Research On High-speed EMU Axle Damage Tolerance Based On Three-dimensional Crack Growth

As the operating speed of high-speed EMU continues to increase,the vehicle operating environment is gradually becoming more complex.As an important component,the reliability of the axle is directly related to the safety of train operation.During the operation of the axle,it is easy to cause defects such as scratches and bumps.For this reason,this paper prefabricates the initial crack in the middle of the axle body,studies the change of the stress intensity factor of the crack tip with the crack depth,calculates the remaining fatigue life of the axle,and determines the damage Tolerance.First,use ANSYS finite element software to analyze the strength of the wheelset,under the load conditions specified in the EN13104-2001 loading standard and the UIC510-5-1993 standard,the load-bearing strength of the axle and the wheel was studied,and the fixed restraint and elastic restraint applied at the wheel seat were compared,completed wheelset press-fitting simulation,analyzed and obtained the corresponding wheel-set press-fit curve with different interference and different friction coefficients;and carried out wheelset modal analysis and harmonious response analysis.The research results show that when there is no defect,the static strength and dynamic stiffness of the axle meet the requirements of standards.Then,considering the influence of the hollow axle center hole on the stress at the crack tip,the thickness correction factor is introduced on the basis of the calculation formula of the surface crack stress intensity factor of a solid cylinder,and the analytical expression of the surface crack stress intensity factor is obtained to obtain an analytical solution.Prefabricated semi-elliptical cracks with different depths and different shape ratios on the surface of the axle finite element model through FRANC3 D software,select the crack propagation model,set the propagation parameters,and obtain the finite element solution of the stress intensity factor at the crack tip when the hollow axle surface cracks continue to grow.Finally,based on the measured data,the equivalent stress of the axle is obtained through derivation and calculation by Miner’s law.The critical crack of the axle is calculated by the Paris formula and the surface crack stress intensity factor formula,the remaining life of the axle is estimated,and the axle damage tolerance is determined.A stress-strength interference model was established,and the operating reliability of the axle under the two conditions of limit crack size and considering the random characteristics of crack growth was preliminarily evaluated by changing the equivalent stress and the coefficient of variation of fracture toughness respectively.