Study On Mechanical Property And Fatigue Life Of Large Rolling Bearing

Large rolling bearings are mainly used in occasions of low speed and heavy load due to its desirable properties such as large-scale structure and high bearing capacity. Currently, the research emphases of large rolling bearings are placed on load distribution, carrying capacity, fatigue life and structure optimization. Several analysis method such as theoretical calculation, mechanical model analysis and finite element analysis has been used in these researches. Unified approach for analysis of large bearing has not been formed because of the complexities of its geometrical structure, materials and heat treatments, as well as the unpredictability of its working conditions. This dissertation is supported by National Natural Science Funds of China (No.51005031) and it is aimed at building a more reasonable mechanical model and putting forward a new analysis method of fatigue life of large rolling bearing. Based on the content and objectives of the Fund, the following research has been done in this dissertation.Firstly, based on the previous studies of large rolling bearing, a simplified finite element model of load distribution and angle variation in a big rolling bearing is presented in this dissertation. The stiffness of the supporting structure and the deformation of the rings have been take into consideration in this model. The comparison of the numerical simulation with simplified the FE model is executed and the result shows that the simplified FE model is feasible.Secondly, in order to analyze the impact of the constrain, the stiffness and the local hard point of the supporting structure on the mechanical properties of large rolling bearings, a series of simplified FE model of large rolling bearing with different constraint and supporting structure has been established in this dissertation. The result shows that the constrain, the stiffness and the local hard point of the supporting structure have great influences on the mechanical properties of the bearing.Again, in order to analyze the contact pressure and the variation of the stress field and strain field with the depth of the raceway, an elastic model of contact between the rolling elements and the raceway has been built by using the FE method. It shows that the maximum equivalent stress and the maximum shearing strain occur at the sub-surface of the raceway. The methods of stress-life and strain-life are adopted to the fatigue life analysis of the large rolling bearing and the influence of the hardness of the raceway on the fatigue life is studied. The results suggest that the hardness of the raceway has a great influence on the fatigue life of large bearing.Finally, the impacts of the distance between the raceways and the radius coefficient of the raceway curvature on the mechanical properties of the double row four contact-point bearing are researched in order to optimize the distance and the radius coefficient. The mechanical properties and fatigue life of the bearing have been improved after optimization.The work in this dissertation may provide a reference for the design of large rolling bearing and its supporting structure.