Links Between Disc Brake Squeal and Pad In-Plane Motion

This paper is focused on links between disc brake squeal and in-plane vibration of pads. A special experimental setup is developed in order to determine correlation between squeal acoustical signals and longitudinal accelerations of both pads. A strong coherence between spectral properties of squeal and pad vibrations is found and quantified. In particular, the dominant frequency of the acoustical and mechanical responses appears to be same. Essentially unharmonic temporal mode shapes of the pad vibrations are detected. Such mode shapes reveal the information about multiple frequency friction forces applied to the disc and pads with a possibility of resonance with their coupled elastic modes. Experimental time history records also show a significant out-of-phase component in the pad motions, which is associated with a bending moment applied to the disc. Major experimental observations admit theoretical interpretation based on a two degrees of freedom model. Theoretical conclusions and experimental results are found to be in a good agreement.