フェライト系球状黒鉛鋳鉄の回転曲げおよびねじり疲労における微小き裂伝ぱ挙動

概要

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Rotating bending and torsional fatigue tests were carried out on the specimens of ferritic spheroidal graphite cast iron. The initiation and propagation of microcracks were investigated through the successive observations by the plastic replica method. The fatigue limits in both types of loading are determined by the limiting stress for crack propagation. That is, after 10^7 cycles of the stresses of fatigue limit, non-propagating cracks can be observed in both types of loading. The ratio of fatigue limit τ_w/σ_w is 0.86. The microcracks appear from both graphite and microshrinkage cavity in both types of loading. However, the crack which is related to final fracture appears from a microshrinkage cavity. The crack growth rate dl/dN of small cracks is determined uniquely by σ^<8.5>lin rotating bending and by τ^<9.0>l in reversed torsion.
一般社団法人日本機械学会の論文
1994-03-25