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Full-Text Articles in Physics

Surface Roughness And Dry Friction, J. Sokoloff Apr 2012

Surface Roughness And Dry Friction, J. Sokoloff

Jeffrey Sokoloff

Persson's multiscale contact mechanics theory combined with a multiscale Brillouin-Prandtl-Tomlinson model is used to show that on the basis of these models “dry friction” [i.e., kinetic friction that remains at exceedingly small velocities (but still above the creep range) close to its value at higher velocities] should almost always occur for self-affine surfaces when the dominant interaction between two surfaces in contact is due to interatomic hard core repulsion, except for extremely smooth surfaces (i.e., surfaces with a Hurst index very close to 1).


Comparison Of The Kinetic Friction Of Planar Neutral And Polyelectrolyte Polymer Brushes Using Molecular Dynamics Simulations, Yangpeng Ou, Jeffrey B. Sokoloff, Mark J. Stevens Apr 2012

Comparison Of The Kinetic Friction Of Planar Neutral And Polyelectrolyte Polymer Brushes Using Molecular Dynamics Simulations, Yangpeng Ou, Jeffrey B. Sokoloff, Mark J. Stevens

Jeffrey Sokoloff

We have simulated the relative shear motion of both neutral and polyelectrolyte end-grafted polymer brushes using molecular dynamics. The flexible neutral polymer brush is treated as a bead-spring model, and the polyelectrolyte brush is treated the same way except that each bead is charged and there are counterions present to neutralize the charge. We investigated the friction coefficient, monomer density, and brush penetration for both polyelectrolyte and neutral brushes with both equal grafting density and equal normal force under good solvent conditions. We found that polyelectrolyte brushes had a smaller friction coefficient and monomer penetration than neutral polymer brushes with ...