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Size Effect in the Initiation of Plasticity for Ceramics in Nanoscale Contact Loading

Published online by Cambridge University Press:  26 February 2011

Tingting Zhu ,
X.D. Hou ,
C. J. Walker ,
K. M.Y. P'ng ,
D. J. Dunstan  and
A. J. Bushby
Tingting Zhu
Affiliation:
t.zhu@qmul.ac.uk, Queen Mary University of London, Materials, Mile End Road, London, E1 4NS, United Kingdom, 02078827418
X.D. Hou
Affiliation:
x.hou@qmul.ac.uk, Queen Mary University of London, Department of Materials, Centre for Materials Research, Mile End Road, London, E1 4NS, United Kingdom
C. J. Walker
Affiliation:
C.J.Walker@qmul.ac.uk, Queen Mary University of London, Department of Physics, Centre for Materials Research, Mile End Road, London, E1 4NS, United Kingdom
K. M.Y. P'ng
Affiliation:
k.m.y.p'ng@qmul.ac.uk, Queen Mary University of London, Department of Materials, Centre for Materials Research, Mile End Road, London, E1 4NS, United Kingdom
D. J. Dunstan
Affiliation:
d.j.dunstan@qmul.ac.uk, Queen Mary University of London, Department of Physics, Centre for Materials Research, Mile End Road, London, E1 4NS, United Kingdom
A. J. Bushby
Affiliation:
a.j.busby@qmul.ac.uk, Queen Mary University of London, Department of Materials, Centre for Materials Research, Mile End Road, London, E1 4NS, United Kingdom
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Abstract

In nanoindentation, the plasticity size effect has been observed for several years, where a higher hardness is measured as indenter size decreases. In this paper, we report the size effect on the initiation of plasticity in ceramics by using spherical indenters. Here, we show a clear method that is able to determine the details of the onset of plasticity in nanoindentation. This enables us to measure the yield pressure with a high degree of accuracy and over a large range of indenter radii (hundreds of nanometers to several tens of micrometers). Our data shows clearly that there is a significant yield strength enhancement, which is inversely proportional to the cube root of the indenter radius. Also after normalization by the bulk yield strength, the increase in yield strength with decreasing indenter radius is shown to follow a single relation for all the ceramics studied in agreement with recent results for metals [1], and consistent with critical thickness theory for the initiation of yielding over a finite volume.

Keywords

nanoscaleceramicstrength
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 976: Symposium EE – Size Effects in the Deformation of Materials – Experiments and Modeling , 2006 , 0976-EE06-12
Copyright
Copyright © Materials Research Society 2007

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