  Engineering wear models are generally empirical and lack connections to the
physical processes of debris generation at the nanoscale to microscale. Here,
we thus analyze wear particle formation for sliding interfaces in dry contact
with full and reduced adhesion. Depending on the material and interface
properties and the local slopes of the surfaces, we find that colliding surface
asperities can either deform plastically, form wear particles, or slip along
the contact junction surface without significant damage. We propose a mechanism
map as a function of material properties and local geometry, and confirm it
using quasi-two-dimensional and three-dimensional molecular dynamics and
finite-element simulations on an amorphous, siliconlike model material. The
framework developed in the present paper conceptually ties the regimes of weak
and strong interfacial adhesion together and can explain that even unlubricated
sliding contacts do not necessarily lead to catastrophic wear rates. A salient
result of the present paper is an analytical expression of a critical length
scale, which incorporates interface properties and roughness parameters.
Therefore, our findings provide a theoretical framework and a quantitative map
to predict deformation mechanisms at individual contacts. In particular,
contact junctions of sizes above the critical length scale contribute to the
debris formation.
