To Investigate the effect of surface coatings on the wear behaviour of the friction contact of ultrasonic motors


Student thesis: Master's Thesis

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  • Chun Kit CHEUNG


Awarding Institution
Award date2 Oct 2007


Nowadays, the ultrasonic motors (USMs) are used widely in a large variety of applications such as camera auto-focus mechanisms, devices in automobiles, industrial servo control in precision positioning, intelligent robotics, ultra-precision measuring and medical equipment. Unlike the traditional motor which utilizes magnetism, the main advantage of USM is its immunity to magnetic fields. In addition, USM is driven by traction force and the characteristics and life of the motor are largely related to the friction material used in the tribological contact. Hence, the evaluation of the wear of the contact is necessary for life and performance predictions of USMs from a designer view point. Two purposely-built test rigs, including a USM and a high frequency reciprocating machine (HFRM), were used in the present work. The reciprocating machine runs with small amplitude and high frequency motion is used to examine the wear behaviour of the friction pairs. The range of speed is from 1000 to 5000rpm and the loading can be varied between 5 and 20N. Different materials such as advanced surface coating (chromium titanium aluminum nitride (CrTiAlN) and diamond-like coating (DLC)) on stainless steel substrates were used to investigate their combined tribological performance with the aim to be used in the USM context. A matrix screening test for material selection purpose was also carried out using the HFRM and the tribological performance of the chosen material pairs was subsequently investigated using the USM. HFRM was found to be a useful material screening tool to identify suitable material pairs to be used in USM applications; and DLC coating was identified as the best candidate with low wear and sufficient traction force used in low payload USMs.

    Research areas

  • Ultrasonic motors, Coatings, Mechanical wear