• 한국압력기기공학회 논문집
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• 제19권2호
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• pp.102-108
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• 2023

A Chloride-induced stress corrosion cracking (CISCC) of austenite stainless steel in dry cask storage system (DCSS) can occur with extending service time than originally designed. Cold spray coating (CSC) not only form a very dense microstructure that can protect from corrosive environments, but also can generate compressive stress on the surface. This characteristic of CSC process is very helpful to increase the resistance for CISCC. CSC with several powders, such as 304L, 316L and Ni can be optimized to form very dense coating layer. In addition, the impact energy generated as the CSC powder collides with the surface of base metal at a speed of Mach 2 or more can remove the residual tensile stress of welding area and serve the compress stress. CSC layers include no oxidation and no contamination with under 0.2% porosity, which is enough to protect from the penetration of corrosive chloride. Therefore, the CSC coating layer can be accompanied by a function that can be disconnected from the corrosive environment and an effect of improving the residual stress that causes CISCC, so the canister's CISCC resistance can be increased.

• Corrosion Science and Technology
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• 제3권1호
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• pp.14-19
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• 2004

Crack growth rate and threshold stress intensity factor for stress corrosion cracking(SCC), $K_{ISCC}$ were measured for type 403 stainless steel in 3,5% NaCl solution at room temperature and SCC was monitored by electrochemical noise technique during $K_{ISCC}$ testing. In rising load test, pits were formed at the tip of pre-crack for the pre-cracked compact tension specimen unlike in smooth round specimen in which only unstable pits were observed and hence immune to SCC. Micro-cracks were found to initiate from the pits in the former specimen, and initiation of micro-crack as well as macro-crack was detected by electrochemical noise technique in rising load $K_{ISCC}$ tests. Crack growth rate increased with increasing either displacement rate or stress intensity factor at crack initiation and was higher in rising load $K_{ISCC}$ test compared to constant load $K_{ISCC}$ test at given stress intensities.

• 수산해양기술연구
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• 제36권2호
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• pp.132-138
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• 2000

The effect of fluid flow on corrosion and erosion-corrosion of metal is a well-recognized phenomenon in pipelines and machinery equipment, and so on. Not only are fluid hydrodynamics important, but also the corrosiveness of the process or production stream affects the corrosion system. Recent research demonstrates that it is possible to erosion-corrosion(E/C) phenomena in terms of hydrodynamics, electrochemical corrosion kinetics and film growth/removal phenomena. Stress corrosion cracking behavior under cavitation erosion-corrosion of mild steel(SS41) was investigated of base metal and weldment under loaded stress. Main result obtained are as follows : 1) The cavitation erosion sensitivity of base metal affected weight loss is more susceptive than heat affected zone, 2) The corrosion sensitivity affected weight loss of welding heat cycle is less susceptive on stress corrosion under cavitation erosion-corrosion than stress corrosion.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1992년도 봄 학술발표회 논문집
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• pp.143-147
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• 1992

Description of the behavior of the R.C structural members fixed on massive concrete is not normally generalization of recognized configuration for regular R.C. design guidanes. This can be due to the complexity of evaluation of internal resistancy and deflection changes of the members subjected to the various external forces. On the base of axially loaded member fixed on footing, however, the estimation of deflection changes due to flexural force shear force and rotational force is to be carried out in ways of specifying the bond characteristics of axial bars embedded in massive concrete. This work is to quantify adhesion of steel-concrete, initial concrete cracking stress near bar rib, maximum bond stress and residual stress in concrete respectively. In addition to quantification of them for particulate behavior, the suggestions of multi-linear bond stress-slip diagram made in carrying out finite element analyses for adhesion failure, examining concrete cracking status and reviewing existing experimental data lead to alternatively constructed relationship between bond stress and slip for a axial bars embedded massive concrete.

• 콘크리트학회논문집
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• 제17권4호
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• pp.631-635
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• 2005

Aggregate gradation effects on cracking-related displacements of concrete are investigated in the laboratory using the German cracking frame. Concrete workability was assessed by use of the slump and drop tests for two different concrete mixtures consisting of gap-graded and dense-graded aggregates. Shrinkage strain, cracking frame strain, and concrete strain were measured and used to compare to strength gain and creep development. The measured and calculated strains of the different aggregate gradations were compared each other. Gradation effects on strength and stress development relative to tensile cracking at saw-cut tip were also investigated. Test results revealed that the gap-graded concrete has indicated larger shrinkage and creep strains than dense-grade concrete perhaps because of its higher volume concrete of cement mortars in the mixture.

• 한국건축시공학회지
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• 제19권2호
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• pp.123-130
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• 2019

환경부하저감 및 동절기 시공의 효율을 위해 환경부하저감형 한중콘크리트 시공기술로서 고로슬래그시멘트와 내한촉진제를 병용한 콘크리트에 있어 열화의 기점이 되는 수축균열에 관해 검토했다. 그 결과, 고로슬래그시멘트 및 내한촉진제를 첨가함으로서 자유수축변형량 및 동일재령에 있어서 균열포텐셜은 증가하는 경향으로 구속조건하에서의 균열의 발생도 빠른 것을 확인할 수 있었다. 이것은, 자유수축변형량의 증가와 함께 크리프에 의한 응력 이완량의 감소나 구속도의 증가 등이 원인으로서 생각할 수 있으며, 동절기 시공에 있어서 고로슬래그 및 내한촉진제를 적용할 때는 수축에 의한 균열발생에 대해 검토할 필요가 있다고 판단된다.

