As loading forces decrease in applications such as MEMS and NEMS devices, the size of the asperity contacts which comprise the real contact area tend to decrease into the nano scale regime. This reduction in size of the contacts is only partially offset by the nominally increased smoothness of these contacting surfaces. Because the friction force depends on the real area of contact, it is important to understand how the material and topographical properties of surfaces contribute to friction forces at this nano scale. In this investigation, the single asperity nano contact model of Hurtado and Kim is incorporated into a multi-asperity model for contact and friction which includes the effect of asperity adhesion forces using the Maugis-Dugdale model. The model spans the range from nano-scale to micro-scale to macro-scale contacts. Three key dimensionless parameters have been identified which represent combinations of surface roughness measures, Burgers vector length, surface energy, and elastic properties. Results are given for the friction coefficient versus normal force, the normal and friction forces versus separation, and the pull-off force for various values of these key parameters.
A Scale-Dependent Model for Multi-Asperity Contact and Friction
Contributed by the Tribology Division for publication in the ASME JOURNAL OF TRIBOLOGY. Manuscript received by the Tribology Division September 24, 2002 revised manuscript received January 14, 2003. Associate Editor: Q. J. Wang.
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Adams , G. G., Mu¨ftu¨ , S., and Azhar, N. M. (September 25, 2003). "A Scale-Dependent Model for Multi-Asperity Contact and Friction ." ASME. J. Tribol. October 2003; 125(4): 700–708. https://doi.org/10.1115/1.1573232
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