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 Karl Franzens University Graz

Graz University of Technology 

Multiscale Contact Mechanics
Bo N. J. Persson
PGI, Research Center Jülich, Germany
17:15 - 18:15 Tuesday 26 November 2013 TUG P2

All solid bodies have surface roughness, often extending from the
linear size of the body down to atomic distances. When two solid bodies are pressed together they will in general only make contact at a small fraction of the nominal or apparent contact area. This fact is of central importance in tribology and determines or influences many quantities of great importance, e.g., the heat and electric contact resistance, mixed lubrication, leakage of seals, sliding friction, sliding wear, adhesion, capillary adhesion, and contact electrification.
Contact mechanics has a long history going back to work done by Hertz for the elastic contact between spherical bodies. The contact between elastic solids with randomly rough surfaces was treated by Greenwood and Williamson and by Bush et al.. However, these studies approximated the surface asperities with spherical (or elliptic) cups of equal radius and neglected the long-range elastic deformation. Recently a multiscale contact mechanics theory has been developed which is accurate, very general and flexible, and can be applied to solids with arbitrary random roughness, including the long-range elastic deformations[1,2]. The theory can also be applied to elastoplastic, viscoelastic, and layered materials. It has been used to study all the problems mentioned above.
In my presentation I will review this theory and briefly describe some applications to the leak-rate of seals and to adhesion.

[1] B.N.J. Persson, J. Chem. Phys. 115, 3840 (2001)
[2] B.N.J. Persson, Phys. Rev. Lett. 99, 125502 (2007)