In Situ Measurement of Contact State between Two Solid Surfaces for Elucidating the Mechanism of Lubrication with Nanometer-thick Liquid Films

Abstract

We improved the performance of a microscopic observation system that has been integrated with a purpose-built pin-on-disk type friction tribotester. This allows us to quantitatively measure the radius and longitudinal depth of deformed region of the sliding pin, and improve the measurement accuracy of the vertical displacement of the sliding pin. As a result, the clearance between the sliding pin and disk can be determined. We found that, even for 1.7 nm thick liquid films, liquid molecules are entrained into the interface between the sliding pin and disk, resulting in upward displacement of the sliding pin and a flattened area at its apex.