Applicability of new CTOD calculation formula to various a0/W conditions and B × B configuration

In the previous report, the authors proposed a new CTOD calculation formula which shows good correspondence with actual CTOD in large thickness materials by introduction of a correction parameter for varied blunting shapes at the crack tip by a strain hardening exponent. However, this formula is limited to the standard range of the crack depth to width ratio, a0/W from 0.45 to 0.55, and hence did not satisfy strong demand for evaluation of a wider a0/W range. Actually, ISO15653 can cover a wider a0/W range from 0.01 to 0.70 in order to respond to this demand, considering the description in the Annex, which specifies a J-integral based CTOD calculation formula. In the context of this situation, the authors' recent report revealed that the plastic hinge model can be applied to a0/W conditions other than the range from 0.45 to 0.55 based on detailed observation of plastic deformation for wider a0/W conditions. Coordination of the rotational center is steady regardless of the load level and strain hardening exponent. In this study, first, based on a B × 2B configuration, expansion of the applicable a0/W range for the proposed CTOD calculation formula is investigated with some modification of the proposed formula. Second, application to the B × B type specimen is investigated. Finally, validation of the FEM analysis for B × B type specimens by the silicone rubber replica method is presented.