| With the improving requirements to the comfort of automotive, NVHcharacteristics of the vehicle become being paied more and more attention by theautomobile manufacturers. Effectively reducing the interior noise has become animportant goal for the design of the vehicle structure and is an important way for thedomestic automobile enterprises to improve their market competitiveness. Heavycommercial vehicles always run on poor road with complex and changing condition.Therefore the body structure especially the cab will produce strong vibration andnoise. This can seriously affect the acoustic comfort of the driver, and can easily leadto fatigue and malaise, resulting in errors of judgment and even causing accidents. Soimproving the cab acoustic environment and reducing the interior noise level are ofgreat significance in terms of economic value or social benefits.Based on a heavy commercial vehicle as the research object in this paper,combining with road test, FEM, BEM and acoustic CAE technology are used toanalyze the structure dynamic performance and interior noise response characteristicsof this cab. Then the influence factor and control measures is discussed, which canprovide the potent support for improve the vehicle interior noise quality. And on theother hand, this dissertation tries to find out a complete forecast, analysis and controlmethod so as to enrich the automotive structural noise control theory and methods.The main contents of this paper are as follows:1. According to the road test, the cab vibration excitation and sound pressureresponse signal are obtained. Then the signal preprocessing, spectrum correction,spectrum analysis and correlation analysis are taken to the signal, which can providedthe data basis for the follow-up CAE analysis.2. The finite element model of the body-in-white is built first. Then modalanalysis and modal test was conducted to understand the dynamic characteristics ofthe major components of the body structure. Then the acoustic finite element modeland acoustic-structure coupling model are built. The acoustic field modes of theacoustic finite element model and the coupled modes of the acoustic-structurecoupling model were analyzed to obtaine the cab acoustic modal characteristics.Applying finite element dynamic analysis techniques, multiple operating frequencyresponse analysis on the body structure of the cab was carried out based on theexperimental data of the road test. Then the simulation results and experimentalresults were compared to verify the effctiveness of the finite element model. And the main vibrating plate member of the cab structure was found out.3. Based on the acoustic field dynamic response analysis method, acoustictransfer functions of the cab were analyzed when each unit excitation is applied inmounting position. Then the acoustic response of the cab acoustic field point wasanalyzed using FEM and BEM on the base of experimental test excitation andcompared with experimental test in order to evaluate the interior acousticcharacteristics, and to identify the response peak frequency band.4. Aim at the peak frequency band, plate contribution analysis of the driver’sright ear field point pressure was conducted to find out which is the largestcontribution plates and to identify structural and acoustic modal participation factor.Then according to the analysis result, the cab structure was optimized and noisereduction processing from three aspects of key plates’s thickness optimizing, structuretopography optimizing and damping treatment. Finally, the effectiveness of theanalysis and optimization to improve the interior acoustic characteristics of the cab isproved throng the simulation verifying. |
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