Structural Performance Analysis And Optimization Design Of Aluminum Alloy Car Body

With the rapid development of China’s rail transit industry,high-speed rail vehicles bear complex loads.As the core bearing structure of vehicles,it is necessary to ensure the reliability and safety of the car body.Therefore,it is of great value to analyze the structural performance and optimize the design of car body.This paper takes a certain aluminum alloy car body as the research object,based on the finite element analysis method,sub model technology,improved NSGA-Ⅱ algorithm,the structural performance analysis,reliability analysis and optimization design are carried out to ensure that the structural performance of the car body meets the standard requirements,improve the safety and reliability of the car body.Firstly,the finite element model of car body is established and the structural performance is analyzed.After reasonably simplifying the geometric model of the car body,the finite element model of the car body is established.According to EN12663 standard,seven typical static strength cases of the car body are loaded,and the static strength of the car body is analyzed based on the fourth strength theory.The stiffness of the car body under the case of overloading is analyzed by applying constraint conditions,and the maximum displacement of the car body and the displacement of the side beam of the underframe are calculated,and the displacement results are compared with the standard values.Then according to TB/T3115-2005 standard,the first ten modal shapes and frequencies of the car body are calculated,analyzing the modal shape of the car body and comparing the modal frequency values with the standard provisions.Then according to EN12663 standard,the fatigue strength of the car body under three fatigue loading cases is analyzed,the fatigue evaluation is carried out on the points where the first principal stress values are larger in the fatigue cases of the car body,evaluation points are calculated using the IIW standard and cumulative damage ratio.Secondly,a reliability analysis method of car body structure based on sub model technology is proposed.The sub model technology is used to create the sub model of car body structure and check whether the sub model is reasonable.Through sensitivity analysis,variables which have great influence on the change of maximum equivalent stress of car body sub model are selected.Then,sample points are obtained by experimental design method,and the response surface model about the maximum equivalent stress and mass of the car body sub model is fitted.The functional functions of static strength reliability analysis and weld fatigue reliability analysis of car body sub model are established respectively,and the command flow of reliability analysis is written by APDL language to carry out static strength reliability analysis and fatigue reliability analysis.Finally,multi-objective reliability optimization design of car body is carried out based on improved NSGA-Ⅱ algorithm.A multi-objective car body reliability optimization model is established with static strength reliability of car body sub model as constraint condition and maximum equivalent stress and minimum mass of car body sub model as optimization objectives.Considering the shortcomings of NSGA-Ⅱ algorithm,chaos mapping,normal distribution crossover factor and adaptive variation adjustment factors are introduced to improve the traditional NSGA-Ⅱ algorithm,and test functions are selected to verify the effectiveness of the improved NSGA-Ⅱ algorithm.The multi-objective car body reliability optimization model is calculated and solved based on the improved NSGA-Ⅱ algorithm,and the maximum individual of the dominant function value in the solution set is determined as Pareto optimal individual by fuzzy set theory.The static strength simulation analysis and static strength reliability analysis of the optimized car body structure are carried out.