| With the rapid development of the automotive industry, motor vehicle has entered the ordinary families, which is convenient for people's daily life. But the automobile noise, especially the brake noise, has become a big nuisance which we can not be ignored, and catches extensive attention of consumers. Control and reduction of brake noise has become urgent demand of all the people, thus to reduce automobile brake noise becames an important problem to be resolved both by the automobile manufacturers and researchers.This topic comes from "Zhejiang Province Key Laboratory Project for Experimental Bases of Automobile Parts", No.2003E10052. After extensive review of the related literature, the approach of adding an insulator at the back of the disc brake back plate has been realized to reduce the structure vibration and noise. Discussion has been done of the performances of several viscoelastic damping materials which showed good results of reduction of noise. The dissertation reveals damping technology in brake antivibration amd noise reduction applications, and provides theoretical basis and test methods for future studies.First of all, a detailed introduction of engineering background of the noise problem is presented. The dissertation analyzes of the disc brake friction mechanism of noise, explains the relationship between noise and vibration, summarizes the current research of commonly used methods of noise and vibration.3D models of the disc brake parts are established respectively. The dynamic characteristics of the model for each brake parts are studied. This paper also analyzes the relationship of dynamic characteristics and noise of the each part. The CAD model and finite element model of the brake assembly is established, analysis is taken using the complex modal analysis method, and the dynamic characteristic of assembly is calculated.Theoretical research of damping noise reduction method of disc brake is stated. Based on the layer of damping mechanism analysis, this paper analyzes the damping layer in the braking system of the vibration damping mechanism and characteristics of its main performance indexes, introduces the structure of the finite element analysis method of damping of viscoelastic materials, the mathematical representation and the solving method of dynamic equations. And an analytic model is used to get relationship of the damping coefficient and squeal characteristics parameters which indicate that increasing system damping can reduce the unstable vibration modes. For damping layer structure modeling, the 8 nodes linear boundary element method is applied and the result shows that the proposed method has better accuracy, and easier to operate, and greatly improvement of the computational efficiency.According to damping layer materials E756-98 standard ASTM test, different structures of the test methods have been disscussed. the data have been calculated and summed, and then the viscoelastic damping materials vibration damping parameters have been measured, including:the loss factor, young modulus and shear modulus. The method of calculating the damping materials characteristics can be widely used in the mathematical model and forecasting system damping performaces of their working conditions. Then the disc brake vibration and noise tests were introduced, and tests have been done in accordance with J2521 SAE method on the inertia-noise-dynamometer 3900 made by Link company. The increase of rubber damping layer on the brake back plates was investigated, and a comparative study of brake noise with and without the damping layer has been done. Results show that, by adding damping layer, the brake noise in the frequency distribution, noise probability and measured peak values have been reduced at different levels, so the tests verified that damping noise reduction method can reduce the noise generated probability. |
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