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Standardized test methods of plain strain fracture toughness KIC and elastic-plastic
fracture toughness JIC are time-consuming and expensive. On the other hand, a
convenient new test method, named J evaluation on tensile test (JETT) of round
bar with circumferential notch, has been proposed to evaluate the fracture
toughness of the tough materials. Since JETT is not standardized yet, the size of
JETT specimen should be carefully selected. Therefore the FEM calculations for
the comparison of the strain constraint around the notch or crack tip of both
specimens are needed before the experiments. In this research, the tables
demonstrating the effective JETT specimen sizes as a function of a workhardening
exponent and a work-hardening coefficient were proposed. A fracture
toughness of a work-hardening material can be evaluated by JETT specimen,
while that of an elastic-perfect plastic material is difficult to be evaluated by it.