Body Structure Dynamic Analysis And Free Damping Layer Treatment Optimization

With the customers’ increasing demand for vehicle ride comfort, and the increasinglyfierce market competition to enhance the competitiveness of their products, car manufacturersregard the ride comfort of one car as a key factor in new product development, so the analysisand research of vehicle noise and vibration plays an increasingly important role in modernvehicle development. Research indicated that vehicle interior low-frequency structure noise isinduced by numerous body structure thin-walled plate vibration radiation. With damping layertreatment on thin-walled panels, the damping composite structure’s damping factor can beincreased, and the radiation noise levels can be reduced, also because visco-elastic dampingmaterial can suppress vibration and noise in a very wide frequency range, so damping materialget a large number of applications in the body structure. However, the body structure itself iscomposed of many panels with complex shape, the location, size, and thickness of dampingmaterial is determined based on engineering experience, and it often do not make efficient useof damping material.The vibration characteristics of the vehicle body structure and the damping characteristicsof the composite structure with free damping layer were studied respectively in this thesis. Andthe modeling method of the body structure and add on damping structure were analyzed infocus. Then the body structure were analyzed respectively using FEM simulation method andexperimental modal analysis method. In the end, the addon free damping layer treatment onthe body structure were optimized. Details are as follows:The FEM analysis model of the body structure were established and the modelingmethod of some key part of established model were analyzed. Also the damping performanceof the composite structure with addon damping layer were analyzed using modal element strainmethod. The influence factor of the damping performance of the composite structure werestudied. The established FEM model of the body structure were analyzed using simulation modalanalysis, the result modal frequency and low frequency modes of vibration were calculated.And the experiment modal analysis were accomplished. The results of the simulation analysisand the experimental analysis were compared, and the validity of simulation were verified.Design optimization of the addon free damping layer on the body structure wereaccomplished respectively using topology optimization method and element strain energydistribution method. The topology optimization choose the real part of one specified modalfrequency of the complex modal analysis as optimization objective, and the mass fraction ofthe free damping layer as design constraint. Considering the number of the body structuremodes is large, the synthesized element strain energy of all the considered modes werecomputed. The final addon free damping layer on the body structure were designed using thesynthesized element strain energy distribution.