Plastic deformation behavior in SEB specimens with various crack length to width ratios

The authors have already proposed a new crack tip opening displacement (CTOD) calculation formula based on the plastic hinge model considering the unique crack tip blunting behavior due to strain hardening of the material. This formula is limited to the standard length-to-width ratio (a0/W) range of between 0.45 and 0.55. However, CTOD calculations are necessary for various other a0/W conditions when the critical CTOD for a specific microstructure must be evaluated in a welded joint. ISO15653, which prescribes CTOD test methods for welds, covers a wide range of a0/W between 0.10 and 0.7 by applying a J-integral based CTOD derived from ASTM E1290 for a0/W from 0.10 to 0.45 and a plastic hinge based CTOD for a0/W from 0.45 to 0.70. This procedure leads to a discontinuity in the evaluated CTOD at a0/W = 0.45. This problem results from the fact that the J-integral based CTOD is inconsistent with the conventional plastic hinge based CTOD, especially in low yield-to-tensile ratio materials. Thus, a single CTOD calculation method for the wide range of a0/W is required for rational evaluation. In this study, the plastic deformation behavior of SEB specimens was analytically examined in the a0/W range from 0.05 to 0.70, and the capacity of the plastic hinge based CTOD was discussed with the aim of establishing a unified CTOD calculation formula for SEB specimens with the wide range of a0/W.