参照塑性勾配法によるJ積分評価

（多直線応力・ひずみ曲線への適用）

抄録

It is difficult to obtain J-integral values (J-values) without performing numerical analyses for materials of which stress-strain relation is given by a poly-linear curve. The current author has proposed the reference plastic slope (RPS) method, which can estimate J-values for arbitrary stress-strain curves. The RPS method derives the J-values for bi-linear stress-strain curves whose plastic slope is determined using the reference stress and original stress-strain curve. This study aimed at showing applicability of the RPS method to straight pipes with a circumferential surface crack subjected to a tensile or bending load. Four poly-linear stress-strain curves were assumed for validation. It was shown that well-approximated J-values were obtained by assuming bi-linear stress-strain curves. Second, it was demonstrated that the J-values for bi-linear stress-strain curves could be estimated by the equations proposed in author’s previous study.