| Abstract |
| Bluntness is inevitable at the tip of a sharp indenter such as the Berkovich indenter used in nanoindentation experiments; this bluntness causes the hardness values observed at low contact depths (<~100 nm) to fall below the Nix and Gao model curve. We present an indentation size effect (ISE) model that extends the available contact depth for ISE application down to several tens of nanometers by considering the tip bluntness effect. The present model reflects the effect of tip bluntness on the distribution of geometrically necessary dislocations needed to accommodate the blunted tip, and the change in the ratio of plastic to total contact depth with contact depth. We applied the present model to nanoindentation results for annealed and strain-hardened Cu, and to previously reported nanoindentation results for surface-nanocrystallized Al-alloy. Good fit was observed between the present model and the hardness results over the full contact depth range. (Received July 22, 2004) |
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| Key Words |
| Geometrically necessary dislocation, Indentation size effect, Nanoindentation, Tip bluntness |
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