The Research On Contact Characteristics Of Interference Surface And Its Influence About High-Power & High-Speed Spindle System

High-power & high-speed spindles is famous for its remarkable features suchas large power,high speed and large journal size.The centrifugal force of spindles and thermal effect of the bearing is stronger in high-speed operation,so the coordination and unification between the assembly parameters and dynamic characteristics of spindle system is one of the key technologies in the process of structure design to be overcome.The problem about contact state of the interference contact surface between the rotor of the high-power & high-spindle and the bearing is discussed and studied under the working state in this thesis.From the macroscopic scale,the contact mechanism of contact surface between spindle rotor and bearing under the combined action of interference,centrifugal force,thermal load and cutting force was analyzed.The influence of rotational speed and interference on the contact characteristics of interference connection interface and the dynamic characteristics of spindle system was obtained.In order to further explore the contact state of interference contact surface,the relationship between contact stiffness and contact load of micro-convex body and contact deformation in three stages of contact deformation was analyzed from the microscopic scale,and the relationship between contact stiffness of micro-convex body in whole contact area and macroscopic interference was explored.The main research contents and results of this thesis are as following:(1)According to the structural characteristics of high-power high-speed spindle,the contact state of interference contact surface between spindle rotor and bearing inner ring under ideal condition is analyzed by using thick-walled cylinder theory and axisymmetrical plane stress theory.It is found that under the condition of the same amount of interference,the radial deformation of the outer diameter of the spindle rotor,the radial deformation of the inner diameter of the bearing inner ring,and the interference reduction of the contact surface of the interference increase with increasing speed,while the contact stress decreases gradually.At the same speed,the radial deformation of inner diameter of bearing inner ring and the reduction of interference contact surface increase linearly with the increase of interference,while the radial deformation of outer diameter of spindle rotor decreases.These results lay a theoretical foundation for analyzing the contact characteristics of interference contact surface between spindle rotor and bearing under working conditions.(2)Aiming at the problem that the thermal effect caused by the friction heating of high-speed bearings affects the contact interface,a thermal-mechanical coupling finite element model of the connecting parts of high-power high-speed spindle rotor and bearing was established by using the three-dimensional thermoelastic theory.The contact characteristics between the roller and raceway of ceramic ball bearing and the interference interface between spindle rotor and bearing under the combined action of centrifugal force,thermal load,broach force and cutting force are analyzed.It is found that the temperature,contact stress and contact stiffness of the contact interface between the rolling body and the raceway of the bearing and the interface between the spindle rotor and the inner ring of the bearing decrease with the increase of the rotational speed,and they affect each other.At the same time,the interface contact characteristics of different interference connection parts are obviously different.The above research results provide relevant data for the establishment of bearing stiffness model and high power high-speed spindle dynamic model.(3)The radial coupling displacement of raceway of bearing inner ring was caused,because of the interaction between the contact characteristics of interference contact surface between spindle rotor and bearing and the contact characteristics of rolling body and raceway of bearing.Based on this displacement,the stiffness model of series bearing was established,and the stiffness of four-row ceramic angular contact ball bearing was calculated.At the same time,the dynamic finite element model of high-power high-speed spindle based on Timoshenko beam theory was constructed by combining the elastic stiffness of interference contact surface between spindle rotor and bearing.The calculation results show that the contact state of interference contact surface between spindle rotor and bearing has certain influence on the dynamic characteristics of spindle system,such as natural frequency,critical speed and rotary accuracy.These results provide a theoretical support for reasonably matching the dynamic characteristics of high-power high-speed spindle with assembly design parameters.(4)Aiming at the relation between the micro contact state and the macro interference,a contact model of the rough surface of the spindle rotor and the smooth rigid surface of the bearing was established.By using the theory of statistical parsing the interference connection interface on a single micro convex body and contact on the whole domain of micro convex body elastic,elasticplastic and plastic deformation,the whole domain slightly convex body contact stiffness and the macroscopic interference quantity relation model,found in the process of contact,the different values range can cause of the over surplus quantity of the micro deformation of different form on the contact interface,The variation of contact stiffness with interference is consistent with the contact mechanism of microconvex deformation under compression.Through the finite element microscopic contact model established,it is proved indirectly that the relationship model between the contact stiffness of micro-convex body and the macroscopic interference is correct in the whole contact domain.The microscopic study of interface contact characteristics of interference connection provides theoretical support for reasonable selection of assembly design parameters.The results of dissertation would provide a basic idea for designing highpower& high-speed spindle system from the view of matching design parameters of interference assembly and dynamic characteristics,and also provide a certain theoretical support for forming accurate design technology of high-power& highspeed spindle system.