Slippery but Tough: The Rapid Fracture of Lubricated Frictional Interfaces

 

E. Bayart, I. Svetlizky, and J. Fineberg*

The Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 91904, Israel

 

(Received 29 January 2016; revised manuscript received 23 March 2016; published 10 May 2016)

We study the onset of friction for rough contacting blocks whose interface is coated with a thin

lubrication layer. High speed measurements of the real contact area and stress fields near the interface

reveal that propagating shear cracks mediate lubricated frictional motion. While lubricants reduce interface

resistances, surprisingly they significantly increase the energy dissipated Γ during rupture. Moreover,

lubricant viscosity affects the onset of friction but has no effect on Γ. Fracture mechanics provide a new

way to view the otherwise hidden complex dynamics of the lubrication layer.