  The contact between rough surfaces with adhesion is an extremely difficult
problem, and the approximation of the DMT theory (to neglect deformations due
to attractive forces), originally developed for spherical contact of very small
radius, are receiving some new interest. The DMT approximation leads to
extremely large overestimate of the adhesive forces in the case of spherical
contact, except at pull-off. For cylindrical contact, the opposite trend is
found for larger contact areas. These findings suggest some caution in solving
rough contacts with DMT models, unless the Tabor parameter is really low.
Further approximate models like that of Pastewka & Robbins' may be explained to
work only for a coincidence of error cancellation in their range of parameters.
