Tribological Behavior of CF/PTFE Composite and Anodized Al-Rotor in Traveling Wave Ultrasonic Motors

The tribological behavior of stator friction material and rotor in the traveling wave ultrasonic motor (TWUSM) shows some particularities because of the applied way and the special contact between stator and rotor. In this investigation, the tribological behavior of carbon fiber-reinforced polytetrafluoroethylene composite, which is used as stator friction material, sliding against an anodized aluminum rotor in a TWUSM is reported. The performances of TWUSM were tested, and the surface topography was examined in different stages. The results shown that the speed of USM remained stable at 120 r/min after 60 h of operating and the holding torque and stall torque tended to stabilize after 100 h. Moreover, the fluctuation of roughness of friction material was small, while the surface roughness of rotor decreased 28.8% after 10 h of operating. Both the roughness of friction material and rotor tended to stabilize after 100 h of operating. The wear mechanisms of stator friction material in steady wear stage were found to be adhesive wear and plastic deformation, which was quite different from that of rotor friction material. The wear rate of friction material decreased with time, and wear 1 μm of height required approximately 68 h. The surface topography of rotor changed little, and the wear height after 200 h of operating was less than 2 μm.