Micro-contact EHL friction and heat generation analysis of high speed ball bearings

A novel method to calculate differential sliding friction heat is proposed to solve the problems that the integral heating method is not accurate in the differential sliding friction heat generation calculation of angular contact ball bearings in motorized spindles, and the calculation of local heating methods depends on expensive traction experimental equipments and huge amount of works. The proposed method is based on EHL and micro-contact theories instead of traction experiments. The rotation speed of balls and the parameters of inner loads are calculated based on a quasi-static method, then the friction shear stress in contact areas of the ball-race is calculated based on EHL and micro-contact theories. Then, the differential sliding friction heat generation is worked out and the total heat generation is calculated. The proposed method is verified by a comparison with the traditional local heat generation method based on traction experiments, and it turns out that the rate of deviation between calculated results of the novel method and the experimental local heat method is below 5% under the work condition of rotation speeds in range 5000 to 20000 r/min for 7008AC ball bearings, and the rate of deviation is 23% under the work condition of rotation speeds in 20000 to 40000 r/min. The effects of designing parameters on heat generation of ball bearings are analyzed, and it is pointed out that designers should try to choose larger radius coefficients for inner ring groove curvature and smaller radius coefficients for outer ring groove curvature while considering other designing demands and influences.