Wear properties of brass and PTFE-matrix composite in traveling wave ultrasonic motors

The wear of a traveling wave ultrasonic motor has certain particularities due to its special drive mechanism. In this investigation, the progression of wear of a brass stator against a PTFE-matrix composite friction material is reported. During 200 h of operation, the performances of an ultrasonic motor and the properties of its friction surfaces were examined. Different wear stages were observed. Surface topography and debris characteristics were analyzed to assess the wear mechanisms that operate in different wear stages. Under the imposed operating conditions the running-in wear stage requires 80 h. In early period of running-in wear stage, adhesive wear is the main wear mechanism of the friction material. The debris forms a multi-layered, agglomerate sheet. In the second part of the running-in period, the main wear mechanisms change to delamination wear and adhesive wear. The debris piles up as small particles. In the steady wear stage, the main wear mechanism is delamination wear result from fatigue. The debris forms small flake-like sheet but they are rare. Abrasive wear exist in all stages of wear. By contrast, the main wear mechanism of the brass stator is abrasive wear.