Frictional Properties in Nano-scal Fretting with Lateral Force Microscope

Abstract

The tribological behavior of micro mechanical systems plays a key role in the performance of such systems. Consequently, it is necessary to quantitatively understand the friction and wear properties in ultra minute region because the influence of the surface topography and the atmospheric gas can't be disregarded for making the component minute. Especially, external disturbance, i.e. vibration may promote fretting, which have been hardly studied in nano/micro-scale. In this paper, we investigated the influence of the normal load, the sliding velocity and the displacement of sliding on lateral force. The lateral forces were measured by using AFM with various conditions under the controlled relative humidity. The test materials of single-crystalline <111> silicon plates were rubbed against a spherical tip made of glass at load ranging from 20nN to 80nN. When sliding velocity is low, lateral forces become large. Lateral force linearly increased with normal load. In the case of spherical tip, tangential micro-displacement is compared with Mindlins model in fretting, it is in agreement with the Mindlins theoretical formula which load is changed into normal load plus pull-off force.