Mechanical Analysis Of Angular Contact Ball Bearings Under Complicated Working Conditions

In industrial equipments, rolling bearings not only need to restrict the radial load as a supporter, but also to bear the axial force created by the rotor system. Angular contact ball bearings are a type of bearings usually to withstand both the radial and axial loads.For its high dn value and high load carrying capacity, angular contact ball bearings are widely used in industrial gas turbines and precision machine tools. Such an operating environment needs the bearings running with high accuracy and high reliability. The mechanical response and running health of the bearing structure need to be studied when working at multiple loading conditions.In this paper, an accurate model of the main bearings of a gas turbine is set up. Based on the finite element software ABAQUS, we first analyze the radial clearance of bearing for the assembled bearing working under a high-speed and high temperature. Then we take these effects into consideration of the subsequent working conditions of high speed and large axial force to make a further analysis. In order to ensure the analysis reliability and accuracy, the sequential coupling and sub-model method were utilized.Based on sub-model method, the results show that the static friction has little influence on the surface layer stress of ball race contact surface, while sliding friction makes the maximum shear stress in the surface layer increased and moved to the surface. The depth of the maximum shear stress occurring under the surface layer by the static loading analysis cannot used to assess the surface hardening thickness.Without considering the impact of centrifugal force on the ball, we establish an axisymmetric model to calculate the bearing radial clearance caused by assembly stress, temperature and centrifugal force. It was found that the temperature increasing and assembly stress have a great influence on the radial clearance of the bearing. The thermal expansion of the ball plays an important role in changing radial clearance, which is larger than 50%. However, the centrifugal force and contact deformation have a marginal effect in changing the radial clearance of bearing.Establish a 3D model and couple the radial clearance caused by the preceding loads. We can get influence on the bearing structure carried by the added axial load. When the bearing works under high speed and large axial load, the inner bearing ring becomes the weak areas of bearing failure destruction because the inner raceway contact stress is higher than the outer raceway at this condition. The additional axial displacement of the inner ring induced by the rolling balls can be constrained through preloading a relatively low axial force. A proper axial preloading can reduce the influence of the axial displacement and improve the resistance ability to axial impact load. Axial preloading can improve the contact condition of balls and reduce the screw rolling ratio of balls at the inner raceway contact position. With increasing the axial load, the friction power increases with a monotone manner. It is not feasible to reduce screw rolling power of the balls only through enlarging the axial preloading. Reducing friction coefficient and decreasing the contact pressure can effectively decrease the spin friction lost power.