The Analysis And Research On Life Influencing Factors Of Four Point Contact Ball Slewing Ring

Four-point-contact ball slewing rings are applied in the field of wind powergenerator, heavy machinery and large precision medical equipment manufacture, andplay an important role in guaranteeing the life of machines and the quality of theequipment as the main parts of them. Unlike the other bearings, most of slewing ringsare with large size and under the condition of heavy loads and mean atmosphere,including the immature technology because of the short time for being introduced andused, which leads to the short service life, such as most life being2-3years, cannotmeet the requirements of clients, so it is necessary to research and further analysis thelife influencing factors of slewing rings. In this paper, the influencing factors of four-point-contact ball slewing ring are analyzed from three main points with thecombination of the background and current research status of them.Allowable contact stress of four-point-contact ball slewing rings, as the firstinfluencing factor for the life, is analyzed with experiments. Firstly, the relationshipsbetween the hardening depth of raceway and the process parameters of heat-treatmentare analyzed according to the process of materials preparation, and then, it concludesseparately that the relationships between the allowable contact stress and the hardeningdepth, surface hardness and the osculation by researching the result data ofexperiments. Finally, the better heat treatment process for better hardening results andthe better hardening depth, surface hardness and the osculation for better allowablecontact stress can be obtained according to the analysis mentioned above. On that basis,the load-carrying properties of four-point-contact ball slewing rings are calculated withFEM (finite element method), which provides some reference for the design of slewingrings.Then, the friction torque of four-point-contact ball slewing rings is analyzed.Firstly, different experimental equations for calculating friction torque arecomparatively analyzed. And then, the relationships between the friction torque and the loads and the clearance are analyzed with experiments and the FEM is used forfurther studies. Finally, the fitting curves between the friction torque and differentloads and clearance are obtained, which provides some basis for the fitting rates.Finally, the performance of connecting bolts for four-point contact ball slewingbearings is analyzed with orthogonal method. The effects of major factors includingthe preload, friction coefficient and height of the bushes on the performance ofconnecting bolts are analyzed with FEM. The analysis indicates that the preload is themost important factor affecting the bolt connection performance, followed by theheight of the bushes less. And the friction coefficient is the least important factor,which is useful for improving the performance of bolts connection.