Study On Establishment Of Standardized Load Spectrum On Bogie Frames Of High-speed Trains

At present,there are mainly three kinds of general design specifications for bogies in the world:EN 13749,UIC615-4 and JIS E 4207.The train bogie frames need to pass the examination of these standards before they are formally put into operation.However,the establishment of these three international standards is based on foreign test lines.Compared with the long mileage and complex conditions of high-speed railway line in China,the mileage is short and the train operation condition is less.Therefore,the standard can not truly reflect the train running condition under the condition of Chinese railway line.In order to be used in the reliability evaluation of bogie frame,the load must truly reflect the load situation of the train running under the actual railway condition in China.In this paper,a standardized load spectrum model based on the measured load and dynamic stress of a certain type of EMU bogie is established.It has strong theoretical and practical significance for the development of high-speed EMU in China.The main contents of this paper are as follows:(1)The principles of frequency domain identification,time domain identification and direct test are compared and analyzed.According to the characteristics of complex load and easy divergence of low damping bogie frame,the direct test method is used to test the load of bogie frame.The dynamic response of the resistance strain gauge is analyzed.Based on the principle of quasi static method and the finite element analysis technique,the location of the load calibration points of the frame with low coupling load system is determined,and the load of the support seat with strong coupling degree is effectively decoupled by the space curved surface interpolation method.The calibration test of load-strain transfer coefficient is carried out in the laboratory and compared with the results of finite element method,which verifies the validity of the direct load testing method.(2)The load dynamic characteristics of the bogie frame are analyzed based on the load data measured.Firstly,the time-domain waveforms of each load system of the frame are analyzed and studied,and the train running state is judged according to the trend characteristics of each waveform,and then the time-frequency diagram of each load system is obtained based on short-time Fourier transform programming.The time-domain characteristics of the measured loads under typical working conditions are analyzed.The measured loads are decomposed into two parts:the trend load and the dynamic load.According to the trend of the load waveform,the running state of the train in each typical working condition is inferred.(3)In this paper,the working condition recognition algorithm for separation of working conditions is studied and the software for condition identification is developed.According to the straight line and curve characteristics of the measured longitude and latitude data on the map,The straight line slope between the first and last data points of two windows is calculated continuously by using the method of data windowing.The line section with zero secondary slope is a straight line working condition.According to the structural characteristics of the switch and the fluctuation characteristics of the data waveform of each sensor and the change of the slope between two points,the working conditions of the normal line over turnout and the side line over the turnout are determined according to the structural characteristics of the switch and the variation of the slope between the two points in the line section where the secondary slope is not zero.According to the burr characteristic of the signal when the train comes into and out of the tunnel,the working condition identification algorithm of the tunnel is established,and the working condition identification software is compiled based on each condition identification algorithm and based on the VB.net language.The condition identification and separation of measured data are carried out.(4)A single function based on parameter estimation and a piecewise function and a kernel density function based on nonparametric estimation are used to test the fitting results of the same measured stress spectrum by means of chi-square test.The kernel density function is selected as the function of load spectrum fitting based on the adaptive index of total chi-square and fitting samples.The extended factor method is used to infer the extreme value of the load spectrum.The accuracy of the extended factor method for estimating the extreme value of the load spectrum is verified by comparing the measured data.Based on the t test of two independent samples and Latin hypercube sampling,the minimum number of times required for load spectrum testing is studied.Based on the measured data,the load spectrum distribution of each load system is obtained,and the slope of each fitting line is obtained by using the linear relationship between the line length and the cumulative frequency of load spectrum.Thus,the standard cumulative frequency is obtained from the measured data.(5)The cumulative frequency formula of the standardized load spectrum is established by using the linear relationship between the operating line length and the cumulative frequency divergence point of the load spectrum.The cumulative frequency formula of the standardized load spectrum is combined with the expansion factor method.The load extremum formula of the standardized load spectrum is derived and the load amplitude formula of the standardized load spectrum is obtained.The probability density function of the kernel density is taken as the parent load spectrum distribution and combined with the cumulative frequency of the standardized load spectrum.In this paper,the formula of each level frequency of the standardized load spectrum is derived,and the formula of the standardized load spectrum is deduced.According to the finite element calculation and calibration test,the load spectrum damage calibration points and the load-stress transfer coefficient between the load and the damage calibration point are determined.In this paper,the fatigue cumulative damage models are compared and analyzed.Based on the basic criteria and requirements of load spectrum compilation,the optimization model of load spectrum damage calibration is established,and the objective function and constraint conditions of standardized load spectrum calibration are given.Based on the mathematical model of the optimization algorithm,the characteristics and operation principle of artificial fish swarm algorithm and genetic algorithm are studied,and the damage consistency calibration of standardized load spectrum is carried out.(6)The accuracy of standardized load spectrum is evaluated based on linear cumulative damage and equivalent stress,respectively.The "Shenyangbei-Dalianbei"line of Harbin-Dalian high-speed railway and "Zhengzhoudong-Xuzhoudong" line of Zhengzhou-Xuzhou high-speed railway are selected as the line sections to evaluate the accuracy of the standardized load spectrum.Through the method of rain flow counting,the measured load spectrum of each load system on each section of the line is obtained,and the standard load spectrum under each typical working condition is calculated by substituting the line length of each typical working condition into the standardized load spectrum formula.According to the basic criteria compiled by the spectrum,the stress spectrum of each load system under different working conditions is converted into equivalent spectrum at the measuring point,and the equivalent stress and measuring point are calculated respectively at the stress measuring point.True equivalent stress ratio,The ratio of the equivalent stress to the real equivalent stress at the measuring point is compared with that of the European standard and the Japanese standard,and the accuracy of the standardized load spectrum for the structural strength evaluation of the bogie frame is verified.