Engenharia Mecânica
URI permanente desta comunidadehttps://repositorio.fei.edu.br/handle/FEI/23
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2 resultados
Resultados da Pesquisa
- Effect of weld parameters on residual stress, hardness and microstructure of dissimilar AA2024-T3 and AA7475-T761 friction stir welded joints(2018) Delijaicov S.; de Oliveira Silva P.A.; Resende H.B.; Batalha M.H.F.© 2018 Universidade Federal de Sao Carlos. All Rights Reserved.This study presents the effect of the welding parameters variation on the results of forces, temperature, residual stresses and Vickers micro hardness of dissimilar butt joints of AA2024-T3 and AA7475-T761 welded by friction stir welding (FSW). The tool rotational speed, feed rate and tool tilt angle were investigated using the Design of Experiments method. The obtained results of penetration force, temperature in the weld zone compared with the microscopic analysis of the microstructure showed that it is necessary a minimum amount of force and heat input to obtain a defect free weld zone. It was also notable that, friction stir welding has a wide stability range of its most significant parameters - rotational speed and feed rate - which grantee this minimum condition. Micro hardness’ profiles showed the effect of the grain size refinement towards the thermo-mechanically affected zone as well as, the effect of recrystallization inside the nugget. Residual stresses’ profiles showed a tensile stress peak at the shoulder contact area due the pressure with the base material on thermo-mechanically affected zone and the stress relief effect caused by high temperatures in the nugget resulting in a decrease in residual stress value. The most significant variables for residual stress results were rotational speed of the tool and welding feed rate, once their interaction rule the heat input in the weld zone.
- 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.