Fatigue Strength Optimization Of Bogie Frame For Subway Vehicle

With the continuous improvement of China’s economic level,the speed of urbanization is getting faster and faster,and urban rail transit is taking an increasing proportion in today’s urban transportation construction.As an important part of urban rail transit system,the safety of subway vehicles has been widely concerned.The bogie is the main load-bearing and traction components of subway vehicles,and is an important component to ensure safe and reliable operation of vehicles.The frame is the core bearing structure of bogie,which connects various components on the bogie.Its performance has a direct impact on the safety of vehicle operation.To this end,in this paper,the bogie frame of a certain subway vehicle is taken as the research object,to study its strength and structure optimization.The specific work is as follows:(1)According to the technical requirements of subway vehicles and the design data of power bogie,the finite element model of bogie frame with welded seam is established.According to UIC615-4 standard,the static strength of the frame under abnormal load condition was carried out with ANSYS software,and the calculated results were evaluated based on the fourth strength theory.the results show that the maximum equivalent stress of the frame under supernormal load is 198MPa,which is located at the position between the auxiliary longitudinal beam and the lateral stop,and does not exceed the allowable stress of the material,the static strength of the frame meets the design requirements.In order to further obtain the dynamic characteristics of the frame,the modal analysis of the frame is carried out.The first 6natural frequencies and vibration modes except the rigid body modes are analyzed.The results show that the lowest natural frequency of the frame is 34.34Hz,which is far away from the excitation of other systems and can effectively avoid the resonance of the vehicle during operation.(2)Analyze the fatigue strength of the frame.The stress results under unit load were obtained by quasi-static analysis method,and the fatigue damage was calculated by N-code software in three stages using UIC615-4 standard load spectrum.The results show that the fatigue damage is the largest at the welded seam between the auxiliary longitudinal beam and the lateral stop.The three-stage cumulative damage is 0.557,the life is 1.79×10~7.Hot spot stress method was adopted to further analyze the nodes with larger damage,the maximum cumulative damage in three stages is 0.542,and the life is 1.84×10~7,which is greater than the standard 1.0×10~7.(3)According to the analysis results of static strength and fatigue strength of the frame,the maximum stress frequently occurs in the welds of the lateral stop of the frame,and the fatigue damage is the largest at the position.The sub-model method is used to optimize the structure of the connecting position between the auxiliary longitudinal beam and the lateral stop of the frame.The new structure is optimized by the topology optimization method.Finally,the strength of the optimized model is checked.The results show that the maximum equivalent stress of the frame is 170 MPa,located at the connection between the primary spring seat and the side beam,and the maximum fatigue damage is located at the welded seam between the rotating arm locator seat and the side beam,the damage is 0.31,which is significantly reduced compared with the original frame.