulo Cordeiro; http://lattes.cnpq.br/0133330144786049; https://orcid.org/0000-0003-4375-6812Residual stresses affect the mechanical component in the same way that external stresses do. These stresses usually arise in the manufacturing process. By knowing the residual stresses, mainly the tensile stresses, present in a component or those that may be generated by some manufacturing process, it is possible to take actions to avoid or minimize their effects, thus extending the component's useful life. Thus, residual stress will always be a demand to be studied, both by academia and by the metal-mechanic industry. Therefore, the objective of this work was to determine the plane state of residual stresses in ASTM A131 steel plates by combined shear and compressive ultrasonic wave methods. A TIG welding torch was used to induce residual stresses in the plates by the high thermal gradient. The specimens were xed by supports to avoid deformation, thus preserving the residual stresses. Three different methods were applied, named, in this paper, as: Hirao I; Clark; and Hirao II. The major difference between them is related to the preferred direction of wave propagation. Stresses in different directions from the anisotropy axis can change this direction. Consequently, the angle between the anisotropy and the preferential direction of propagation of the ultrasonic wave (φ) is changed. To measure the propagation time of the ultrasonic waves, a software was developed for the acquisition of the ultrasonic response signals and another one for the data processing.To end the preferential angle of wave propagation, a support was made by 3D printing, which allowed the transducer to be moved using a stepper motor. In all three methods, very high tensile stresses were observed near the melt zone, which decreased rapidly as the distance from this region increased. In addition, the values of φ were lower in the center line than in the lateral lines, indicating variation in residual stress levels as function of distance from the constraints.Item Acesso aberto (Open Access) Avaliação da resistência ao desgaste do aço hadfield e ferro fundido branco alto cromo em ensaio pino-disco com fragmentação de abrasivo para aplicações na mineração(Universidade Federal do Pará, 2024-11-12) SILVA, Rute Nara de Jesus Farias da; MACHADO, Paulo Cordeiro; http://lattes.cnpq.br/0133330144786049Mining, as an industry with processes that include excavation, crushing, and grinding, faces high levels of wear, resulting in component failures, increased energy consumption, and operational costs. Studies indicate that global energy consumption in mining activities is significant, with a large portion used to overcome friction and replace worn parts. The present work investigates the efficiency of different materials, such as Hadfield steel with 15% Mn (Mn15) and high-chromium white cast iron (HCWCI), in resisting abrasive wear, as well as parameterizing the test equipment for the two materials. The Pin-on-Disc Abrasive Wear Test with Abrasive Fragmentation (PDFA) was used to simulate and evaluate the abrasive wear resistance of these materials. The research compares the wear micromechanisms observed in the PDFA test with those found in the jaw crusher test, aiming to identify less complex and more cost-effective ways to evaluate the studied materials. This emphasizes the importance of tests that closely replicate real operational conditions, optimizing material selection while reducing costs, energy consumption, and CO2 emissions in mining. The characterization of the worn samples was performed using optical microscopy and scanning electron microscopy (SEM) in SE, BSE, and EDS modes. The wear rates were 0.0006 g/min for HCWCI and 0.0021 g/min for Mn15 steel. Additionally, similar micromechanisms, such as microgrooving, microcutting, and microcracking, were observed on the surfaces of both materials, comparable to those identified in fixed jaw samples tested under jaw crusher conditions.Item Acesso aberto (Open Access) Efeito da temperatura, tempo e taxa de resfriamento na formação do eutetóide divorciado em soldas de trilhos de aço perlítico(Universidade Federal do Pará, 2021-06-01) BARBOSA, Matheus dos Santos; MACHADO, Paulo Cordeiro; http://lattes.cnpq.br/0133330144786049The hardness reduction that occurs at the end of the Heat Affected Zone (HAZ) of welded joints of railway is generated through of the Divorced Eutectoid formation (DE). This transformation happens in the weld during the cooling of the austenite when there is presence of undissolved carbides, which, in turn, act as preexisting cores for the formation of this microstructure, forming a combination of spheroidized cementite + ferrite. In order to understand this microstructural transformation, samples of premium and superpremium rails were tested by dilatometry, with a full factorial Design Of Experiments (DOE) that evaluated the effects of variables temperature, holding time and cooling rate; and their interactions. The samples after thermal cycling were characterized by microhardness test and scanning electron microscopy analysis. The results showed that the highest DE fractions were obtained at higher temperatures (750 °C) and with higher equivalent carbon. However, by increasing the cooling rate, from 1.5 to 9 °C/s, resulted in a reduction of the DE fraction of 49% for the premium rail at 750 °C and 75% for the superpremium rail at 740 °C. Regarding hardness, the behavior was inversely proportional, where the increase in the cooling rate provided an increase in the hardness of the rails (about 21%), in addition, the samples simulated at 740 and 750 °C and cooled to 1.5° C/s showed hardness similar to that was found in the region of lower hardness of rails welded by Flash Butt Weld (FBW). The factors that had the greatest effect on DE formation, in increasing order, were temperature, equivalent carbon and cooling rate.Item Acesso aberto (Open Access) Influência da taxa de resfriamento nas tensões residuais de solda por centelhamento de trilho ferroviário(Universidade Federal do Pará, 2021-12-22) BARILE, Iury Klay Peres; COSTA, Ednelson da Silva; http://lattes.cnpq.br/0045584096510351; HTTPS://ORCID.ORG/0000-0002-7290-3810; MACHADO, Paulo Cordeiro; http://lattes.cnpq.br/0133330144786049; https://orcid.org/0000-0003-4375-6812The process of manufacturing and welding in rail induces residual stresses that can act in a deleterious way to the structural integrity of this component, especially in cases where the tractive stresses, can favor the nucleation and propagation of cracks, may cause premature rail failure. The objective this work is evaluate the residual stresses of rails welded by flash butt welding (FBW) with and without heat treatment post welding with forced air cooling. The techniques measurement of residual stress ultrasound using shear waves in the metal base and hole Drilling in the center of the weld and in the zone thermally affected (HAZ). The techniques presented similar results to those found in the literature, for the head, tensile stresses were found in the base metal region, and compressive stresses in the HAZ and center of the weld. In the web, tensile stresses were found at the HAZ and the center of the weld.