Adhesive wear law at the single asperity level

Macroscopic wear experiments in mid 1950s suggested an empirical wear relation: wear volume is linearly proportional to load and sliding distance. Recent asperity-level wear experiments and simulations reported a breakdown of this law at the nanoscale, posing the fundamental question: Is the macroscopic wear relation recoverable at the asperity level? Here we show that discrepant observations of wear relations can be reconciled into a unified framework. Using systematic long-timescale coarse-grained molecular dynamic wear simulations, we show that a linear adhesive wear law can be recovered at the single-asperity level only if the material removal is dominated by plastic deformation, confirming the longstanding Archard's theoretical hypothesis. Alternatively, the relation breaks down when cleavage fracture or thermally activated atomic detachment governs the loss of material at the asperity level. (C) 2020 Elsevier Ltd. All rights reserved.