Study On Fatigue Life Of Welding Frame For209P Bogie

209series bogie frames have been widely used in25type passenger cars since the first railway speed promotion. Recently, with the travel distance increasing, the fatigue crack occurred in the welding joint between the transverse and the longitudinal beams, which have a major impact towards the railway operating security. This paper focused on the209P bogie welding frame, making a clear research on the important fatigue weak area, finally explained the reason of the appearance of crack.Firstly, the discrete finite element model of welding frame is built, and the UIC515-4specification is taken use of for analysis of static and fatigue strength. The results prove that the bogie frame designed by TB1335-96cannot meet the UIC demand. Then, a test between Xi’ning and Geermu about dynamic stress and acceleration in the important fatigue area of the bogie frame has been taken. The character of amplitude and simulation show that the bogie fame is about to lose the transverse stability when the speed is higher than110km/h, which lead to a sharp increase of damage in some key spots. The equivalent stress in the weld joint between the transverse and longitudinal beams is higher than any other zones. The fatigue life is only28thousand kilometers. In order to getting the equivalent stress of bogie frame in the proper running, a dynamic stress test was taken in the typical route between Dalian and Chifeng. The results show that the equivalent stress from the weld joint outside between the transverse and the longitudinal beams, coinciding with the actual crack position, is133.3MPa, which is higher than any other position. Moreover, the load identification is taken based on the actual route test. The results show that the main loads leading to the stress concentration in weld joint between transverse and longitudinal beams are yaw force and lozenging force. Finally, the best improvement structure is got by the finite element analysis based on above loads.The method and the content of this paper will make a contribution to the improvement of the209P bogie frame and provide the reliability design experience for bogie frame for the ordinary speed trains.