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,欠陥および残留応力の影響

概要

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In order to clarify the complex effects of surface roughness, transition of microstructures from surface to interior, defects and residual stress, tension-compression fatigue tests have been conducted by using shot blasted ferrite-pearlitic ductile cast irons with as-cast surfaces. Regardless of applied stress levels, the fracture origins of specimens were mostly at a defect near an as-cast surface, slag or pinhole, at N_f<10^7. At a relatively lower stress amplitude, some fatigue fractures occurred from an inner defect far from the surface, shrinkage, mostly at N_f>10^7. The √<area> parameter model was applied to the quantitative evaluation of fatigue limit. The equivalent hardness considering transitional layers and the effective defect size with the interaction between surface roughness and a defect were defined. Moreover, the relief of residual stress during fatigue tests was detected. The mean value of the relieved residual stress acting on a defect was employed for the quantitative evaluation. By using these parameters, the complex effects of ductile cast irons have been evaluated successfully for practical use.
社団法人日本機械学会の論文
2005-12-25