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VAMAS TWA #3
Project #13: Flexural Strength of Silicon Nitride at High Temperature was completed in September 2000.

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Organized by

Approach

A round robin was organized whereby each laboratory tested ten to twelve flexure specimens in four-point loading at 1200^oC.  Participants used either 10 mm x 30 mm span or 20 mm x 40 mm span fixtures.  Either semi-articulating or fully-articulating fixtures were used.

Outcome

The project was completed in 2000.  Thirteen laboratories in six countries participated.   Two hundred and nine specimens were tested.     Information gathered was helpful in refining the draft ISO standard in ISO Technical Committee 206, Fine Ceramics.

 Principal Findings

Strengths of specimens tested in the 10 m x 30 mm fixtures were slightly greater than those from the 20 mm x 40 mm fixtures, but the difference was accounted for by ordinary Weibull strength scaling with size.  Specimens tested in fully-articulating fixtures were slightly stronger than those tested on semi-articulating fixtures.  The limited number of specimens tested by each laboratory led to a large reproducibility uncertainty (between-laboratory strength variation).  Much of the variability was attributed to small sample size statistical effects predicted by Weibull statistics.  Supplemental experiments verified that friction constraints from fixed loading points or rollers in square slots can affect data.

Standards Impact

Draft ISO Draft International, ISO 17565, “Fine Ceramics (Advanced Ceramics, Advanced Technical Ceramics) – Test Method for Flexural Strength of Monolithic Ceramics at Elevated Temperature” was modified in March 2001.  An annex including the results of the VAMAS round robin was added.  The ISO standard was approved and adopted in 2001.

Publications

A. Okuda and M. Mizuno, “VAMAS Round Robin on Flexural Strength of Silicon Nitride at High Temperature,” VAMAS Technical Report 39, Japan Fine Ceramics Center, Nagoya, Japan, September 2000.

For more information or copies of the reports, contact:

A. Okuda and M. Mizuno, Japan Fine Ceramics Center, 2-4-1 Mutsun0, Atsuka-ku, Nagoya, Japan email:  okada@jfcc.or.jp   mizuno@jfcc.or.jp