Material Processing And Optimization For Noise Reduction And Damping Of Car Body Based On Finite Element Analysis

The main source of interior low frequency noise comes from the vibration of body panels,so suppressing the vibration of body panels becomes an effective way to control interior noise.Due to its excellent effect of vibration and noise reduction,convenient implementation and low price,damping materials are often used in the process of vibration and noise reduction of car bodies.In this paper,a domestic SUV model is taken as the research object,and the NVH performance of the vehicle body is simulated and analyzed.By laying a free damping structure on the vehicle body and optimizing the thickness of the damping layer,the interior noise is reduced.The main research contents of this paper are as follows:Based on the geometric model of an SUV,the finite element models of body in white,interior body and sound cavity were established in Hyper Mesh software.Through the free modal analysis and static stiffness analysis of BIW,interior body and sound cavity finite element models,the basic performance of the body structure is preliminarily judged.Through the analysis of the noise transfer function,it is found that the peak value of the sound pressure level in the driver’s right ear is too high when the right mount is excited to the Y direction,the rear mount is excited to the Z direction,the front sub-frame is excited to the Z direction,and the front sub-frame is excited to the Z direction.Through the analysis of panel contribution,the body panels with large contribution at the corresponding frequency of the peak sound pressure level at the problem point were found.In order to understand the vibration and noise reduction characteristics of freely damped structures,the modeling methods and analysis methods of freely damped structures are studied.Through the plate vibration response test,it is verified that the free damping structure can effectively suppress the vibration of the composite structure.Through the simulation analysis,the influence of different free damping layer thickness on the vibration reduction performance of the structure is explored.The position of the damping material was determined by the comprehensive modal strain energy analysis of the BIW.After the 3mm free damping material was laid at the position where the comprehensive strain energy of the car body panel was larger,the peak value of the sound pressure level at the problem point inside the car was reduced to different degrees,which verified the effectiveness of the location of the damping material.In order to further reduce the interior noise and improve the utilization rate of damping materials,the thickness of four free damping layers on the roof was optimized by constructing a response surface approximate model.After optimization,the optimal combination of free damping thickness was found.The peak value of sound pressure level at the driver’s right ear was reduced by 0.9d B and the total mass of damping material was reduced by 0.43 kg when the driver was excited in the Z-direction of rear suspension.