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, tribological research between stator and promoter of the linear ultrasonic motor is of great significance. This paper introduced the improvements of the friction and wear test device for linear ultrasonic motors - realization of temperature and humidity control. Through this device, the relationship between the wearing rate of stator driving foot and temperature, humidity was studied. Furthermore, wearing capacity of friction pair was tested by electronic analytical balance and wear rate was calculated; Using a force transducer and DAQ Card to collect the preload and the output force, friction coefficient between stator and promoter was obtained. The driving foot of stator and promoter used in the test were made of 45 steel and alumina ceramic respectively. Test results show that friction coefficient increases (decrease) with temperature (humidity) rise. With the temperature (humidity) rise, the wear rate of the stator decreases first and increases later. The wear mechanisms of the ceramic are brittle flaking off and fatigue wear. When the temperature and humidity is low, abrasive wear is the major reason of stator wearing.