Experimental observations of coupled-mode instability in disc brake systems leading to squeal vibration

A brake system test rig was used to simulate braking operation and measure acoustic pressure, disc temperature and brake pressure during squeal events. Experimental results presented are the strong dependence of squeal frequency content on engagement pressure, the broadening of required brake pressure range for squeal existence as temperature increases, and a periodic squeal behaviour. A model was developed to analyse the stability for squeal prediction. This model is a reduced order modal model, based on component finite element modal properties. Additional support for the coupled mode instability is the correlation of experimental squeal frequencies with analysis.