Research On Service Safety Of Bogie Frame For Type B Metro Vehicles

With the vigorous development of China's economy and the continuous expansion of the city scale,the urban population has also increased rapidly,which makes modern cities face a series of traffic congestion problems.At present,the development of urban rail transit in China is mainly based on metro,which provides effective measures to solve urban congestion and heavy traffic.As the key structure of bogie supporting car body and connecting various parts,the safety and reliability of service performance of welded frame directly affects the safety of train operation.For this reason,this paper takes the welded frame of metro type B car as the research object,and to study its fatigue strength and structural optimization.Firstly,a refined finite element model of the bogie frame of metro type B car is established,the boundary conditions are determined according to UIC615-4 standard,the static strength simulation analysis under abnormal load conditions is carried out with ANSYS software,and the analysis results are evaluated with the fourth strength theory.The analysis results show that the maximum stress of the frame under extraordinary load is 238.7 MPa,which appears at the joint between the longitudinal auxiliary beam and the cross beam,meeting the requirements of static strength.Then,the free mode analysis is carried out on the frame,and the first 13 modes are selected,of which the first 6 modes are rigid mode and the vibration frequency is 0.The lowest natural frequency of the 7-13 modes is 45.49Hz,and the highest natural frequency is 137.11Hz.Secondly,fatigue damage analysis was carried out on the welded frame.The quasi-static method is mainly used for damage calculation.The calculation is performed in nCode software in three load steps.The analysis results show that the fatigue damage under the three load steps is mainly concentrated in the lateral stop,and the cumulative damage finally obtained appears in the lateral stop.At the bottom of the baffle support plate,the cumulative damage value is 0.676,the life is 1.48×10~7,and the damage value is less than 1 indicating that the studied bogie frame meets the requirements of use.Finally,the structural optimization design is combined with the results of static strength and fatigue damage.The sub-model method is used to establish the sub-models of the connection between the longitudinal auxiliary beam and the beam,and the lateral stop.The main purpose is to improve the calculation efficiency.The optimization method uses topology optimization.The strength of the optimized finite element model is checked again.The results show that the maximum stress of the optimized frame is 177.3 MPa,which occurs at the arc transition between the side beam and the beam;the cumulative fatigue damage after optimization appears at the lateral stop support At the weld toe of the slab and side beams,the cumulative damage is also reduced compared to before.