Elastic and viscoelastic indentation of flat surfaces by pyramid indentors

The present work presents the results of frictionless and adhesionless contact of flat surfaces by pyramid indentors. The materials of the contacting solids were modelled as homogeneous and isotropic, linear elastic, as well as linear viscoelastic. The theoretical analysis is complemented by experiments and numerical calculations. The results include explicit relations between the normal applied load and the depth of penetration, details of the contact area shapes, the surface stresses and the contact pressure distributions. The standard shapes of the Vickers, Berkovich and Knoop pyramids were examined in particular. Certain aspects of geometrical imperfections, transverse isotropy and adhesion were considered. When elasticity or viscoelasticity provide adequate models of material behavior, micro- or nano-indentation by sharp pyramid indentors can be very useful and perhaps the only possible test in probing mechanical properties of small volumes of materials. The results can be particularly useful in using instrumented indentation for assessing mechanical properties of materials at cryogenic temperatures, of bio-materials and of micro-electro-mechanical components.