Brake Squeal Suppression Through Structural Design Modifications

This paper details the use of experimental and test data based analytical techniques to resolve brake squeal. External excitation was applied to the brake system during operation on an inertia dynamometer and FRF measurements were taken. The operating conditions were varied with respect to disc velocity and brake line pressure. An experimental modal analysis under operating (EMA-OC) was performed on a disc brake, with a 2.6 kHz squeal, during squealing and non-squealing operational conditions. Two modes close in frequency to the 2.6 kHz squeal were identified from modal analysis of the brake system in a non-squealing operational condition which were not individually present during squealing conditions. These two modes were assumed to be the modes which couple due to friction and thus produce squeal in operation. A sensitivity analysis was then conducted on the modal model obtained from an EMA-OC non-squealing operational case. Candidates locations on the anchor bracket were chosen for modifications with the aim of increasing the frequency separation of the coupling modes by way of mass or stiffness modification. Using the sensitivity analysis as a guide, structural design modifications were analyzed. The predicted modification that created the largest frequency separation of these coupling modes was prototyped. Significant reductions in amplitude and frequency of squeal occurrence were seen from inertia dynamometer tests of the brake system with the modified anchor bracket.