A Critical Evaluation of Indentation Techniques for Measuring Fracture Toughness: I, Direct Crack Measurements

Authors

  • G.R. ANSTIS,

    1. Department of Applied Physics, School of Physics, University of New South Wales, New South Wales 2033, Australia
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  • P. CHANTIKUL,

    1. Department of Applied Physics, School of Physics, University of New South Wales, New South Wales 2033, Australia
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  • B.R. LAWN,

    1. Department of Applied Physics, School of Physics, University of New South Wales, New South Wales 2033, Australia
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    • *

      Member, the American Ceramic Society.

  • D.B. MARSHALL

    1. Department of Applied Physics, School of Physics, University of New South Wales, New South Wales 2033, Australia
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    • *

      Member, the American Ceramic Society.

    • Now with the Materials and Molecular Research Division, Lawrence Berkeley Laboratory, Berkeley, California 94720.


  • Supported by the Australian Research Grants Committee, the Australian Department of Defence, and the U. S. Office of Naval Research.

Abstract

The application of indentation techniques to the evaluation of fracture toughness is examined critically, in two parts. In this first part, attention is focused on an approach which involves direct measurement of Vickers-produced radial cracks as a function of indentation load. A theoretical basis for the method is first established, in terms of elastic/plastic indentation fracture mechanics. It is thereby asserted that the key to the radial crack response lies in the residual component of the contact field. This residual term has important implications concerning the crack evolution, including the possibility of post indentation slow growth under environment-sensitive conditions. Fractographic observations of cracks in selected “reference” materials are used to determine the magnitude of this effect and to investigate other potential complications associated with departures from ideal indentation fracture behavior. The data from these observations provide a convenient calibration of the Indentation toughness equations for general application to other well-behaved ceramics. The technique is uniquely simple in procedure and economic in its use of material.

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