Faculdade de Engenharia Mecânica - FEM/ITEC
URI Permanente desta comunidadehttps://repositorio.ufpa.br/handle/2011/2551
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Item Acesso aberto (Open Access) Efeitos do comprimento de reversão e do ângulo de ataque sobre a estrutura de solidificação do cordão em soldagem MIG/MAG com "Switch Back"(Universidade Federal do Pará, 2012-06) ALMEIDA, Hélio Antônio Lameira de; MOTA, Carlos Alberto Mendes da; SCOTTI, AméricoThe welding technique denominated switch-back technique consists in a torch oscillation in the welding direction rather than transversally. However, there is not much information in literature about the solidification structure of the bead when this technique is applied. Therefore, in this work is presented a study on the effect of the torch leading angle and of the reversion course length over the bead solidification structure. Welds were carried out with Pulsed MIG/MAG Process on plain carbon steel plates. The results showed that the parameters under analysis modify the solidification mode of the bead. In general, when the angle of torch leads to pushing-pulling movement, equiaxial grains near the fusion line is favored. In relation to the course length, its increase leads to finer solidification structure.Item Acesso aberto (Open Access) Estimativa de vida útil do pbx (plastic-bonded explosive) com envelhecimento acelerado(Universidade Federal do Pará, 2016-07) KIRCHHOF, Edemar; ROCHA, Roberta Jachura; NAKAMURA, Nanci Miyeko; LAPA, Camila Maria; PINHEIRO, Glaci Ferreira Martins; GONÇALVES, Rene Francisco Boschi; ROCCO, José Atílio Fritz Fidel; ILHA, KoshunThis article aims to estimate the shelf life of the PBX by thermal analysis estimated by the Arrhenius equation, equivalent to the time of storage at accelerated aging. The PBX was subjected to accelerated aging in an oven at controlled temperature 60 ºC for periods of 5, 10, 15 and 25 weeks, which are equivalent to 5, 10, 15 and 25 of natural aging, respectively, at a temperature of 25 ºC. The curves of thermal decomposition of the samples were obtained by the DSC (Differential Scanning Calorimetry) technique. The kinetic parameters, such as the activation energy and pre-exponential factor, were determined by the Ozawa method and the Kissinger method. Initial results of this study indicated that, for a period of 25 years of storage in the cargo hold, the material did not change this aging significantly. To study the life of PBX analyzes, vacuum chemical stability were also conducted to verify the safety of explosive handling.Item Acesso aberto (Open Access) Revestimento de níquel depositado pela soldagem MIG e MIG com arame frio(Universidade Federal do Pará, 2016-12) MOTA, Carlos Alberto Mendes da; NASCIMENTO, Alexandre Saldanha do; GARCIA, Douglas Neves; SILVA, Diego Almir Silva da; TEIXEIRA, Felipe Ribeiro; FERRARESI, Valtair AntônioThis paper presents a study about the operational, geometrical and microstructural characteristics of GMAW and GMAW-CW (GMAW Cold Wire) welds applied on a coating of steel AISI 1020 plate, with a nickel superalloy ER NiCrMo-4, Hastelloy 276C type. The welding was automated in flat position, and executed with an electronic source on DC+ and having instantaneous acquisition of the welding voltage and current oscillograms. The input variables were the speeds of the electrode and cold wires and the welding speed. It was evaluated the operational processes and the effect of heat input on the geometrical characteristics (reinforcement and width), dilution, microstructure and microhardness of the coating. The results indicated a good operating performance, the absence of defects in single passes and in the GMAW-CW coatings. Furthermore, it has been found the lowest level of dilution.