Influence of Artificial Defect on Fatigue Limit in Austempered Ductile Iron

Title & Authors
Influence of Artificial Defect on Fatigue Limit in Austempered Ductile Iron
Kim, Min-Geon; Kim, Jin-Hak;

Abstract
Rotary bending fatigue tests were carried out to investigate the influence of artificial defects on fatigue limit in annealed and austempered ductile iron. Obtained main results are as follows : (1) Artificial defect(micro hole type, dia.<0.4 mm) on specimen surface did not bring about a obvious reduction of fatigue limit in austempered ductile iron(ADI) as compared with annealed ductile iron. (2) According to the investigation of $\small{\sqrt{area}_c}$ which is the critical defect size to crack initiation at artificial defect, $\small{\sqrt{area}_c}$ of ADI is larger than that of annealed ductile iron. This shows that the situation of crack initiation at artificial defect in ADI is more difficult in comparison with annealed ductile iron. (3) One of the reasons for the low rate of crack initiation from artificial defect in ADI is that the resistance of matrix to crack initiation is higher than that of annealed ductile iron. (4) In case that the $\small{\sqrt{area}}$ of artificial defect and graphite nodule is the same, the rate of crack initiation from graphite nodule is higher than that from artificial defect. This reason is that the serious ruggedness around graphite nodule is formed by austempering treatment.
Keywords
Fatigue;Fatigue Limit;Austempered Ductile Iron;Internal Defect;Artificial Defect;
Language
Korean
Cited by
1.
내부 결함을 고려한 주조 제품의 피로수명 예측을 위한 결함 형상단순화 해석모델,곽시영;김학구;

대한기계학회논문집A, 2011. vol.35. 10, pp.1243-1248
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