STP1295: Link Between Results of Small- and Large-Scale Toughness Tests on Irradiated Zr-2.5Nb Pressure Tube Material

    Davies, PH
    Research scientist, AECL, Chalk River Laboratories, Chalk River, Ontario

    Shewfelt, RSW
    Research scientist, AECL, Whiteshell Laboratories, Pinawa, Manitoba

    Pages: 26    Published: Jan 1996


    Abstract

    The link between the results of small- (curved compact) and large-scale (burst) toughness tests on irradiated Zr-2.5Nb pressure tube material was investigated using material from tubes of different toughness values. Comparison between the crack growth resistance (deformation J-R) curves from the small- and large-scale specimens reveals the material dependence of geometry effects and shows that the crack-tip constraint in the compact specimen is generally higher than that in the burst specimen. For higher toughness material, the crack-extension region over which there is good correspondence between the J-R curves from the small- and large-scale specimens is in agreement with current knowledge of validity requirements for J-controlled crack growth of bend-type specimens. Fractographic studies were conducted and the results shown to be consistent with the observed geometry effects, a larger proportion of highly constrained, flat fracture being produced with the small bend-type specimens than with the burst tests. The results are discussed using a volume-controlled fracture model for bend-type specimens in which it is assumed that the toughness is governed by the development of the plastic zone associated with an intermediate-constraint, transition region between the central, flat-fracture zone and surfaceshear or slant-fracture zone. Applying scaling factors from the volume-controlled fracture model, good agreement is obtained between scaled values of the maximum pressure/load toughness from the small- and large-scale tests over a range of normalized plastic zone size of 0.4 to 1.

    Keywords:

    fracture toughness, Zr-2.5Nb, irradiation, pressure tubes, crack growth resistance (, J-R, ) curve


    Paper ID: STP16187S

    Committee/Subcommittee: B10.01

    DOI: 10.1520/STP16187S


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