Study On Vibration And Strength Of Local Structure Of A High-speed EMU Frame Under High-frequency Excitation

With the increase of train speed and operating mileage,the wheel tread of the train and the steel rail carrying the train are inevitably worn,which makes the frequency of line excitation gradually increase and close to the natural frequency of the bogie frame,resulting in the problem of high-frequency vibration of the bogie frame.When these abnormal line disturbances act on the frame for a long time,the fatigue strength of the main stress parts on the frame will be gradually reduced and fatigue damage will occur,and pose a great threat to the life and property safety of passengers on the train at high speed.Therefore,it is of great significance to study the mode and fatigue strength of the frame when it resonates under highfrequency excitation.The main work of this paper is as follows:(1)Taking CRH380 BL EMU frame as the research object,this paper studies the response of frame end and brake boom under different frequency excitation by placing the frame on the roller table test-bed equipped with polygonal wheels.It is found that the vibration of frame end at 589 Hz and brake boom at 574 Hz is the most intense.Then,the flexible working modes of the frame end and the brake boom structure are identified by LMS software,and the corresponding sixth-order modes are obtained respectively.(2)The finite element analysis models of CRH380 BL EMU frame,frame end and brake boom are established.The modal analysis is carried out by using ANSYS,and then the modal analysis models are compared and modified based on the working modal results identified in the test until an accurate modal analysis model is obtained.(3)The harmonic response of the whole and local models of the modified frame end and the brake boom are analyzed by setting an appropriate loading mode,and then the harmonic response results of the frame end and the brake boom at different frequencies are solved,Then,based on the response results of the frame end at 589 Hz and the brake boom at 574 Hz in the test,the parameters of the steel spring and shock absorber are verified and modified,and finally an accurate harmonic response analysis model is obtained.(4)Through the analysis of the overall and local finite element models of the modified frame end and the brake boom,the stress nephogram of the frame end at 589 Hz and the brake boom at 574 Hz is obtained,the position and maximum stress amplitude of the maximum stress point calculated by the overall and local models of the frame end and the brake boom are obtained,and the results calculated by the overall model and the local model are compared and analyzed.(5)The maximum stress amplitude is reduced by modifying the structural dimensions at the end of the frame and the position of the maximum stress point of the brake boom,which provides a basis for the optimal design of the end of the frame and the brake boom.