Adhesive contact between a rigid toroidal indenter and an elastic half-space

The adhesive contact between a rigid toroidal indenter and an elastic half space is investigated numerically. The traction is modeled using the Lennard-Jones potential with Derjaguin's approximation. It is found that toroidal Johnson-Kendall-Roberts (JKR) model can predict the adhesive contact for large toroidal Tabor parameters and larger radius of the cross section of the torus, while toroidal Bradley model can predict the adhesive contact for small toroidal Tabor parameters. Toroidal indenter can generate larger adhesion than spherical indenter. The contour for the ratio of the pull-off forces between toroidal indenter and spherical indenter is plotted. The pull-off force is larger for larger radius of the cross section of the torus. Thus, the pull-off force of volcano-shaped indenter is larger than that of donut-shaped indenter.