Study On The Effect Of Bolted Joints On Load Capacity And Life Of Slewing Bearing

The large-scale slewing bearing is a key component of all kinds of large equipment, which is simple in structure and can bear the combined load of radial force, axial force and overturning moment, so it is widely used. Large-scale slewing bearings and its supporting structure have large size and thick wall, and often be connected with their supporting structure with slender plain bolt. Therefore, the contact load, carrying capacity and fatigue life of the large-scale slewing bearing are easy to be affected by their low stiffness support structure and the connecting bolt. This dissertation is supported by National Natural Science Funds of China (No.51465025) and it is aimed at researching the effect of bolted joints and supporting structure on the life of the large-scale slewing bearing. This dissertation is aimed at exploring the influencing of the bolt connection parameters for internal contact load distribution, carrying capacity and fatigue life of the large-scale slewing bearing.First of all, a complete finite element simplified model of the large-scale slewing bearing with support structure and bolt connection is established in this paper, which uses the pre-tightening element to simulate the effect of preload. The effect of bolt pre-tightening force on the contact load and contact angle of rolling elements and the relationship between the bolt preload and the maximum contact load of the rolling elements in the large-scale slewing bearing have been studied using the finite element model with 54 bolts. And the relationship between the number of bolts and the distribution of the contact load and contact angle of rolling element in the large-scale slewing bearing has been researched using the finite element model with 560kN pre-tightening. The relationship between the number of bolts and the maximum contact load of the rolling elements in the bearing has been researched with 560kN pre-tightening force and 720kN pre-tightening force respectively.Next in importance, this paper established four finite element simplified model which have different supporting structure stiffness to analyze the effect of the supporting structure stiffness of the large-scale slewing bearings on internal rolling elements contact load, contact angle and elliptic boundary angle distribution. And the four models are a rigid outer ring model, a no bolt-part of the elastic support structure model, a no bolt-elastic support structure model and a bolt-elastic support structure model. And the effect of the supporting structure stiffness on the bearing capacity have been researched using the material limit stress, channel boundary angle and the maximum permissible slippage between bolt and bolt hole respectively as the judgment criterion.Ultimately, the effect of bolt pre-tightening force, bolt number and support structure stiffness on bearing fatigue life has been researched respectively by the Lundberg-Palmgren life theory and improved Lundberg-Palmgren life theory.