Research On Dynamic Characteristics Of High Speed Train Axle Box Bearings

In recent years,high-speed railways have developed rapidly,not only has the operating mileage increased year by year,but the speed of train operation has also gradually increased.As the key components of high-speed train running parts,the operating environment of axle box bearings have become more complex.The performance of axle box bearings plays a vital role in the safety,stability and steadiness of high-speed train operation because they not only realize the connection between the frame and the wheelset,but also ensure relative movement between them.Thus,study into the dynamic performance of axle box bearings of high-speed train under various operating conditions is conducive to clearly understanding the law of influence of operating conditions on the dynamic characteristics of bearing components and providing theoretical basis for improving safety and stability of train operation.This paper,with the cylindrical roller bearings of high-speed train as the object of study,through using ANSYS/LS-DYNA establish a two-dimensional finite element model of highspeed train axle box bearings and by adopting the central difference method to solve the model's explicit dynamics,analyses the dynamic characteristics of the axle box bearings under changing conditions.By comparing with the simulation results,the revolution speed of the cage of axle box bearings and the rotation speed of the rolling elements gained from theoretical formulas calculation,verify the accuracy of finite element modal of high-speed train axle box bearing.Firstly,the slip velocity between the rolling elements and the raceway is calculated according to the simulation results and with the slip velocity formula between the rolling elements and the raceway,and slippery conditions between rolling elements and raceway in bearing and non-bearing areas are analyzed.The result shows that with the increase of the train speed,the track excitation amplitude and vibration frequency,the RMS value of the sliding speed between the rolling elements and the raceway in bearing areas increases,and the RMS value of the sliding speed between the rolling elements and the outer ring is greater than the RMS value of the sliding speed between rolling elements and the inner ring.Under the deceleration condition,the rolling element and the inner ring produce negative slip.With the increase of the deceleration,the RMS value of sliding speed between the rolling element and the raceway in bearing areas increases,and the RMS value of sliding speed between rolling elements and the inner ring increases more.Secondly,the dynamic performance of the bearing cage under variable working conditions is studied by analyzing the slip rate,centroid trajectory and centroid velocity deviation ratio of the cage.The result shows that with the increase of train speed,the trajectory of the mass center of the cage is more concentrated,the speed deviation ratio is smaller,and the cage movement tends to be more stable.With the increase of the deceleration,the absolute value of the average value of cage slip rate becomes larger,the displacement of cage center of mass on both sides of X and in the negative direction of Y increases,the speed deviation ratio increases and the cage stability decreases.And the track excitation has little effect on the dynamic characteristics of the cage.Thirdly,according to the Archard adhesive wear calculation model,the instantaneous wear rates of the inner and outer rings of bearings in different areas are calculated,and the changes of the instantaneous wear rate and distribution in the raceway under different operating conditions are analyzed.The result shows that the instantaneous wear rate of the bearing raceway in the bearing areas is larger,and it is smaller in the non-bearing areas,which is close to zero.The magnitude and change of the instantaneous wear rate of the inner ring and the outer ring of the bearings are similar under stable working conditions and track excitation working conditions and the instantaneous wear rate of the inner ring of the bearings is larger than that of the outer ring under deceleration working conditions.The increase of the train speed increases the instantaneous wear rate of the bearings outer ring.The increase in deceleration increases the instantaneous wear rate of the inner ring,and the instantaneous wear rate of the outer ring changes little.Track excitation will affect the distribution of the instantaneous wear rate of the raceway.Finally,the experimental speed of NU306 bearing cage under stable working condition was measured by rolling bearing test bench.A two-dimensional finite element model of NU306 bearing was established,and the simulated rotational speed of the cage was compared with the experimental and theoretical rotational speed of the cage.The results show that the simulated speed of NU306 bearing cage is consistent with the experimental rotational speed and theoretical rotational speed under the same working conditions,which verifies the validity of the two-dimensional finite element model of the bearing.