Nanoindentation of compliant materials using Berkovich tips and flat tips

Nanoindentation testing of compliant materials has recently attracted substantial attention. However, nanoindentation is not readily applicable to softer materials, as numerous challenges remain to be overcome. One key concern is the significant effect of adhesion between the indenter tip and the sample, leading to larger contact areas and higher contact stiffness for a given applied force relative to the Hertz model. Although the nano-Johnson–Kendall–Roberts (JKR) force curve method has demonstrated its capabilities to correct for errors due to adhesion, it has not been widely adopted, mainly because it works only with perfectly spherical tips. In this paper, we successfully extend the nano-JKR force curve method to include Berkovich and flat indenter tips by conducting numerical simulations in which the adhesive interactions are represented by an interaction potential and the surface deformations are coupled by using half-space Green’s functions discretized on the surface.