Analysis And Optimization Of Light Bus Structure And Acoustic Characteristics

The low frequency noise inside the vehicle structure directly affects the ride comfort of occupants, properly reducing the sensory impact on occupants caused by the low frequency noise inside the vehicle structure and improving vehicle riding comfort effectively are important directions for car manufactures to elevate markettheir competitiveness and upgrade their products. Taking a light bus as the research object in this paper, first,modal the characteristics of the white-in-body were optimized and predicted by using the methods of modal sensitivity analysis and structure optimization; then studied interior noise,the bus’ s roof、front and rear floor which have greatly impact on acoustic pressure inside the bus have been optimized and improved based on the contribution of acoustic panels, reducing low frequency noise inside the bus. The main research contents and consequent conclusions as follow:1,The body-in-white finite element modal and acoustic finite element modal were established based on the geometric modal of the light bus, getting the natural frequencies and vibration type through the structure modal analyzed and acoustic modal analyzed, then the body FEM is justified by comparative the structure modal results to analysis and experiment.Finding the first three modal natural frequencies of body are too low according to the body structure modal calculation results, the first three modal natural frequencies of body-in-white should be appropriately increase in order to ensure the bus has a good ride and to avoid the human body resonance frequency range.2, Aiming at the problem of low order modes natural frequencies of body-in-white in the light bus are too low, learned the sensitivity of natural frequencies of the first three order flexible modes to plate thickness and sensitivity of mass to plate thickness by adopting the method of sensitivity analysis. Then by the method of topography optimization and adjusting the thickness of the correlative sensitive panels, the first three modal natural frequencies of body-in-white were improved to avoid the human body resonance frequency range 4-12.5Hz,while the weight of body-in-white was added less.3,The structure-acoustic coupling finite element modal of the light bus was established,on this basis, the dissertation analyzes bus compartment acoustic response of coupling system by the stimulation of the motor, getting the peak pressures and peak frequencies by analyzing the sound pressure level frequency response curve of the target point.4,The acoustic panel contribution of body is calculated, getting the results of the contribution coefficient corresponding to each peak frequency of the field points, finding the bus’ s roof、front and rear floor which have greatly impact on acoustic pressure inside the bus,the result can provide guidance to improve NVH performance. The bus’ s roof、front and rear floor were improved by topography optimization measure. The sound pressure frequency response of the optimized structure is calculated, each field point decreased 3-5dB(A) in the most sensitive peak frequency, improving the acoustic environment of the bus and the ride comfort of passengers effectively.