To develop the most suitable material for brake pads, a new method to more accurately evaluate the frictional properties is needed. Information like microscopic friction and wear phenomena, both of which cannot be detected by changes in the friction force and vibrational acceleration, can be obtained using an acoustic emission (AE) technique that measures elastic stress waves caused by the deformation and fracture of materials. This study attempted to identify tribological phenomena of brake pad materials using an in situ observation and AE measurement method. It is crucial to visualize what is happening between the sliding surfaces. As a result, it was found from the in situ observations that the macroscopic deformation and fracture behavior of the brake pad materials is caused by crack growth (slip deformation) and the separation of the material under the sliding surface. Rapid fracturing immediately under the sliding surface was the cause of the difference in the fluctuations of the friction force. In addition, deformation and fracture of the tribofilm increased fluctuations in the AE signals.

Alan Hase- Saitama Institute of Technology; Kazuho Mizuta, Yukio Nishizawa, Kojo Sugimoto, Katsuya Okayama - ADVICS Co., Ltd., Japan