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.
Despite turning could be replaced by grinding as a finishing machining process, it is considered not satisfactory for elongating the fatigue life of the component because of the produced tensile residual stresses and irregularities formed at the surface. Therefore, a complimentary operation should be applied after hard turning. Slide diamond burnishing process is a mechanical finishing operation used after hard turning to further decrease the surface roughness, introducing compressive residual stresses, increasing the microhardness, and refining the microstructure of the surface and subsurface layer of the workpiece. The main result is increasing the fatigue life of the rotating components subjected to cyclic loading. In this work, the simultaneous effect of changing the burnishing speed, feed, and force of slide diamond burnishing on surface roughness, residual stresses, and microhardness of 42CrMo4 hard-turned steel was studied. It was found that the effect of one parameter was highly affected by the others. As a result, the optimal burnishing parameters were specified, with which better surface quality was obtained than after grinding.
Surface roughness characterization plays an important role in the qualification of machined surfaces. As a result of the development of high resolution 3D scanning techniques, researchers and technologists have more possibilities to analyze surface topography in a more detailed way. The purpose of this study is determining the minimal measurement area size of surfaces hard machined by single-point and abrasive tools. Some important height parameters were analyzed: Sa, Sq, Sp, Sv, Ssk and Sku. It was found that the minimum area sizes vary for the different roughness parameters, however, in several cases minimization is possible, depending on the purpose of the surface analytics.
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