Engenharia Mecânica
URI permanente desta comunidadehttps://repositorio.fei.edu.br/handle/FEI/23
Navegar
7 resultados
Resultados da Pesquisa
- Surface integrity of INCONEL 718 turned under cryogenic conditions at high cutting speeds(2019-06-26) PEREIRA, W. H.; Sergio Delijaicov© 2019, Springer-Verlag London Ltd., part of Springer Nature.Nickel alloys such as Inconel 718 have been widely used in the aerospace, oil and gas, and chemical industries, since they have excellent properties that combine high creep resistance and high mechanical strength, fatigue and corrosion. However, these properties make these alloys extremely difficult to machine, due to a high level of heat generation during material removal, causing rapid wear of cutting tools and a detrimental effect on the surface integrity, reducing the fatigue life of the machined component and lowering the productivity. Looking at the literature, it seemed that there is an opportunity to study the surface integrity of Inconel 718, turned under cryogenic conditions at cutting speeds of 250, 275 and 300 m/min. For these reasons, this work aims to evaluate the influence of the cutting parameters on the surface integrity of Inconel 718 turned under cryogenic conditions using liquid nitrogen (LN2) at high cutting speeds. A whisker-reinforced ceramic tool was used in order to provide wear and shock resistance at high cutting speeds; these are factors that are associated with surface integrity in terms of roughness Ra, residual stresses, microhardness and cutting forces. A central composite design was chosen as factorial planning for the independent variables including cutting speed, feed rate and depth of cut when carrying out the experiments. Cryogenic cooling resulted in an average cutting force of 267 N, where the penetration force was higher. The roughness Ra was 0.52 μm and was influenced by the feed rate and depth of cut. The highest tensile residual stresses in the circumferential direction with LN2 and under dry conditions were 1394 MPa and 1237 MPa, respectively and were influenced by the depth of cut. Small changes in microhardness occurred at a depth of 0.3 mm from beneath machine surface and the presence of a white layer was not observed. Although tensile residual stresses were slightly higher when using LN2 compared to dry machining on the surface, the use of LN2 caused higher compressive residual stresses at the subsurface, which can improve the fatigue life of machined components at high cutting speeds. The results showed that lower cutting parameters tend to give the best results in terms of the cutting force and surface integrity.
- Development of a cyclic liquid nitrogen injection system and its application to minimum quantity lubrication milling of the Ti-6Al-4V alloy(2022-01-05) PASCHOALINOTO, N. W.; BATALHA, G. F.; LADIVEZ, P. S.; BORDINASSI E. C.; LIMA FILHO, A. F. DE; RIBEIRO, G. DE L. X.© 2021, The Author(s), under exclusive licence to Springer-Verlag London Ltd., part of Springer Nature.The Ti-6Al-4V alloy represents a large portion of the material used in medical and aerospace applications due to its excellent properties. Its machining requires unique conditions, and new machining proposals are presented every day. This work describes a condition of sustainable manufacturing, minimizing the waste of cutting fluid by a cycle lubrication approach. The system developed has an electronic circuit for controlling the flow of liquid nitrogen under pressure applied to a commercial valve. A 23 factorial planning design following the recommendations of the cutting insert manufacturer was carried out; the machining tests were performed under the conditions stipulated. Roughness studies were carried out for different cooling strategies as well as the insert flank wear. The cycle system showed that liquid nitrogen is saved and there are lower Sa and Sz roughness values compared with machining without lubrication and classical nitrogen injection. Simulations using the computational fluid dynamics approach were implemented. The behavior of a drop of liquid nitrogen under the action of gravity and its behavior in the bulkhead were simulated. The specified tool height when machining allows the adequate lubrication of the tool.
- 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.
- Correction to: Superficial residual stress, microstructure, and efficiency in similar joints of AA2024-T3 and AA7475-T761 aluminum alloys formed by friction stir welding (The International Journal of Advanced Manufacturing Technology, (2021), 116, 1-2, (117-136), 10.1007/s00170-021-07238-5)(2021-09-05) PERANDINI, J. P. B.; Ed Claudio Bordinassi; BATALHA, M. H. F.; CARUNCHIO, A. F.; Sergio Delijaicov© 2021, Springer-Verlag London Ltd., part of Springer Nature.The original article contained a mistake. The Figs. 14 and 15 are the same. The Fig. 14 needs to be changed to: (Figure presented.). The Figs. 16 and 17 are the same. The Fig. 16 needs to be changed to: (Figure presented.). The original article has been corrected.
- Numerical and experimental modeling of thermal errors in a five-axis CNC machining center(2018) dos Santos M.O.; Batalha G.F.; Bordinassi E.C.; Miori G.F.© 2018, Springer-Verlag London Ltd., part of Springer Nature.This work aims at the establishment of methodology to model and analyze the thermal errors of a five-axis CNC machining center, from an estimated temperature field, to finally model an artificial neural network (ANN) algorithm to accurately predict with robustness the thermal error. The thermoelastic behavior of the machining center was modeled through two different approaches: experimental (or data-driven) model and numerical (or physical) model. The thermal behavior of the machine was first modeled using finite element method (FEM) techniques based on theory of friction heat and convection heat and validated with the various experimentally raised temperature fields using temperature sensors and thermal imaging. The main machine subsystems were initially validated, such as ball screw system, linear guides, and spindle, which allowed for validating of the thermal behavior of the entire machine for five different duty cycles obtaining a maximum error of less than 8% when comparing the numerical results with the experimental results. The components of the thermal errors in X, Y, and Z directions were obtained through FEM by measuring the displacement of the spindle tip in relation to the reference bushing located on the worktable. The same procedure was experimentally performed using a touch probe system clamped in the spindle, and the results were compared obtaining a maximum deviation of 17 μm. The validation of the finite element model allowed for the use of the results obtained by the simulation to train and validate an ANN for predicting the thermal errors of the machining center. The relative errors between the thermal errors predicted by the ANN and the FEM simulation results were less than 1% indicating that the methodology developed in this work that combines the use of physical models with data-driven models is an accurate and robust tool to predict the thermal errors of the machine for various working conditions, even with the machine moving at different speeds or alternating the movement of the axles.
- 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.