鋳肌を有するフェライト・パーライト球状黒鉛鋳鉄の疲労強度評価 : 疲労強度に及ぼす表面粗さ,組織遷移層および欠陥の影響

概要

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Ductile cast iron is often used for automobile parts as having cast surfaces with shot blast. Influences of surface roughness, microstructure transition layers, a lot of kinds of defects and residual stresses on fatigue strength are very complicated. The microstructure in the cast transition layer contains a work hardening layer due to shot blast and a pearlitic layer or a ferritic layer produced by casting. To clarify the effect of surface roughness, microstructure transition layers and defects on fatigue strength, tension-compression fatigue tests have been carried out on the specimens composed of a ferrite-pearlitic structure. The residual stresses were relieved by annealing to evaluate various factors independently. The fatigue strength has been evaluated using the √<area> parameter model. The effective defect size √<area>_<eff> with the interaction between surface roughness and defects has been defined so as to evaluate the effect of surface roughness on fatigue strength. The evaluation of the maximum defect size by statistics of extreme and the lower bound of the scatter of fatigue strength have been proposed for practical design.
社団法人日本機械学会の論文
2005-01-25