Experiments and Prediction of Hold Time-Dependent Static Friction of a Wet Granular Layer.

Frictional properties of sliding surfaces have practical importance in a variety of applications. Therefore, the present study investigates the ageing or holding time-dependent static friction of a wet granular layer using a slide-free-slide (SFS) friction test. It is observed that the static friction varies as a logarithm of hold time. Further, the Mohr–Coulombs' law of friction is used to determine adhesive friction and normal stress-dependent friction. The scaling law analysis has shown that the exponent of adhesive friction is more prominent in magnitude than the corresponding coefficient of friction. A static friction model, based on the formation and rupture of capillary bridges, has also been proposed for predicting the peaks of static friction at different hold times. At the end, the power laws, which correlate the number of attached capillary bridges and adhesion constant with hold time, are proposed to justify the present results. [ABSTRACT FROM AUTHOR]