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Fatigue properties of ultrafine grained low carbon steel produced by equal channel angular pressing

Title
Fatigue properties of ultrafine grained low carbon steel produced by equal channel angular pressing
Author
신동혁
Keywords
Low carbon steel; Equal channel angular pressing; Utrafine grain size; Fatigue; Crack; growth rate
Issue Date
2003-01
Publisher
ELSEVIER SCIENCE SA
Citation
Materials Science & Engineering A v.340, no.1, page.243-250
Abstract
Ultrafine grained low carbon (0.15 wt.% C) steel produced by equal channel angular pressing (ECAP) was tested for investigating fatigue properties, including cyclic softening and crack growth rate. Emphasis was placed on investigating the effect of load ratio on the fatigue crack growth rates of ultrafine grained microstructure. The ECAPed steel exhibited cyclic softening. After the first cycle, the tension and compression peak stresses decreased gradually with the number of cycles. Fatigue crack growth resistance and the threshold of ECAPed ultrafine grained steel were lower than that of an as-received coarse grained steel. This was attributed to a less tortuous crack path. The ECAPed steel exhibited slightly higher crack growth rates and a lower ΔKth with an increase in R ratio. The R ratio effect on growth rates and ΔKth was basically indistinguishable at a lower load ratio (R>0.3) compared with other alloys, indicating that the contribution of the crack closure vanished. This was explained by the fact that finer grained materials produce a lower opening load Pop due to a relatively less serrated crack path. Consequently, Kmin can reach Kop readily with a smaller increment of load ratio. The crack growth rate curve for the ECAPed ultrafine grained steel exhibited a linear extension to the lower growth rate regime than that for the coarse grained as-received steel. This behavior can be explained by a reverse crack tip plastic zone size (rp) that is always larger than the grain size.
URI
https://www.sciencedirect.com/science/article/pii/S0921509302001788https://repository.hanyang.ac.kr/handle/20.500.11754/155150
ISSN
0921-5093
DOI
10.1016/S0921-5093(02)00178-8
Appears in Collections:
COLLEGE OF ENGINEERING SCIENCES[E](공학대학) > MATERIALS SCIENCE AND CHEMICAL ENGINEERING(재료화학공학과) > Articles
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