Analysis On Dynamic Characteristics Of Shaft System Coupling With High-speed Four-point Angular Contact Bearing

Rolling bearing is one of the most important parts of aero-engine,its performance is related to the safety and reliability of aero-engine.In order to obtain the performance and reliability of the rolling bearing in different working conditions,it is a common method to evaluate the bearing performance by using high speed bearing testing machine.As an important rotating part of the bearing test machine,the dynamic characteristics of the shafting directly affect the stability and the accuracy of the test results.In this paper,the high speed bearing test system is researched as the main object and the three-dimensional model of the test machine is established.The structural features,functions and working principles of the loading device,the chassis and the shaft system are described.The static and dynamic characteristics of the loading device and the chassis of the test machine are studied by the finite element method.It is concluded that the maximum stress of the loading frame is less than the allowable stress of the material,and the natural frequency of the loading frame and the chassis is greater than the natural frequency of the highest speed.According to the structure and test conditions,the finite element model of the internal and external spindle system is established.The stiffness of the angular contact ball bearing and the stiffness of the cylindrical roller bearing are calculated.The static characteristics of shafting under different working conditions are analyzed,and the influence of the static characteristics of the shaft and the radial stiffness of the bearing on the stress and deformation of the shaft system is discussed.The results show that the maximum stress value of the inner and outer shafting is less than the allowable stress of the material under different working conditions.The change of the bearing radial stiffness can obviously change the deformation of the shaft,but has no effect on the stress of the shaft system.The first natural frequency of shafting is obtained by theoretical calculation method,which is 411 Hz.The finite element model of the coupling shaft is established and the finite element method is used to analyze the modal shape and natural frequency of the coupling shaft.The influence of axial preload,static load and rotating speed on the shafting mode is discussed.The results show that the first order natural frequency of finite element analysis is 359.68 Hz,and the natural frequency of shafting changes with the change of axial preload.When the radial stiffness of the bearing is invariable,the natural frequency of the shafting can be reduced with the increase of speed.It is shown that the natural frequency of the shafting is influenced by the speed.Based on the Campbell diagram,the critical speed of the coupling shaft under different test conditions is analyzed.The results show that the critical speed is much larger than the test speed under various operating conditions,and the axial preload can be reduced under the condition of satisfying the test speed.