Despite the importance of other particles sources (tires, exhaust gases ... [Tomasz Gonet & Al., 2019]), the disc brake is a system that favours the emission of particles, especially by the wear of the brake disc which is a key factor [Florian Philippe, 2021]. Among the wear factors, tribo-oxidation, exacerbated by high temperatures induced by friction during braking, encourages the emission of very fine and ultrafine particles, which are particularly harmful to humans because they are fine enough to cross natural barriers and infiltrate the neurological and/or cardiovascular system [Tomasz Gonet & Al., 2021]. Cast iron, which is a commonly used material for automotive brake discs, produces lots of particles (iron oxides). In order to make a comparative analysis of tribological behaviour, wear and particle emissions emitted during braking, a cast iron and stainless-steel discs are studied. A specific experimental protocol was set up on a tribometer. The developed experiment is based on a small disk, adapted to the observation tools and ex-situ analysis (scanning electronic microscope, optical microscope, optical profiler) while reproducing solicitations of braking corresponding to moderate and dense urban traffic, from the thermal point of view. The experimental set-up allows a visual access to the friction track in infrared thermography and in fast video. The ambition of the experiment is to correlate the evolution of the friction track (with the third body flows) to particle emissions. The test bench is instrumented for the counting of particles emitted during braking (range [5.6 nm 10 µm]) in a hygrometry-controlled chamber. The analysis frequency of 10 Hz, the configuration of the enclosure and the sampling point offer a better understanding of the dynamics of emissions during braking. This study presents the methodology and the experimental configuration developed, as well as the first results related to the tribological couples composed of a sintered metal pad and a cast iron/stainless steel disc, regarding the nature of the tribological mechanisms and the wear processes associated with the observed particle emissions.

University of Lille: Mr. Mathis Britatte, Prof. Yannick Desplanques, Mr. Laurent Coustenoble, Prof. Alexandre Mege-Revil