Indentation behavior, interpreting

For interpreting indentation behavior, a useful parameter is the ratio of the hardness number, H to the shear modulus. For cubic crystals the latter is the elastic constant, C44. This ratio was used by Gilman (1973) and was used more generally by Chin (1975) who showed that it varies systematically with the type of chemical bonding in crystals. It has become known as the Chin-Gilman parameter (H/C44). Some average values for the three main classes of cubic crystals are given in Table 2.1. 

Thouless et al. derived a model based on buckling of an edge flake that predicted n=3. An indentation fracture mechanics model by Chai and Lawn for edge chip resistance is also consistent with the power law eq, 2, but only for the case of /r = 1.5. Although some of our data matched the power law with rr = 1.5, much of it did not. Exponents ranged from as small as 1 to as large as 2. Problems remain with the interpretation of the exponent n and the constant A. Is /r a fundamental material parameter indicative of a material s chipping behavior Can it be related to other material properties What are the units of A ... 

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