Evaluating initial unloading stiffness from elastic work-of-indentation measured in a nanoindentation experiment


Differentiation of the energy-based power function used to represent the nanoindentation unloading response at the peak indentation load generally overestimates the contact stiffness. This is mainly because of the larger curvature associated with this function and the proximity between the contact and maximum penetration depths. Using the nanoindentation data from ceramics and metals, we have shown that these two errors can be eliminated if the derivative is multiplied by the geometric and stiffness correction factors, respectively. The stiffness correction factor is found to be a function of the elastic energy constant and is independent of the peak indentation load. The contact stiffness evaluated by the proposed method is in excellent agreement with that obtained from the power law derivative for a wide range of elastoplastic materials and peak indentation loads. The relationship between the elastic recovery ratio and elastic energy constant developed in this study further simplifies the proposed procedure.

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KKJ gratefully acknowledges the Dissertation Year Fellowship (DYF) from the University Graduate School, Florida International University. AA would like to acknowledge support from the National Science Foundation CAREER Award (NSF-DMI-0547178), the US Air Force Office of Scientific Research Grant (Grant No. FA9550-09-1-0297), and the DURIP Grant (N00014-06-0675) from the Office of Naval Research.

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Correspondence to Nakin Suksawang.

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Jha, K.K., Suksawang, N., Lahiri, D. et al. Evaluating initial unloading stiffness from elastic work-of-indentation measured in a nanoindentation experiment. Journal of Materials Research 28, 789–797 (2013). https://doi.org/10.1557/jmr.2013.3

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