• 한국전산구조공학회논문집
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• 제15권1호
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• pp.69-84
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• 2002

본 논문에서는 축방향 인장 부재의 균열거동과 철근콘크리트 부재의 인장강화현상을 고려하기 위한 새로운 해석적 기법을 제시하였다 균열 후 거동 규명을 위하여 부착응력-슬립의 관계나 부탁 응력의 분포를 가정하는 기존의 해석방법과는 달리, 철근과 콘크리트의 변형률 분포 함수를 다항식으로 가정하여, 이를 바탕으로 일축 인장부재의 균열 해석 기법을 구성하였다. 제시한 균열 해석모델은 기존의 해석기법과 비교하여, 철근콘크리트 구조물의 유한요소해석을 위한 균열 후의 평균 응력-변형률 관계를 정의하거나, 부재의 길이방향으로 철근과 콘크리트가 분담하는 하중 및 슬립량 산정시 매우 효율적이다. 제안된 모델을 이용하여 얻어진 균열하중과 보강철근의 신장률 값을 다른 해석기법 및 실험값과 비교한 결과 만족할만한 정확도를 보여주었다.

• Computers and Concrete
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• 제13권6호
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• pp.709-737
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• 2014

Fibre-reinforced self-compacting concrete (FRSCC) is a high-performance building material that combines positive aspects of fresh properties of self-compacting concrete (SCC) with improved characteristics of hardened concrete as a result of fibre addition. To produce SCC, either the constituent materials or the corresponding mix proportions may notably differ from the conventional concrete (CC). These modifications besides enhance the concrete fresh properties affect the hardened properties of the concrete. Therefore, it is vital to investigate whether all the assumed hypotheses about CC are also valid for SCC structures. In the present paper, the experimental results of short-term flexural load tests on eight reinforced SCC and FRSCC specimens slabs are presented. For this purpose, four SCC mixes - two plain SCC, two steel, two polypropylene, and two hybrid FRSCC slab specimens - are considered in the test program. The tests are conducted to study the development of SCC and FRSCC flexural cracking under increasing short-term loads from first cracking through to flexural failure. The achieved experimental results give the SCC and FRSCC slabs bond shear stresses for short-term crack width calculation. Therefore, the adopted bond shear stress for each mix slab is presented in this study. Crack width, crack patterns, deflections at mid-span, steel strains and concrete surface strains at the steel levels were recorded at each load increment in the post-cracking range.

• 한국재료학회지
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• 제19권1호
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• pp.1-6
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• 2009

In this study, the stress-strain response and the cracking behaviors of ITO film on a PET substrate are investigated. The cracking behaviors of ITO thin films deposited on a thermoplastic semi-crystalline polymer developed for flexible display applications was investigated by means of tensile experiments equipped with an electrical measurement apparatus and an in-situ optical microscope. Electrical resistance increased gradually in the elastic-to-plastic transition region of the stress strain curves and cracks formed. Numerous cracks were found in this region, and the increase of the resistance was linked to the cracking of ITO thin films. Upon loading, the initial cracks perpendicular to the tensile axis were observed at about 1% of the total strain. They propagated to the entire sample width as the strain increased. The spacing between the horizontal cracks is thought to be determined by the fracture strength and the thickness of the ITO film as well as by the interfacial strength between the ITO and PET. The effect of the strain rate on the cracking behavior was also investigated. The crack density increased as the strain increased. The spacing between the horizontal cracks (perpendicular to the stress axis) increased as the strain rate decreased. The increase of the crack density as the strain rate decreased can be attributed to the higher fraction of the plastic strain to the total strain at a given total strain. The higher critical strain for the onset of the increase in the resistance and the crack initiation of the ITO/PET with a thinner ITO film (300 ohms/sq.) suggests a higher strength of the thinner ITO film.

• Nuclear Engineering and Technology
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• 제49권4호
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• pp.817-824
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• 2017

Residual stress is a critical element in determining the integrity of parts and the lifetime of welded structures. It is necessary to estimate the residual stress of a welding zone because residual stress is a major reason for the generation of primary water stress corrosion cracking in nuclear power plants. That is, it is necessary to estimate the distribution of the residual stress in welding of dissimilar metals under manifold welding conditions. In this study, a cascaded support vector regression (CSVR) model was presented to estimate the residual stress of a welding zone. The CSVR model was serially and consecutively structured in terms of SVR modules. Using numerical data obtained from finite element analysis by a subtractive clustering method, learning data that explained the characteristic behavior of the residual stress of a welding zone were selected to optimize the proposed model. The results suggest that the CSVR model yielded a better estimation performance when compared with a classic SVR model.