Toughness and Flaw Responses in Nontransforming Ceramics: Implications for NDE

  • Brian R. Lawn
  • Carolyn J. Fairbanks
Conference paper
Part of the Review of Progress in Quantitative Nondestructive Evaluation book series (RPQN, volume 6 A)


Recent developments in the characterization of the strength of ceramics have made it necessary to re-examine several “tradition”, long-standing definitions and assumptions that form the modern-day fracture mechanics basis of NDE. Ceramics are very brittle materials. They are highly susceptible to failure from small scale (1–100 μm) “flaws”. These flaws may be in the form of machining damage, grain boundary fissures, processing defects (pores or inclusions), etc. Theoretically, flaws have been represented as scaled-down versions of large cracks, so that the macroscopic “laws” of fracture might be assumed to apply at the microsale. This philosophy is embodied in the Griffith strength formalism, σm = Τo/Yc1/2 where c is the flaw size, To is the toughness (KIC in metallurgical terminology) and Y is a geometrical constant. Implicit in Eq. 1 are two major conclusions which dictate the entire approach to NDE in ceramics:
  1. (i)

    Failure occurs spontaneously at the critical stress (σm);

  2. (ii)

    Toughness (To) is single-valued.



Flaw Size Crack Interface Frontal Zone Crack Size Critical Flaw Size 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Springer Science+Business Media New York 1987

Authors and Affiliations

  • Brian R. Lawn
    • 1
  • Carolyn J. Fairbanks
    • 1
  1. 1.Ceramics DivisionNational Bureau of StandardsGaithersburgUSA

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