Residual stresses are those stresses which remain in solid materials after removing the external load. Residual stresses which are induced by machining processes play important role in determining the service life of the machined components, depending on its magnitude, sign, and direction. This research provides a comprehensive correlation between three turning parameters and the resulting residual stresses formed on the surface of the outer ring of tapered roller needle bearing, made of 100CrMnSi6-4 type steel. The examined parameters were cutting speed, feed and tool nose radius. Radial and axial residual stresses on the surface were measured using sample cutting-free X-ray diffraction method. It is shown that the effect of one processing parameter can even be opposing depending on the other parameters. Thus, the effects of turning parameters on residual stresses must be examined in a comprehensive manner.
Nowadays lot of scientific work inspired by industry companies was done with the aim to avoid the use of cutting fluids in machining operations. The reasons were ecological and human health problems caused by the cutting fluid. The most logical solution, which can be taken to eliminate all of the problems associated with the use of cooling lubricant, is dry machining. In most cases, however, a machining operation without lubricant finds acceptance only when it is possible to guarantee that the part quality and machining times achieved in wet machining are equalled or surpassed. Surface finish has become an important indicator of quality and precision in manufacturing processes and it is considered as one of the most important parameter in industry. Today the quality of surface finish is a significant requirement for many workpieces. Thus, the choice of optimized cutting parameters is very important for controlling the required surface quality. In the present study, the influence of different machining parameters on surface roughness has been analysed. Experiments were conducted for turning, as it is the most frequently used machining process in machine industry. All these parameters have been studied in terms of depth of cut (ap), feed rate (f) and cutting speed (vc). As workpiece, material steel S235 has been selected. This work presents results of research done during turning realised on conventional lathe CDS 6250 BX-1000 with severe parameters. These demonstrate the necessity of further, more detailed research on turning process results.
The optimization of surface roughness values considered as one of the most significant issues regarding turning process of titanium alloys with the use of minimum quantity lubrication (MQL) method. With such an aim in mind, the application of TOPSIS-AHP method is implemented in order to establish the most favourable cutting parameters for the following values of surface roughness: Ra, Rq and Rz in machining of titanium alloys regarding MQL conditions. The proposed methodology consists of the two stages. At the beginning, tests on turning process were performed on CNC lathe, taking feed rate, approach angle, and cutting speed as input parameters. Then, the TOPSIS-AHP method was applied on the given experimental data and the optimum machining parameters were determined. The findings from current investigations showed that, lower values of cutting speed, feed rate and middle value of approach angle shows the optimal results.
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