12th International Conference on Damage Assessment of Structures | |
Fatigue limit prediction of ferritic-pearlitic ductile cast iron considering stress ratio and notch size | |
Deguchi, T.^1 ; Kim, H.J.^2,3 ; Ikeda, T.^4 | |
Graduate School of Engineering, Fukuoka University, 8-19-1, Nanakuma, Jonan-ku, Fukuoka | |
814-0180, Japan^1 | |
Department of Mechanical Engineering, Fukuoka University, 8-19-1, Nanakuma, Jonan-ku, Fukuoka | |
814-0180, Japan^2 | |
Institute of Materials Science and Technology, Fukuoka University, 8-19-1, Nanakuma, Jonan-ku, Fukuoka | |
814-0180, Japan^3 | |
RandD Center HINODE, Ltd., Iwasaki, Harakoga, Miyaki-cho, Miyaki-gun, Saga | |
849-0101, Japan^4 | |
关键词: Area parameter model; Fatigue limit prediction; Fracture mechanics approach; Material parameter; Mechanical behavior; Microscopic observations; Tension-compression; Threshold condition; | |
Others : https://iopscience.iop.org/article/10.1088/1742-6596/842/1/012067/pdf DOI : 10.1088/1742-6596/842/1/012067 |
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来源: IOP | |
【 摘 要 】
The mechanical behavior of ductile cast iron is governed by graphite particles and casting defects in the microstructures, which can significantly decrease the fatigue strength. In our previous study, the fatigue limit of ferritic-pearlitic ductile cast iron specimens with small defects (√area = 80 ∼1500 μm) could successfully be predicted based on the √area parameter model by using √area as a geometrical parameter of defect as well as the tensile strength as a material parameter. In addition, the fatigue limit for larger defects could be predicted based on the conventional fracture mechanics approach. In this study, rotating bending and tensioncompression fatigue tests with ferritic-pearlitic ductile cast iron containing circumferential sharp notches as well as smooth specimens were performed to investigate quantitatively the effects of defect. The notch depths ranged 10 ∼ 2500 μm and the notch root radii were 5 and 50 μm. The stress ratios were R = -1 and 0.1. The microscopic observation of crack propagation near fatigue limit revealed that the fatigue limit was determined by the threshold condition for propagation of a small crack emanating from graphite particles. The fatigue limit could be successfully predicted as a function of R using a method proposed in this study.
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