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および組織遷移層の影響

概要

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For evaluating fatigue strength of ductile cast irons, influences of many complicated factors such as surface roughness, transition of microstructures from surface to interior, defects and residual stresses must be considered separately. In order to clarify the effects of surface roughness and microstructure transition layers on fatigue strength, plane bending fatigue tests have been carried out on the specimens with as-cast surface, composed of ferritic and pearlitic structures. The residual stress introduced by shot blast to surface layers of a specimen was relieved by annealing in order to evaluate the independent influence of various factors separately. The fatigue strength has been evaluated by using the √<area> parameter model. Surface roughness was regarded to be mechanically equivalent to a defect. The size of the defect has been defined by the projected square root of area, √<area>_R. The equivalent hardness HV was also defined by considering microstructure transition layers. The evaluation method of the maximum defect size by statistics of extreme and the lower bound of the scatter of the fatigue strength have been proposed for practical design.
社団法人日本機械学会の論文
2005-02-25