The stretch zone width (SZW = 1/2CTOD, the crack lip opening displacement) method for determining J{sub}(IC) involves fewer specimens and lesser size restrictions compared to the conventional J-R curve method. However, the accuracy of theSZW-based procedure depends on each term of the J-CTOD relationship, i.e., J{sub}(IC) = m·σ·CTOD{sub}C. This paper presents a numerical investigation of the J-CTOD relationship, which has been carried out using a large-deformation finite element method (FEM). The slope of the blunting line (m) is computed for various combinations of yield strength-to-elastic modulus ratio (σ{sub}0/E), power law strain-hardening exponent (n), and different measures of stress (σ in the J-CTOD relationship). This workbrings out the importance of the correct choice of the stress measure, and the one suggested here is the integral average of the flow stress σ*=∫{sub}0{sup}ε*σdε/∫{sub}0{sup}ε*dε. Also, an effective CTOD approach is numerically validated where a sharp fatigue precrack of fracture specimens can be substituted by one with a finite notch root radius without loss of accuracy in J{sub}(IC).
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