応力・ひずみ集中部の欠陥評価に関する一提案

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This paper deals with the significance of the crack exisitng in the stress concentrated region from a view point of brittle fracture. The relation between the J-integral of the cracks existing in the stress concentrated regions and the local strain is investigated experimentally and theoretically with the aid of elastic-plastic finite element analysis. The finite element analysis and test results lead to the following conclusions : (1) A non-dimensionalised J, JE/(σ_Y^2a), computed in a plane stress condition for several kinds of stress concentrated regions with a short crack under tension gives a reasonably compact group of data, when plotted against the averaged strain across the assumed cracked area, e^^-. The upper bound of a J design curve is defined as follows : JE/(σ_Y^2a)=4(e^^-/e_Y)^2 for e^^-/e_Y<1 JE/(σ_Y^2a) =4(~/ e^^-/e_Y) for e^^-/e_Y⪈1 where E : Young's modulus, σ_Y : yield stress a : half length of crack, e_Y : yield strain (=σ_Y/E) (2) Use of this curve provides a good estimation for the brittle fracture from a crack existing in the stress and strain concentrated region.
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