A Study On The Distribution Characteristics Of Automobile Floor Damping Materials

As car design and manufacturing technology improves continually and the relation between vehicle manufacturers and suppliers at all levels of the increasingly close and communicate more effective,resulting in different car brands of vehicle performance and safety performance are improvement and the gap is getting smaller and smaller.In this situation,the comfort of the car is regarded as an important indicator of a brand and a model of good or bad.Low-frequency noise is mainly produced by the body structure of the thin-walled plate radiation generated by vibration.Among so many body panels,particularly the vibration of the car floor structure is the highest radiation.The addition of viscoelastic damping material to the thin-walled plate is an effective mean to improve the damping of the composite structure,to improve the vibration and reduce noise level of the plate structure.And the applicative frequency range of the damping material is very wide,so it is widely used in car manufacture.However,due to the complex shape of the car floor structure,it is difficult to carry out effective analysis.Therefore,in general on the floor of the car with additional damping material structure,its distribution location,size and thickness are mostly based on engineering experience,so it cannot achieve the efficient use of damping materials.In this paper,the vibration characteristics of the floor structure are analyzed by using the floor structure of a car.The characteristics of the viscoelastic damping material,the modeling method of the viscoelastic damping composite structure are discussed.The effect of vibration and noise reduction of viscoelastic damping composite structure is affected by frequency,damping layer thickness,elastic modulus and Poisson's ratio.So the scheme of unequal thickness of damping material of automobile floor structure based on modal strain energy is studied,which effectively improves the utilization rate of damping material.The following specifically work is carried out.The finite element model of the car floor structure is established,and the free mode and the constrained modal analysis are carried out.The influence of the frequency variation characteristics of the viscoelastic material on the loss factor of the damping composite structure is studied.The method of calculating the loss factor of the damping composite structure considering the frequency variation of the adhesive material is obtained by the modal strain energy method.In the forced vibration response the simulation of frequency variation characteristics of damping material is realized.The influence of damping layer thickness,Poisson's ratio,elastic modulus and other factors on the damping compound structure loss factor was analyzed.The modal strain energy of the car floor structure is calculated,and the scheme of the unequal thickness of the viscoelastic damping material based on the integrated modal energy of the automobile floor structure in the frequency range of less than 200 Hz is proposed.And three different arrangement schemes are designed.The superiority of the unequal layout scheme is proved by the forced vibration response analysis.At the same time,according to the change of modal strain energy with frequency,the optimal frequency characteristic of damping material is determined.Based on this,the damping material type can be selected.