## 3 Results and Discussion
### Residual Stresses  
In general, compressive stresses are considered beneficial to the fatigue life of the machined part, its creep life, and resistance to cracking under stress corrosion, while tensile residual stresses are rather harmful [35]. Residual stresses \(\sigma\) on rings were compressive in all analyzed positions, i.e., all their values were negative. From the practical perspective of an inner surface of bearing, this nature of the stresses can be considered favorable in terms of the component functionality and surface integrity. Figure 10a shows the diagram of normal residual stresses for samples O1 and O2 machined with the WIPER tool. On the surface of O2, it is seen that the differences between the values obtained in the areas around the cylinder were less dispersed compared with O1. In the case of O2 samples, the difference between the lowest and the highest value was found to be only around 50 MPa, which is about 10%, while O1 samples exhibited dispersion of the results of ca. 125 MPa, which is close to 20%. In turn, comparison between P1 and P2 samples (Figure 10b) showed that residual stresses varied from 450 MPa up to 540 MPa in P1, while P2 exhibited dispersion varied from 500 MPa up to 690 MPa. The samples P1 and P2 were machined with the same WIPER tool, but at higher cutting speed. Figure 9: Average results on a material proportion of the profile \(\overline{Rmr1}\) and respective topography parameter \(\overline{Smr1}\) of the bearing ring samples. Other machining methods generated much higher residual stresses in the upper layer of material, as presented in Figure 11. The lowest absolute value of stress \(\sigma\) obtained for the Q1 sample was 630 MPa, which was close to the highest values for the respective O1 and O2 samples. The rest of the tested samples exhibited higher absolute values of residual stress. Based on the graph in Figure 11, it can be concluded that all examined replaceable cutting inserts have generated a certain strengthening of the surface layer, which was manifested by the formation of compressive normal residual stresses. Thus, it is possible to assume a sufficient service life of the machined part. It should be noted that the highest compressive normal residual stresses were identified in the surface layers machined with XCEL cutting inserts denoted as S1 and S2. Variations between individual measurements in different angular positions were found to be close to 100 MPa, which was approximately 12-15%. Notably, it was suggested in the literature [20] that the wiper geometry of the tool enlarged the contact area between the cutting edge and the workpiece, which resulted in higher compressive residual stress. In our study, it appeared that the WIPER cutting inserts denoted O and P generated all the smallest absolute values of stress \(\sigma\) below 600 MPa. In addition to normal residual stresses, shear stresses \(\tau\) were also identified in the surface layer of the bearing rings. Their values are presented in the diagram shown in Figure 12. The presence of shear stress represents the displacement of individual microstructural layers of the material, resulting from imperfect cutting or excessive stretching of the material during the machining process. Figure 11: Results of normal residual stress \(\sigma\) measurement. Figure 10: Comparison of normal residual stresses \(\sigma\) after machining with WIPER insert: (**a**) samples O1 and O2; (**b**) samples P1 and P2. In general, shear stresses \(\tau\) were both negative and positive, but their absolute values did not exceed 40 MPa. Due to their low values compared with the material yield strength \(R_{e}\) = 590 MPa, the shear stresses can be considered negligible from the perspective of functionality and wear resistance. This observation leads to the conclusion that none of the tested cutting inserts generated outstanding shear stresses inside the surface layer of the machined bearing ring.