A robust inverse analysis method for elastoplastic behavior identification using the true geometry modeling of Berkovich indenter

Abstract

The parameters describing the elastoplastic behavior of the 316 L austenitic stainless steel are identified through inverse analysis based on finite element modeling of the Berkovich nanoindentation test. The true geometry of the Berkovich indenter is introduced in axisymmetric and 3D finite element models using experimental nanoindentation data obtained by adapting the calibration method proposed by Oliver and Pharr [1]. Then, using these true indenter shape models, the elastoplastic parameters of the 316 L are estimated with high accuracy compared to the parameters obtained from tensile test identification. The indentation curve was correctly described by the numerical model for all the analyzed indentation depths, even for indentations inferior to 100 nm, which is a challenge until today. The 3D indenter model produces a residual imprint very close to the experimental indentation mark. The friction analysis between the indenter and the sample surface reveals small changes in the surface deformation, introducing an increase on the hardness, which disappears as the indentation depth decreases.These studies demonstrate that the most important aspect in the elastoplastic parameter identification is the correct representation of the indenter geometry in the finite element model.