Molecular dynamics study of adhesion effects in spherical indentations of FCC metals

• Identification of reliable contact models for FCC metals nanoindentations. • Hybrid procedure to analysis adhesion from continuum models and molecular dynamics. • Adhesion energy and Younǵs modulus determination from permanent indentations. Adhesive interaction of surfaces is present in all systems where contacts between surfaces occurs. This is precisely the situation that occurs in the indentation tests available to estimate the mechanical properties of MEMS/NEMS. These are tests in which an indenter penetrates the surface of the material whose properties are to be determined. Due to the low scale, both geometric and displacements of the indenter, adhesion phenomena have a significant effect that, if not considered, can compromise the reliability of the obtained results. In this study, the effect of adhesion in diamond spherical indentation tests on Al, Au, Ag, Cu, Pt, and Ni – metals of industrial interest – has been analysed. Molecular dynamics (MD) simulation tools have been selected for this purpose. The corresponding force–displacement indentation curves were obtained. The Maugiś adhesion contact model was applied on these curves to determine the elastic modulus of these metals and the adhesion energy of each indenter-sample contact. Additionally, a methodology was established to determine the maximum contact radius between indenter and sample surface from MD simulations. This radius was compared with the predictions of the continuum models, which allowed a critical analysis of the validity of these models at the atomic scale.