Substrate and fluid film mechanics in rolling-sliding soft contact tribology

The wealth of soft contact tribological (SCT) investigations utilising ball-on-disc tribometers assume Hertzian contact model to describe substrate deformation. We hypothesise this is invalid for soft-adhesive viscoelastic discs with a finite thickness. Here, we uniquely use the wear transducer in the mini-traction machine to indirectly measure the load-dependent deformation and fluid film thickness of rigid-soft, soft-rigid, and soft-soft contacts across a range of loads, speeds and viscosities. Macroscopic deformation within these configurations and compliance of the respective tribopairs vary considerably, which is not predicted by the Hertzian model. We consider how to account for these deformation effects in SCT.