The Compelling Case for Indentation as a Functional Exploratory and Characterization Tool |
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| Authors: | David B Marshall Robert F Cook Nitin P Padture Michelle L Oyen Antonia Pajares Jodie E Bradby Ivar E Reimanis Rajan Tandon Trevor F Page George M Pharr Brian R Lawn |
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| Affiliation: | 1. Teledyne Scientific Co, Thousand Oaks, California;2. Materials Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland;3. School of Engineering, Brown University, Providence, Rhode Island;4. Department of Engineering, Cambridge University, Cambridge, UK;5. Departamento de Ingeniería Mecánica, Energética y de los Materiales, Universidad de Extremadura, Badajoz, Spain;6. Research School of Physics and Engineering, Australian National University, Canberra, Australia;7. Department of Metallurgical and Materials Engineering, Colorado School of Mines, Golden, Colorado;8. Analytical Technologies, Sandia National Laboratories, Albuquerque, New Mexico;9. School of Chemical Engineering and Advanced Materials, Newcastle University, Newcastle Upon Tyne, UK;10. Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee;11. Oak Ridge National Laboratories, Materials Science and Technology Division, Oak Ridge, Tennessee |
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| 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 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. |
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