Statistic Analysis Of Load Spectrum Of Metro Axle And Study On Spectrum Of Experiment Bench

Axle is one of the key parts of the running section of metro vehicles.With the rapid development of urban rail transit in China,the 14 th Five-Year Plan puts forward the requirements of the genetical standard metro,which puts forward higher requirements for the service life and fatigue strength evaluation of the axle.In this paper,based on line dynamic stress test and finite element simulation,the axle load spectrum is studied and applied in bench test.The specific contents are as follows:(1)Formulate load test plan:The wheelset finite element model was established,and the loading simulation was carried out according to the EN standard.The stress distribution characteristics of the axle were obtained according to the finite element results,then,the load identification area as well as the axle section measurement point were determined at the corresponding maximum axial strain.Based on the principle of Wheatstone bridge,the strain gage group bridge was designed,and a set of feasible test scheme was completed by using the Austrian PJM data acquisition system.(2)Obtained the load-strain transfer coefficient and processed the line measured data:The static calibration condition of the wheelset was designed,and the simulation loading and analysis were carried out by using the finite element simulation method.The strong linear relationship between the vertical load and the axial strain of the axle was obtained.The real time load history of axle was obtained by processing the measured line data with the load-strain transfer coefficient.According to the on-board speed records and gyroscope signals,different speed grades,straight and curve conditions were distinguished,and the load distribution characteristics of each condition under different speed grades were analyzed.The load spectrum under typical conditions was compiled by using the wave center method.(3)Study on fitting extrapolation of load spectrum:The distribution fitting estimation of the measured load spectrum was carried out,and the fitting effect of the fitting parameters under 95% confidence was analyzed by H-test method.The least square method was used to calculate the variation rule of distribution parameters of different velocity classes,and the extrapolated load spectrum of 120km/h was determined,which was extended into the life cycle load spectrum and extrapolated to get the maximum load value.(4)Compilation of fatigue test spectrum and evaluation of axle fatigue strength:According to the modified Miner linear cumulative damage theory and the S-N curve of the material,the 120km/h lifetime load spectrum was compressed,and the 4-level program load spectrum was compiled by using the method of equal damage,which was convenient for experimental operation.The effect of the loading sequence of the spectrum block on the damage was preliminarily discussed.Based on the rain flow counting method,the stress spectrum of the axle section was compiled,and the fatigue strength of the axle was checked by the equivalent stress method.As a result,the axle can meet the service mileage of 3.6 million kilometers.