Vibro-Acoustic Analysis And Optimization Of Damping Panel In Auto-Body

As the development of automobiles in high speed and lightweight direction, the noise problem is getting more and more remarkable. This can destroy the ride comfort directly. With the rising of people's requirements, auto manufacturer is getting more and more attention to NVH (Noise, Vibration and Harshness) performance of auto-body. Therefore, vibro-acoustic analysis of auto-body becomes an important target for automobile development.In this study, vibro-acoustic analysis and optimization of structural-acoustic coupled system of auto-body and its damping panel have been performed using numeric method. Theoretical and experimental methods are utilized as accessorial ways to analysis and verify the presented methods. The study mainly includes the following items:Structural-acoustic analysis of commercial auto-body is performed, which is based on wet modal method. It includes modal analysis and frequency response analysis. Panels and shells are main parts of auto-body. These panels will induce most of the sound energy when they are excited. To analysis and control of the vibration of these panels are very important. So, panel contribution analysis of peak value at driver's ear is performed to find the critical panels. This can make the following structural modification more efficiently and effectively.In order to improve the precision of vibro-acoustic analysis of damping structure, dynamic performances of visco-elastic damping structure are studied by CAE and experimental methods. On considering the property of frequency dependency of visco-elastic damping material, the modified modal strain energy method(MSE) is presented to model the loss factor of damping structure. The physical experiment is adopted to verify the accuracy and reliability of the method. Because the property of frequency dependency is considered, the simulation results are close to the experimental results. It indicates that the method addressed in this study is reliable and accurate.The effect of structural parameters of damping system on its vibro-acoustic and damping property is studied. These parameters include dimensions, material parameters and layout of damping layer. As a result, it could be found that the parameters like material parameters, geometry properties and shape of damping layer are very important to damping effects. Besides, under the modal frequency and total mass constraints, it is necessary to search the optimum combination of these parameters.Response surface method (RSM) which based on approximate theory is addressed to analysis and optimize the vibro-acoustic properties of the damping structure in this study. In order to search optimum results in area of feasible solution, inner penalty function method is adopted. It can not only transfer multi-objective optimization problem to optimization model without constraint, it can also provide multiple optimum results for response surface models. With RSM, the difficulty of building the sensitivity function is avoided and simplified. The optimized results also show that proper arrangement of structure parameters can reduce vibration and sound radiation power distinctly.