The indenter tip radius effect in micro- and nanoindentation hardness experiments. |
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Authors: | Fan Zhang Yonggang Huang Keh-Chih Hwang |
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Institution: | (1) FML, Department of Engineering Mechanics, Tsinghua University, Beijing, 100084, China;(2) Dept. of Mechanical and Industrial Engineering, University of Illinois, Urbana, IL 61801, USA |
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Abstract: | Nix and Gao established an important relation between the microindentation hardness and indentation depth. Such a relation
has been verified by many microindentation experiments (indentation depths in the micrometer range), but it does not always
hold in nanoindentation experiments (indentation depths approaching the nanometer range). Indenter tip radius effect has been
proposed by Qu et al. and others as possibly the main factor that causes the deviation from Nix and Gao's relationship. We
have developed an indentation model for micro- and nanoindentation, which accounts for two indenter shapes, a sharp, conical
indenter and a conical indenter with a spherical tip. The analysis is based on the conventional theory of mechanism-based
strain gradient plasticity established from the Taylor dislocation model to account for the effect of geometrically necessary
dislocations. The comparison between numerical result and Feng and Nix's experimental data shows that the indenter tip radius
effect indeed causes the deviation from Nix-Gao relation, but it seems not be the main factor.
The project supported by the National Natural Science Foundation of China (10121202) and the Ministry of Education of China
(20020003023) |
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Keywords: | Taylor dislocation model Strain gradient plasticity Indentation Nix-Gao relation |
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