Optimization On Vibration Reduction Of Car Roof Based On Phononic Crystals

With the improvement of people's comfort requirements while driving,vibration and noise control problems of the car is highlighted,At present,for the noise problem in the car,Measures include the use of sound-absorbing materials and the installation of sealing methods such as noise treatment,the method to a certain extent,can effectively inhibit the car's high-frequency vibration and noise,but for the low and medium frequency noise the treatment effect is not very satisfactory.Therefore,The NVH problem has become one of the important factors to suppress the development of the car to a higher level.Based on the theory of phononic crystals,this paper intends to establish the local resonant phononic crystals structure by introducing phononic crystals periodicity into the structure design of car roofs,and use the advantage of "small size control large wavelength"to achieve the effect of vibration and noise reduction.This paper mainly focuses on the optimal research of the parameters on the band gap,and the optimal combination of the parameters of the plate-shaped local resonant phononic crystal structure is obtained,which can provide a reference for suppressing the vibration and noise generated by the car roof.The following work has been carried out:(1)The bending vibration curve of the model is calculated by the dynamic simulation of the finite element software Comsol,and the cloud diagram is used to support the correctness of the finite element method.(2)The calculation of the bending propagation response of the corrugated sandwich phononic crystals and the plate-like phononic crystals is carried out and compared with the vibration pattern of the corresponding frequency point of the model.Besides,the effects of the geometric parameters and the material parameters on the structure band gap are systematically analyzed,and the mechanism of the band gap adjustment is analyzed according to the vibration morphology of the structure.Thus,the optimal parameter scheme based on the band gap characteristic is proposed.Finally,the combined type of phononic crystals structure is formed by the optimized structure in the way of series connection to achieve the effect of widening the band gap.(3)This paper takes the plate phononic crystals structure as an example,and applies it to NVH treatment of car.The band gap characteristic of the periodic thin plate structure is obtained by introducing the plate-like phononic crystals structure on the basis of the original structure of the car roof.By comparing the transmission characteristics curve diagram of the thin-plate structure before and after the introduction of the phononic crystals periodic disposal technology,to prove the effect of noise reduction can be achieved by introducing phononic crystals structure in the car roof.