Optimization Design Of Roof Structure Of EMU Car Body Based On Stiffness Maximization

With the rapid development of high-speed rail,the technology of EMU is also constantly upgrading and improving.More intelligent,more environmentally friendly and more comfortable new EMUs are constantly put into use.The advent of Fuxing has injected new vitality into the development of high-speed rail in China.As the main bearing structure,the safety performance of EMU body is very important.As an important part of the car body,the roof has an important influence on the performance of the car body structure.Therefore,this paper takes the car body of Fuxing EMU with a speed of 160 km/h as the research object,and simulates and analyzes the car body structure.Based on the finite element simulation analysis,the roof of the car body is taken as the research object for optimization design.The main research contents include the following aspects :(1)On the basis of simplifying the structure of the car body,the finite element model of the Fuxing EMU car body was established by using Hyper Mesh software.According to the TB/T 3550.1-2019 standard,the static strength of the car body is checked.The ANSYS calculation results show that the Von.Mises stress of the car body under 19 load cases is lower than the allowable stress.According to the TB/T 1335-1996 standard,the stiffness of the car body is checked,and the equivalent bending stiffness and equivalent torsional stiffness of the car body are greater than the standard values.According to the BS7608 standard,the fatigue strength of the car body is evaluated,and the cumulative damage of the fatigue evaluation points of each part of the car body is less than 1.(2)Considering the influence of the section shape of the roof structure on the stiffness of the car body structure,the section selection of the roof beam is carried out.Based on the results of static strength analysis,three worse load cases are selected as the section selection conditions.Under the premise of ensuring the mass of the roof beam structure unchanged,the original structure is changed to four different cross-section shapes of steel : T-beam,I-beam,channel steel and B-beam.By analyzing the deformation of the underframe side beam under three harsh load cases,the contribution of the roof beam with different cross-section shapes to the stiffness of the car body structure is obtained.The type B beam can increase the stiffness of the car body structure by 2.044%.(3)In view of the influence of the section size of the roof structure on the stiffness of the car body structure,the size of the roof structure of the car body is optimized.Based on the Opti Struct optimization platform,the method of grouping size optimization is used to set different grouping methods for the design variables of the roof beam and roof panel of the car body.Based on the mass constraint,the optimization design is carried out with the goal of maximizing the stiffness of the car body structure.Through calculation,the stiffness optimization results under different grouping methods of design variables are obtained,and the changes of car body stiffness under different grouping methods are analyzed.The optimized car body structure stiffness can be increased by 3.92% at most.On the basis of the optimization results of the stiffness of the car body structure,the grouping method of the design variables is optimized.Under the condition of keeping the stiffness unchanged,the lightweight design is carried out with the goal of minimizing the mass of the car body structure.The optimized roof is 13.402% lighter than the original structure,and the car body is 3.112% lighter than the original structure.