Analytical and experimental investigations of disc brake noise using the frequency-time domain

The influence of non-linearity and randomness of contact forces on generating noise of low and high frequencies in disc brake systems is studied analytically and experimentally. The analytical model of the disc includes transverse (out-of-plane) and circumferential (in-plane) displacements. The disc is modelled using Mindlin's theory for relatively thick plates and pads as one-dimensional continuous beams. The contact normal pressure includes a non-uniform distribution and the friction is represented by a distributed follower-type force. Numerical simulations reveal a multi-frequency modulated-intermittency of disc and pads oscillations. It is found that the frequency component corresponding to circumferential vibrations of the disc is always dominant in the case of deterministic friction. However, random friction creates impulsive forces that excite the transverse mode and has little effect on circumferential mode. Discrete wavelet transform (DWT) is applied to decompose, filter, and separate deterministic and random frequency components of the measured friction coefficient. The time–frequency analysis is useful in identifying the nature of generated noise. Copyright © 2005 John Wiley & Sons, Ltd.