Abstract: To understand the basic mechanism of time-varying frictional squeal, a pin-on-disc system is established and the rig test of frictional squeal is carried out, in which both intermittent and continuous squeals are produced repetitively. During the tests, the squeal sound pressure, the three-directional contact forces and the acceleration of the pin end are sampled under various speeds and normal loads conditions. Through the wavelet analysis, time-frequency analysis and feed-in energy calculation, the generation mechanism and key impact factors of time-varying squeal is investigated. It is found that the intermittence or the continuity of squeal depends on the quasi static normal force. When the normal force is less, intermittent squeal will appear, and there will appear continuous squeal vice versa. The mode coupling between the disc and the clamped pin cause the squeal in the system. The squeal frequency changes with the quasi static normal force variation pro rata, and there is also an obvious hysteresis effect between the squeal frequency and the resultant contact force. Energy feed-in is the precondition of squeal generation, and the variations of feed-in power and energy result in the fluctuation of amplitude envelop of the squeal noise pressure.

Key words: Contact force, Energy feed-in, Frictional squeal, Mode coupling, Pin-on-disc system, Time-varying characteristics