For quality control purposes as well as for brake friction and noise modeling purposes, there is urgent need to establish good database if one is to establish correlations or trends between material properties and brake friction/noise. This investigation was undertaken to find out how pad properties change when the pads are subjected to repeated SAE J2707B wear cycles, wearing out roughly 40% of the available pad thickness. Pad natural frequencies continued to decrease while disc natural frequencies decreased initially and then slowly increased. The pad dynamic modulus continued to decrease from Wear Cycle #1 to Wear Cycle #5. Within a Wear Cycle, the pad dynamic modulus changed from one Wear Block to another Wear Block. A good relation was found between the friction coefficient and dynamic modulus, which was adjusted for pressure dependence and temperature dependence. Pad thickness loss measurement was always smaller than the thickness loss calculated from the pad weight loss due to expansion of the pad contact surface region (heat-affected layer) caused by exposure to high braking temperatures. The pad dynamic modulus increased with time while waiting for the next test and the increase was linear with waiting time.
Compact International: Mr. Meechai Sriwiboon; SKR Consulting LLC: Mr. Seong Kwan Rhee