Influência da utilização do fluido de corte com adição de grafeno na temperatura de usinagem e formação de rebarba no processo de micro fresamento

As time passed, humanity needed the development of new materials used in various activities. High strength materials such as titanium and Inconel for example, had been studied because they are widely used for implants in biomedicine, as well as their use in aerospace and automotive industries. Because of its thermal and mechanical properties, these materials are considered difficult to machine, promoting a rapid wear of cutting tools, primarily caused by the high temperatures in machining. With the development of new materials has emerged the need of developing new manufacturing processes. One of today’s innovative processes is the micro-manufacturing. Being a process with a defined cutting tool geometry, burr formation is a constant and undesirable phenomenon formed during the machininig process. Being detrimental to the manufacturing process, overspending deburring operations are constantly employed leading to increase the aggregate cost to the manufactured material. Assembly components are also impaired if there is no control of the burr, with consequences including the disposal of components due to the occurence of this phenomenon. This paper presents the study of micro-milling Inconel 718, investigating influential parameters in the formation of burrs in order to minimize the occurrence of this phenome non. Different feed rates per tooth and cutting speed are evaluated, and different cutting fluids with different methods of applying the fluid. Adding graphene to cutting fluids was considered as a variable to be investigated, which is considered an excellent solid lubricant, in addition to increasing the thermal conductivity of the cooling solution (AZIMI; MOZAF FARI, 2015). The micro-milling temperature was evaluated in the present work. It was observed a new phenomenon that causes the machined surface temperature decreases below room temperature when using the solution water + oil. This phenomenon is explained in further chapters. In order to unravel this phenomenon, a new test was proposed and, from this test, it can be concluded, comparatively, which cutting fluid has a better cooling property.Using cutting fluid with different thermal properties has shown influence when analy zing burr formation and reducing machining temperature.

Investigação experimental das propriedades termofísicas e da convecção forçada de nanofluido de grafeno

This work presents an experimental investigation of thermal hydraulic performance of the nanofluid composed by graphene nanoparticles dispersed in a mixture of water and ethylene glycol at a ratio of 70:30% by volume. The tests were carried out under forced convection inside a circular tube with uniform heat flux on the wall for the laminar-turbulent transition regime. The mass flow rate ranged from 40 to 70 g/s corresponding to Reynolds numbers between 3000 and 7500. The heat flux was maintained constant at values of 11, 16 and 21 kW/m², as well as the inlet temperature of 15, 20 and 25°C. Three samples were produced with the nanofluid volumetric concentration of 0.05%, 0.10% and 0.15%. Thermophysical properties were experimentaly measured for all samples that were critically compared and discussed with theoretical models most commonly used in the literature. Initially, experiments with distilled water confirmed the validity of the experimental equipment for the thermo-hydraulic tests. Therefore, nanofluid samples that showed the highest thermal conductivity, corresponding to the volumetric concentrations of 0.15% and 0.10%, were subjected to the tests. The thermal-hydraulic performance for both samples was unsatisfactory. The heat transfer coefficients for convection of nanofluids reduced 21% in average, for the sample with = 0.15% and 26% and for =0.10%. The pressure drop of the samples was higher than the base fluid. Finally, the pressure drop and heat transfer coefficient by convection of both samples were also compared to theoretical models. The models used for pressure drop showed an excellent agreement with experimental results, which is remarkable considering the transitional flow.