• 대한금속재료학회지
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• 제49권2호
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• pp.112-120
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• 2011

The out-of-phase thermo-mechanical fatigue (OP TMF) in a <001> oriented single crystal nickel-based superalloy CMSX-4 has been studied. OP TMF life was less than a half of low cycle fatigue(LCF) life in spite of a small hysteresis loop area of OP TMF compared to that of LCF. The failure was caused by the initiation of a crack at the oxide-layered surface followed by its planar growth along the <100> ${\gamma}$ channel in both LCF and OP TMF. However, deformation twins appeared near the major crack of OP TMF. The multiple groups of parallel twin plates on {111} planes provided a preferential path for crack propagation, which caused a significant decrease in OP TMF life. Additionally, the analysis on the surface crack morphology revealed that the tensile strain at the minimum temperature of OP TMF was found to accelerate the crack propagation.

• 대한기계학회논문집A
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• 제41권3호
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• pp.193-198
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• 2017

Alloy 617은 초고온가스로(VHTR)의 중간열교환기(IHX)의 유력한 후보 재료 중의 하나이다. $850^{\circ}C$의 고온에서 Alloy 617 용접재의 저사이클 피로 거동을 고찰하기 위하여, 완전 양진 변형률제어 피로시험이 0.6에서 1.5%의 전변형률범위에서 수행되었다. 용접재 시험편은 V-그루브 형상의 가스텅그스텐아크 용접한 용접 패드로부터 가공되었다. 피로수명은 전변형률범위가 증가할수록 감소하였다. 모든 실험조건에서 Alloy 617 용접재 시험편의 반복 응력 반응 거동은 초기 수 사이클에서 반복 변형률 경화현상을 나타내었다. 또한 모든 피로 균열의 발생과 전파는 입내파괴의 파손 모드를 보였다.

• 대한기계학회논문집A
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• 제21권10호
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• pp.1626-1635
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• 1997

It is important to ensure the reliability of the first localized reactor vessel steel. To satisfy with this purpose, a study on the impact/hardness, low cycle fatigue(LCF), crack growth rate(da/dN) and fracture toughness( ) of base material(BM) and weld metal(WM) were performed under room temperature air and corrosion conditions. A summary of the results is as folows : (1) Charpy impact absorbed energy of BM was the highest value, heat affected zoon(HAZ) and the lowest, WM. The hardness of BM was similar to HAZ. (2) Coefficients of Manson equation using the monotonic tensile test data were obtained for the present material. (3) The effects of stress ratio and ambient (120.deg. C and NaCl) condition on da/dN were investigated, da/dN with NaCl condition expressed the highest value. (4) The results of Charpy V-notch impact test had good correlation with $K_{IC}$ characteristics and the lowest curve of $K_{IC}$ for BM was derived, more researches about WM and HAZ are required hereafter.

• Structural Engineering and Mechanics
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• 제66권2호
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• pp.151-160
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• 2018

With the aim to evaluate the fatigue damage accumulation and predict the residual life of engineering components under variable amplitude loadings, this paper proposed a new strain energy-based damage accumulation model by considering both effects of mean stress and load interaction on fatigue life in a low cycle fatigue (LCF) regime. Moreover, an integrated procedure is elaborated for facilitating its application based on S-N curve and loading conditions. Eight experimental datasets of aluminum alloys and steels are utilized for model validation and comparison. Through comparing experimental results with model predictions by the proposed, Miner's rule, damaged stress model (DSM) and damaged energy model (DEM), results show that the proposed one provides more accurate predictions than others, which can be extended for further application under multi-level stress loadings.

• 한국항공우주학회지
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• 제31권3호
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• pp.15-22
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• 2003

피로균열성장모델을 유도하고 지연모델을 제안하였다. 피로균열성장모델은 피로균열선단의 소성변형으로 인하여 균열표면에 발생하는 잔류소성스트레치를 고려하고 있다. 균열 성장률은 균열선단 재료요소의 소성변형에너지와 누적피로손상으로부터 계산된다. 유도한 균열성장모델로부터 계산한 균열성장률은 AL6061-T651과 17-4PH 주강의 시험결과와 잘 일치하고 있다. 피로균열성장지연모델은 인장과대하중으로부터 생성된 잔류소성스트레치를 근거로 하고 있으며, 인장과대하중은 다음 하중 사이클의 소성변형률을 감소시킨다. Strip-yield모델을 이용하여 균열선단의 소성역을 계산하였다. 새로 제안된 지연모델은 인장과대하중하의 피로균열선장특성 및 지체지연 현상을 잘 기술하고 있다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2010년 춘계학술대회논문집
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• pp.468-472
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• 2010

To develop the Exhaust Maniverter(Manifold and converter) it needs to consider flow characteristics related to durability and performance of the catalyst, manufacturability, etc. This paper presents the analysis results regarding to flow characteristics such as flow uniformity, tangential speed, O2 sensor sensitivity and CHT (conjugate heat transfer) for the LCF(Low Cycle Fatigue) for gasoline 2.0 liter engine. The results are satisfactorily corresponded to the general criteria. Also skin temperature and pressure drop wire measured at the Engine Bench. These results can be useful for the design guide for Exhaust Maniverter.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.126-131
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• 2001

Materials property data are necessary to secure the reliability of failure prevention techniques such as inspection and remaining life assessment of civil infrastructure and industrial facilities. However, there is no properly collected data in Korea, and those foreign data are hard to use because of the scattering of the sources, the difference of standards, etc. In this paper, materials property database system which has been constructed at Korea Research Institute of Standards and Science is introduced. Constructed database contains 145,000 numeric data of materials property for 600 kinds of metals and can be retrieved on the internet. The database system provides graphical user interface-based information searching functions necessary for the life evaluation and safety analysis.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 춘계학술대회 논문요약집
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• pp.90-90
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• 2004

반도체 집적회로 제작 기술을 기반으로 하여 각종 물리량 감지를 위한 미세기계구조물과 각종 물리량의 전기신호로의 변화, 증폭, 보정을 위한 전자회로를 동시에 제작하여 하나의 칩 상에 집적화시킬 수 있는 MEMS 기술이 등장하게 됨에 따라 센서의 소형화, 경량화, 다기능화, 고성능화와 함께 비용을 최소화할 수 있는 장점을 가진 반도체 센서가 급격하게 개발되어 자동차 산업에 상용화되고 있다. 특히 반도체 압력센서는 엔진 제어용 MAP센서에서 가장 먼저 상품화되었으며, 현재 타이어압 센서 그리고 탱크 연료압력센서가 상품화되었고, 에어콘 압력 센서등도 실리콘 센서로 대체하기 위한 단계에와 있다.(중략)