Fatigue Life Prediction Of Axle Based On Dynamic Stress Of Long-Term On-Track Test

The design criteria for high-speed train axles are infinite-life designs based on the nominal stress method,however,axles may experience stresses or damage that were not adequately considered in the design during service.Although the design standard takes into account factors such as axle load,speed,starting,braking and over-curve,the axle will inevitably be affected by wheel out-of-roundness,peeling,abrasion and rail corrugation during the 30-year service period,resulting in high frequency and high frequency.The dynamic stress of the amplitude will inevitably suffer from accidental damage caused by corrosion,sandstorm environment and foreign objects.In this paper,through the combination of line test and simulation analysis,the fatigue life prediction of high-speed train axles in service is carried out.The specific research work is as follows:(1)The dynamic stress test of the key section of the long-term line axle was carried out,and the effective value of the axle box acceleration and the axle stress spectrum characteristics were compared at different running speeds,different running intersections,and before and after repairing.The axle stress spectrum of 900,000 kilometers was obtained through the actual measurement of the line,and the axle stress spectrum of the whole life cycle was obtained by linear extrapolation.(2)The distribution fitting of the equivalent stress and the effective value of the acceleration is carried out,and the fitting results show that the equivalent stress obeys the normal distribution;the correlation analysis and the independent relationship between the effective value of the acceleration of the axle box and the equivalent stress of the axle are carried out.The results show that there is a strong correlation between the two;the two-dimensional normal distribution is used to fit the distribution of the two,and the fitting effect is good,indicating that it is feasible to use the axle box acceleration to calculate the axle equivalent stress and predict the axle fatigue life.(3)The wheelset was elasticized,and a rigid-flexible coupling dynamic simulation model with flat scars was established,and the accuracy of the dynamic simulation model was verified by the wheelset bench test;The axle stress at different running speeds was obtained,and the influence law of the flat scar on the axle stress was obtained.(4)The fatigue performance test of the axle material at the sample level was carried out,and the S-N curve performance parameters of the axle bar specimen with smooth surface in the water vapor environment were obtained.The research shows that the water vapor environment has a great influence on the fatigue limit of EA4 T axle materials.Compared with the air environment,the water vapor environment reduces the fatigue strength by 67.3%.(5)Combined with the S-N curves of the axle material in the air and water vapor environments,the cumulative damage and fatigue life of the key sections of the axle in the two environments were calculated respectively.At the same time,the influence of the wheel flat scar on the stress spectrum of the axle life cycle was considered,and the cumulative damage of the axle was estimated.The results show that the water vapor environment will sharply decrease the fatigue life of the axle,and the fatigue life of the axle will drop to 2.54 million kilometers,which cannot meet the 25-30-year service life of the design requirement of the fatigue life of the axle.2.1‰ of the scar condition.51 figures,36 tables,and 81 references.