高強度・高靱性球状黒鉛鋳鉄の疲労信頼性に関する基礎的研究 : 第2報, オーステンパ球状黒鉛鋳鉄の疲労強度に及ぼす微小欠陥の影響

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In order to estimate fatigue reliability of austempered ductile iron (ADI) with austempered ferrite-retained austenite dual structures, the influence of casting defects on the fatigue strength was examined through fractography. Fatigue testing as conducted under tension-tension loading, R=0. 05. It was found through fractography that the fatigue crack initiated at the micro porosity. This, the fatigue life, N, was mutually related to a presented parameter K_a=2S √<πa>, where S is the stress amplitude and as the dimension of micro defect initiating a fatigue crack. By comparing ADI with spheroidal graphite iron of full pearlite matrix structure in using K_a-N diagrams, it could be understood that austempered Ferrite-retained Austenite dual structures had higher resistance against the meso scopic crack initiating at the micro porosity than the full pearlite matrix structure.
1995-05-25