Natural Modal Optimization Of A High-speed Train’s Car Body

The vibration of high-speed trains is related to the safety and ride comfort of trains.Increasing the natural frequency of the car body can avoid the resonance between the car body and the bogie frame,reduce the vibration of the car body,and improve the running stability and riding comfort.In this paper,the car body of a high-speed train is taken as the object of study.Aiming at the problem of the low vertical bending mode of car body,the car body mode is optimized by means of refined modeling of car body,layout optimization of equipment under vehicle,sensitivity analysis and optimization design of car body,strain energy analysis of car body and structure optimization,so that the vertical bending frequency of car body is improved.Finally,the stiffness and strength of the optimized car body are checked,and the results meet the relevant requirements.The main research contents are as follows:(1)Refined modeling and modal analysis of car body.The simplified modeling and refined modeling of the car body in the preparation conditions are carried out,and the first-order vertical bending mode shapes and corresponding frequencies of the car body under two modeling methods are calculated.Compared with the simplified modeling of car body,refined modeling method can make the car body model center of gravity closer to the actual car body center of gravity,and then the modal value of the car body can be estimated more accurately in the design stage.(2)Layout optimization of equipment under vehicle.Aiming at the location arrangement of five auxiliary equipment under the vehicle,the problem of equipment arrangement under the vehicle is transformed into the problem of minimizing the deviation of vehicle axle load,further into the problem of minimizing the absolute value of the sum of moment,and finally into the problem of quadratic programming for extreme value.With the help of quadratic programming toolbox of MATLAB,20 feasible layout schemes are obtained from 120 possible layout methods.By comparing the first-order vertical bending frequency of the servicing vehicle of each scheme,the most reasonable arrangement scheme of the equipment under the vehicle is determined.(3)Sensitivity analysis and optimization design of car body.The sensitivity of first-order vertical bending modal frequency and the mass of the car body to the design variables are calculated.Through the method of relative sensitivity analysis,19 plate thickness values which have great influence on the car body mode are selected as the design variables,then a mathematical model is established to optimize the solution.After optimization,the first-order vertical bending frequency of car body is improved.(4)Strain energy analysis of car body and structure optimization.Based on the analysis of the strain energy of the car body in preparation conditions,the larger strain energy aera of the car body structure is determined,that is,the area with weak stiffness,and the corresponding structural improvement scheme is proposed for the area with weak stiffness.Finally,the effective optimization scheme is integrated to improve the car body structure,so that the car body modal is further improved.(5)Stiffness and strength check of optimized car body.According to the evaluation standard TB / 1335-1996 for railway vehicles,the stiffness of the optimized servicing car body is evaluated.According to en12663:2010,under 10 severe static strength conditions,the load constraints are added to the vehicle body for calculation,and the verification results meet the relevant requirements.