Determination of the effective zero-point and the extraction of spherical nanoindentation stress-strain curves

In this paper, we present a novel approach to converting the load-displacement data measured in spherical nanoindentation into indentation stress-strain curves. This new method entails a new definition of the indentation strain, a new procedure for establishing the effective zero-load and zero-displacement point in the raw dataset, and the use of the continuous stiffness measurement (CSM) data. The concepts presented in this paper have been validated by finite element models as well as by the analysis of experimental measurements obtained on aluminum and tungsten samples. It is demonstrated that the new method presented in this paper produces indentation stress-strain curves that accurately capture the loading and unloading elastic moduli, the indentation yield points and the post-yield characteristics in the tested samples. (c) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.