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An Explanation for the Shape of Nanoindentation Unloading Curves based on Finite Element Simulation

Published online by Cambridge University Press:  21 February 2011

A. Bolshakov
Affiliation:
Department of Materials Science, Rice University, P.O. Box 1892, Houston, TX 77251
W.C. Oliver
Affiliation:
Nano Instruments, Inc., P.O. Box 14211, Knoxville, TN 37914
G.M. Pharr
Affiliation:
Department of Materials Science, Rice University, P.O. Box 1892, Houston, TX 77251
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Abstract

Current methods for measuring hardness and modulus from nanoindentation load-displacement data are based on Sneddon's equations for the indentation of an elastic half-space by an axially symmetric rigid punch. Recent experiments have shown that nanoindentation unloading data are distinctly curved in a manner which is not consistent with either the flat punch or the conical indenter geometries frequently used in modeling, but are more closely approximated by a parabola of revolution. Finite element simulations for conical indentation of an elastic-plastic material are presented which corroborate the experimental observations, and from which a simple explanation for the shape of the unloading curve is derived. The explanation is based on the concept of an effective indenter shape whose geometry is determined by the shape of the plastic hardness impression formed during indentation.

Type
Research Article
Copyright
Copyright © Materials Research Society 1995

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References

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