ABSTRACT
He et al. [213] derived an equation for a nano-contact without restricting it to a large sphere radius, or Rt 3> rm. The authors deduced capillary force for nanocontacts from the sphere-plane approximation, with the distinction that they did not require a large contact area and, thus, did not restrict the capillary force equation to large sphere radius. The equation applicable to small contacts is given by:
COS0 K)' which is important for small asperity contacts, i.e., large 0 values (Fig. 12); for small 0, equation (29) is reduced to equation (27). Note that equation (29) is based on a much simplified cylindrically shaped geometry. Geometries for nanocontacts that are more sophisticated can also be found in the literature [219].
