Mechanical Analysis And Optimization Design Of Lager-size Double Row Four-point Contact Ball Bearings Used In Wind Turbines

The large-size double row four-point contact ball bearing is used in a wind-power generator system. The working characteristics and reliability of it will directly decide whether the wind-power generator can be operating smoothly. The special working environment in which a wind-power generator used requires the large-size double row four-point contact ball bearing has the advantage of long life, high reliability and low friction torque. The structural parameters of the large-size double row four-point contact ball bearing directly affect the distribution of the contact stress, lifetime, load-carrying capability and friction torque.Based on the Hertz contact and friction theory, this paper discusses the mechanical properties, load-carrying capability, fatigue life, oil film thickness, structure optimization and friction torque of the large-size double row four-point contact ball bearing in theory. The friction torque of the large-size double row four-point contact ball bearing is measured by the wind-power variable paddle bearing simulation test machine under the combined loads. Firstly, the mechanical analysis model can be established according to the structural characteristics of large double row four-point contact ball bearing and the loads of the bearing. ANSYS finite element analysis software is used to analysis the distribution of the stress of bearing and its results are compared with the results of numerical computation. According to the Lundberg-Palmgren theory, this paper presents the calculation method of the fatigue life of large row four-point contact ball bearing. The calculation model of the friction torque can be established according to analysis the friction characteristics of large row four-point contact ball bearing. Above all, this paper studies the effect of the structural parameters of the large-size double row four-point contact ball bearing on the distribution of the load, maximum contact stress, fatigue life, load-carrying capability, oil film thickness and friction torque. Then use the genetic algorithm theory to optimize the structural parameters of the bearing. Finally, by comparing the experimental value with the calculation value of the friction torque to verify the correctness of the calculation method of the friction torque mentioned in this paper.Results show that the structural parameters of the large-size double row four-point contact ball bearing have effect on the distribution of the load, fatigue life, minimum oil film thickness, load-carrying capability and friction torque. With the absolute value of the negative clearance of bearing increases the maximum contact stress and load decreases first and then increases; the original contact angle of the bearing increases with the increase in the maximum contact stress and load; the bearing groove curvature radius coefficient increases, the maximum contact stress and load increases. By comparing the calculation values of the contact stress by ANSYS with the numerical calculation values, there is little error between them. The structural parameters of the bearing affect the load-carrying capability. When the radial force is0kN, the bearing clearance has little influence on bearing capacity. With the increase of groove curvature radius coefficient, the load-carrying capacity decreases; the original contact angle increases, load-carrying capacity increases. With the radial force of the bearing increasing, the influence on the clearance and the groove curvature radius coefficient has the same tendency on the bearing capacity. The influence trend of the original contact angle on the bearing capacity of bearing is different. With the increase of absolute value of bearing negative clearance, the bearing fatigue life increases first and then decreases. The fatigue life decreases with the increasing bearing groove curvature radius coefficient. The minimum oil film thickness first increases and then decreases with the increasing clearance, groove curvature radius coefficient and original contact angle of bearing.