In order to solve the crack problem of bogie frame end during the normal operation of a B-type subway,this paper adopts operation mode analysis and line test to study the fracture mechanism.First of all,based on the PolyMAX method,this paper identifies the working modes of the structure in actual operation,in which the end of the structure has a natural mode of longitudinal oscillation with a frequency of 222.9 Hz and a damping ratio of 0.72％.And then through the analysis of axle box,frame end acceleration and dynamic stress frequency characteristics,as well as to the typical range of track survey vehicle to 60 km/h operating speed through a short wavelength for 80 mm wave rail grinding of elastic sleeper section,the natural frequency of the frame end coincides with the track,which leads to structural resonance caused by fatigue damage.Under the same working condition,the vibration acceleration and dynamic stress of the improved structure are reduced by about 90％compared with the original scheme after the end of the frame is installed with reinforcing bars.Meanwhile,the life evaluation of the end of the frame before and after the improvement is carried out,and the results show that the end of the frame after the installation of reinforcing bars meets the service requirements.
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