Contact Area Measurements Reveal
Loading-History Dependence of Static Friction
S. M. Rubinstein, G. Cohen, and J. Fineberg
The Racah
Institute of Physics, The Hebrew University of
Jerusalem, Jerusalem 91904, Israel
(Received 31 January 2006; revised manuscript
received 30 March 2006; published 30 June 2006)
We perform quantitative measurements of the actual
area of contact, A, formed by two rough solids that
are subjected to different normal loading protocols.We show that microscopic motion, induced by
Poisson
contraction or expansion, produces a strong memory
dependence of A on the loading history with a large
corresponding influence on the system’s frictional
strength. These effects, together with accompanying
transient dynamics, are independent of humidity, loading rates, and material contrast across the interface.