Case study: Identification of brake squeal source mechanism through experimental and computational approaches

In this case study, mechanism leading to squeal noise in an automotive disc brake system is investigated with focus on systematic laboratory experiments and associated computational models. First, experimental modal analyses are conducted on the brake corner assembly components, and the natural frequencies and corresponding mode shapes are obtained. Second, finite element models of same components are developed, updated and validated by comparing predicted modal characteristics with those measured. Third, a controlled laboratory experiment is designed, constructed and operated in a semi-anechoic room. Experiments are conducted at many operational disc speeds and brake line pressures, and acceleration on the caliper and sound pressure are measured. Squeal events at distinct frequencies are successfully identified in the experiments. Fourth, a comprehensive computational model of the brake corner assembly is constructed using validated component models, and squeal investigation is then conducted through complex eigenvalue analyses while mimicking the operational conditions of experiments. The system model yields unstable frequencies at several operational conditions. It is observed that experimentally detected squeal frequencies match well with predicted unstable frequencies. Finally, operational deflection shape measurements on the caliper are also carried out during squeal events, and the predictions are found to be similar to those measured. In conclusion, the squeal generation mechanism of the brake system is understood from the perspective of friction-induced modal coupling, and an experimentally validated computational model of the brake system is successfully developed that may be used to find solutions to mitigate squeal. (C) 2020 Institute of Noise Control Engineering.