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VAMAS TWA #3
Project #6: Fracture Toughness by the Surface Crack in Flexure (SCF) Method Round Robin
Fracture Toughness III
Organized by the National Institute of Standards and Technology, USA (Mr. Quinn and Gettings) and the Swiss Federal Laboratories for Materials Testing and Research, Switzerland (Mr. Kübler).

Objective

Evaluate the Surface Crack in Flexure (SCF) test method.

Approach

Test 2 silicon nitrides and 1 zirconia.
A Knoop indenter was used to create a small surface crack in a flexure specimen. Residual stresses were removed by hand grinding or polishing. Can participants make, find, and measure the precracks after fracture? Over 700 specimens distributed Nov. 1992.

Outcome

Round robin completed, September 1993.
20 of 24 laboratories completed their work.

Principal Findings

Excellent consistency for the hot pressed silicon nitride. All labs had some level of success. Fractographic experience helpful. Hipped silicon nitride and zirconia progressively more difficult. Computed KIc is insensitive to the crack size measurement.

Standards Impact

ASTM PS 070-97 was prepared and includes the SCF method as one of three techniques. NIST prepared Standard Reference Material SRM 2100 based in part on the success with the hot-pressed silicon nitride in this round robin . This is the first reference material for the property fracture toughness for any class materials in the world.

Publications
  1. G. Quinn, J. Kübler, and R. Gettings, "Fracture Toughness of Advanced Ceramics by the Surface Crack in Flexure (SCF) Method: A VAMAS Round Robin," VAMAS Technical Report #17, June, 1994, (Avail. NIST)
  2. G. Quinn, J. Kübler, and R. Gettings, "Fracture Toughness of Advanced Ceramics by the Surface Crack in Flexure (SCF) Method: Results of the VAMAS Round Robin," Ceram. Eng. and Sci. Proc., Vol. 15, #5, 1994, 846-855.
  3. G. D. Quinn, J. J. Kübler, and R. J. Gettings, "Fracture Toughness of Advanced Ceramics: A New VAMAS Round Robin," in New Horizons for Materials, Proceedings of the 8th World Ceramic Congress, CIMTEC, Florence, Italy, ed P. Vincenzini, Techna, Faenza, 1995., pp. 577- 584.
For more information or copies of the reports, contact:
Mr. George Quinn, NIST Ceramics Division, Gaithersburg, MD 20899, USA, Tel: (+001) 301 975 5765, email: geoq@nist.gov
or
Mr. J. Kübler, EMPA, Uberlandstrasse 129, CH 8600 Dubendorf, Switzerland, Tel: (+41) 1 823 5511, email: jakob.kuebler@empa.ch


The VAMAS TWA #3 Round Robins Between 1987 and 1999.

Click on the numbered projects in the image below for round robin details.



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