Particles Emissions and Understanding the Braking Tribological Circuit

Abstract

Particles detached from the first bodies (disc and pad) travel in the braking system by forming a tribological circuit. As the flows of particles in this circuit interact with the friction and wear mechanisms at the braking interface, their comprehension is crucial to better understand how the braking system behaves. Currently, identifying and quantifying those flows constitutes a scientific and technical challenge. The wear flow in particular, is made of the particles that permanently leave the system. Most of this wear goes airborne and disseminates quickly in the atmosphere.Many techniques measuring the brake particles emissions focus mainly on the resulting air quality, or on health hazard, and collect the particles far from the contact. These techniques, although very informative, do not enable to establish a clear link between the measurements and a wear flow. We thus designed a setup able to trace the quick evolutions of emissions during and after braking, while allowing to compare the relative quantities of particles between different configurations, for the range of 5 to 10000nm. Emissions showed a clear temporal signature, with in some cases, a strong release at contact opening. As expected, configurations causing severe wear mechanisms such as adhesive wear caused a much larger emissions than configurations featuring more conventional oxidation based mechanisms. The effects of other parameters, such as contact vibrations could also be witnessed.