| NVH(Noise?Vibration?Harshness)performance can directly reflect the driving feeling and is gradually valued by customers and automotive enterprises,and interior noise level has a profound impact on NVH performance,so the interior noise level must be under control.There are various means of controlling the interior noise level,and the acoustic package is one of the main means to reduce the noise level,which can be effective in the medium frequency and high frequency noise.Vehicle firewall is between the engine room and the cab,whose sound insulation ability is limited.Acoustic package covered on the surface of firewall cannot only help insulate the outside noise from the engine room effectively,but also absorb the interior noise.It is of great engineering significance to carry out research on the acoustic package.In this paper,the research object is firewall acoustic package of a vehicle.Reliable simulation models were established through CAE method.What's more,the subsystem partition method,the influence factors of model precision,the sensitivity of material parameters and the orthogonal optimization design were analyzed.The specific research work is as follows:(1)In order to research the influence of subsystem partition on the simulation results,three different kinds of partition methods(coarse division,medium division,and detailed division)were given.Based on the hybrid FE-SEA method and SEA method,hybrid FE-SEA model and SEA model of each subsystem partition method were established.(2)The influence factors of model precision was analyzed,and the influence of each modeling parameter(model basic parameters,PET material parameters,EVA material parameters,and PU material parameters)on the simulation results was researched.When these parameters are obtained,the precision of the parameters which have great influence on the simulation results should be strictly guaranteed to ensure the accuracy of the model.While,the accuracy requirement of the parameters which have little influence on the simulation results can be reduced appropriately to help improve efficiency.(3)The modeling parameters were obtained,including the material parameters(porosity,resistivity,tortuosity,viscous length,thermal length,young's modulus,poisson's ratio,damping)of each material layer of the acoustic package which were obtained through the combination of simulation and experiment,and the accuracy and error sources were analyzed;the other else parameters(modal density,damping loss factor,coupling loss factor,the insulation loss and absorption coefficient of acoustic flat parts)were obtained through numerical method,analytical method and experimental method.What's more,the data for validating the models was obtained,and the insulation loss was obtained through semi-elimination room & reverberation room method while the absorption coefficient was obtained through reverberation box.The simulation results were taken into comparison with test results to validate the best subsystem partition and the effective frequency range of hybrid FE-SEA model and SEA model,and the results of the two models were combined.(4)The sensitivity of the material parameters of each layer of acoustic package was analyzed,and 11 more sensitive parameters were selected from the original 19 parameters for subsequent optimization process to help improve efficiency.In the optimization analysis,it's not limited to the thickness,density,leakage and coverage of the acoustic package materials,but the orthogonal optimization was carried out through the material parameters of the acoustic package.The innovation of subject:(1)The influence factors of model precision was analyzed.the influence of each modeling parameter on the simulation results was researched.When these parameters are obtained after knowing the influence of each modeling parameter on the simulation results,the precision of the parameters which have great influence on the simulation results should be strictly guaranteed to ensure the accuracy of the model.While,the accuracy requirement of the parameters which have little influence on the simulation results can be reduced appropriately to help improve efficiency.(2)The influence of subsystem partition on simulation results was analyzed.The influence of three partition methods(coarse division,medium division,and detailed division)on simulation results was analyzed,and hybrid FE-SEA model and SEA model of each subsystem partition method were established.The simulation results were taken into comparison with test results to choose the best partition method to improve the accuracy of simulation model.(3)The optimization analysis of acoustic package was carried out from the aspect of material parameters.In the optimization analysis,it's not limited to the thickness,density,leakage and coverage of the acoustic package materials,but the influence of material parameters on the mass,acoustic insulation and absorption performance of acoustic package was researched.And then,the orthogonal optimization was carried out to get the best solution of acoustic package materials. |
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