Noise And Vibration Performance Analysis And Experimental Research Of A Certain Automobile Rear Axle

The rapid development of the automotive industry has made the car more and more an irreplaceable means of transportation,profoundly affecting and changing our daily travel.In the past,consumers have paid special attention to the safety,power and economy of the car.With the development of the economy,the comfort of the car has slowly entered the public's vision,which is also increasing in the minds of consumers and the proportion.As an indispensable component of the vehicle transmission system,the performance of the rear axle NVH(Noise,Vibration and Harshness)will directly affect the NVH performance of the entire vehicle,which in turn affects the comfort of the car.Therefore,it is necessary to carry out the analysis of the NVH performance of the rear axle.In this paper,the dynamic simulation of the rear axle is carried out,and then the noise of the rear axle shell to the air is solved.Finally,the specific vibration and noise reduction measures were taken and the vehicle road test was carried out to test the noise value.The results of this paper are as follows:(1)Research on the mechanism of vibration and noise of the rear axle.The excitation and its transmission route for the vibration and noise of the rear axle are discussed.Based on the vibration shock theory,the torsional vibration model of the main driven gear system of the final reducer is simplified into a vibration system with single degree of freedom.The dynamic equations of the gear system are created and analyzed.Based on the Helmholtz integral method,the sound field analysis and discussion of the rear axle is carried out,which provides a powerful basis for the subsequent noise simulation.(2)Dynamic simulation of the rear axle assembly.The dynamic characteristics of the rear axle at 30 km/h and 120 km/h are simulated,and the vibration displacements of the five nodes in the axial and circumferential directions are obtained respectively.The displacement curve shows that the displacement curves of the bearings in the axial and circumferential directions are very similar,and the magnitudes are basically the same,so we can select the displacement of any node above the outer surface of the bearing as input excitation for the back noise simulation.(3)Simulation calculation of rear axle radiation noise.The structural vibration analysis of the rear axle housing is carried out,and the vibration displacement of the rear axle housing is solved.Then,based on the boundary element method,the solved vibration displacement is regarded as the boundary condition,the noise that rear axle housing distributing to the environment was simulated.In the noise cloud diagram,the location where the noise is relatively large is located at the back cover of the rear axle housing.And the comparison found that the average noise of the rear axle housing is 79.38 dB when driving at 30km/h,and the average noise of the rear axle housing is 96.32 dB when the speed is 120km/h,and when the vehicle speed is at 120km/h,the maximum noise of the rear axle housing is larger than that at 30km/h,which indicates that under certain circumstances,the noise of the rear axle will increase as the vehicle speed increases.(4)Vehicle road test.Firstly,the common methods of vibration reduction and noise reduction of the rear axle are summarized.It is determined that the main reducer gear modified and the damping device added on the rear axle shell to reduce the vibration and noise of the rear axle.The vehicle road test was carried out to test the noise values under the two schemes.The results showed that both schemes can reduce the vibration and noise.In the first scheme,the noise peak at the front and rear seats is reduced by about 7 dB,and the second scheme reduces the noise peak size by about 10 dB.Compared with the two schemes,the addition of the damping device is more effective in reducing the noise.