The elastic deformation of a semi-infinite substrate containing a nanosized
hemispherical pit on its plane boundary crucially relies on the mechanical response of
the pit surface. In this paper, we develop a micromechanical model that couples
Gurtin and Murdoch’s model of surface mechanics with the classical theory of
elasticity, and we explicitly evaluate the stress concentration, displacement and stress
distribution resulting from a family of statically equivalent shear tractions applied on
the pit surface. We found that two intrinsic dimensionless parameters, both
constructed from the characteristic length and material properties, govern the highly
localized elastic field. Both the magnitude and sign of these parameters are of great
importance. Negative values tend to increase stress concentrations, whereas positive
ones have the opposite effect. We further highlight the consequences of our
analysis by comparing a number of shear tractions that correspond to the
same torque. The comparison provides the means of evaluating the degree of
difference in elastic fields in the immediate vicinity of statically equivalent force
distributions.