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Finite Element Studies of the Influence of Pile-up on the Analysis of Nanoindentation Data

Published online by Cambridge University Press:  15 February 2011

A. Bolshakov ,
W. C. Oliver  and
G. M. Pharr
A. Bolshakov
Affiliation:
Department of Materials Science, Rice University, 6100 Main St., Houston, TX 77005
W. C. Oliver
Affiliation:
Nano Instruments, Inc., 1001 Larson Drive, Oak Ridge, TN 37830
G. M. Pharr
Affiliation:
Department of Materials Science, Rice University, 6100 Main St., Houston, TX 77005
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Abstract

Methods currently used for analyzing nanoindentation load-displacement data give good predictions of the contact area in the case of hard materials, but can underestimate the contact area by as much as 40% for soft materials which do not work harden. This underestimation results from the pile-up which forms around the hardness impression and leads to potentially significant errors in the measurement of hardness and elastic modulus. Finite element simulations of conical indentation for a wide range of elastic-plastic materials are presented which define the conditions under which pile-up is significant and determine the magnitude of the errors in hardness and modulus which may occur if pile-up is ignored. It is shown that the materials in which pile-up is not an important factor can be experimentally identified from the ratio of the final depth after unloading to the depth of the indentation at peak load, a parameter which also correlates with the hardness-to-modulus ratio.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 436: Symposium CC – Thin Films Stresses and Mechanical Properties VI , 1996 , 141
Copyright
Copyright © Materials Research Society 1997

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References

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6. Bolshakov, A., Oliver, W.C. and Pharr, G.M., to be published.Google Scholar