Static Friction Coefficient Is Not a Material Constant

Oded Ben-David and Jay Fineberg

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

(Received 28 April 2011; published 20 June 2011)

The static friction coefficient between two materials is considered to be a material constant. We present

experiments demonstrating that the ratio of shear to normal force needed to move contacting bodies can,

instead, vary systematically with controllable changes in the external loading configuration. Large

variations in both the friction coefficient and consequent stress drop are tightly linked to changes in

the rupture dynamics of the rough interface separating the two bodies.

DOI: 10.1103/PhysRevLett.106.254301 PACS numbers: 46.55.+d, 46.50.+a, 62.20.Qp, 81.40.Pq