Friction and wear test device of linear ultrasonic motor and experimental studies

Linear ultrasonic motors are known for their various advantages such as direct actuating, stepping and servo working, as well as excellent controllable performance. Hence, linear ultrasonic motors are becoming increasingly important in the studying field of ultrasonic motors around the world. As the output characteristics of ultrasonic motors are directly influenced by the friction characteristic and wear of the interface between stator and promoter, it is necessary to study the tribology between stator and promoter of the linear ultrasonic motor. Friction and wear test device for linear ultrasonic motor was manufactured based upon its working principle. With this device, the relationship between the wearing rate of stator driving foot and the preload of linear ultrasonic motors, the relative motion velocity of contact point of promoter was studied. Friction characteristics of driving foot interface were also analyzed in this paper. Furthermore, wearing capacity of friction pair was tested by electronic analytical balance, wear rate was calculated and friction surface was analyzed as well. The driving foot and stator used in the test were made of 45 steel and alumina ceramic respectively. The results of the test indicate that the friction coefficient increases (decreases) as pre-pressure (relative speed) increases, and wear rate of the stator increases (decreases at first and then increases) while preload (relative speed) increases. The wear mechanisms of the ceramic are brittle flaking off and fatigue wear. Moreover, abrasive wear is the major reason of stator wearing, while adhesive wear and fatigue wear are minor reasons.