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Similarity Relationships in Creep Contacts and Applications in Nanoindentation Tests

Published online by Cambridge University Press:  31 January 2011

Jinhaeng Lee
Affiliation:
jhlee.sg@gmail.com, University of Tennessee, Materials Science and Engineering, Knoxville, Tennessee, United States
Cong Zhou
Affiliation:
czhou3@utk.edu, University of Tennessee, Materials Science and Engineering, Knoxville, Tennessee, United States
Caijun Su
Affiliation:
csu2@utk.edu, University of Tennessee, Materials Science and Engineering, Knoxville, Tennessee, United States
Yanfei Gao
Affiliation:
ygao7@utk.edu, University of Tennessee, Materials Science and Engineering, Knoxville, Tennessee, United States
George Pharr
Affiliation:
pharr@utk.edu, University of Tennessee, Materials Science and Engineering, Knoxville, Tennessee, United States
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Abstract

The study of indentation responses of rate-dependent (viscoplastic or creeping) solids has generally focused on the relationship between indentation hardness and an effective strain rate, which can be defined from a similarity transformation of the governing equations. The strain rate sensitivity exponent can be determined from the slope of a log-log plot of the hardness versus effective strain rate, while determining other constitutive parameters requires a knowledge of the relationship between contact size, shape, and indentation depth. In this work, finite element simulations have shown that the effects of non-axisymmetric contact and crystallography are generally negligible. Theoretical predictions agree well with real nanoindentation measurements on amorphous selenium when tested above glass transition temperature, but deviate quite significantly for experiments on high-purity indium, coarse-grained aluminum, and nanocrystalline nickel. Such a discrepancy is likely to result from the transient creep behavior.

Type
Research Article
Copyright
Copyright © Materials Research Society 2010

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