Influence of mean stress on fatigue strength of ferritic-pearlite ductile cast iron with small defects

Because of their excellent mechanical properties, low cost and good workability, the application of ductile cast iron has been increased in various industries such as the automotive, construction and rail industries. For safety designing of the ductile cast iron component, it is necessary to underst...

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Bibliographic Details
Published in:Journal of physics. Conference series 2017-05, Vol.843 (1), p.12049
Main Authors: Deguchi, T, Kim, H J, Ikeda, T, Yanase, K
Format: Article
Language:English
Subjects:
Bending fatigue
Cast iron
Compression tests
Crack propagation
Defects
Diamond pyramid hardness
Fatigue cracks
Fatigue limit
Fatigue strength
Fatigue tests
Mechanical properties
Nodular iron
Pearlite
Physics
Stress propagation
Stress ratio
Tensile strength
Workability
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Summary:Because of their excellent mechanical properties, low cost and good workability, the application of ductile cast iron has been increased in various industries such as the automotive, construction and rail industries. For safety designing of the ductile cast iron component, it is necessary to understand the effect of stress ratio, R, on fatigue limit of ductile cast iron in the presence of small defects. Correspondingly in this study, rotating bending fatigue tests at R = −1 and tension-compression fatigue tests at R = −1 and 0.1 were performed by using a ferritic-pearlitic ductile cast iron. To study the effects of small defects, we introduced a small drilled hole at surface of a specimen. The diameter and depth of a drilled hole were 50, 200 and 500 μm, respectively. The non-propagating cracks emanating from graphite particles and holes edge were observed at fatigue limit, irrespective of the value of stress ratio. From the microscopic observation of crack propagation behavior, it can be concluded that the fatigue limit is determined by the threshold condition for propagation of a small crack. It was found that the effect of stress ratio on the fatigue limit of ductile cast iron with small defects can be successfully predicted based on area parameter model. Furthermore, a use of the tensile strength, σB, instead of the Vickers hardness, HV, is effective for fatigue limit prediction.
ISSN:1742-6588
1742-6596
DOI:10.1088/1742-6596/843/1/012049