| With the rapid development of high-speed rail,the traffic time between cities becomes shorter and shorter,and high-speed rail has become the first choice tool for more and more people to travel.Therefore,the safety of high-speed rail,comfort has become particularly important.Long-term vibration under the uncomfortable frequency and amplitude will lead to fatigue damage in the weak parts of the body,so as to reduce the reliability of the body structure and shorten the service life of the body.When serious,it will even affect the safety of people’s lives.Therefore,under the condition of vehicle body vibration,the research on fatigue strength and life of car body has become an important subject.In this paper,CRH2 EMU as the research object,through the Proe three-dimensional modeling software,the establishment of three-dimensional model;The static strength of the car body is checked according to the EN12663 standard and the principle of maximum principal stress by using ANSYS Workbench simulation software,and the fatigue strength of the key parts of the car body is checked by using the modified Goodman diagram.According to the modal analysis software,the modal parameters of vehicle body under different speed levels are identified by the modal test of EMU,and the first order vertical bending modes of the car body are evaluated according to the TB/T3115 standard,and the analysis of the first order vertical bending modes of the car body under different speed level operating conditions is carried out.Then,the final frequency of the typical mode is determined by the method of taking the mean value under different working conditions.The method of equivalent mass is used to carry out mass-point equivalence under vehicle mass.The free mode under no-load condition,free mode under preparation condition and constrained modal analysis under complete condition are analyzed by finite element analysis software,and the free mode is analyzed by finite element analysis software under the condition of no-load,free mode and constrained mode analysis.The first-order vertical bending mode of the body is checked according to TB/T3115.In order to check the reliability of the body model,the simulation mode of the body is compared with the test mode by using the correlation analysis method.On the basis of long-term tracking and collecting data of EMU,the basic method of signal analysis and processing is selected to carry out zero mean value and filter processing,and the simulation load spectrum is edited by rain flow counting method.Then the fatigue life of the vehicle body is simulated and analyzed by the method of time domain and frequency domain by using the software of nCode fatigue analysis based on workbench.On the basis of the frequency domain analysis,the fatigue damage of the vehicle body in the frequencydomain of 8-9 Hz,12-13 Hz,15-16 Hz,17-18 Hz and 1-18 Hz frequency band is simulated by using PSD method and sweep frequency method.Finally,the same square is used to simulate the fatigue damage.The damage caused by the method in different frequency bands and the damage caused by different methods in different frequency bands are compared and analyzed.Finally,the modal frequency which affects the most damage of the vehicle body and the parts where the body is damaged are obtained at the end of the paper.The damage caused by the vehicle body in different frequency bands is compared with that caused by the different frequency bands.The results show that the maximum von mises stress occurs at the junction between the cross beam and the side beam under abnormal conditions,and the maximum stress is 169.98 MPA,which is less than the yield strength requirement of the material.According to the requirements of the EN12663 standard,the maximum stress of the vehicle body is lower than that of the material.It is shown that the strength of the body model meets the requirements of the standard.On the basis of satisfying the static strength,the fatigue strength of the key parts of the body is evaluated,and the final results are all in the Goodman fatigue limit evaluation chart,which indicates that the fatigue strength of the body model meets the standard requirements.Through the study of the modal test of the EMU body,the first-order droop of the EMU under different speed stages is studied.The bending modal frequencies meet the standard requirements of no less than 10 Hz.Through the comparison of different speed stages,it is found that the modal frequency of the first-order torsional mode increases obviously under the acceleration-deceleration condition,and the rising range is about within the 2Hz range,while the other typical modal parameters have little change with the speed.Finally,according to different working conditions,the first-order vertical bending frequency is11.46 Hz,the first-order transverse bending frequency is 13.10 Hz,the first-order torsional frequency is 15.1Hz and the first-order rhombic mode is 9.95 Hz.The modal frequency of the first-order vertical bending of the body is more than 10Hz;The simulation modal analysis shows that the difference between the simulation mode and the test mode is less than 20%,which satisfies the requirements of this paper under the condition of considering the comprehensive factors.Through the analysis of the data collected from the actual line operation of the body,it is found that within the range of 0.2 g acceleration,the horizontal and vertical stability of the body belongs to the optimal level.Through the spectrum analysis,it is found that the calculated modal frequencies appear in or near the peak position.Then the reliability of the body model is verified again.Through the fatigue life simulation analysis,it is found that the most damaged position appears at the intersection of the pillow beam and the side beam,at the corner of the door above the pillow beam,and near the window corner of the door window.The junction of the side beam and the side wall above the pillow beam and the junction of the bottom frame beam and the side beam,etc.The damage caused by the combined load is the greatest,and the damage caused by the vehicle body frequency in the frequency of 8-9 Hz,、12-13 Hz、 15-16Hz、 17-18 Hz and 1-18 Hz frequency band is compared and analyzed,and the damage causedby the damage.It is found that the damage caused by the 8-9Hz frequency band(near the rhombic modal frequency)is the greatest,followed by the first-order vertical bending frequency,and then by the first-order vertical bending frequency.The first-order transverse bending frequency is near and the last is the first-order torsional frequency,which shows that the lower the frequency is,the greater the influence on the fatigue life will be.Finally,the frequency sweep method is used to simulate the load spectrum in different frequency bands,and the fatigue life simulation results show that the results of fatigue life simulation are different from those of actual line data simulation,which shows that there is a great difference in fatigue simulation between the simulated data and the actual line data.Through the research and analysis of this paper,it is shown that the vibration mode of the car body has a great influence on the fatigue life,and the modes and damage parts which have great influence on the fatigue life of the body are found,which provides a reference for the structure and dynamic design of the body. |
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