A novel gradient method for extracting elastoplastic properties of metals from spherical indentation force-contact radius data

A new methodology for determining the representative strain in spherical indentation is presented in this paper. This methodology is based on the one defined by Hernot et al. (Mech. Mater. 68:1-14, 2014) for the case of Vickers indentation. It consists in calculating the gradients of a measured quantity according to the mechanical parameters of the behavior law of the tested material. The application of the proposed method is performed based on a new numerical approach to spherical indentation. From the representative strain and stress values obtained, it can be concluded that there is no constant universal constraint factor independent of the dimensionless ratio (a/R) and the properties of the indented material. In the case of an experimental application, these representative strain and stress values allow obtaining a strain hardening curve very close to the one obtained classically by a tensile test.