Research On Mechanical Properties Of Large Pitch Bearing Under Complex Load Conditions

Harsh environmental conditions, complex load cases, large size and complex structure, particularly channel, all of these factors led to the methods of design general bearing cannot suitable for pitch bearing. Therefore, to establish reasonable theoretical mechanics model and finite element model that was suitable for large pitch bearing, study on the mechanical properties under complex service environment, reveal the influence of different structural parameters will provide a basis theoretical and data to make it possible for large turntable bearings wider application and its operational reliability.In this paper, the pitch bearing of Megawatt class wind turbine was researched, the load spectrum was analyzed and its extracted flow was established, by this way, the desired value was obtained. According to the empirical formula and Hertz elastic contact theory, the maximum contact load of pitch bearing was calculated. By analyzing the changes of the geometry of pitch bearing structure before and after applying load, according to the theory of elasticity, the calculation model that used to compute load distribution of pitch bearing with rigid and flexible ring was established. The contact stress distribution was calculated with FEM, and the effect of the contact angle, the radius of curvature coefficient and the clearance to maximum contact stress was analyzed. On the basis of the finite element calculation, based on Kriging model, the fast response model was constructed between the contact angle, the radius of curvature of the groove, the clearance value and the maximum contact stress.The research show that: Pitch bearing load distribution mechanical model of a rigid ring showing a cosine curve distribution. The gap of contact force between different position angle is reduced under a flexible ring raceway, and the load on each rolling element is more uniform, the number of the rolling elements under four-point contact state is increased. Under the same external load conditions, with the decrease of clearance values, the maximum contact stress value of the pitch bearing firstly decrease up to a certain value, and then increase; with the increase of the contact angle, the maximum contact stress of pitch bearing decreases and then increase, the contact angle is too large so that the contact area near the end of the circular surface of raceway, contact area is too small to making it easy to form a stress concentration, leading to excessive contact stress. The smaller the groove curvature radius coefficient, the greater the contact ellipse and the smaller the maximum contact stress.