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Title: The compelling case for indentation as a functional exploratory and characterization tool

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. Thus misconceptions in the critical literature concerning the fundamental nature of crack equilibrium and stability within contact and other inhomogeneous stress fields are discussed.
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ;  [8] ;  [9] ;  [10] ;  [3]
  1. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
  2. Teledyne Scientific Co., Thousand Oaks, CA (United States)
  3. National Institute of Standards and Technology, Gaithersburg, MD (United States)
  4. Brown Univ., Providence, RI (United States)
  5. Cambridge Univ., Cambridge (United Kingdom)
  6. Univ. de Extremadura, Badajoz (Spain)
  7. Australian National Univ., Canberra (Australia)
  8. Colorado School of Mines, Golden, CO (United States)
  9. Newcastle Univ., Newcastle Upon Tyne (United Kingdom)
  10. Univ. of Tennessee, Knoxville, TN (United States)
Publication Date:
OSTI Identifier:
1235351
Report Number(s):
SAND--2015-4302J
Journal ID: ISSN 0002-7820; 590426
Grant/Contract Number:
AC04-94AL85000
Type:
Accepted Manuscript
Journal Name:
Journal of the American Ceramic Society
Additional Journal Information:
Journal Volume: 98; Journal Issue: 9; Journal ID: ISSN 0002-7820
Publisher:
American Ceramic Society
Research Org:
Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE