報告書番号

U99026

タイトル（和文）

球状黒鉛鋳鉄と鍛鋼の非線形破壊力学による延性破壊評価（その1） - -表面き裂付き大型試験片による引張試験--

タイトル（英文）

Ductile Fracture Evaluation of Ductile Cast Iron and Forged Steel by Nonlinear-fracture-mechanics(Part-1) -Tensile Test by Large Scaled Test Pieces with Surface Crack-

概要 （図表や脚注は「報告書全文」に掲載しております）

金属キャスクの非線形破壊強度評価方法を提案するために、キャスク用球状黒鉛鋳鉄と鍛鋼の表面切欠き付き大型破壊試験片による延性引張試験を実施し、Ｊ積分で評価、以下の結果を得た。 1）金属キャスクのき裂存在下での延性破壊を評価するためのＪ積分設計曲線の策定に必要な引張応力負荷時のＪ積分－歪関係が得られた。 2）球状黒鉛鋳鉄では、歪ゲージから実験的に求めたＪ値は、室温ではRaju & Newman の線形式にほぼ合致したが、70℃では塑性域に入ると線形式とYagawaらの全面塑性解等に基づく非線形式の中間的な値を示した。 3）鍛鋼では、歪ゲージから実験的に求めたＪ値は、弾性域ではRaju&Newmanの線形式にほぼ従うが、塑性域では歪が大きくなるに従って線形式から離れ、全面塑性解に近づく複合的挙動を示した。

概要 （英文）

The ductile fracture tests of Ductile Cast Iron and Forged Steel under a tensile stress condition were conducted using large-scaled flat test specimens with a surface crack and were evaluated by the J-integral values, in order to propose an evaluation method of initiation of ductile fracture of a cask body with crack by nonlinear-fracture-mechanics. Following results were obtained. 1) J -strain relations of Ductile Cast Iron and Forged Steel under the tensile stress condition were obtained, which is neccessary for the development of J-integral design curves for evaluating the initiation of ductile fracture of the cask body. 2)In case of Ductile Cast Iron , the experimental J-integral values obtained from strain-gauges showed a good agreement with the linear-elastic-theory by Raju & Newman at room temperature, in both elastic and plastic regions. But, at 70℃ in plastic region, the experimental J-integral values showed middle values between those predicted by the linear-elastic-theory and by the non- linear-elastic- theory (based on the fully plastic solution by Yagawa et al.). 3)In case of Forged Steel at both ‐25℃ and room temperature, the experimental J-integral values obtained from strain-gauges showed a good agreement with those predicted by the linear-elastic-theory by Raju & Newman, in the elastic region. In the plastic region, however, the experimentall J-integral values fell apart from the curve predicted by linear-elastic-theory by Raju & Newman, and also approached to those by the non-linear-elastic-theory with increasing strain.

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