Analysis And Optimization On Low-frequency Interior Acoustic Characteristics Of A Vehicle

With the development of the automobile industry,consumers are becoming more and more rational when buying vehicles.In the automotive performance indicators,NVH performance due to the comfort of ride has become one of the important indicators for consumers to consider.Noise has a direct impact on people’s driving experience,often also be given priority.The 20-200 Hz low-frequency noise associated with the car structure could cause the driver and the passengers greatly discomfort,so the acoustic characteristics of this frequency segment should be considered in the research and development of a new vehicle.The low-frequency noise in the vehicle is largely due to the vibration of the sheet during the process of car driving.In order to ensure the ride comfort of the driver and the passenger,the level of noise that radiated by the vibration of the sheet structure in the compartment should be reduced as much as possible.Based on a integrated acoustic contribution which considers multiple field points and peak frequencies,to determine the key plate,the optimization of the low-frequency acoustic characteristics of the electric vehicle is carried out by using the optimization of the topography,the optimization of the size,the optimization of the genetic algorithm based on the response surface model and the arrangement of the anti-vibration damping material based on the modal strain energy.First of all,to establish a finite element model of body-in-white of a pure electric vehicle and do free modal analysis in the finite element software HyperWorks.The validity of the finite element model of body-in-white of the electric vehicle is verified by comparing with the modal data of body-in-white of benchmarking model.Then the finite element model of trimmed body is established,and 0-400 Hz free modal analysis of trimmed body is completed in NX NastranSecondly,a boundary element model of cavity that includes a driver and seats is established,considering impedance coefficient of the interior.The acoustic transfer vector method based on modal superposition method is used to calculate the 20-200 Hz low-frequency acoustic characteristics.The paper based on the integrated acoustic contribution which considers multiple field points and multiple peak frequencies,to determine the roof,back door,left rear door,left lower back,right rear,firewall and rear flooring and other plate as the key plates of optimization of the low-frequency acoustic characteristics in the vehicle.Thirdly,for the roof structure with the largest integrated acoustics contribution,the optimization scheme of adding auxiliary stiffeners and laying damping materials is determined by comparing with the benchmarking models.The position of auxiliary ribs is determined based on topography optimization;the optimal thickness of each part of the ceiling structure is obtained based on the size optimization;based on the contribution of the integrated acoustic contribution of the roof structure,the effective arrangement area of the damping material is obtained;based on the genetic algorithm optimization of approximate model,the optimal thickness distribution of the damping material is obtained.Through the above combination optimization,the optimal structure of the roof area could be obtained,and the low-frequency acoustic characteristics of the electric vehicle are optimized effectively.Finally,based on the new structure of the roof area,another optimization is carried out.Based on the 20-200 Hz integrated modal strain energy,the layout areas of anti-vibration damping material of the key plates are determined.By laying the free damping,the low-frequency acoustic characteristics of the electric vehicle are further controlled.