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Title: Microscopic basis of Archard's wear law
Plain: The amount of material lost by wear grows in proportion to load and sliding distance, but the proportionality constant varies by a factor of a million between materials and cannot be predicted. Its link to what happens at single contacts is unclear.
Precise: Archard's law $V = K N s / H$ (wear volume V, load N, sliding distance s, hardness H) has an empirical dimensionless coefficient K spanning roughly $1e-8 \text{ to } 1e-2$. Derive K from asperity-scale mechanisms, including the critical junction size $d*$ proportional to $G w / \tau_j^{2}$ (shear modulus G, surface energy w, junction strength $\tau_j$) below which junctions deform plastically instead of shedding debris, and predict wear rates for specified material pairs.
Settled by: A multiscale theory predicting K for several metal and ceramic pairs that matches measured wear rates without adjustable parameters.
Kind: phenomenon
Answer type: mechanism
References: (empty)
Literature status: partially-resolved
Status note: Atomistic simulations since 2016 identify a critical junction size for debris formation; quantitative prediction of K for real surfaces is lacking (2026).
Posed since: (empty)