Research On The Structure Analysis And Lightweight Of Metro Vehicle Car Body

With the development of the country’s modernization process,it is necessary to improve the carrying capacity of rail trains and alleviate the problem of traffic congestion.The lightweight of the subway car body structure has become a hot spot for researchers.With the maturity of structural optimization technology,scholars at home and abroad have mastered the size optimization technology of rail car body.However,the research on the topology optimization of the cross section of the train extrusion profile is still in the development stage.The design of the cross-sectional structure of complex extruded profiles still relies on the designer’s experience.It is difficult to design a better lightweight structure in this way.Therefore,it is necessary to design and improve the car body structure through topology and size optimization technology on the premise of ensuring the safety of the performance of the subway car body structure.This design method is of great significance to the lightweight of subway vehicles.In this paper,the middle car structure of a B-type aluminum alloy subway is selected,and the following work is carried out for the lightweight problem:(1)Taking into account factors such as the mechanical characteristics and calculation accuracy of the car body structure,the car body structure is simplified and the shell element is used to establish the car body finite element model.In the welding place and the main load-bearing part,the grids of different sizes are adopted to realize the gradual transition of grids of different sizes.According to the relevant evaluation standards of the car body and the actual operating conditions,select the appropriate working conditions to calculate the strength,stiffness and modal of the intermediate car body.The results show that although the local stress concentration phenomenon occurs in the car body structure,its strength,stiffness and modes still meet the structural design requirements,and it has a large space for lightweight.(2)Comprehensive consideration of the lateral wind acting on the side of the car body.Based on the finite element method and variable-density topology optimization method,the volume,cross-sectional moment of inertia,and minimum flexibility(maximum stiffness)are used as boundary conditions and objective functions.Topological optimization was carried out on the section of roof and side wall of the car body under single working condition,and the section structure with minimum flexibility under wind load at different angles was obtained.The weighted compromise planning method is used to maximize the bearing capacity of the structure.The minimum flexibility under each working condition is taken as the objective function under the corresponding load,so that the multi-objective function optimization problem under multiple working conditions is transformed into a single objective function optimization problem.While the mass of the car body is reduced,its strength,stiffness and modal are still within a reasonable range.Finally,a new light car body and part of the side wall structure are obtained.(3)On the basis of the cross-sectional structure of the new car body,the sensitivity analysis of the subway car underframe structure is carried out based on the sensitivity theory.The sensitivity of the thickness of the chassis structural plate to its stress and displacement is obtained.In order not to change the strength and stiffness of the overall structure of the car body as much as possible,the thickness of the plate insensitive to its stress and displacement is selected as the design variable.Size optimization is performed with stress,displacement and first-order bending frequency as constraints and minimum mass as the objective function.After optimization,the mass is reduced by 0.77 t,and the weight loss ratio is 21.6%.The modal,stiffness,and strength of the car body meet the requirements.