Beyond Quality and Quantity: Contact Distribution Encodes Frictional Strength

Kavli Affiliate: Shmuel M. Rubinstein

| First 5 Authors: Sam Dillavou, Yohai Bar Sinai, Michael P Brenner, Shmuel M Rubinstein,

| Summary:

Classically, the quantity of contact area $A_R$ between two bodies is
considered a proxy for the force of friction. However, bond density across the
interface – quality of contact – is also relevant, and contemporary debate
often centers around the relative importance of these two factors. In this
work, we demonstrate that a third factor, often overlooked, plays a significant
role in static frictional strength: the distribution of contact. We perform
static friction measurements, $mu$, on three pairs of solid blocks while
imaging the contact plane. By using linear regression on hundreds of
image-$mu$ pairs, we are able to predict future friction measurements with 3
to 7 times better accuracy than existing benchmarks, including total quantity
of contact area. Our model has no access to quality of contact, and we
therefore conclude that a large portion of the interfacial state is encoded in
the spatial distribution of contact, rather than its quality or quantity.

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