Direct Measurement of Energy Dissipation in Nanoscale Tribomechanical Interfaces: Dissipative Transfer Steady State

This study examines the development of a steady state in the cyclic wear process for various combinations of metallic and inorganic materials. Energy dissipation is widely acknowledged as a significant parameter in wear mechanisms. However, at the nanoscale, the linear correlation between energy dissipation and wear progression is not consistently applicable. In this study, experimental observations of cyclic wear between scanning probe microscopy (SPM) cantilevers and substrate displacement were conducted. Substrate vibrations were monitored using a laser Doppler vibrometer, which facilitated the direct estimation of energy dissipation at nanocontacts during cyclic loading. The wear rates of the substrates decreased with an increase in the number of cyclic loadings, indicating the formation of a transfer steady state at the interface. Symmetric contact mode, based on the viscoelastic behavior of the contact, and asymmetric mode, based on adhesion between the interfaces, are commonly observed. The asymmetric mode evolved in the later stages of cyclic wear, suggesting the transfer of the steady state between the interfaces. A linear relationship between energy dissipation and wear rates was still observed for metallic substrates, whereas a steady state was observed for inorganic materials. This difference can be attributed to material exchange at the interfaces.