The Role of Counter-Face Roughness on the Tribological Performance of a Clutch System Tested with a Pin-On-Disc Tribometer

Abstract

This study was a continuous investigation of the roles played by the tribofilm on dry automotive clutch system performance. Tribological experiments were performed by the addition of wear debris at the beginning of tribometer tests and by reducing the surface roughness of a cast iron counter-face. The initial surface conditions of cast discs were 0.2 and 1.2 µm. The pin-on-disc tests were carried out at three different PV levels: 3.08, 7.88, and 10.09 MPa¨ms´1, and the current results were correlated to those previously obtained in the standard tribometer procedure. When the wear debris was added into the tribosystem, the friction coefficient level dropped drastically while the assembly wear rate rose. In contrast, the modified cast discs provided a reduced wear rate of assembly and a higher and more stable friction coefficient level. These improvements were obtained in a severe condition where higher temperature levels were reached. For the tests with added debris, SEM observations revealed a more intense tribofilm development over the worn surfaces of the clutch friction material. The smoothest cast disc did not damage the developed tribofilms and maintained them more stably due to a reduction in contact area stresses at the highest tribometer test.

Effects of Automotive Test Parameters on Dry Friction Fiber-Reinforced Clutch Facing Surface Microgeometry and Wear

“…Kubiak et al [16] found that initial surface roughness significantly influences the coefficient of friction at the transition between partial slip and full sliding. Furthermore, Fernandes et al [17] investigated effects of cast discs with modified surface roughness values on the wear rate and friction coefficient (COF) of a clutch system. They found that a smooth surfaced cast iron disc reduced wear rate and contributed to a higher and more stable running-in period friction coefficient level by not damaging the developed tribofilms and maintained them more stably due to a reduction in contact area stresses at the highest tribometer test.…”