Subsize specimens for fatigue crack growth rate testing of metallic materials

Research output: Contribution to journalConference articlepeer-review


In this work, the potential for obtaining reliable fatigue crack growth data from miniature notched bar specimens in three-point bend loading is examined. These specimens, at 2.0 mm wide by 0.8 mm thick by 7.9 mm long, are substantially smaller than any existing fatigue crack growth specimens. This work describes the development of subsize specimen fatigue crack growth rate test techniques using these miniature bar specimens. Fatigue crack growth data are reported for three alloys, 304L SS, Alloy 718 and Mod. 9Cr-1Mo steel. The data obtained using the subsize specimens compare favorably to crack growth rate data obtained on ASTM standard size specimens. The fracture surface microstructures of the subsize and standard size specimens are compared to show the similarities of the crack growth mechanisms in the two specimen configurations. Since three different materials were tested, it is possible to draw conclusions about the limitations of using these extremely small specimens in terms of material yield and ultimate strength and other standard tensile properties.

Original languageEnglish (US)
Pages (from-to)321-335
Number of pages15
JournalASTM Special Technical Publication
Issue number1418
StatePublished - 2002
Externally publishedYes
EventSmall Specimen Test Techniques - Reno, NV, United States
Duration: Jan 23 2000Jan 25 2000


  • 304L steels
  • Alloy 718
  • Fatigue crack growth
  • Miniature specimens
  • Mod 9Cr-1Mo Steel
  • Three-point bending

ASJC Scopus subject areas

  • General Engineering


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