Brake features enhancing the wear debris bimodal distribution

Investigated is wear debris separation from dry friction interface of a vehicle brake system. Owing to structural and operational properties of the interface between the disc hard surface and the pad soft surface, the study focuses on the abrasive wear process of the pad profile. A theoretical dependence is sought between debris size distribution and governing parameters such as surface roughness, unevenness, and levels of normal loading. The analysis describes interacting surface profiles in terms of discrete probabilities of their heights. Enforced by motion constraints, the disc hard profile is monitored while clearing its way through the stationary pad overlapped profile by shearing of likely encountered asperities as estimated by their conditional probability. As a result, a single tangential stroke leads to a pad redistributed profile along with a collection of separated debris. A pre-stroke approach of the pad closer to the disc simulates the effect of a normal loading increment. Accordingly, three types of shear strokes may develop, namely; the superficial, the shallow subsurface, and the deep subsurface. It is found that the range of debris size only extends up to the mean height of surface profile. The debris size distribution is generally bimodal with large-size and small-size peaks, both being distinct during superficial strokes. The position and level of either peak depend on the two interacting profiles just before each individual stroke. For a disc Gaussian profile, sharply wavy profile of the pad surface makes the debris large-size peak to lie evidently near the complementary of the disc mean height. An originally Gaussian or a disc-induced profile of the pad surface enhances the level of the debris small-size peak whose position is constant. In addition, deep subsurface strokes yield an invariable debris distribution with a single small-size peak.