Chapter 30. Fracture Toughness by the Surface Crack in Flexure (SCF) Method: Results of the Vamas Round Robin

  1. John B. Wachtman Jr.
  1. George D. Quinn1,
  2. Robert J. Gettings1 and
  3. Jakob J. Kübler2

Published Online: 28 MAR 2008

DOI: 10.1002/9780470314555.ch30

Proceedings of the 18th Annual Conference on Composites and Advanced Ceramic Materials - B: Ceramic Engineering and Science Proceedings, Volume 15, Issue 5

Proceedings of the 18th Annual Conference on Composites and Advanced Ceramic Materials - B: Ceramic Engineering and Science Proceedings, Volume 15, Issue 5

How to Cite

Quinn, G. D., Gettings, R. J. and Kübler, J. J. (1994) Fracture Toughness by the Surface Crack in Flexure (SCF) Method: Results of the Vamas Round Robin, in Proceedings of the 18th Annual Conference on Composites and Advanced Ceramic Materials - B: Ceramic Engineering and Science Proceedings, Volume 15, Issue 5 (ed J. B. Wachtman), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470314555.ch30

Author Information

  1. 1

    National Institute of Standards and Technology Gaithersburg, MD 20899

  2. 2

    Swiss Federal Laboratories for Materials Testing and Research Dübendorf, Switzerland

Publication History

  1. Published Online: 28 MAR 2008
  2. Published Print: 1 JAN 1994

ISBN Information

Print ISBN: 9780470375334

Online ISBN: 9780470314555

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Keywords:

  • versailles advanced materials and standards project;
  • fracture toughness;
  • prestandardization research;
  • advanced technical ceramics;
  • surface crack in flexure method

Summary

Fracture toughness was measured by the surface crack in flexure method (also known as the controlled surface flaw method) on three monolithic advanced ceramics: hot-pressed silicon nitride, hot-isostatic pressed silicon nitride, and a sintered and post-hipped yttria-stabilized tetragonal zirconia polycrystal (Y-TZP). These materials present different degrees of difficulty in the application of this test method. Very consistent results were obtained for the hot-pressed silicon nitride, 4.6 (±0.4, standard deviation) MPa · √m; reasonably consistent results for the hipped silicon nitride, 5.0 (±0.6) MPa · √m and fair agreement for the Y-TZP, 4.4 (±0.4) MPa · √m The calculated toughness depends upon the stress at fracture and the precrack size and shape. The stress can be measured very accurately and precisely. Toughness is proportional to the square root of crack size so that uncertainty in the size measurement is diminished in the calculated results. Indeed, the round robin showed that the method was surprisingly robust with respect to the crack size measurements. Fractographic experience or skill is a prerequisite for the assurance of correct results, however.