AUTHOR=Du Junxiao , Franklin Steve , Weber Bart TITLE=A force controlled tribometer for pre-sliding measurements at the nanometer scale JOURNAL=Frontiers in Mechanical Engineering VOLUME=9 YEAR=2023 URL=https://www.frontiersin.org/journals/mechanical-engineering/articles/10.3389/fmech.2023.1019979 DOI=10.3389/fmech.2023.1019979 ISSN=2297-3079 ABSTRACT=

In the pre-sliding friction regime, interfaces partially stick and partially slip. The pre-slip is thought to be locally initiated at regions of the interface where the ratio of shear stress to normal stress exceeds a critical value. The displacements involved in pre-slip can be limited to the nanoscale, especially for stiff interfaces. Furthermore, little is known experimentally about the interplay between surface topography, pre-sliding behavior and wear. In this work, we introduce a pre-sliding tribometer that enables the study of how the pre-sliding friction at various types of ball-on-flat interfaces evolves as a function of wear. Polytetrafluoroethylene-on-silicon (PTFE-on-Si) pre-sliding measurements covering interfacial displacements up to 50 nm, conducted with the new instrument, show good agreement with Mindlin theory predictions, without adjustable parameters.