The role of pad-mode instabilities in disc brake squeal

Publication Type:
Conference Proceeding
20th International Congress on Sound and Vibration 2013, ICSV 2013, 2013, 4 pp. 2861 - 2868
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Automotive disc brake squeal remains an economically significant and technically challenging problem to solve, owing to customer complaints' associated warranty costs and the many interacting parameters. While industrial practice aims at identifying unstable vibration modes using complex eigenvalue analysis, in this paper, we show how to identify pad-mode instabilities using vibration forced response analysis complemented by acoustic radiation calculations for simplified brake systems in the form of a pad-on-plate model. Our recent results indicate that pad-mode instabilities might trigger so-called instantaneous mode squeal without the necessity of mode coupling. Pad-mode instabilities, which complex eigenvalue analysis fails to detect, are revealed by the dissipated energy spectrum at frequencies where the dissipated energy is negative (i.e. providing energy instead of dissipating energy). Pad-modes seem to radiate locally higher sound pressure depending on the phase shift between the structural vibration and the sound pressure while exciting the underlying plate's or disc's modes. Pad-mode instabilities are shown to be one mechanism of brake squeal. In order to identify pad-mode instabilities, it is beneficial to perform a full range of vibration analysis which includes complex eigenvalue value analysis, forced response and dissipated energy spectra as well as acoustic radiation calculations for a range of different parameters such as friction coefficient, operating pressure, temperature and contact conditions.
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