One way to increase bearing fatigue life and thus improve resource utilization is to improve surface and subsurface properties. It is known from the literature that the residual stress in the components subjected to rolling stress has an effect on the fatigue life of the components. Residual stress in the shear stress depth caused by the maximum load continues to increase bearing fatigue life. Voskamp conducted bearing tests in the running-in phase under increased load conditions and continued under more generalized loads. Since the bearing generates residual stress during the running-in phase, it has a positive effect on the bearing fatigue life. The results show that the fatigue life of deep groove ball bearings equipped with inner rings with residual stress generated by the above-mentioned short-term increased load running-in stage is 3 times higher than that of bearing rings without running-in stages. Bearings on the market are mostly machined by grinding and superfinishing, a production method with high yields and good machined surface quality, and can generate residual stresses up to 20 μm deep. In contrast, a production method using a combination of hard turning and deep rolling produces residual stress at the depth of maximum stress induced by the load, while achieving surface roughness comparable to that after grinding and superfinishing. The first step in improving bearing fatigue life is to conduct a study of changes in the subsurface area of ​​a standard bearing. Next, a manufacturing process combining hard turning and deep rolling was developed and tested to determine how to specifically tune surface and subsurface properties. A model for calculating bearing fatigue life based on bearing pre-residual stress is established. Finally, the bearings produced by the new process are verified on a four-bearing test rig. 1. Test technology Use Hembrug Microturn100 lathe to hard turn the inner ring of NU206 cylindrical roller bearing. The bearing material is 100Cr6 steel with a hardness of 62 HRC after quenching and tempering. Carbide cutters, model DNMA150616, were used as hard turning tools, and the micro-geometry of the cutting edge was adjusted by brushing and grinding. These tools are provided by the manufacturer and have a conventional Al2O3+Ti(C,N) coating. The deep rolling process uses hydrostatic rolling tools for processing. Bearings are run on a four-bearing test rig. On the one hand, so-called screening tests are used to record the changes in boundary area properties over test time and to determine suitable surface and boundary area properties. On the other hand, statistics of fatigue tests are performed. Under pure radial load, 4 sets of test bearings are run on the test bench at the same time, and each set of bearings bears the same load. The test bench is equipped with the lubricating oil temperature control function, which can realize precise control of the lubricating oil temperature of the test bearing. During the test, a fully synthetic lubricating oil with a viscosity of η40 of 68 mm2/s (η100 of 8.9 mm2/s) was used. The set speed n is 4050 r/min, and the oil temperature is 60 ℃. During the test, the specific oil film thickness λ is not less than 3 to ensure that the bearing is lubricated by full oil film. The peeling damage of the bearing is monitored by the vibration signal, and the test is stopped as soon as the damage is detected. Selecting a radial load with C/P of 4, the Hertz stress pmax generated on the bearing at this time is 2500 MPa. Bearing fatigue life test is carried out by sudden death method. 2. Cylindrical roller bearings produced by hard turning-rolling process As shown by Denkena et al., turning and deep rolling have similarities in process control, so they can be well combined. The precise positioning of the rolling ball on the surface is more conducive to the precise processing of the surface topography of the raceway, so this process is suitable for the manufacture of rolling bearings. The concept shown in Figure 1a has been developed for the machining of inner rings. The machining tool is shown in Fig. 1b. In order to ensure the positioning of the rolling ball in the rotation channel in the feed direction, the ball diameter (dk is 3.175mm) and the corner radius of the insert (r is 1.6mm) should be matched. The positioning of the ball adopts a wedge-shaped guide rail to ensure the positioning accuracy of ±2 μm. Fig. 1 Hard turning-rolling composite process tool The hard turning process cannot obtain better internal stress while ensuring the surface roughness. During machining, the surface roughness is determined by the feed rate and the radius of the cutting edge. If the radius of the cutting edge is too large, the surface roughness will be reduced, and a large residual stress will be generated at the depth of z up to 300 μm. The surface roughness can be effectively reduced by the deep rolling process, and a large residual compressive stress can be obtained at the same time. The effects of feed rate and coverage u on surface roughness during hard turning and turning-rolling are shown in Fig. 2. The surface finish quality is only affected by the coverage u. A process control variable Nw is introduced as an offset factor to describe the position of the ball on the surface. Here Nw is the ratio of the displacement χf in the feed direction to the feed amount f. The influence principle of residual stress is similar to that of Hertz contact stress. The penetration depth of residual stress increases with the size of the sphere. Rolling stress affects the magnitude of residual compressive stress.