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Illustrative analysis of load-displacement curves in nanoindentation

Published online by Cambridge University Press:  31 January 2011

A.C. Fischer-Cripps
A.C. Fischer-Cripps*
Affiliation:
Industrial Physics, Commonwealth Scientific and Industrial Research Organization (CSIRO), West Lindfield, New South Wales, 2070 Australia
*
a)Address all correspondence to this author. e-mail: tony.cripps@csiro.au
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Abstract

The nature of the elastic unloading after an elastic-plastic contact with a conical or Berkovich indenter is studied. Three representative specimens having different mechanical properties were tested. Finite-element results for the pressure distribution beneath the indenter during unloading suggest that the effective indenter is in fact very closely approximated by a sphere in the case of fused silica (a material with a relatively low value of E/H) and a more uniform pressure distribution in the case of silicon and sapphire (materials with higher values of E/H). The proposed reason for these observations is the extent and influence of an elastic enclave directly beneath the indenter as revealed by finite-element analysis. The results also show that the pressure distribution retains its form during the entire unloading. The work seeks to provide a physical reason for the value of the fitting exponent m as used in popular nanoindentation data analysis procedures.

Keywords

Hardness
Type
Articles
Information
Journal of Materials Research , Volume 22 , Issue 11 , November 2007 , pp. 3075 - 3086
Copyright
Copyright © Materials Research Society 2007

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References

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