Instabilities generated by friction in a pad–disc system during the braking process |
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Authors: | A Meziane S DErrico L Baillet B Laulagnet |
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Affiliation: | aLaboratoire de Mécanique des Contacts et des Solides, INSA-Lyon CNRS UMR 5259 20, Avenue Albert Einstein, 69621 Villeurbanne, France;bLaboratoire de Géophysique Interne et Tectonophysique, Université Joseph Fourier-CNRS, B. P. 53, 38041 Grenoble Cedex 9, France;cLaboratoire de Vibrations et Acoustique, INSA-Lyon 20, Avenue Albert Einstein, 69621 Villeurbanne, France |
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Abstract: | This paper presents a numerical and experimental study of a pad–disc tribometer. The explicit dynamic finite element software PLAST 3 in 3-D is used to simulate the behaviour of the two bodies involved. Coulomb's friction law is used at the contact surface with a constant coefficient. For this application, temporal simulations show that separation occurs between surfaces, proof of instabilities. This unstable state is characterized by a stick–slip–separation wave. We show that instabilities describe a periodic shock phenomenon at the contact interface. Consequently, the acceleration spectrum recorded on the surface of the pad reveals periodicity in the frequency domain. It shows also that, in this case, the vibrations responsible for the instability are localized in the pad. The mode responsible for squealing can be obtained by a modal analysis of the pad–disc system by assuming that the interface is stuck. We highlight the importance of the pad Poisson's ratio in the occurrence of this unstable state. A numerical/experimental comparison has been performed and the fundamental frequency of squeal obtained experimentally and its magnitude agree with those calculated numerically with PLAST 3. |
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Keywords: | Friction Contact Dynamic Instability Finite element Squeal |
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