Robust Optimization Design Of EMU Bogie Frame

As an important part of the undercarriage structure of EMU,bogie frame has been in complex and changeable operation state for a long time,and its structural performance directly affects the safety of vehicle operation.Therefore,in order to improve the running performance of vehicles,it is very important to consider the structural design and manufacturing process of bogie frame,and carry out structural simulation analysis and optimization design.This paper takes the EMU bogie frame as the research object,and uses the strength analysis and robust optimization theory to complete the robust optimization design of the bogie frame with the help of numerical simulation and programming technology.The main research contents of this paper are as follows:Firstly,the structural strength performance of bogie frame is analyzed.The finite element modeling of bogie frame is completed by using Hyper Mesh software.Based on UIC515-4 and EN 13749-2011 standards,10 abnormal load cases and 9 simulated operation cases for static strength simulation analysis are determined.The maximum node equivalent stress under corresponding working cases is simulated by ANSYS software,and the static strength evaluation of the whole frame is completed by calculating the safety factor.The working cases and corresponding structures that do not meet the static strength evaluation criteria are selected as the basis for the subsequent robust optimization of static strength.Then determine10 working cases of frame fatigue strength simulation,write the fatigue evaluation calculation program with ANSYS Parametric Design Language,select 12 fatigue evaluation points,obtain the average stress and stress amplitude through ANSYS simulation,and complete the fatigue strength evaluation with Goodman fatigue limit diagram.Fatigue evaluation points that do not meet the evaluation criteria are selected as the basis for subsequent robust optimization of fatigue strength.Secondly,the static strength robust optimization design of bogie frame is carried out.According to the characteristics that the original Salp Swarm Algorithm is easy to fall into local optimal solution,a Double Mutation Adaptive Salp Swarm Algorithm considering local development and global exploration is proposed,and the algorithm is used to optimize the relevant parameters of Kriging surrogate model,so as to improve Kriging surrogate model and reduce the error of the model.Based on the improved Kriging model,the first layer surrogate model is established with the static strength as the output response.Through sensitivity analysis,the key design variables for robust optimization of static strength are selected.Through Monte Carlo sampling,taking the mean and standard deviation of Kriging proxy model of static strength as the basis for establishing the second level proxy model,and then establishing the static strength deterministic optimization model with the first level surrogate model as the optimization target and the static strength robustness optimization model with the second level surrogate model as the optimization target.The two optimization models are calculated by using the Double Mutation Adaptive Salp Swarm Algorithm.By comparing the optimization results,it is proved that the static strength fluctuation of the frame structure is reduced after robustness optimization,and then the quality characteristics of the frame under abnormal case are improved.Finally,the fatigue strength of the bogie is optimized.Based on the improved Kriging model,the first layer surrogate model is established with fatigue strength as the output response.According to the results of fatigue strength analysis,the key design variables for robust optimization of fatigue strength are selected through sensitivity analysis.Through Monte Carlo sampling,the mean and standard deviation of the Kriging surrogate model of fatigue strength are used as the basis for establishing the second level surrogate model,and then the deterministic optimization model of fatigue strength with the first level surrogate model as the optimization target and the robust optimization model of fatigue strength with the second level surrogate model as the optimization target are established.According to the characteristics of uneven Pareto solution set and slow convergence speed of the original Non-dominated Sorting Genetic Algorithm Ⅱ,a Cauchy Mutation Adaptive Non-dominated Sorting Genetic Algorithm Ⅱ considering the convergence speed and distribution uniformity of Pareto solution set is proposed to determine the multi-objective robust optimization algorithm.Cauchy Mutation Adaptive Non-dominated Sorting Genetic Algorithm Ⅱ is used to calculate the two optimization models.By comparing the optimization results,it is proved that the fatigue strength fluctuation of the frame structure is reduced after robustness optimization,and then the quality characteristics of the frame under fatigue cases are improved.