Background and General Information
This site complements ASTM standard C 1322-96a and U. S. Army Military handbook MIL HDBK 790. These were designed to provide an efficient and consistent methodology to locate and characterize fracture origins in advanced ceramics.

MIL HDBK 790, "Fractography and Characterization of Fracture Origins in Advanced Structural Ceramics" was created by the U. S. Army Materials Technology Laboratory, Watertown, MA in 1992.

MIL HDBK 790 was expanded and superseded in 1996 by ASTM Standard Practice C 1322-96, "Fractography and Characterization of Fracture Origins in Advanced Ceramics."

C 1322 has already had one minor revision (to the 96a version) and undoubtedly will experience further refinements and expansions.

C 1322 and MIL HDBK 790 are applicable to advanced ceramics which are brittle; that is, the material adheres to Hooke's law up to fracture and fracture commences from a single location which is termed the fracture origin.

Techniques for finding fracture origins are described in detail in C 1322. Visual, optical microscope, and scanning electron microscope examination are recommended.

Testing of specimens or components should be done, if possible, in a manner that preserves the primary fracture surfaces and associated fragments for further fractographic analysis.

Specimen reconstruction and examination of the general fracture patterns is the first essential step in fractographic analysis. Fracture patterns can help determine the stress state (uniaxial, biaxial, etc), whether the specimen or component fractured properly, and help the observer find the fracture origin.
Fractography Round Robin
The general methodology has been tested in an Versailles Advanced materials and Standards (VAMAS) international round robin in 1993-1994. The following reports on this project are available upon request from geoq@nist.gov or jswab@arl.mil:
  1. J. J. Swab and G. D. Quinn, "Fractography of Advanced Structural Ceramics, Results from the VAMAS Round Robin Exercise," U.S. Army Technical Report, ARL-TR-656, Dec. 1994. (Also published under the same title as VAMAS Report #19, February 1995, NIST, Gaithersburg, MD 20899)
  2. J. J. Swab and G. D. Quinn, "Findings of the VAMAS Fractography Round Robin Exercise," in Fractography of Glasses and Ceramics, Ceramic Transactions, Vol. 64, ACS, Westerville, OH, 1996, pp 55 -70.
Definitions
Flaw
A structural discontinuity in an advanced ceramic body that acts as a highly localizer stress raiser.

Note - the presence of such discontinuities does not necessarily imply that the ceramic has been prepared improperly or is faulty. (ASTM C1322-96a)
Fracture Origin
The source from which brittle fracture commences. (ASTM C 1322-96a)
Fracture Origin
That flaw (discontinuity) from which cracking begins. (Failure Analysis of Brittle Materials, by V. D. Frechette, Advanced in Ceramics, Vol. 28, American Ceramic Society, Westerville, OH, 1990.
Fractography
Means and methods for characterizing a fractured specimen or component. (ASTM C 1145)
Mirror
As used in fractography of brittle materials, a very smooth region in the immediate vicinity of and surrounding the fracture origin. (ASTM C1322-96a)
Further Information
C 1322 has an extensive bibliography on the following topics:
  • Books on Advanced Ceramic Fractography
  • Microscopic Techniques
  • Fractography of Ceramics - Overview Papers
  • Origins in Advanced Ceramics
  • Fracture Mirrors
  • Fracture Mechanics - Estimates of Flaw Size
  • Fracture Mechanics - Stress Intensity Factors
For Fractography of Glasses, see: ASTM Standard C1256-93, "Standard Practice for Interpreting Glass Fracture Surface Features," ASTM Annual Book of Standards Vol. 15.02.


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Date created: 08 February 2001
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