Research On Fatigue Limit Design And Finite Life Design Of High-speed Train Axle

As one of the most important supporting and load-bearing components of high-speed trains,the fatigue strength and life of axles are extremely important for the safety of train operation.The traditional fatigue design of axles uses the nominal stress method,which is an infinite life design that controls the stress amplitude generated by the axle during service within its fatigue limit,and a safe life design that ensures that the cumulative fatigue damage of the axle is less than the specified value when the axle is subjected to random loads..The fatigue design of the axle based on the nominal stress method does not consider the defects that may occur during the actual service of the axle,and the stress concentration phenomenon caused by the defects and the influence of crack initiation and propagation are not considered in the life assessment.Therefore,in order to ensure absolute reliability during the operation of the axle,a damage tolerance design method must be adopted to conservatively design the remaining life of the defective axle.The main work of this paper are as follows:(1)Refer to the literature to understand the current axle fatigue design method and analyze its adaptability,and in-depth investigation of the possible defects of the axle in the process of machining,pressing and service.The fatigue and fracture performance parameters of EA4 T axle steel are determined,including fatigue limit,S-N curve parameters,crack growth threshold,notch S-N curve calculation method,and Paris formula empirical model for evolving defects into life evaluation.(2)Establish the finite element model of a standard moving wheel axle,through Abaqus software simulation calculation and analysis,get the stress distribution state and dangerous parts of the wheel axle,select the dangerous section to lay out the bridge,follow the car to collect the dynamic stress signal and obtain the required stress spectrum through processing,according to the actual measurement The stress spectrum is used for fatigue strength check and life calculation of axles.(3)Insert a semi-ellipsoidal defect at the dangerous part of the axle,establish a finite element model of the axle containing the defect,apply load and restraint according to EN13104 standard,establish the interference relationship of the axle,and calculate the stress concentration factor at the axle gap according to the simulation results to further obtain its fatigue Notch coefficient,thereby using the smooth SN curve to estimate the notched SN curve.Based on the obtained axle stress spectrum data and the notch S-N curve,the Miner’s law is used to estimate the crack initiation life,and the influence of the stress concentration factor on the crack initiation life of the axle damage is analyzed.(4)The defect is simplified as a crack inserted into the axle measurement point.According to the basic model of Paris crack growth rate and the concept of effective stress intensity factor proposed by Elber,based on the measured stress spectrum,Franc3 D and Aabqus software are used to simulate and analyze the crack growth of the axle to predict its remaining life.The stress intensity factor of the surface crack tip of the hollow axle is solved by the analytical method and the simulation method respectively,and the results are compared to verify the rationality of finite element simulation.There are 68 pictures,16 tables and 53 reference.