SEDL / STP / STP1389-EB / STP14806S

Transition Fracture Toughness Testing with Notched Round Bars (NRB)

Wilson, CD
Assistant professor, Tennessee Technological University, Cookeville, TN

Landes, JD
Professor, The University of Tennessee, Knoxville, TN

Pages: 13    Published: Jan 2000

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Abstract

The notched round bar (NRB) geometry was assessed for use with ASTM E 1921-97 Standard for Test Method for the Determination of Reference Temperature, T⁰, for Ferritic Steels in the Transition Range. Instead of precracking the NRB specimens, apparent fracture toughness using three different notch root radii was extrapolated to a zero radius to infer sharp crack fracture toughness. The reference temperature using A302B NRB specimens was determined to be -89°C, while A302B C(T) specimens yield T⁰ of -87.3°C. In applying ASTM E 1921 to the NRB geometry, a simple scheme to remove notch root radius bias from apparent fracture toughness was developed. In addition, a size correction for converting NRB results to comparable 1T-C(T) results was investigated.