| Vibration of automobile brake system not only produces serious noise pollution, which affects occupants’ comfort and health, but also causes the auto parts fatigue failure. The material of silencing sheet is viscoelastic damping material, so that, it has a obvious effect on vibration and noise reduction and appears extremely promising in the future.Based on the modal theory of viscous damping material, we firstly get the modal parameters that can describe the damping performance of the silencing sheet. Then we develop the corresponding test method and process by consulting the national standard and ASTM standard, and get the time travel curve of the silencing sheets with different thickness through this test procedure.Preprocessing, digital filtering on the vibration signal of silencing sheet and identificating modal parameters will be conducted by MATLAB. The modal damping ratio parameters of various silencing sheets will be fitted by Rayleigh method to get the material damping ratio with high fitting precision. And then the material damping ratio and loss factor will be studied to get the effect of silencing sheet thickness on the loss factor. The results show that:with the increase of silencing sheet thickness, the loss factor increases, but the growth rate gradually reduces; As steel plate coated with0.1mm rubber material, the damping effect is remarkably enhanced, and the loss factor increases about3.8times.Finite element analysis method and modal extraction method of the brake noise are studied based on ANSYS to get the calculation method and modal analysis method. We establish the finite element model of the brake and the silencing sheet, and verify it by the experimental data of noise matrix.The study on the influence of friction coefficient on the brake noise without silencing sheet is conducted. Meanwhile, we also conduct a study on the influence of silencing sheet thickness on the brake noise under the condition of different friction coefficient and different brake pressure. The results show that:under the condition of different friction coefficient, the number of unstable mode increase gradually with the increase of friction coefficient and there are some of the same unstable modal frequency. The effect of silencing sheet thickness on the brake noise propensity under the condition of different friction coefficient and brake pressure is different. By comparison, we get the best damping thickness of silencing sheet respectively under the condition of different friction coefficient and the brake pressure, which is0.8mm (or1.2mm) and1.2mm. |
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