A methodology to simulate automotive disc brake tribology and emissions

Airborne particle emissions from road vehicles are one of the main issues affecting urban air quality. Vehicle disc brakes are one of the most important sources of non-exhaust emissions, which have recently been considered to be as important as exhaust emissions. In disc brakes, the pads are pushed against the rotating disc to slow down the vehicle. The contact surfaces of the disc and pads are worn, some of the debris becomes airborne and can be harmful to human health if inhaled. Particle emissions from disc brakes are influenced by a greater amount of contact phenomena at the sliding interfaces, e.g. friction, wear, contact temperature, contact pressure and surface topography. Due to the difficulty in accessing the pad-to-disc contact in the brake system during testing, it is hard to study contact phenomena. Moreover, experiments need the friction material and brake system to be produced at least in their prototype configuration. The aim of this thesis is to develop a methodology based on simulation to better understand contact phenomena and to evaluate the tribological and emission performance of friction material and brake systems in the early design phase. Different simulation approaches can be adopted, depending on what is to be evaluated. A macro-scale approach based on finite element analysis (FEA) can be used to evaluate wear, particle emission and the coefficient of friction (COF) of the entire brake system. A meso-scale approach based on cellular automaton (CA) simulation can be used to evaluate the local contact behaviour on the disc and pad surfaces, and the influence of the single components of the friction mixture. These two different-scale simulation approaches can be integrated to generate an overall multi-scale simulation procedure to investigate and predict the contact phenomena in brake systems.