Contact Stress Field Analysis Of Raceway Of High-speed Angular Contact Ceramic Ball Bearings

High-speed angular contact ceramic ball bearings has become an important part of high-speed machine tools for its outstanding functional advantages. The fatigue life of it has been the focus of attention. The actual stress field of the raceway surface layer has a huge influence on the fatigue life. The actual stress field is formed by the coupling of the residual stress induced by machining process and the working stress under specific working conditions. Therefore, it has much guiding significance for the machining of the bearing rings to analyze and summarize the characteristics of the residual stress of the raceway surface layer which are good for improving the fatigue life, when in given conditions. For this purpose, this paper mainly deals with B7008C bearing, analyze the working stress of raceway layer in given conditions, and couples it with residual stress with different characteristics. The actual stress was then calculated and used to analyze the influence of the residual stress characteristics on fatigue life. The main researches are as follows:For B7008C bearing, the basic theories of high-speed angular contact ceramic ball bearing has been concluded, preparing for the analysis and calculation of the quasi-dynamic model. The theories are:the basic geometry and motion relationship in the angular contact ball bearings; the calculation of contact stress and deformation based on Hertz theory; the EHL theory of rolling bearings; the influence and calculation formulas of the centrifugal force and gyroscopic torque induced by high speed. Then the quasi-dynamic model was chosen to calculate the parameters needed in FEM.In the quasi-dynamic model, taking the ball spinning into consideration, the formula to calculate the tangential stress between the ball and the raceway was established based on the EHL theory. Then according to the force analysis of the bearing, the equilibrium equations of the ball and the rings, the compatibility equations of deformation, the load-deformation equations were established. The normal forces, the tangential forces, the contact angles, the rotation and revolution speed of the ball were calculated from those simultaneous equations in Matlab.The inner raceway model of B7008C bearing was established in ANSYS Workbench. Making the quasi-dynamic parameters solved as boundary conditions, the working stress field of the raceway surface layer was calculated. The results of the normal stress shows that the stress in the contact area is mainly positive, while the rest part is mainly negative stress of low value. Besides, the results of the maximum shear stress shows that as the bearing speed increases, the peak value of the maximum shear stress will increase and the depth of it will be shallow, leading to a lower fatigue life.Baed on the residual stress of bearing raceway induced by grinding, the surface stress value, the stress value of turning point and the depth of the turning point were taken as variables to form different residual stress fields. The residual stress fields with different characteristics were coupled with the working stress in ANSYS. According to the distribution of the maximum shear stress, the conclusions are: the residual stress of grinding is beneficial for the fatigue life of the raceway; the fatigue life will increase as the surface stress value, the stress value of turning point and the depth of the turning point increase. However, the positive effect for fatigue life of the characteristic values has a critical point as the effect is much less obvious when the characteristic value reaches a certain point. Besides, the critical value of the characteristics will fall as the bearing speed increases.