Study On The Vibration And Noise Of Full-vehicle Based On The Super-element Method

As the main transport means in our daily life,cars have gaining more attention for its comfortableness.The vehicle body structural vibration and noise are important indexes for the comfortableness evaluation.Most of the structural noises are of low-frequency,which are formed from the vibration caused by the vehicle body panels and its cavity radiation.Therefore,the control on the structural vibration is the key to improve the vehicles' low frequency NVH performance(Noise,Vibration and Harshness,NVH).In the perspective of automotive R&D,large amounts of full-vehicle NVH dynamic simulation calculations should be done based on the Finite Element Method to achieve the ideal vehicle NVH performance.Due to the large scale of finite element model of full-vehicle and long simulation calculation cycle,work efficiency will be greatly reduced in the model based multi-program optimization process.In order to solve the problems ofvehicleinterior noises in low frequency and the efficiency of simulation calculation,a mini-car is taken as the object,and a Super-element Method is proposed toapply to NVH dynamic simulation analysisof full-vehicle,then the vibration and noise control programs are explored and the NVH performance is improved in two aspects of the vibration transmission path and acoustic contribution.The research contents of this thesis are the following four aspects:Establish the NVH performance analysis model of simple structure based on the Super-element Method.Based on the finite element theory and the super-element theory,simple structure is taken as the object,comparing the simulation calculation results of the modal,frequency response and sound-solid coupling of the super-element model built in different divided ways and the traditional FE model in the computational accuracy,the result shows that super-element model has high computational accuracy,which meets thecalculation requirments of the NVH finite element simulation analysis of full-vehicle.Study on the vibration transmission characteristics of full-vehicle based on thesuper-element model.the traditional full-vehicle FE model is built,and thesimulation and experiment modal ofthe BIW models are calibrated to verify the accuracy of the FE model,then combined with the power flow theory,super-element model is built,the vehicle vibration transmission characteristicsare studied;the dangerous transmission pathsare ranked and identifiedbased on the power contribution;and then the parameters of vibration isolation device are adjusted and obviously reduce the interior noise.Study on the acoustic contribution of body structure.The noise transfer function analysis is done based on traditional body FE model to identify dangerous noise frequencies;and theacoustic contributions of modal and panel are analyzed to find the body-panelswhich account for major contribution in dangerous frequencies;then the super-element model is built to optimize the hazardous panel structures,which provides reference for the specific implementation of structural optimization scheme.Analyzeon the effectiveness of Super-element Method in the full-vehicle NVH dynamic simulation calculation.Theerror of interior noise peak frequency between simulationanalysis of vehicle superelement model and real-vehicletest were respectively 6.5% and 5.4%.Respectivelycompared to the traditionalFinite Element Method,the computation time of the initial model for the Super-element Method can bereducedby 26% and 28.9%,and the computation time of optimization model can be maximallyreducedby 99.8% and 98%;for the optimizationanalysis on the transmission shaft system modal under full-vehicle condition,the storage space can be saved by 98.5%.Therefore,the Super-element Method has a strong practical engineering value in the field of vehich NVH simulation analysis.