Fatigue Life Analysis Of High Speed Train Bogie Frame

Bogie frame is the main bearing structure of locomotive and vehicle,and also the main component to bear and transfer the wheel-rail interforce,which plays a key role in the quality,speed and safety of the vehicle during operation.Therefore,it is required that the car body and running part system have enough stability and reliability.Complex alternating loads will come on the critical part of the structure for a long time,and the fatigue failure of the weld line will occur,resulting in safety accidents.In order to ensure the normal and smooth operation of high-speed train and improve the performance of frame,this paper studies the fatigue strength evaluation and structure optimization method of bogie frame,mainly doing the following work:(1)Hypermesh software is used to establish the finite element model of em U bogie frame.Load values are calculated according to UIC 615-4 standard and working conditions are applied to the model.Then ANSYS software is used to analyze the static strength of frame under different working conditions and judge whether the frame meets the strength requirements.(2)The low order free mode of bogie frame is calculated by MSC.Nastran software.The natural frequency and modal shape characteristics of the frame are analyzed and compared with wheel/rail excitation frequency to further evaluate whether the performance of the frame meets the design requirements and provide a basis for subsequent optimization design.(3)Based on the principle of Goodman fatigue limit diagram,a structural fatigue analysis software of Multiple Conditions based on Goodman Diagram method V1.0 was developed by using Abaqus software through Python programming,which integrates opening,extraction,calculation and output.Realize automatic calculation and analysis of multi-condition or single-condition fatigue life of the model.(4)According to the selection principle of evaluation points,14 welds of the structure were taken as evaluation points and fatigue strength was evaluated one by one using Goodman curve diagram,IIW standard and BS standard.Firstly,Goodman curve,average stress,safety factor and other parameters of the evaluation points were calculated under simulated operating conditions,and then fatigue loads were applied to the framework.The grade of the evaluation points was determined according to IIW standard and BS standard respectively,and the fatigue strength of the weld was evaluated.Finally,the three methods are compared to illustrate their respective characteristics and application scope.(5)Using Hypermesh software to set the sensitivity of the bogie frame,and MSC.Nastran software was used to analyze the mass sensitivity and modal sensitivity of frame,and the concept of sensitivity ratio was introduced.With the thickness of the plate as the optimization variable,improving the modal frequency of the frame and reducing the quality of the frame as the optimization objective,the strength as the constraint condition,the mathematical model of the frame optimization design was established,and the structure was optimized based on the results of the sensitivity ratio.