A novel analytical model for prediction of forces in elliptical vibration-assisted turning using a dynamic friction model is presented in this article and verified with experimental elliptical vibration-assisted turning tests. In elliptical vibration-assisted turning process, the main cause of force reduction is the reversal of the friction force direction in a fraction of vibration cycle time. In analytical modeling of elliptical vibration-assisted turning, the change of the relative sliding velocity direction causes a stick–slip condition which cannot be detected with static friction models like Coulomb model. In this research, a dynamic friction model, named LuGre model, is used to predict the machining forces in elliptical vibration-assisted turning. To derive the model coefficients, a series of orthogonal cutting experiments are performed on Al 6061, Al 7075 T6, Copper and Inconel 718, and the friction coefficients are identified using genetic algorithm optimization method. The cutting forces are determined by incorporating the friction forces calculated from LuGre model. To verify the results, a series of elliptical vibration-assisted turning experiments are performed on four above-mentioned workpiece materials using an elliptical vibration-assisted turning tool. The machining forces are then compared with the analytical results. The results achieved from the analytical solution using LuGre dynamic friction model are in a good agreement with experimental results.
Corrosion resistance of materials is predominately dependent on their surface roughness. Therefore, surface finishing techniques can effectively improve the corrosion resistance of the components. Ultrasonic-assisted burnishing (UAB) process is a newly developed surface finishing technique capable of flattening the surface of components without material removal. This research experimentally investigated the effects of amplitude in the UAB process on surface roughness and corrosion performance of AA7075-T6 aluminum alloys. Turned sample (control) was treated by conventional burnishing (CB), followed by UAB with an amplitude of 10, 20, and 30 µm. Then, the surface roughness, microstructure, microhardness, and corrosion resistance of the treated samples were assessed. The surface roughness showed an improvement upon burnishing of the samples, where the best surface was achieved by UAB with an amplitude of 10 µm. UAB process also led to grain refinement such that finer grains could be achieved by increasing the amplitude. Microhardness also increased after the UAB process which got intensified by increasing the amplitude. The turned sample showed the least corrosion resistance, while the UAB-treated specimens (amplitude of 10 µm) exhibited minimal corrosion rate. Furthermore, the enhancement of UAB amplitude increased the surface roughness, causing a decline in corrosion resistance.
Nowadays, 7000 series aluminum alloys, especially, Al 7075 have found extensive applications especially in aerospace industries. Compared to high-strength steel alloys, Al 7075 has exhibited desirable mechanical properties such as high specific strength. However, their corrosion susceptibility and poor abrasion properties have limited the application of these alloys. Complementary operations such as ultrasonic-assisted ball burnishing have been suggested to overcome these limitations. Therefore, in this study, a newly developed 28 kHz ultrasonic-assisted ball burnishing device was designed and fabricated. Then, the effect of burnishing process was experimentally assessed on surface roughness, surface hardness, grain size, friction coefficient, and wear rate of the workpieces made of Al 7075. The results reveal the greater effectiveness of the ultrasonic-assisted ball burnishing process compared to conventional burnishing processes, in terms of improvements in surface roughness, surface hardness, grain size, frictional behavior, and wear rate. The friction coefficient was declined by 36.09% in the case of ultrasonic-assisted ball burnishing which was remarkably higher than conventional burnishing process with 7.39% reduction.
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