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Advances in Materials Science and Engineering
Volume 2016 (2016), Article ID 9213841, 8 pages
http://dx.doi.org/10.1155/2016/9213841
Research Article

A Modified Method for Hardness Determination from Nanoindentation Experiments with Imperfect Indenters

1School of Mechanical and Instrumental Engineering, Xi’an University of Technology, Xi’an 710048, China
2Business Intelligence and Knowledge Engineering Lab, Henan University of Technology, Zhengzhou 450001, China

Received 14 July 2015; Revised 2 November 2015; Accepted 30 November 2015

Academic Editor: Luciano Lamberti

Copyright © 2016 Wei Chao Guo et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Nanoindentation is an effective nondestructive method for small scale determination of mechanical properties of materials. However, indentation response of metallic materials is very sensitive to indenter tip roundness, size effects, loading rate, and so forth. This study will analyze the effect of indenter shape imperfections on hardness determination. For this purpose, experimental investigations and finite element simulations are carried out. At first, it is found that hardness values determined with Oliver and Pharr’s method are affected by errors caused by imperfect indenter tip: errors increase for imperfect indenters with larger tip radii. Afterwards, several commonly used methods accounting at different extents for tip radius variations are compared. However, most of those methods are found not to be accurate for shallow indentation. For this reason, a novel hardness determination method based on geometrical relations of the imperfect indenter tip is developed. Results show that the new approach is very effective even in the case of shallow indentation.