| The carbody is an important part of a high-speed train to carry passengers and integrate other train systems.However,the higher speed of the train exacerbated the complexity of the load on the carbody,and the lightweight of carbody weakened the carbody stiffness,which will lead to the mismatch between natural vibration characteristics and excitation frequency and exacerbate the carbody vibration.It will also lead to the deterioration of train operation quality and limit or even endanger the structural safety capabilities and the functions of vehicle equipment.As well as,the current diversity and customizability of customer needs drive a fast,multi-concept design of carbody,which makes the rapid analysis and optimization of the vibration characteristics of carbody in the concept design phase become more and more urgent.However,there are a lot of issues in the finite element modal analysis and real vehicle modal test,such as long cycle,low efficiency,poor flexibility,and poor dynamic modification repeatability and so on.Those issues can't meet the needs of rapidity,flexibility and convenience of the analysis,prediction and optimization of the vehicle vibration characteristics in the concept design phase.Therefore,based on the analysis of the vibration characteristics of the carbody during the concept design phase,and absorbing the research results of carbody vibration at home and abroad,as well as based on the theoretical knowledge of beam vibration,shell vibration and optimization design,the analysis and optimization method of the natural frequency of the carbody during the concept design phase are carried out and studied further.The research work of this dissertation mainly focuses on "the analysis and optimization design methods of natural frequency of the carbody ".The research process includes:(1)Based on a high-speed train,the vibration characteristics of the carbody are studied by numerical simulation and test.It is found that the elastic vibration of the carbody is in the form of vertical bending,transverse bending,torsion,rhombus,respiration and local vibration.According to the results of the study,the characteristics vibration of the carbody are the same to "beam" from the structural characteristics of the carbody and the elastic vibration forms of vertical bending,transverse bending and torsion.From the structural characteristics of the carbody and the elastic vibration forms of rhombus,respiration and local vibration,the characteristics vibration of the carbody are the same to "shell".(2)According to the characteristics of the "beam-type vibration" of the carbody,in order to effectively reflect the structure and layout characteristics of the carbody flat andcross section,the carbody is equivalent to the beam model with variable section parameters."Beam-type vibration" equation is proposed and the method of solving the vibration equation with variable cross-section beam is introduced to get the rapid solution method of the natural frequency of the "beam-type vibration ".The method has also been validated with simplified carbody and real carbody.Compared with finite element method and modal test,the error of this method can meet the engineering design requirements,and the calculation is flexible,efficient and short in cycle.(3)According to the characteristics of the "tube vibration" of the carbody,in order to effectively reflect the vibration characteristics of the carbody as a whole and part of the shell,an equivalent plate element model with or without openings and hanging blocks is established,and corresponding vibration equation and its solution method are given.On this basis,according to the structural characteristics of the carbody,the corresponding plate element model is assembled to obtain the assembly plate element model of the carbody,and the assembling method of the assembly plate element model and the solution method of the vibration equation are given.And then the rapid solution method of natural frequency of "Cylinder Vibration" can be obtained.The method is validated by the example analysis of the equivalent plate element model.The influence of the layout of openings,such as doors and windows,and hanging blocks on the natural frequency of the carbody and the influence of the vibration characteristics of the plate elements on the vibration characteristics of the assembly carbody are given.Compared with the real car finite element analysis,its error can meet the engineering requirements,and the calculation is flexible,efficient and short in cycle.The above-mentioned natural frequency rapid algorithm of the carbody has the characteristics of flexible calculation,high efficiency,short time,easy programming and less resource consumption.(4)The optimization design of the natural frequency of the carbody is a process of multiple-goal optimization of natural frequency,rapid collaborative optimization design,and obtaining the optimal structural design parameters.Therefore,based on the above-mentioned rapid algorithm of natural frequency of carbody,the response surface method is introduced to calculate the natural frequency of carbody,and the response surface model between the natural frequency of carbody and the design parameters is established.After that,combining the response surface model with optimization design methods such as non-linear constraints and parameter space approximation,a multi-objective optimization function of carbody natural frequency is established and its solution method is given.This method is used to optimize the natural frequency of the carbody and get the optimal structural designparameters,which shows the rationality and applicability of the method.This dissertation expounds the methods,process and steps for the analysis and its optimization design of the natural frequency of the carbody which are suitable for the concept design phase.The method can be used to predict the vibration characteristics of the carbody earlier in the concept design phase and provide design suggestions for engineering optimization of the flat and section layout of the carbody,further enriching the vibration design methods of the carbody of the high-speed train. |
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