Fatigue Calculation And Optimization Of Steel And Aluminum Metro Car Body

The car body is the carrier of railway vehicles and one of the main load-bearing parts,it carries complex and changeable dynamic alternating load in the actual operation line.In recent years,the car is developing towards the direction of high speed,high comfort and lightweight,which leads to the more complex alternating dynamic load carried by the car body and greatly increases the possibility of fatigue failure of the car body structure.Therefore,the research on the fatigue life and optimization of the car body is of great significance.In this paper,based on the finite element preprocessing software Hyper Mesh,the modal,stiffness,strength and fatigue performance of the steel aluminum hybrid metro car body are studied,and the size and topology optimization of the car body are carried out.The main work is as follows:Firstly,the finite element model of the steel aluminum hybrid metro car body is established by Hyper Mesh software,and the modal,rigidity and strength of the car body are calculated by ANSYS.The modal,rigidity and strength of the car body are checked according to the relevant standards,and the results show that the modal,rigidity and strength of the car body are in line with the relevant standards,and most of the structural safety margin and part of the structural stress set are surplus.As a result,the lightweight of the car body and the topology optimization of the part of the car body are carried out.Secondly,the fatigue characteristics of the key welds of the steel aluminum hybrid metro car body are analyzed.The first step is to work out three fatigue calculation conditions according to the relevant standards,and get the stress range under three conditions.The second step is to select the dangerous weld based on IIW standard,and determine the weld type and weld grade "to seat".The third step is to draw the conclusion that the cumulative damage ratio of 16 dangerous welds of metro car body is less than 1 according to Miner’s cumulative damage theory.Finally,based on the Optistruct software,the size optimization with the goal of lightening and the topology optimization with the goal of reducing the stress concentration are carried out.For the size optimization,the objective function,constraints,design variables and other parameters are set.After many iterations,the convergence feasible solution is obtained.The lightweight effect of the size optimization is obvious and meets the evaluation criteria of the body stiffness and strength,so it meets the purpose of the optimization.For the topological optimization of the car body structure,the relevant parameters are set.After several iterations,the convergence feasible solution is obtained.According to the cell density nephogram,the stiffener is set.After the stiffener is set,the stress value of the structure has a large reduction,so the purpose of the optimization is met.