Using the Dugdale approximation to match a specific interaction in the adhesive contact of elastic objects

In the Maugis–Dugdale model of the adhesive contact of elastic spheres, the step cohesive stress σ0σ0 is arbitrarily chosen to be the theoretical stress σthσth to match that of the Lennard-Jones potential. An alternative and more reasonable model is proposed in this paper. The Maugis model is first extended to that of arbitrary axisymmetric elastic objects with an arbitrary surface adhesive interaction and then applied to the case of a power-law shape function and a step cohesive stress. A continuous transition is found in the extended Maugis–Dugdale model for an arbitrary shape index n  . A three-dimensional Johnson–Greenwood adhesion map is constructed. A relation of the identical pull-off force at the rigid limit is required for the approximate and exact models. With this requirement, the stress σ0σ0 is found to be k(n)Δγ/z0k(n)Δγ/z0, where k(n)k(n) is a coefficient, Δγ   the work of adhesion, and z0z0 the equilibrium separation. Hence we have σ0≐0.588Δγ/z0σ0≐0.588Δγ/z0, especially for n=2n=2. The prediction of the pull-off forces using this new value shows surprisingly better agreement with the Muller–Yushchenko–Derjaguin transition than that using σth≐1.026Δγ/z0σth≐1.026Δγ/z0, and this is true for other values of shape index n.

A 3D adhesion map is constructed. A relation with the identical pull-off force at the rigid limit is supplemented to make the approximate adhesive contact model match the exact one.Figure optionsDownload as PowerPoint slide