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A combined experimental and analytical study was conducted to assess the ability of J-resistance curves obtained from small fracture toughness specimens to predict large amounts of crack growth in highly ductile nuclear piping materials. Tests were conducted at 288C (550F) on 25.4-mm (1-in.)-thick compact tension specimens of 1T, 3T, and 10T planar dimensions. The materials investigated included Type 304 austenitic stainless steel and ASTM A516, Grade 70 carbon steel. Resistance curves were developed from the data using both deformation J, JD, and modified J, JM, estimation schemes. Some of the tests on austenitic stainless steel also were analyzed by performing elastic-plastic finite-element calculations, and the results were used to evaluate extrapolation procedures. Extrapolation of small-specimen JD resistance curves to large amounts of crack growth resulted in sizable underestimations of resistance to fracture for the ductile materials studied. The JM-resistance curves, on the other hand, showed much less specimen-size dependence but tended to overestimate fracture resistance when small-specimen data were extrapolated. A tentative empirical method for extrapolating small-specimen data was developed. It was found also that the finite-element far-field J-R curves were very similar to the JM-R curves, and that the far-field finite-element J-R curve for the 10T specimen was virtually an extension of the J-R curves calculated for the 1T and 3T specimens.

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