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The brake torque variation (BTV) generated due to geometric irregularities in the disc surface is generally accepted as the fundamental source of brake judder; geometric imperfections or waviness in a disc brake caliper system is often quantified as the disc thickness variation (DTV). Prior research has mainly focused on the vibration path(s) and receiver(s), though such approaches grossly simplify the source (frictional contact) dynamics and often ignore caliper dynamics. Reduction of the effective interfacial contact stiffness could theoretically reduce the friction-induced torque given a specific DTV, although this method would severely increase static compliance and fluid volume displacement. An experiment is designed to quantify the effect of disc-pad contact modifications within a floating caliper design on BTV as well as on static compliance.

Modal sound radiation of a brake rotor is expressed in terms of analytical solutions of a generic thick annular disk having similar geometric dimensions. Finite element method is used to determine structural modes and response. Vibro-acoustic responses such as surface velocities and radiated sound pressures due to a multi-modal excitation are calculated from synthesized structural modes and modal acoustic radiation of the rotor using the modal expansion technique. In addition, acoustic power and radiation efficiency spectra corresponding to a specific force excitation are obtained from the sound pressure data. Accuracy of the new semi-analytical method has been confirmed by purely numerical analyses based on finite element and boundary element models. Our method should lead to an improved understanding of the sound radiation from a brake rotor and strategies to minimize squeal noise radiation could be formulated.