A dimensionless measure for adhesion and effects of the range of adhesion in contacts of nominally flat surfaces

Dimensional analysis is combined with computer simulations to identify a useful dimensionless measure for adhesion in contacts of nominally flat surfaces. The measure is a simple function of a few mostly local, well-defined parameters and allows one to estimate how adhesion alters the true contact area in unsticky contacts. For these contacts, we find that the range of adhesion barely affects the gross features of the contact geometry - at a given relative contact area. However, short-range adhesion compactifies contact patches, changes various microscopic distribution functions qualitatively and boosts dissipation when a generalized Tabor coefficient is of order one or greater.