In this paper, the frictional behaviours of single and multi-balls slid against micro-grooved silicon surfaces were investigated by using a micro-tribotester built inside a scanning electron microscope. Various micro-grooves were fabricated on the silicon surface to investigate the frictional behaviour with respect to the contact geometry between the surface asperities. Particularly, fast Fourier transform (FFT) analyses of the friction signals were performed with the motivation to assess the contact conditions. The primary objective of this paper was to understand better the asperity interaction condition at the sliding interface by analysing the frictional force signal using FFT.

The experimental and numerical simulation results showed that the relative geometric ratio and the distribution of contact asperities on the surfaces could be predicted by the power and frequency spectra of the FFT analysis of the friction signal. Also, the frictional behaviour for multi-asperities was found to be the result of superposition of the frictional interaction of each asperity contact. It is expected that these observations will be utilized for the design of micro-structured surface with optimum geometry for better tribological performance.