Proposal for a new CTOD calculation formula

•CTOD calculation from P–Vg curve was discussed using FE-analysis results.•The rotational factor, rp was newly calibrated and examined for the experiments.•A new CTOD calculation formula, considering yield-to-tensile ratio is proposed.•Prediction of numerical CTOD by the proposed CTOD was examined in wide range of YR.•The proposed CTOD calculation was also examined by the experiment results.

A new CTOD calculation method is investigated in this work, considering the variation of crack tip blunting due to strain hardening. The calculation formula is constructed assuming that CTOD45FEM based on three-dimensional elasto-plastic FEM is the target CTOD to be calibrated. A new factor f is introduced to correct the plastic term. In this factor, the blunted crack tip shape is considered to depend on the strain hardening exponent, and f is given as a function of the yield-to-tensile ratio (YR) of the material and the specimen thickness. The appropriateness of the investigated CTOD calculation is verified numerically and experimentally.