Development of a Miniaturized Bulge Test (Small Punch Test) for Post-Irradiation Mechanical Property Evaluation
SourceTo examine the effectiveness of the small punch test for evaluating strength and toughness of irradiated ferritic steels, detailed procedures are described aiming at standardization of the test. The statistical approach to analysis of the SP energy as a function of temperature for evaluation of DBTT was also reviewed. The method was then applied to neutron-irradiated ferritic steels, which included F-82, F-82H, HT-9, and 2¼Cr-1Mo steel. Fluence and irradiation temperatures ranged from 2 to 12 x 1023 n/m2 (E ⩾ 1 MeV) and from 573 to 673 K, respectively. Comparison of parameters obtained from the small punch test with the properties measured by the conventional method indicated that: (a) the 0.2% offset stress and the ultimate tensile strength at room temperature can be correlated well with the parameters, Py/(t0)2 and Pmax/(t0)2, respectively. Here, Py and Pmax are the loads corresponding to the yield and the maximum, and t0 is the initial thickness of a specimen; (b) fracture toughness, JIC, can be evaluated using equivalent fracture strain, ϵ¯qf, and the previously established relationship between these values; and (c) DBTT measured by a Charpy test can be predicted from the results of temperature dependence of SP energy determined from the area under the load-deflection curve using a statistical analysis based on a Weibull distribution.