Three-dimensional Modeling Of EMU Bearing Interference Fit And Damage Mechanism Analysis Based On Cylindricity

With the increasing speed of high-speed trains,the important components of high-speed train are required to have higher technical performance.As the important component of the EMU bogie,the axle box bearing is affected by the operating conditions,dynamic load and road spectrum impact load,so the force is complicated,Its main failure mode is the contact fatigue damage between the rolling elements and the rings.In the research of contact fatigue damage,the three-dimensional factor of the interference fit surface of wheel axle and bearing is ignored,which cannot explain the phenomenon that the early fatigue damage of the bearing is randomly generated in practice.In order to explore the mechanical mechanism of the random bearing damage,this thesis takes into account the influence of the interference fit between the axle and the bearing,establishes a three-dimensional random contact model of the axle and the bearing based on the cylindricity of the mating surface,and analyzes the bearing contact stress under static interference assembly and operation.The impact of the cylindricity error on the uneven distribution of the bearing contact stress is studied,which reveals the mechanism of local random bearing fatigue damage,and provides the theoretical basis for the design and strength check of the axlebox bearing.The main research contents of the thesis are as follows:(1)Research on the interference fit three-dimensional profile of the axle and the bearing.Use random number model and improved cubic Hermite interpolation method to generate circumferential contour curve,then establish axial surface through polynomial interpolation method,complete the three-dimensional contact surface contour modeling based on cylindricity,and establish the three-dimensional contact solid model of the wheel axle and the bearing through reverse modeling.(2)Analysis on static and dynamic simulation of assembly model.The finite element contact model of the wheel axle and the bearing assembly was established,and the assembly prestress and deformation state were simulated by finite element software.The unevenness of contact prestress and deformation was analyzed by comparing the ideal model and the three-dimensional contact model,and the influence law of interference on the prestress and deformation is obtained.According to the actual load and circuit spectrum data,the dynamic simulation of bearing assembly was carried out,and the influence of cylinder error and running speed on the dynamic stress distribution and magnitude was analyzed,and the stress spectrum was simulated.(3)Research on local fatigue damage mechanism and fatigue life model.Based on the simulation results,the bearing damage mechanism is qualitatively analyzed.the stress spectrum is corrected and processed by the rain flow counting method,Goodman equation and Weibull fitting,the fatigue life model of the bearing based on the stress spectrum was established by P-S-N curve and linear cumulative damage method,and the bearing life was predicted.The fatigue damage test of axle box bearings was completed,and the damage state was monitored by acoustic emission technology.The fatigue damage mechanism was verified by analyzing the signals in different test stages.The experimental results show that the cylindricity factor is the reason for the randomness of the damage.