Orientadores: Renato Pavanello, Janito Vaqueiro Ferreira / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-12T21:02:40Z (GMT). No. of bitstreams: 1 Oehlmeyer_AlbertoKury_M.pdf: 8739503 bytes, checksum: ddb3ab5d5e0619a4b4d24a8b7f30f563 (MD5) Previous issue date: 2008 / Resumo: Entender, modelar e mitigar os problemas de ruído de freio a disco ainda e um dos grandes desafios da indústria automotiva. E importante para fabricantes e fornecedores predizer o ruído de freios automotivos ainda na fase de projeto. O Squeal e um ruído de freio em uma faixa de freqüência entre 1 e 15 kHz, e pode ser definido como uma vibração auto-excitada em um problema de atrito, que pode gerar instabilidades. Este trabalho resume como modelar e validar um modelo para predizer o Squeal, bem como fazer uma analise paramétrica do modelo. Este trabalho pode ser dividido em 3 partes conforme a idealização adotada: um modelo de 2 graus de liberdade, um modelo de 5 graus de liberdade, e um modelo de elementos finitos. O primeiro e usado para explicar uma instabilidade divergente, e o segundo para explicar e encontrar uma instabilidade vibracional. Então, o modelo numérico é criado, composto por disco e pastilhas. O atrito e incorporado usando o modelo de Coulomb, com elementos discretos entre as áreas de contato, considerando malhas conformes entre os corpos. Essas molas formam uma matriz de rigidez não-simétrica, tornando a matriz de rigidez global também nao-simétrica e gerando autovalores complexos. As freqüências instáveis são definidas pela parte real do autovalor. Se a parte real for positiva, então o sistema é instável. Finalmente uma analise paramétrica e realizada para se demonstrar a influência de alguns parâmetros nos autovalores / Abstract: To understand, model and mitigate disc brake noise is still one of the greatest challenges for the automotive industry. It is substantially important for manufacturers and suppliers to predict the disc brake noise in a design phase. Squeal is a brake noise in the 1-15 kHz frequency range, and can be defined as a self-excited friction problem, which can generate instabilities. This work comprises how to design and validate a model to predict Squeal, as well as a parametric analysis of such model. This work can be divided in 3 parts: a 2 degree of freedom model, a 5 degree of freedom model, and a finite element model. The first one is used to explain a divergent instability, and the second one to explain and find flutter instability. Then the numeric model is created with a rotor and two pads. The friction is incorporated using the Coulomb model, with spring elements between the contact areas, using mapped and conform meshes. These spring elements form a non-symmetric stiffness matrix, thus the global stiffness matrix will be non-symmetric and yield complex eigenvalues. The unstable frequencies are found through the real part of the eigenvalues. If the real part is positive, then the system is unstable. Finally, a parametric analysis is carried out to depict the influence of some parameters in the eigenvalues / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestre em Engenharia Mecânica

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Brake squeal is an old and well-known problem in the vehicle industry and is a frequent source for customer complain. Although, brake squeal is not usually affecting the performance of the brakes, it is still important to address the problem and to predict the brakes tendency to squeal on an early stage in the design process. Brake squeal is usually defined as a sustained, high-frequency vibration of the brake components, due to the braking action. By using simulation in finite element (FE) method it should be possible to predict at what frequencies the brakes tend to emit sound. The method chosen for the analysis was the complex eigenvalues analysis (CEA) method, since it is a well-known tool to predict unstable modes in FE analysis. The results from the CEA were evaluated against measured data from an earlier study. Even though there are four main mechanism formulated in order to explain the up come of squeal, the main focus in this project was modal coupling, since it is the main mechanism in the CEA. A validation of the key components in model was performed before the analysis, in order to achieve better correlation between the FE model and reality. A parametric study was conducted with the CEA, to investigate how material properties and operating parameters effected the brakes tendency to squeal. The following parameters was included in the analysis; coefficient of friction, brake force, damping, rotational velocity, and Young’s modulus for different components. The result from the CEA did not exactly reproduce the noise frequencies captured in experimental tests. The discrepancy is believed to mainly be due to problems in the calibration process of the components in the model. The result did however show that the most effective way to reduce the brakes tendency for squeal was to lower the coefficient of friction. The effect of varying the Young’s modulus different components showed inconsistent results on the tendency to squeal. By adding damping one of the main disadvantages for the CEA, which the over-prediction of the number of unstable modes, where minimized.