Brake squeal is a friction induced instability leading to limit cycle vibrations associated to a mode coupling. To analyze in detail this non-linear time varying phenomenon, a test campaign of a full brake system has been performed on an industrial test bench.

The first objective of this campaign is to extract squeal features. Squealing conditions where the disk velocity is imposed, and the brake pressure slowly evolves are chosen. To extract squeal features from measurements, a Harmonic Balance Vector (HBV) signal model based on the squeal signal characteristics is proposed. HBV signal model parameters are identified using a demodulation technique, providing slow time evolution of squeal fundamental frequency, fundamental shape and harmonic shapes. The model relevance is confirmed by analyzing the difference between the measured and the identified signals.

The second objective is to evaluate the relationship between squeal and operating parameters. The pressure evolution during the measurement leads to a strong evolution of the squeal. The analysis of the identified HBV signal highlights shape evolution with frequencies. At some fixed pressures, intermittent squeal occurs. The growth/decay rate is computed from the HBV signal and an experimental root locus is shown.

System modes also contain lots of information about the system dynamics. The last objective is to perform Experimental Modal Analysis in braking conditions. For several fixed pressures, the system is excited using a shaker. Two strategies are analyzed: excitation with sine-chirps and with pseudo-random signal.