Detection of friction-induced instabilities at the origin of the squeal of wet poly-V belts

In the presence of water, the v-ribbed belts of the Automotive Accessory Belt Drive System can produce a typical squeal noise. The conditions of its appearance must be investigated as it could damage the brand image of car manufacturers.The squeal noise has been reproduced on a laboratory test rig whose purpose is the investigation of diverse friction-induced instabilities at a belt-pulley interface.This noise shows a characteristic harmonic pattern whose natural frequency depends on the belt surface coating. A special attention has been paid to the negative slope of the friction-velocity curve. The study showed that a negative slope is present when the noise appear but there isn't any correlation with its magnitude which is an usual cause for the appearance of self-excited vibrations. On another side the study of the vibrations of the belt has highlighted the presence of stick-slip in the same time that the noise appears but only for a particular belt coating.The participation of other friction-induced instabilities (sprag-slip, mode-coupling) has been investigated by comparison of instability domains obtained by variations of several parameters in theoretical model and experimental study.Finally, a microscopic study of the contact try to link noise appearance and tribological phenomenons.