Body Structure Free Damping Layer Optimization And Local Vibration Control

With the rapid development of science technology, the automotive performance has got anentire improvement, at the meanwhile, its riding comfort has attracted more and more attention.The condition of automobile vibration and noise is an important factor affecting the vehicleriding comfort. In the automobile ’s high-speed and lightweight developing period, theeffective control of automobile vibration and noise is an important research direction of thepresent automobile technology. The vehicle interior low frequency noise often stems from carbody structure vibration, therefore, it’s quite important to analyze and control its features.In this paper, we discussed the modeling method and vibration characteristic of the dampingcomposite structure and analyzed its vibration quality, taking a car as the research object.Basing on the comprehensive modal strain energy method, we analyzed and optimized the carbody free damping layer position and material choosing, which effectively controls the carbody panels vibration. Through optimizing the rear windshield beam, we increased thestructure stiffness and also controlled the local vibration of the car body.We have established the finite element modal of body in white structure and also carried onthe modal analysis. The accuracy of the model was verified through the white body modal test,furthermore, the closed body finite element model was established and analyzed. This paperdiscussed the characteristics of viscoelastic damping material, and its composite structurefinite element modeling and dynamic characteristics analysis method. Considering of thefrequency dependence of the viscoelastic damping material in the forced vibration responseanalysis, we performed the direct frequency response method, and also compared thefrequency response calculation results between viscoelastic damping material frequencydependent parameters and constant parameters, then calculated the modal loss factor ofcomposite structure using the modal strain energy method.The main panel modal strain energy was calculated. The car body free damping layingposition was optimized basing on the modal strain energy distribution. According to the panelelement modal strain energy changing, the feature frequency range was determined, furthermore, the type of damping material was confirmed on the basis of the former. In theactual road test, we have tested the vibration acceleration of the rear windscreen beam underdifferent operating conditions. Then the beam was improved, which enhanced the rigidity ofits structure, reduced the local model number of the BIW and also decreased the amplitude onthe local mode. Through the above optimization and improvement measures, the roof averageacceleration response under the engine mounting excitation was reduced to40%.