球状黒鉛鋳鉄の低サイクル疲労における微小き裂伝ぱ則の検討

概要

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Plastic-strain-controlled low cycle fatigue tests were carried out using cylindrical specimens of two kinds of spheroidal graphite cast iron (ferritic ; FDI and pearlitic ; PDI). The relationship between plastic strain range and fatigue life was investigated in the two cast irons, and the propagation of small cracks was measured through successive observations by the plastic replica method. The fatigue life satisfies the relation of Manson-Coffin's type and the fatigue lives of the two cast irons are almost equal. That is, the difference in fracture ductility does not reflect the fatigue life. The behavior of a main crack is the factor controlling fatigue fracture and most part of fatigue life is consumed by the growth of a small crack. Crack growth rate dl/dN of the main crack is determined uniquely by σ_<a^n>l in these materials.
1995-09-25