Constraint-corrected<i>J-R</i>curve based on three-dimensional finite element analyses

Three-dimensional (3D) finite element analyses are carried out on single-edge bend (SE (B)) specimens for which the J-integral resistance curves ( J-R curves) have been exper- imentally determined to develop the constraint-corrected J-R curves for the X80 grade pipe steel. The constraint parameters considered in this study include QHRR, QSSY, QSSY_m, QLM, QBM1, QBM2, A2, h and Tz. The constraint-corrected J-R curves were de- veloped on the basis of the constraint parameters obtained from finite element analysis and experimentally determined J-R curves associated with deeply cracked and medium-cracked SE(B) specimens and validated against shallow-cracked SE(B) speci- mens. The analysis results indicate that all the constraint parameters considered in this study except QHRR, QSSY, QSSY_m and QLM lead to reasonably accurate constraint- corrected J-R curves if the crack extensions are relatively small (≤0.7mm). For larger crack extensions (≤1.5mm), the QBM1-based constraint-corrected J-R curve leads to the most accurate predictions of J among all the constraint parameters considered.