The duality in mechanical property extractions from Vickers and Berkovich instrumented indentation experiments

This work extends prior analysis and methodology for extracting yield strength, sigma(ys), Young's modulus, E, strain hardening exponent, n, and hardness, (p) over bar, from instrumented indentation experiments. The paper is predicated on comprehensive dimensional analysis and extensive finite element simulations of Vickers and Berkovich indentation. This work reveals that when instrumented indentation experiments are analyzed on the basis of accurate dimensionless functions, a maximum of two different sets of sigma(ys), E, n, and (p) over bar can be rigorously inferred from a single applied load (P)-penetration depth (h(s)) curve. The present methodology predicts these two sets of properties, indicating that it may be possible to obtain unique mechanical properties only in solids where n similar to 0.2. The intrinsic duality of mechanical property extractions from instrumented indentation experiments is related to the lack of measurement of the amount of pile-up or sinking-in, which cannot be fully compensated through further analysis of the P-h(s) curve. Along these lines, qualitative observations on whether bulging or pincushion effects occur around the imprint are found to be sufficient to establish which of the two potential sets of inferred properties corresponds to the indented material. (c) 2005 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.