Engenharia Mecânica
URI permanente desta comunidadehttps://repositorio.fei.edu.br/handle/FEI/23
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2 resultados
Resultados da Pesquisa
- Characterization of the surface and mechanical properties of the friction stir welding in tri-dissimilar joints with aluminum alloys and titanium alloy(2018) Delijaicov S.; Yakabu D.Y.; De Macedo B.; Resende H.B.; Batalha M.H.F.© 2017, Springer-Verlag London Ltd., part of Springer Nature.The search for lighter and more resistant structures contributed to the development of effective welding methods. Among them, friction stir welding, a recent technique patented in 1991, in which welding is performed by the friction between a rotating tool and the materials to be welded, has widely been studied in the last decades. Among the advantages the technique provides, are the possibility of welding aluminum alloys series 2xxx and 7xxx, and the possibility of welding materials of different chemical compositions. The industry is still cautious about using this technique, yet several studies have been performed to improve knowledge on it. This research investigated the three dissimilar junctions between aluminum alloys 2024-T4 and 7475-T6 with titanium alloy Ti6Al4V. The aluminum alloys were positioned on the top portion of the welding creating a butt weld. The titanium alloy was placed on the bottom portion of the weld creating a lap welding with the aluminum alloy. The parameters of rotation, welding speed, and tilt were varied, following a central composite experimental design. Through the response surface analysis, it was possible to identify the correlation between the input and output parameters. This correlation is used to identify main influence between the parameters and can be used to optimization of the process. The influences of these parameters were evaluated on the welding surface by measuring residual stress and microhardness. The residual stress was analyzed by the hole drilling method on the aluminum side and by X-ray diffraction on the titanium side. The microhardness was analyzed by the Vickers test. On the aluminum side, residual stress and microhardness show a strong relation; high value of residual stress resulted in low value of microhardness. On the titanium side, residual stress shows a relation with temperature; the high value of temperature resulted in low value of stress. The tensile test was used to compare joint efficiency between different welding parameters and the base metal. It was possible to reach parameters in which the welding ultimate tensile stress exceeded the AA2024 value.
- CAF—a simplified approach to calculate springback in Al 7050 alloys(2017) Brandao F.M.; Delijaicov S.; Bortolussi R.© 2017, Springer-Verlag London.Aeronautical industries have looked for news fabrication processes to reduce the costs and the waste of the material during milling operations. One of these new processes is the creep age forming (CAF). The purpose of this work was based on springback analysis during the forming of single- and double-curved sheets of Al 7050 by the process of CAF. A simplified model based on a Norton power law was used in order to, alongside with a program of finite elements, allow the calculation of springback after the process. The experimental verification was carried out. Beside the springback results, other results were a decrease in the Young’s module of 11.5% in the creep aging temperature, in relation with ambient temperature during the CAF process and the variation of aluminum alloy’s yield stress during the process. The springback effect increased on the basis of aging time and then decreased due to intense aging of the alloy; an ideal time of 8 h is estimated for the Al 7050 alloy to carry out the CAF process. The research is limited to the use of the simplified model and its applicable results to Al 7050 alloys. Al 7050 is aligned with its vast use in the aeronautical industry, and the simplified model’s application may rapidly offer the necessary values of springback for the tooling project.