Research On Multi-Objective Structural Optimization Design Of A Type Of Subway Car Body

In engineering,the problem of optimizing two or more objectives at the same time is called multi-objective optimization problem.Because the evaluation of car body structure performance needs to consider multiple indicators comprehensively,multi-objective optimization is more in line with engineering practice and more practical than single-objective optimization.On the other hand,it is often difficult to optimize multiple objectives at the same time.There may be contradictions among these objectives,even a trade-off relationship,so it is difficult for engineers to achieve the optimal solution at the same time.this paper defines the method of multi-objective optimization based on response surface approximation model.Because the car body is mainly of sheet metal structure,it is considered to optimize its thic Kness,that is,size optimization.The finite element model of subway car body is established.Based on the structural performance analysis of the car body,the optimization objectives are determined as the first-order bending mode,bending stiffness and mass of the car body.Especially for the first-order bending mode of the car body,its frequency value is 9.73 Hz,which is lower than the recommended value,and it is easy to be excited by the outside to produce global resonance of the car body,which is extremely destructive,so it needs to be optimized urgently.For the bending stiffness of the car body,the calculation shows that its performance meets the standard,but in view of the importance of this index,it is also optimized;The optimization of the quality of the prepared car body is based on the lightweight requirement of the car body.Before optimizing the structure of subway car body,sensitivity analysis method is used to obtain the sensitivity data of the panels of each part of the car body for each target response.By comparing the relative sensitivities,21 groups of panel variables of the car body are selected to participate in the optimization.In order to avoid the distortion of the optimization effect after rounding the optimization results,combined with the dimensional machining accuracy,the design variables are discretized and then solved by multi-objective optimization,and finally an effective design scheme is successfully obtained.The final scheme makes the first-order vertical bending modal frequency of the prepared car body exceed the standard value of 10 Hz,reaching 10.15 Hz,which is increased by 0.42 Hz and 4.3% compared with the initial structure.The midpoint deflection of the side beam of the underframe of the car body is 8.25 mm,which is 0.97 mm and 10.5% lower than the initial structure,and the bending stiffness of the car body is further improved.At the same time,the prepared mass of the car body under this scheme is 22.03 ton,which is more original.