Instabilities Arising From the Frictional Interaction of a Pin-Disk System Resulting in Noise Generation

Abstract

A steel pin, supported on a flexible cantilever, is pressed against a thin steel disk which rotates at a uniform angular speed. The orientation of the pin’s central axis to the plane of the disk, the bending and torsional stiffnesses of the pin support, the stiffness of the disk, and the line of action of the resultant interactive force are all shown to affect the self-induced coupled frequencies and modes generated. The analysis of the experimental arrangement in terms of a three-degree-of-freedom pin subsystem and a single-degree-of-freedom disk element suggests that the system is unstable for certain combinations of the variables. The instabilities are shown to belong to a class of “geometrically induced” or “kinematic constraint” instability. The region of squeal-noise generation within the experimental rig is shown to correspond to the oscillatory unstable region predicted theoretically. The noise generated is similar to disk-brake squeal, and so the work furthers the understanding of this practical problem.