Microscopic and macroscopic effects of surface lubricant films in granularshear

Experiments were conducted to investigate the link between particle-particl e interaction forces and the bulk properties of granular shear using an ide alized system of near-spherical, monosized glass beads. The atomic force mi croscopy colloidal probe technique was employed to investigate the adhesion and friction between a single bead and a second glass surface, while the a nnular shear cell was used to measure the shear properties of the bulk gran ular material. A covalently bound monomolecular film of aliphatic chains wa s introduced to alter the tribological interactions between the particles. The atomic force microscope was used to measure the reduction in the partic le-particle surface forces resulting from the addition of the boundary lubr icant, while the shear cell showed that the effect of the lubricant film wa s to reduce the coefficient of internal friction and the dilation during sh eer. This is an experimental study to provide quantitative data linking par ticle-particle interaction forces and the shear properties of a granular bo dy.