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Modified 9Cr-1Mo 강의 크리프 균열성장 거동에 관한 통계적 해석
정익희 ( Ik Hee Jung ),김우곤 ( Woo Gon Kim ),윤송남 ( Song Nan Yin ),류우석 ( Woo Seog Ryu ),김선진 ( Seon Jin Kim ) 대한금속재료학회 ( 구 대한금속학회 ) 2009 대한금속·재료학회지 Vol.47 No.5
This paper dealt with a statistical analysis for evaluating the creep crack growth rate (CCGR) for Modified 9Cr-1Mo (ASTM Grade 91) steel. The CCGR data was obtained by the creep crack growth (CCG) tests conducted under various applied loads at 600℃. To obtain logically the B and q values used in the CCGR equation, three methods such as the least square fitting method (LSFM), the mean value method (MVM) and the probabilistic distribution method (PDM) were adopted and their CCGR lines were compared, respectively. In addition, a number of random variables were generated by using the Monte Carlo simulation (MCS), and the CCGR lines were predicted probabilistically. It was found that both the B and q coefficients followed a 2-parameter Weibull distribution well. In the case of the ranges of 10~90% for the probability variables, P(B, q), the CCGR lines were predicted. Fractographic study was conducted from the specimen after the CCG tests. (Received January 19, 2009)
윤송남(Song-Nan Yin),김우곤(Woo-Gon Kim),정익희(Ik-Hee Jung),김용완(Yong-Wan Kim) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
The nickel-based Hastelloy X alloy is one of the candidate materials for structural components of the high temperature gas-cooled reactor (HTGR). Its creep data was obtained from the creep tests under several stress levels at 950℃, and using this data, the creep behavior was investigated by the θ-projection model. The proper fitting range was determined from the creep curves at any stress level because the θ<SUB>i</SUB>-parameters are dependent on a fitting strain range. A stress dependency for the B-parameters was established to accurately predict the creep curve of a low stress level. The time to 1%-low strains was predicted for various stress levels, and the ratios between the time to 1%-low strain and time to rupture were lower than 15%. Also, a predicted minimum creep rate revealed a good agreement with the experimental data.
Alloy 617 의 장시간 크리프 수명 예측을 위한 다중회귀 선형 모델의 제안 및 평가
윤송남(Song-Nan Yin),김우곤(Woo-Gon Kim),정익희(Ik-Hee Jung),김용완(Yong-Wan Kim) 대한기계학회 2009 大韓機械學會論文集A Vol.33 No.4
Creep life prediction has been commonly used by a time-temperature parameter (TTP) which is correlated to an applied stress and temperature, such as Larson-Miller (LM), Orr-Sherby-Dorn (OSD), Manson-Haferd (MH) and Manson-Succop (MS) parameters. A stress-temperature linear model (STLM) based on Arrhenius, Dorn and Monkman-Grant equations was newly proposed through a mathematical procedure. For this model, the logarithm time to rupture was linearly dependent on both an applied stress and temperature. The model parameters were properly determined by using a technique of maximum likelihood estimation of a statistical method, and this model was applied to the creep data of Alloy 617. From the results, it is found that the STLM results showed better agreement than the Eno’s model and the LM parameter ones. Especially, the STLM revealed a good estimation in predicting the long-term creep life of Alloy 617.
세대유닛을 적용한 2차측 지역난방의 순환유량에 관한 연구
김용은(Kim Yong-Eun),박병식(Park Byung-Sik),정익희(Jung Ik-Hee),이재용(Lee Jae Yong),임용훈(Im Yong-Hoon),김혁주(Kim Hyouk-Ju),허만기(Heo Man-ki) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11
2pipe system and household substation is a method to reduce the heat loss of the pipe lines and manage efficiently. In this study, the proper conditions of circulation flow to adopt household substation was suggested. The experiment was conducted to investigate the characteristics of the household substation. And then annual operation of the 2pipe system with the household substation was simulated and evaluated. To keep the hot water temperature of final users, secondary supply temperature was decided by the result of the experiment and the simulation. Under the conditions which the secondary supply temperature is 50℃ and the temperature drop is less then 3℃, the circulation flow was derived. By using 2pipe system and household substation, annual heat loss was evaluated by approximately 25% reduction against present 4 pipe system.