Lightweight Acoustic Design And Optimization Of Metro Train Car Body

Lightweight and low-noise are two contradictory design goals in the process of railway vehicle design.How to carry out the acoustic design under the constraint of lightweight for the composite car body structures of metro train,which is composed of aluminium extrusions,porous sound-absorbing materials and layered interior structures,so as to reduce the weight of the car body and ensure the interior noise performance can meet the design objectives,it is a key problem to be solved at present and has very important engineering application value.Aiming at the lightweight acoustic design problem of metro train,a lightweight acoustic design method is proposed,which includes three aspects: "the broadband acoustic index decomposition of car body composite structures","the lightweight acoustic design of composite structures" and "the evaluation of interior noise reduction effect".Based on this method,taking 72 d BA as the interior noise design target,taking the floor structure of the metro train as an example,the lightweight acoustic design of the car body structure is carried out under the constraint of 5% mass reduction.While the car body is lightweight,the interior noise performance is also excellent.The main research contents are as follows:(1)The interior noise design target is determined with the interior noise test results of metro trains running in the open field,the wheel and rail surfaces of the metro trains are in good condition.The interior noise prediction model of the metro train is established based on the Statistical Energy Analysis method,the sound insulation of car body components in the model is parameterized.The accuracy of the model is verified by the test results,which provides the basis for the lightweight acoustic design of the composite car body structures.(2)The sound insulation index of the composite car body structures is optimized based on the multi-objective optimization method and the interior noise prediction model.The parameterized sound insulation of car body components is taken as the design variable,the interior noise design objective is taken as the total index,the minimum sound insulation index of each component at different frequencies is taken as the acoustic index of each component,when the sound insulation index meets the interior noise design objective.Finally,the acoustic index of the composite structures(floor,side wall,roof,door,window,etc.)is established.(3)The lightweight acoustic design of composite car body structures,which is composed of aluminium extrusions,porous sound-absorbing materials and layered interior structures,is carried out.Three acoustic analysis models are established,including the vibroacoustic characteristics prediction model of aluminium extrusions based on the orthotropic plate theory and the hybrid FE-SEA method,the sound absorption prediction model of porous materials based on the Johnson-Champoux-Allard model,and the vibroacoustic characteristics prediction model of layered structures based on the transfer matrix method.Based on these models and the multi-objective parameter optimization method,the lightweight acoustic design of three kinds of structures or materials is carried out to increase the stiffness of aluminium extrusions,improve the sound insulation performance,sound absorption performance,and reduce the sound radiation performance of three kinds of structures or materials.The lightweight acoustic design is carried out under the constraint of 5% mass reduction based on the multi-island genetic algorithm.(4)The vibroacoustic characteristics prediction model of composite car body structures including three kinds of structures or materials is established based on the principle of Statistical Energy Analysis.The aluminium extrusions are described by the equivalent plate subsystem,the elastic support structure is described by the beam element subsystem,the porous sound-absorbing material is described by the sound-absorbing cavity subsystem,and the layered interior structure is described by the layered plate subsystem.The energy transfer of each structure or material under the reverberation sound excitation and force excitation is analysed.Combine the lightweight acoustic design results of aluminium extrusions,porous materials and layered structures,the effects of three structures or materials on the composite structures are evaluated.The influence of the lightweight acoustic design of composite car body structures on the interior noise reduction is evaluated based on the interior noise prediction model.The research work in this thesis can not only realize the lightweight design of metro train body structure,but also take consideration to the low-noise design goal,and provide a scientific basis and reference for the research of lightweight design based on the perspective of acoustics.