NVH Performance Analysis And Optimization Of Vehicle Body Based On Constrained Damping Structure

NVH performance is an important performance index for evaluating the comfort of vehicle,which is related to vibration and noise level of vehicle.It is also one of the research and development directions of automotive OEMs in recent years.The noise radiated by the vibration of thin-walled panel is the main source of low-frequency noise in the car.Restraining the vibration of thin-walled panel is an effective way to reduce the noise in the car.Because of its low cost and obvious effect of reducing vibration and noise,laying the restrained damping structure on the thin-walled panel becomes a common way to reduce the vibration and noise in the car.However,the damping material has obvious nonlinear characteristics,and its shear modulus and loss factor vary with temperature and frequency.Therefore,it is difficult to accurately simulate and analyze the influence of constrained damping structure on the interior vibration and noise level of vehicle.Based on the above problems,this paper takes the body structure of a SUV as the research object,studied the modeling method of restrained damping structure,NVH performance simulation analysis of body structure,and robust optimization analysis of body transfer function with restrained damping structure.The main research contents are as follows:Modeling methods of constrained damped structures are studied.Different types of elements are used to simulate constrained damped structure and carry out simulation analysis.Considering the error of modal frequency,loss factor with analytical solutions in references,the solid element is used for modeling the damping layer,and the shell element is used for modeling the constrained layer.Considering the computational efficiency,modal method is used to solve the problem.The modal test under simple boundary conditions is carried out,the results show that structure damping defined as frequency variation can better fit the test results.NVH performance analysis of body structure.The grid model of the body-in-white is built and modal analysis is carried out.The results of modal simulation are compared with the experimental results to show the rationality of the body-in-white model.The grid model of the trimmed body is constructed and modal analysis,vibration transfer function analysis and noise transfer function analysis are carried out.Noise transfer function analysis results of the body before and after laying the restrained damping structure are compared,and the sound pressure in the car can be reduced up to 5.2dB.Robust optimization analysis of transfer function of body structure.Based on the body finite element model,the response surface model between design variables and objective functions is established.On the basis of response surface model,the robust optimization of vibration transfer function is carried out.After optimization,the?level is obviously improved.The robust optimization results are substituted for the finite element model to verify,and the peak value of response is reduced by up to 18.18mm/s~2 after optimization.