Low cycle fatigue behaviors of a type 316LN stainless steel in a high-temperature deaerated water산소가 제거된 고온 수화학환경에서의 316LN 스테인리스강의 저주기 피로거동

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The low cycle fatigue (LCF) tests of type 316LN austenitic stainless steel (SS) were carried out to investigate the cyclic hardening behaviors and the fatigue life in 310oC deaerated water. The strain rates were 0.008, 0.04, and 0.4 /s, and the applied strain amplitude varied from 0.4 to 1.0 %. The dissolved oxygen concentration of the test water was kept under 1 ppb. The relationship between the cyclic hardening and the dislocation structure was investigated using a transmission electron microscope (TEM). In additional, the environmentally assisted cracking (EAC) mechanisms were investigated by observation of the fatigue surfaces, the sectioned area, and the dislocation structure. The reliability of the experimental fatigue life data produced in the current study was evaluated by a comparison with the prediction models. In 310oC deaerated water, primary hardening behaviors were observed in all loading conditions. Primary hardening occurred during the LCF tests in 310oC deaerated water was caused by dynamic strain aging (DSA). The increase in the bulk dislocation density can induce an increase in flow stress, which is in good agreement with the enhancement of primary hardening. In addition, the tangled dislocations and the pinned dislocations formed in the bulk by solute atoms are responsible for the primary hardening. However, as mentioned previously, it is difficult to clarify the cause of primary hardening from the dislocation structure observation of the test-finished specimen. Thus, the LCF tests interrupted at the primary hardening stage and the further TEM observation are required to address the reason of the primary hardening. Secondary hardening behavior occurred for a strain amplitude of 0.4 % and a strain rate of 0.4 %/s. The pinned dislocations and strings of loops were found in the bulk and the corduroy contrast at the crack tip appeared at the loading condition where the secondary hardening occurred. Therefore, it is thought that the secondary har...
Advisors
Jang, Chang-Heuiresearcher장창희researcher
Description
한국과학기술원 : 원자력및양자공학과,
Publisher
한국과학기술원
Issue Date
2007
Identifier
268723/325007  / 020025883
Language
eng
Description

학위논문(박사) - 한국과학기술원 : 원자력및양자공학과, 2007. 8, [ xi, 120 p. ]

Keywords

fatigue; stainless steel; slip dissolution/oxidatoin; hydrogen-induced cracking; 피로; 스테인리스강; 슬립 용해/산화; 수소유기균열

URI
http://hdl.handle.net/10203/49001
Link
http://library.kaist.ac.kr/search/detail/view.do?bibCtrlNo=268723&flag=dissertation
Appears in Collection
NE-Theses_Ph.D.(박사논문)
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