'SCRATCHING THE SURFACE OF LATERAL SIZE EFFECTS (LSE): A CRITICAL COMPARISON BETWEEN INDENTATION AND SCRATCH HARDNESS SIZE EFFECTS'

摘要

All tribological interactions have (by definition) a shear component and it is the general experience (going back to the invention of the Mohs hardness scale) that a harder material is one that is more resistant to scratch deformation. Indentation hardness is, however, more reproducible, has a smaller footprint than a scratch test, and so has become the "go to" material parameter for predicting tribological performance. This implied relationship relies on the assumption that a material's plastic properties depend only on the crystallographic direction of deformation and not on the test direction with respect to a free surface. Indentation size effects (ISE) and the realisation that material strength is genuinely length-scale dependent suggests anti-tribological wear applications. The question remains, however, as to whether further performance enhancement can be realised in practice and this requires study of scratch deformation and LSE itself.