| The thermo-mechanical couplinganalysis modelof the spindle-bearing systembased on Hertz's contact theory and the point contact non-Newtonian thermal elastohydrodynamic lubrication(EHL) theory is established. In this model, the effect of preload, centrifugal force, gyroscopic moment, and lubrication state of the spindle-bearing system are considered. According to the heat transfer theory, the calculation model for thetemperature field of the spindle system is established and the effect of the spindle cooling system on the distribution of the spindle temperature field is analyzed. The theoretical simulation and the experimental results show that, the installation preload of the bearing has great effect on the heat generation while the cooling fluid has great effect on the heat balance of the spindle system. If the steady-state heat balance between the friction heat generation and the cooling system cannot be reached, the thermal-induced preload will lead to further increase of the friction heat generation and then cause thermal failure phenomenon of the spindle. The following works have been accomplished:1. Based on Hertz contact theory, the dynamics of rolling bearing and raceway control theory, the mathematical model of the mechanical properties of high speed rolling bearing is developed by considering external loads, preload and inertial load. Ball-inner and ball-outer raceway contact deformation and internal load distribution are analyzed and calculated.2. According to the fractal geometry theory and statistical theory, bearing surface morphology were characterized, based on the Reynolds hydrodynamic lubrication theory, using the dimensionless mathematical equation of oil film thickness, grease oil film thickness equation is obtained with considering the temperature change.3. Based on point contact non-Newtonian thermal elastohydrodynamic lubrication theory, thermal- mechanical coupling analysis modelof the spindle-bearing system is developed. This model considers the influence of bearing preload, centrifugal force, the gyroscopic moment and lubrication state.4. According to the theory of heat transfer, heat transfer model of the spindle system is developed, the model of rolling element and the contact thermal resistance between inner and outer raceway, the heat transfer coefficient of the grease, cooling system and the convection heat transfer coefficient of the natural environment are detailed analyzed and calculated.5. Heat flow analysis of the spindle-bearing system was carried out, the temperature nodes system equations is developed, node area of heat flow and the heat flow path length are set.Through experimental measurements and references of research results, the temperature nodes system have initial temperatures, and then the bearing temperature distribution is predicted.6. The mathematical model of the spindle cooling system is developed, cooling system of main parameters such as the temperature of the cooling fluid, coolant flow rate and cooling channel characteristic length are effected convective heat transfer coefficient of the cooling system is analyzed. Through the coolant temperature control, to adjust the temperature distribution of the spindle-bearing system.7. Thermally induced preload and the thermal displacement caused by temperature rise of the spindle-bearing system are calculated.thermal failure of the spindle caused by preload and the spindle thermal deflection phenomenon caused by the radial temperature difference is analyzed.8. A set of measurement system is designed, including five groups of laser triangulation sensors, the infrared thermal imager and the data acquisition system.axis x, y, z three directions of thermal displacement are real-time monitoring by laser triangulation sensors, the use of infrared thermal imager for spindle system transient temperature real-time monitoring.By experimental verification, on the basis of theoretical model to analyze the main parameters affect the thermal characteristics of spindle, the mathematical model proposed in this paper can be applied to research and development of precision spindle. |
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