The effect of braking conditions on the particular matter emissions and brake squeal

Particular matter (PM) and squeal noise emitted from disc brakes are essential research subjects in the automotive industry. This study investigates the effect of braking conditions on the PM emissions and brake squeal of low metallic (LM), semi-metallic (SM) and non-asbestos organic (NAO) brake friction materials (BFMs) with a pin-on-disc tester. Braking conditions significantly affect the total number concentration (TNC) for all three BFMs. Generally, the geometric mean diameter (GMD) for NAO BFM is smaller than that for SM and LM BFMs. Moreover, the effect of braking conditions on the GMD for SM and LM BFMs is higher than that for NAO BFM. The speed has a more significant effect on GMD than contact load. The braking conditions can significantly affect the PMC. SM and LM BFMs exhibit larger particle mass concentrations (PMCs) than NAO BFM in most cases. All three BFMs show comparable A-weighted sound pressure levels (SPLs). The influence of braking conditions on brake squeal for SM and LM BFMs is stronger than that for NAO BFM.