Experimental analysis on squeal modal instability

In this paper, an experimental analysis performed on a simplified brake apparatus is presented. Brake squeal is a major concern in braking design. During past years a common approach for squeal prediction was the complex eigenvalues analysis. Squeal phenomenon is treated like a dynamic instability. When two modes of the brake system couple at the same frequency, one of them becomes unstable leading to increasing vibration. The presented experimental analysis is focused on correlating squeal characteristics with the dynamic behavior of the system. The experimental modal identification of the set-up is performed and different squeal conditions and frequencies are reproduced and analyzed. Particular attention is addressed to the system dynamics in function of the driving parameters on squeal occurrence. Squeal events are correlated with the modal behavior of the system in function of the main parameters, like contact pressure, friction material properties and system geometry. The robustness of the obtained squeal events permits a further analysis on the triggering of the squeal instability during braking, including the values of parameters that bring to instability. The obtained results agree with the modal coupling approach for squeal prediction, and confirm the characterization of squeal as dynamic instability.