Analyses On Vibro-acoustic Characteristics Of A Cavity With Passive Constrained Layer Damping

At present, the noise problems of Automotive is attached more and more attentionby domestic and foreign automobile manufacturers and the Ministry of EnvironmentalProtection. How to improve the Internal and external acoustic environment of automotive,reduce interior noise levels, and improve comfort to ride the vehicle has become one ofthe hotspots for automotive research. Passive constrained layer damping material is verysignificance for reducing the noises of the box structure like automotive. This paperanalysis the free vibration characteristics and the internal sound field characteristicswhich are caused by the harmonic excitation force for a cavity with passive constrainedlayer damping using the finite element method.The primary researching contents and methods are as follows: Firstly, the methods,which are how to set up and solve the model about the passive constrained layer dampingstructure and the acoustic-structure coupled model of a cavity, are explored inMSC.PATRAN/MSC.NASTRAN. And the methods are right through verifying theresult of the instance. Secondly, the acoustic-structure coupled model of a cavity withpassive constrained layer damping is established in MSC.PATRAN, because the methodsare combined to set up the model about the passive constrained layer damping structureand the acoustic-structure coupled model of a cavity, the complex modal of the coupledmodel of a cavity and the acoustic characteristics of the internal of the cavity because theharmonic excitation force are analyzed thought MSC.NASTRAN. Then, theacoustic-structure coupled model of a cavity with passive constrained layer damping areset up and solved again, while the parameters of the structure for passive constrainedlayer damping, and then the relationship between the parameters and the effect forreducing noise can be found. Lastly, the first loss factor of the acoustic-structure coupledmodel of a cavity with passive constrained layer damping is optimized by MATLABwhich is used to control the cycle and MSC.NASTRAN which is used to find the result.The achievements and conclusion are as follows: The methods which set up andsolve the model about the passive constrained layer damping structure and theacoustic-structure coupled model of a cavity are right; there are some regulars which arefound between the natural frequency, the modal loss factor, the acoustic characteristics ofthe internal of the cavity and the parameters of the structure for passive constrained layerdamping, so setting up these parameters reasonable can find the optimal value about theeffect of the damping structure for reducing noise; The optimal value of the viscoelastic layer thickness and the constraint thickness are found by optimizing the model, when thefirst loss factor of model is maxmum.