A Critical Evaluation of Indentation Techniques for Measuring Fracture Toughness: II, Strength Method

Autor: Brian R. Lawn, G. R. Anstis, David B. Marshall, P. Chantikul
Rok vydání: 1981
Předmět:
Zdroj: Journal of the American Ceramic Society. 64:539-543
ISSN: 1551-2916
0002-7820
DOI: 10.1111/j.1151-2916.1981.tb10321.x
Popis: An examination is made of the sharp-indentation technique of strength-test precracking for toughness evaluation. The experimental approach follows that proposed by other workers but the theoretical analysis contains one vital new feature; the residual-stress term discussed in Part I of this study is now introduced explicitly into the strength formulation. This modification overcomes a major systematic discrepancy evident in the previous models and at the same time, by virtue of attendant changes in the nature of the crack stability prior to attaining a failure configuration, eliminates the need for frac-tographic measurements. Other advantages are also apparent, notably an insensitivity to postindentation radial crack extension. The main disadvantage is that only one result is obtained per specimen. Indentation/strength data from ceramics listed in Part I confirm the essential features of the theory and provide a suitable calibration factor. The method has special application to those materials which do not necessarily produce a well-defined radial crack pattern, in which case an “effective”Kc appropriate to fracture properties at the flaw level is obtained.
Databáze: OpenAIRE
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