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Critical issues in making small-depth mechanical property measurements by nanoindentation with continuous stiffness measurement

Published online by Cambridge University Press:  31 January 2011

G.M. Pharr ,
J.H. Strader  and
W.C. Oliver
G.M. Pharr*
Affiliation:
Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996-2200; and Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831
J.H. Strader
Affiliation:
Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996-2200
W.C. Oliver
Affiliation:
Agilent Technologies, Nanotechnologies Measurement Division, Oak Ridge, Tennessee 37830
*
a) Address all correspondence to this author. e-mail: pharr@utk.eduThis author was an editor of this focus issue during the review and decision stage. For the JMR policy on review and publication of manuscripts authored by editors, please refer to http://www.mrs.org/jmr_policy
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Abstract

Experiments were performed on a (100) copper single crystal to examine the influences that small displacement oscillations used in continuous stiffness measurement techniques have on hardness and elastic-modulus measurements in nanoindentation experiments. For the commonly used 2-nm oscillation, significant errors were observed in the measured properties, especially the hardness, at penetration depths as large as 100 nm. The errors originate from the large amount of dynamic unloading that occurs in materials like copper that have high contact stiffness resulting from their high modulus-to-hardness ratios. A simple model for the loading and unloading behavior of an elastic–plastic material is presented that quantitatively describes the errors and can be used to partially correct for them. By correcting the data in accordance with model and performing measurements at smaller displacement oscillation amplitudes, the errors can be reduced. The observations have important implications for the interpretation of the indentation size effect.

Keywords

CuHardnessNanoindentation
Type
Articles
Information
Journal of Materials Research , Volume 24 , Issue 3 , March 2009 , pp. 653 - 666
Copyright
Copyright © Materials Research Society 2009

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References

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