最近の球状黒鉛鋳鉄の疲労強度に及ぼす黒鉛と人工微小欠陥の影響(破壊力学特集)

概要

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The fatigue strength of ductile cast irons is strongly influenced by small defects such as graphite, casting defects, etc. In order to investigate quantitatively the effects of these small defects, rotating bending fatigue tests of specimens containing an artificial small defect(hole or notch) as well as smooth specimens were performed on FCD400 and FCD700. The effect of the interaction between cracks or between a crack and a hole was dicsussed based on fracture mechanics. The microscopic observation of the surface and interior of specimens revealed that the fatigue limit is the threshold stress for propagation of a small crack emanating from a graphite or an artificial defect. Graphites distributed in the structure of current high-quality ductile cast irons are well separated so that the fatigue limit can be modelled regardless of interaction of graphites. Consequently, the fatigue limit is predicted by the Murakami and Endo's equation, which has been applied to many fatigue problems of metals containing a single defect or crack, in terms of √<area> for a maximum graphite or defect and the Vickers hardness H_V of matrix.
社団法人日本材料学会の論文
1994-10-15