Performance Study Of High-Speed Ball Bearing Based On Thermal-Mechanical Coupling Model

Ball bearing is an important support of high-speed CNC machine tool spindle unit,and its thermal properties are one of the main reasons affecting the machining accuracy of the machine tool.Therefore,small and evenly distributed temperature field of spindle unit is very important for the manufacturing of precision parts.This dissertation used the rolling bearing mechanics,tribology and heat transfer theory,combined with the research method of bearing multi-physical field,analyzed the influence of temperature rise on the geometric size and mechanical properties of bearing,and investigated the various tribological factors causing the bearing temperature rise.Based on the thermal-mechanical coupling analysis theory,a full Quasi-Dynamic mathematical model of high-speed ball bearing with coupling effect of multiple physical fields was established.Further,the dynamic performance of thermal-force coupling of bearing was studied.The main work and the results are as follows:Learning from bearing dynamics,using the analysis of the relative position of bearing parts in space to obtain contact deformation between contact parts,and to calculate contact stress,and on the basis of the existing bearing Quasi-Dynamic analysis method,a complete Quasi-Dynamic analysis model of angular contact ball bearing was established which the cage degrees of freedom has two or three more degrees of freedom than before.By using this model,the force between ball and ring,ball and cage,cage and guide ring can be analyzed more comprehensively.The correctness of this model analysis results was verified by comparing with the steady state calculation values of commercial software ADORE,thus laying a foundation for the establishment of the thermal-mechanical coupling simulation model of ball bearing.In order to reveal the temperature distribution of the spindle unit,first,using the local analysis method,the tangential friction and relative sliding speed of the contact parts of ball bearing were calculated to obtain the bearing heat generation,which would be as the initial parameters applied for establishing a simulation model of heat generation of spindle unit.Second,based on the heat transfer theory and Kirchhof's law,the thermal network node method was used to establish the steady-state temperature field simulation model of spindle unit under grease lubrication and oil-gas lubrication conditions,respectively.According to the constant pressure preload assembly conditions of transition fit between the ball bearing outer ring and bearing seat and interference fit between the inner ring and rotating shaft,a simulation analysis model of thermal-mechanical coupling mechanical properties of ball bearing was established by analyzing the coupling mechanism between the stress field,velocity field,lubricant flow field and temperature field of each part in ball bearing,taking the bearing structural parameters,the contact load between the ball and the raceway,the relative sliding speed and the characteristic parameters of the lubricant as the key coupling factors of multi-physics coupling,and combining with the ball bearing complete Quasi-Dynamic model and the spindle unit temperature field simulation model.Self-developed electric spindle directly driven ball bearing testing machine was used to measure the heat generation rate of the bearing and bearing outer ring temperature.Results show that the simulation model of heat generation is accurate and can provide reliable initial parameters for the analysis of the temperature field of the spindle unit,and simulation analysis model of thermal-mechanical coupling mechanical properties of ball bearing is also accurate.The simulation model of heat generation of spindle unit is used to explore the changing behave of heat generation of bearings with different structural parameters under different working conditions.Results indicate that with different speeds and thrust loads,the radius of curvature coefficient of the inner and outer ring raceways of the bearing takes a value within a specific range,which will get less heat generation,which provides a theoretical basis for the optimization of the bearing structure.Appling the simulation analysis model of thermal-mechanical coupling mechanical properties of ball bearing,the calculation and analysis of the dynamic performance parameters of the thermal-mechanical coupling state of the ball bearing under several working conditions suggest that with the increase of speed,the value of the contact load and spin-roll ratio between the ball and inner or outer raceway affected by temperature is larger than the value without considering the temperature effect,and the ball's rotation angular velocity is lower than the condition that the temperature effect is not considered.The increase of rotation speed causes the gradual increase in contact load and spin-roll ratio,and the decrease in the ball's rotation angular velocity also gradually increase.Such phenomena show that the increase of speed will increase the relative friction between ball parts,resulting in bearing temperature rise,which in turn leads to changes in bearing structure parameters.Excessive rotation speed will cause the bearing rolling element to "stuck" between the inner and outer ring raceways.With the increase of load,the value of contact load between the ball with the inner and outer raceways will significantly increase when the temperature is considered,and the rotation angular speed is reduced compared with the condition that the temperature is not affected.And the spin-roll ratio increases,indicating that the ball has a tendency to be clamped between the inner and outer raceways.In this paper,through the organic combination of the complete Quasi-Dynamic model of the ball bearing and the unit temperature field model of the main shaft,the thermal-mechanical coupling analysis model of the ball bearing is established.And the accuracy of the model is verified by the comparison of experimental results.The analyzing results of the dynamic performance of high-speed ball bearings using the established model suggest that the research results of this paper are helpful for guiding the design of high-speed ball bearings,the selection of external load and speed.