Friction Instability Induced by Corrosion of Gray Iron Brake Discs

This study examined the frictional force oscillation induced by the corrosion of brake discs when two different types of brake friction materials (low-steel and non-steel types) were used. Corrosion of the disc was carried out in an environmental chamber using burnished discs to simulate disc corrosion in a parked vehicle. The thickness of the oxide layers on the discs after corrosion was examined using non-contacting distance probes, and the change in brake torque was analyzed using a single-end brake dynamometer. The results showed that the oxide thickness on the disc was affected by the friction film on the burnished disc surface, and the friction force oscillation was closely related to the removal of the oxide layers while applying the brake. The low-steel friction material removed the oxide layer faster in the early stage than the non-steel friction materials so that it produced small oscillations in the friction force. However, the low-steel friction material increased the amplitude of the friction force in the later stage of the extended brake tests due to the excessive DTV (disc thickness variation). On the other hand, the non-steel friction material produced large friction force oscillations in the early stage with the amplitude decreasing in the later stage of brake application due to removal of the oxide film.