Brake Noise Study (Part I) - Low Frequency Squeal

This two-part paper provides a systematic approach for identifying the fundamental causes of both low and high frequency brake squeal using advanced analytical and experimental methods. Also shown are methods to develop solutions to reduce or eliminate squeal by investigating effective structural countermeasures. Part I presented here is focused on low frequency squeal (2.2 & 5.5 kHz). In order to better understand the mechanism of squeal generation, this study started with the component modal alignment analysis around problem frequencies based on the component EMA (Experimental Modal Analysis) data in free-free condition. Then, the brake system EMA was conducted to gain insight into the potential system modes which caused the squeal. The last step of the brake squeal diagnosis utilized the ODS (Operational Deflection Shape) result to identify the key components involved in the squeal event. The above experimental results were also used to correlate with CAE normal mode predictions on both component and system level as well as system stability analysis on each stage respectively. The coordination of both analytical and experimental activities made it possible to identify root cause and, most importantly, to find the effective structural countermeasures to reduce or eliminate the squeal. In this work, the inertia and chassis dynamometer tests were used to evaluate promising modifications of the brake system.