Research On The Influence Of The Suspension Stiffness Of Equipments On The EMU Car Body Modals

With the increase of EMUs speed,the dynamic performance of the car body is deteriorating.The large-scale equipment such as air conditioners,transformers,brake module units under the car will have a greater impact on the dynamic performance of the car body.Taking a certain type of high-speed EMU as the research object,the frequencies and vibration shape of the car body modals were calculated and analyzed by changing the vertical,longitudinal and lateral suspension stiffness values of the equipment under the car.The change laws of the car body modal frequencies with suspension stiffness were achieved,and a design basis for the suspension stiffness of the equipment under the car was provided.The main contents of this paper are as follows:(1)The finite element model of car body is set up.According to the geometric model of the high-speed EMU and relevant parameters of the equipment under the car,the pre-processing work was carried out with the Hypermesh software,and the car body grid was divided,and the finite element model of the car body is established by the rigid connection.(2)The modals of the car body under preparation condition were calculated.The Inp files were exported by Hypermesh software and imported into Abaqus software for modal analysis of the car body.Based on the Abaqus software and by using of finite element method,the first five orders modal frequencies and vibration shape of the car body are obtained.(3)The optimization designs of car body are accomplished.Taking the plate thicknesses of side wall,chassis,roof,chassis side beam as the design variables,the total weight of the car body is taken as constrain,and the sum of the first three orders modal frequencies of the car body is maximized as the target,the optimization designs of the car body are accomplished.In this process,two optimization schemes are used.The first scheme is to select 56 plates thicknesses as design variables and the car body optimization were performed.The 56 plates thicknesses have been changed by a optimization design.Taking the optimization result as the initial value,the same optimization model and optimization algorithm were used to optimize the car body again.The other scheme is to increase the number of design variables to 76,and use the same optimization model and optimization algorithm to achieve the optimization designs of the car body structure.(4)The influence of the suspension stiffness of the equipment on the car body modal was studied.Based on the optimized car body structure,the car body modals with the elastic suspension for under the car equipments were analyzed;the effect of changing the suspension stiffness of all equipments under the car on the car body modals were calculated and analyzed;the influence of the suspension stiffness value of each equipment was increased by 1/4 and decreased by 1/4 on the car body modals were also computed and analyzed;lastly,the effect of changing vertical,longitudinal and lateral suspension stiffness values of all equipments under the car on the car body modals were calculated and analyzed.The change laws of the car body modal frequencies with the suspension stiffness of the equipments under the car were achieved.