Kinetics of stick-slip friction in boundary lubrication

We show that new important features are brought to the kinetics and dynamics of frictional stick-slip motion in an earthquakelike model of boundary lubrication by introducing a distribution of static breaking thresholds of individual contacts. In particular the condition for elastic instability and details of the slip motion are heavily affected. Among the novel emerging properties is the role of other parameters such as the delay time of contact reforming, the strength of elastic interaction between the contacts, and the elasticity of the contacts and of the slider. We simulate the model dynamics, choosing parameters appropriate to describe a recent surface force apparatus experiment (Klein J., Phys. Rev. Lett., 98 (2007) 056101) whose results are now explained with a totally normal boundary lubricant film viscosity.