The Compelling Case for Indentation as a Functional Exploratory and Characterization Tool

Authors
Marshall, DB 
Cook, RF 
Padture, NP 
Oyen, ML 
Pajares, A 

Change log
Abstract

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 pre-crack 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.

Publication Date
2015
Online Publication Date
2015-07-30
Acceptance Date
Keywords
40 Engineering, 4016 Materials Engineering, Bioengineering
Journal Title
Journal of the American Ceramic Society
Journal ISSN
0002-7820
1551-2916
Volume Title
98
Publisher
Wiley