Study On Vibration Analysis And Noise Reduction Optimization Of A Monocoque Body

With the improvement of automobile dynamic property and security, consumers have a higher request for automobile comfort. Traffic noise is mainly produced by vehicle, it seriously affects people’s life and health, so automobile noise reduction can meet the requirements of automobile comfort and ensure the environment is not affected. Therefore, studying automobile vibration is of great significance to reduce automobile noise.This paper studies on the vibration analysis and optimization of the monocoque body. First of all, a finite element model for the white body, the cavity acoustics and the coupling acoustic-structure system are established by using Hyper Mesh. Secondly, modal analysis and frequency response of the original model are completed using Nastran. Meanwhile, by the modal shapes nephogram, this paper gains a conclusion which the vehicle first natural frequency is low.Then, the floor, which mainly bears a vibration and impact from motion, has an important influence on the comfort. The first natural frequency of the vehicle is improved after optimizing the floor. The noise of driver’s right ear is reduced under the excitation of left engine mount.Finally, the modal analysis of the cavity acoustics system is carried out and the acoustic resonance frequency is found out. The noise of the driver’s ear is analyzed respectively under the excitation of left engine mount and right engine mount using LMS Virtual. Lab. On the basis of the theory of acoustic contribution analysis, the larger contribution plates are found out. By using modal strain energy method, free damping layer is arranged on the panels of car. It effectively reduces the noise of driver’s ear under the excitation of left engine mount after arranging free damping layer.