Research On Vibration Fatigue Monitoring Technology Of Bogie Frame Under High Frequency Excitation

In recent years,China’s rapid development of railway enterprise,ranks the world’s first high-speed railway running mileage,with the high speed train running speed and the increase of the train operation mileage,on a line of high-frequency vibration fatigue accidents increased year by year,the domestic and foreign scholars also attaches great importance to the high frequency vibration fatigue problems of high-speed train,and carry out the related research.Aiming at the problems of frequent high-frequency excitation and low efficiency of traditional line monitoring methods,this thesis proposes a method to monitor high-frequency vibration fatigue state of EMU bogie frame using power spectral density transfer rate combined with axle box vibration acceleration.The accuracy and feasibility of the proposed method are verified by comparing the time domain amplitude and fatigue damage results of the predicted data with the measured data of an EMU with the same type of bogie wheel polygon.Around this method,the following work is done:(1)High frequency excitation is carried out on the bogie on the high frequency excitation test bench,and the high frequency vibration data and stress data of the bogie are collected through the sweep frequency and fixed frequency test of the bogie.Based on the timefrequency analysis and modal analysis of the test data,the modal parameters such as the natural frequency and modal shape of the bogie frame end are obtained.(2)The vibration acceleration and stress data of the frame obtained from the bench test are analyzed,and the vibration acceleration of the axle box is used as the system input signal to obtain the vibration acceleration transfer rate curve and stress transfer curve of the measuring point near the bogie frame spring cap barrel.(3)Fatigue damage analysis was carried out on the stress data obtained in the bench test.The stress situation near the natural frequency point of bogie frame was determined through the joint analysis of time-frequency diagram and time-domain data,and the equivalent stress and equivalent fatigue damage value of each natural frequency point were obtained by equivalent to 15 million km of operating distance.(4)By Fourier transform of vibration data and stress data of the line,the main excitation frequency of the line is 579 Hz,and the analysis shows that there is a modulation frequency conversion band around the main frequency with the wheel shaft frequency as the modulation frequency,and the polygon order of the wheel is 19.(5)Taking the impulse response and frequency response function of the system as a pair of Fourier transform,the impulse response of the system is obtained by inverse Fourier transform of the transfer curve obtained from the bench test.Then,the impulse response is convolved with the measured vibration acceleration data of the axle box in time domain to obtain the prediction data by using the time-domain convolution theorem.The time domain amplitude and fatigue damage of the predicted data were compared with the measured data to verify the accuracy of the proposed monitoring method.