Numerical Simulation Of Automotive Interior Vibra-acoustic Characteristics In Low Frequency Range

With the rapid development of modern automotive industry, the traditional economic and dynamic properties of automotive have reached a high level. Therefore, the requirements of vehicle comfortableness are increasing and it has become an important standard of vehicle performance. Noise and vibration are the main factors affecting the comfort, with the improvement of software, hardware and numerical analysis, CAE technology has been widely used to simulate automotive interior noise in the stage of design and development new cars.In this thesis, taking a car model as the main study object, made the prediction of dynamic and vibra-acoustic characteristics in low frequency using finite element and boundary element methods, and improved the noise performance by changing the structure of the roof. Firstly, on the basis of the finite element theory, the BIW model, front and rear door model, interior acoustic cavity finite element model were established by HyperMesh, using beam and rigid element to simulate the connection model. Through the analysis of body free modal, mastered the performances of modal shape in order that avoiding resonance and providing evidence for prediction of vehicle interior noise and diagnosis of noise source.The modal frequency and shape of acoustic cavities FEM with and without seat were comparative analyzed by using LMS Virtual. Lab, the modal frequencies with seat were lower than those without seat and the sound pressure distribution was symmetrical. The structural finite element and boundary element coupling model were established by importing acoustic cavity on the basis of structural model. The interior acoustic characteristics of coupled system were greatly affected by the vibrations of body panels. The response results of interior noise under engine excitation were based on the frequency response analysis theory, making a prediction of front and rear passengers’ sound pressure in order to provide references for noise reduction.Lastly, according to the results of structural modal analysis, interior noise transfer function and sound pressure curve of driver’s right ear, come up with an improvement program of roof panel, and the contrast results showed that SPL were reduced on the peak frequency nearby 78 Hz and 165 Hz, reaching the provision of vehicle interior sound pressure level and good effects have been obtained.