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Lookup NU author(s): Emeritus Professor Trevor Page
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The utility of indentation testing for characterizing a wide range of mechanical properties of brittle materials is highlighted in light of recent articles questioning its validity, specifically in relation to the measurement of toughness. Contrary to assertion by some critics, indentation fracture theory is fundamentally founded in Griffith-Irwin fracture mechanics, based on model crack systems evolving within inhomogeneous but well-documented elastic and elastic-plastic contact stress fields. Notwithstanding some numerical uncertainty in associated stress intensity factor relations, the technique remains an unrivalled quick, convenient and economical means for comparative, site-specific toughness evaluation. Most importantly, indentation patterns are unique fingerprints of mechanical behavior and thereby afford a powerful functional tool for exploring the richness of material diversity. At the same time, it is cautioned that unconditional usage without due attention to the conformation of the indentation patterns can lead to overstated toughness values. Limitations of an alternative, more engineering approach to fracture evaluation, that of propagating a precrack through a "standard" machined specimen, are also outlined. Misconceptions in the critical literature concerning the fundamental nature of crack equilibrium and stability within contact and other inhomogeneous stress fields are discussed.
Author(s): Marshall DB, Cook RF, Padture NP, Oyen ML, Pajares A, Bradby JE, Reimanis IE, Tandon R, Page TF, Pharr GM, Lawn BR
Publication type: Article
Publication status: Published
Journal: Journal of the American Ceramic Society
Year: 2015
Volume: 98
Issue: 9
Pages: 2671-2680
Print publication date: 01/09/2015
Online publication date: 30/07/2015
Acceptance date: 23/05/2015
ISSN (print): 0002-7820
ISSN (electronic): 1551-2916
Publisher: Wiley-Blackwell Publishing Ltd.
URL: http://dx.doi.org/10.1111/jace.13729
DOI: 10.1111/jace.13729
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