• Title/Summary/Keyword: Creep Life Estimation

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Creep Property Assessment and Creep Life Estimation for High-Temperature Tube Material(2.25Cr1Mo Steel) in Power Plants by LMP (발전용 고온 배관재료 2.25Cr1Mo 강의 크리프 특성과 LMP에 의한 크리프 수명의 예측)

  • Lee, Sang-Guk;Jeong, Min-Hwa;O, Se-Gyu;Song, Jeong-Geun
    • Journal of Ocean Engineering and Technology
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    • v.12 no.2 s.28
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    • pp.65-70
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    • 1998
  • In this report, the creep properties and creep life estimation by Larson-Miller Parameter(LMP) Method for 2.25Cr1Mo steel to be used as power plant tubes or other components were presented at the high temperatures of 500, 550, and $600^{\circ}C$. It was confirmed experimentally and quantitatively that a creep life estimation equation at such various high temperatures was well derived by LMP and could be used very effectively within the creep life of 10$^3$ hours, but very unreliable and even dangerous for design in a long term of creep life such as 10$^4$ or $10^5$ hours.

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Evaluation of Creep Behaviors of Alloy 690 Steam Generator Tubing Material (Alloy 690 증기발생기 전열관 재료의 크리프 거동 평가)

  • Kim, Jong Min;Kim, Woo Gon;Kim, Min Chul
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.15 no.2
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    • pp.64-70
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    • 2019
  • In recent years, attention has been paid to the integrity of steam generator (SG) tubes due to severe accident and beyond design basis accident conditions. In these transient conditions, steam generator tubes may be damaged by high temperature and pressure, which might result in a risk of fission products being released to the environment due to the failure. Alloy 690 which has increased the Cr content has been replaced for the SG tube due to its high corrosion resistance against stress corrosion cracking (SCC). However, there is lack of research on the high temperature creep rupture and life prediction model of Alloy 690. In this study, creep test was performed to estimate the high temperature creep rupture life of Alloy 690 using tube specimens. Based on manufacturer's creep data and creep test results performed in this study, creep life prediction was carried out using the Larson-Miller (LM) Parameter, Orr-Sherby-Dorn (OSD) parameter, Manson-Haford (MH) parameter, and Wilshire's approach. And a hyperbolic sine (sinh) function to determine master curves in LM, OSD and MH parameter methods was used for improving the creep life estimation of Alloy 690 material.

Mechanical Reliability(Life-Time) Estimation for 25.8kV Eco Solid Insulated Switchgear (25.8kV급 친환경 고체절연차단기(Solid Insulated Switchgear)에 대한 기계적 신뢰성(수명) 평가)

  • Lee, Do-Hoon;Lee, Seog-Won;Park, Seok-Weon;Kim, Young-Geun;Lee, Jhong-Ho
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.59 no.2
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    • pp.202-205
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    • 2010
  • In this paper, mechanical reliability(Life-time) estimation method for 25.8kV SIS(Solid Insulated Switchgear) has been studied. Recently enacted KEPCO's standard includes clause that have to submit a warrantable reliability data for life-time(over B10 25 years) of an epoxy-solid insulating material. Accordingly, this research was carried out on the ALT(Accelerated Life Test) and Life-Estimation method for SIS's insulating material. Mechanical life-time estimation for SIS's insulating material is to verify reliability for tensile creep & fatigue stress, which is the major mechanical stress of SIS. This study proved that SIS's reliability for mechanical stress and established that confidence for estimation results in further verification test.

Assessment of Creep Properties of 9Cr Steel Using Small Punch Creep Testing (소형펀치 크리프 시험을 이용한 9Cr강의 크리프 상수 평가)

  • Yun, Gi-Bong;Park, Tae-Gyu;Sim, Sang-Hun;Jeong, Il-Seok
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.25 no.9
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    • pp.1493-1500
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    • 2001
  • Recently small punch creep testing (or miniature disc bend creep test) has received much attention through European collaborative research projects. This method was considered as a substitute for the conventional creep rupture testing by which the residual creep life is measured from the specimen taken out from serviced components of high temperature plants. It would be beneficial if the material creep properties such as power law creep constants as well as the creep rupture life can be measured from the small punch creep test. In this paper a method of assessing creep constants from the small punch creep testing is proposed. Finite element analyses were performed to investigate evolution of stress and strain rate at the weakest locations of the small punch creep specimen. Elastic-plastic-secondary creep analyses were carried out. The estimation equations for creep constants by the small punch creep testing are proposed based on the finite analysis results. Small punch creep tests were also performed with 9Cr steel and the accuracy of the proposed equation was verified by the experimental results.

Assessment of Material Properties Using Finite Element Analysis for Small Punch Creep Testing (SP 크리프 시험의 유한요소해석을 이용한 재료물성 평가)

  • Park, Tae-Kyu;Ma, Young-Wha;Yoon, Kee-Bong;Jeong, Ill-Seok
    • Proceedings of the KSME Conference
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    • 2001.06a
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    • pp.511-516
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    • 2001
  • Recently small punch creep testing (or miniature disc bend creep test) has received much attention through European collaborative research projects. This method was considered as a substitute for the conventional creep rupture testing by which the residual creep life is measured from the specimen taken out from serviced components of high temperature plants. It would be beneficial if the material creep properties such as power law creep constants as well as the creep rupture life can be measured from the small punch creep test. In this paper a method of assessing creep constants from the small punch creep testing is proposed. Finite element analyses were performed to investigate evolution of stress and strain rate at the weakest locations of the small punch creep specimen. Elastic-plastic-secondary creep analyses were carried out. The estimation equations for creep constants by the small punch creep testing are proposed based on the finite analysis results. Small punch creep tests were also performed with 9Cr steel and the accuracy of the proposed equation was verified by the experimental results.

