Engenharia Mecânica
URI permanente desta comunidadehttps://repositorio.fei.edu.br/handle/FEI/23
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Resultados da Pesquisa
- Superficial residual stress, microstructure, and efficiency in similar joints of AA2024-T3 and AA7475-T761 aluminum alloys formed by friction stir welding(2021-09-05) PERANDINI, J. P. B.; Ed Claudio Bordinassi; BATALHA, M. H. F.; CARUNCHIO, A. F.; Sergio Delijaicov© 2021, The Author(s), under exclusive licence to Springer-Verlag London Ltd., part of Springer Nature.Friction stir welding (FSW) represents a conceptually simple technique that consists of joining either similar or dissimilar solid-state materials through higher plastic deformation rates. FSW is an important technique in the aeronautical and aerospace industries, and its development is vital because of the significant difficulty in joining higher resistance AA 2000 and AA 7000 aluminum alloys with conventional techniques, like fusion welding, due to porosity and mechanical property losses. Thin sheets with a 1.6-mm nominal thickness of AA2024, heat treated to condition T3, and thin sheets with a 1.6-mm nominal thickness of AA7475, heat treated to condition T761, were used to investigate the influence of welding parameters under superficial residual stress and the efficiency of joints by FSW of AA2024-T3 and AA7475-T761 aluminum alloys. A central composite design (CCD) was used as a statistical model in this study (23 factorial points, six stellar points, two central points, and two replicas). Micrographic analysis showed that in the nugget zone of the AA7475-T761 alloy, there was hardness recovery. The fractography images showed that failures occurred mainly due to the joint line remnant defect, evidenced by the presence of cracks. The superficial residual stresses show a maximum value of 81 MPa at the advancing side in run 27 (hot welding) of AA2024-T3, whereas in AA7475-T761, a value of 57 MPa was found in the same run. Finally, tensile strength represents an efficiency of ~92% of the AA2024-T3 base metal value, while for AA7475-T761, this value was ~85%. From a component design perspective, the parameter window of this study is identified as interesting for its evaluation in the possible application in component manufacturing, due to the low values of superficial residual stresses found compared to those in previous work.
- 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.