The effect of hard particle grit size on friction coefficients and particle embedmentof braking system was investigated using a model brake test rig. Silica sand gritsizes ranging from 180 - 355 μm were used in drag and stop mode brakingapplication and results were compared to the tests without the grit particles inorder to determine the changes in friction coefficient (CoF) and the percentage ofparticle embedment. Sliding speeds of 4 m/s, 8 m/s, 10 m/s and 12 m/s at constantpressures of 0.6 MPa, 0.8 MPa and 1 MPa were applied during the tests. Resultsshowed that the presence of hard particles and grit size has significant effect onthe CoF values. The values of CoF tend to reduce when grit particles are present.However, CoF values increase with sliding speed and applied pressure. Weardebris and particle embedment of silica sand was analyzed using SEM and opticalmicroscopy after the test. Particle embedment (PE) of 1- 2 % of the pad area wasobserved. Fragmentation of hard particle has occurred only at high appliedpressures. Also correlation between PE and CoF values was found to be slightlyan inverse relationship as small reduction of CoF values with higher percentageof PE was determined.
|Publication status||Published - 2009|