Figure 1.
(a) force-displacement (F-d) curve with indication of the contact point (see also the inset) and adhesion force Fad; (b) force-penetration depth (F-h) curve equivalent to F-d, with indication of the effective (hf) and maximum (hmax) penetration depths and the maximum loading force Fmax. In the inset, the colors evidence the areas under the load (Sload) and unload (Sunload) curves, respectively; (c) schematic of the spherical indentation, with graphical indication of h, hf and hmax; and (d) compression by a rigid sphere of radius R, with indication of the contact radius rc and the contact depth hc.