Analysis Of The NVH Characteristic Of The Four Wheel Vehicle Transfer Case

In this paper,we mainly use modal test,NTF test,structural finite element method and acoustic boundary element method to study the vibration characteristics of the gear transmission system of the transfer case gear and the radiation noise of the transfer case box are tested and simulated.Through the noise reduction optimization method to deal with the transfer case gear box to achieve the purpose of vibration and noise reduction.The main contents of this paper are as follows:Calculation and analysis the dynamic excitation oftransfer case gear: The transmission systemof the transfer case gear is modeled by using the lumped parameter model,and the dynamic equations are normalized by the dimension.On this basis,the three-dimensional model of the transfer case is established,and the multi-body dynamics model is built using Adams.Analyzing the dynamic ex-citing forces.Modal analysis and vibration response analysis of the transfer case box: The finite element model of the transfer case structure is established,and the modal test of the transfer case is carried out.The accuracy of the finite element model is verified by comparing the results obtained by the modal test and simulation analysis.The gear excitation force is used as the boundary condition;calculate the vibration response based on the modal.Then,the vibration acceleration response of the surface of the box is obtained.Calculate the radiation sound field of transfer case: The acoustic boundary element model of the transfer case box is established,and the accuracy of the proposed model is verified by comparing the NTF test data with the data calculated by the acoustic numerical calculation.Calculate the frequency response on the transfer case filed point;The frequency response curve is obtained.The causes and mechanism of noise peak sound pressure are studied by using the contribution method of ATV and MATV method.Noise control optimization: According to the results of sound field analysis,the free damping layer optimization is based on the integrated strain energy and size optimization method.Effectively reducing the peak ofradiation noise.