Engenharia Mecânica
URI permanente desta comunidadehttps://repositorio.fei.edu.br/handle/FEI/23
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2 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.