Friction-induced vibrations of squeal type due to transverse contraction in a flexible disk

The mechanism of excitation of friction-induced vibrations in a system comprising a flexible annular disk and two rigid surfaces is studied analytically. The surfaces are pressed together, and the rotating disk slides between them. It is shown that the sliding friction in the contact between the disk and the surfaces, together with the transverse contraction in the disk material, set up a feedback between the orthogonal eigenmodes of the disk corresponding to the same eigenfrequency, thus initializing instability. The instability mechanism is illustrated by simple analytical considerations. The obtained results are confirmed by finite-element analysis.