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Suggestion and Evaluation of a Multi-Regression Linear Model for Creep Life Prediction of Alloy 617 (Alloy 617의 장시간 크리프 수명 예측을 위한 다중회귀 선형 모델의 제안 및 평가)

  • Yin, Song-Nan;Kim, Woo-Gon;Jung, Ik-Hee;Kim, Yong-Wan
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.33 no.4
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    • pp.366-372
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    • 2009
  • 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.

Reliability Estimation of Door Hinge for Home Appliances (가전제품용 경첩의 신뢰성 추정)

  • 문지섭;김진우;이재국;이희진;신재철;김명수
    • Proceedings of the Korean Reliability Society Conference
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    • 2004.07a
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    • pp.303-311
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    • 2004
  • This paper presents the reliability estimation of door hinge for home appliances, which consists of bushing and shaft. The predominant failure mechanism of bushing made of polyoxymethylene(POM) is brittle fracture due to decrease of strength caused by voids existing, and that of shaft made of acrylonitrile-butadiene-styrene(ABS) is creep due to plastic deformation caused by excessive temperature and lowering of glass transition temperature by absorbed moisture. Since the brittle fracture of bushing is overstress failure mechanism, the load-strength interference model is used to estimate the failure rate of it along with failure analysis. By the way, the creep of shaft is wearout failure mechanism, and an accelerated life test is then planned and implemented to estimate its lifetime. Through the technical review about failure mechanism, temperature and humidity are selected as accelerating variables. Assuming Weibull lifetime distribution and Eyring model, the life-stress relationship and acceleration factor, B$_{10}$ life and its lower bound with 90% confidence at worst case use condition are estimated by analyzing the accelerated life test data.a.

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Reliability Estimation of Door Hinge for Rome Appliances (가전제품용 경첩의 신뢰성 추정)

  • Kim Jin Woo;Shin Jae Chul;Kim Myung Soo;Moon Ji Seob
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.29 no.5 s.236
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    • pp.689-697
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    • 2005
  • This paper presents the reliability estimation of door hinge for home appliances, which consists of bushing and shaft. The predominant failure mechanism of bushing made of polyoxymethylene(POM) is brittle fracture due to decrease of strength caused by voids existing, and that of shaft made of acrylonitrile-butadiene-styrene(ABS) is creep due to plastic deformation caused by excessive temperature and lowering of glass transition temperature by absorbed moisture. Since the brittle fracture of bushing is overstress failure mechanism, the load-strength interference model is used to estimate the failure rate of it along with failure analysis. By the way, the creep of shaft is wearout failure mechanism, and an accelerated life test is then planned and implemented to estimate its lifetime. Through the technical review about failure mechanism, temperature and humidity are selected as accelerating variables. Assuming Weibull lifetime distribution and Eyring model, the life-stress relationship and acceleration factor, $B_{10}$ life and its lower bound with $90\%$ confidence at worst case use condition are estimated by analyzing the accelerated life test data.

Creep life Prediction for W.M. of High Cr-Mo Steel using Modified Power-law (고 Cr-Mo강의 수정멱수법칙을 이용한 W.M. 크리프 수명예측)

  • An, Jong-Kyo;Yu, Hyo-Sun;Yang, Sung-Mo;Kang, Hee-Yong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.32 no.11
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    • pp.951-956
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    • 2008
  • The high temperature creep properties of the generating plant's high temperature tube, pipe and header and such are very significant in accordance with long-time exposure to the high temperature and pressure environment. Not only this, but as the welding procedure is compulsory for the cohesion of components, the creep properties regarding the local microstructures of steel weldment are very important. In order to understand the creep properties regarding the local microstructures of steel weldment, the SP-Creep test which is easy to get sample from the field component was conducted. The local microstructure of steel weldment, that is, W.M. and B.M.'s microstructures were observed using the SEM. The rupture time of W.M. was longer as 110 % averagely in a same condition, which is the consequence of the difference of the microstructure. Each lethargy coefficient of B.M. and W.M. is evaluated by the relation among the temperature, load and the rupture time from SP-Creep Test. The life estimation equation can be induced by the transformation of Power-law. B.M. and W.M. for each $550\;^{\circ}C$ and $575\;^{\circ}C$, the very similar to normal temperature of the domestic thermal power generation in working, are estimated.

Taylor Series-Based Long-Term Creep-Life Prediction of Alloy 617 (Taylor 급수를 이용한 617 합금의 장시간 크리프 수명 예측)

  • Yin, Song-Nan;Kim, Woo-Gon;Park, Jae-Young;Kim, Soen-Jin;Kim, Yong-Wan
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.34 no.4
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    • pp.457-465
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    • 2010
  • In this study, a Taylor series (T-S) model based on the Arrhenius, McVetty, and Monkman-Grant equations was developed using a mathematical analysis. In order to reduce fitting errors, the McVetty equation was transformed by considering the first three terms of the Taylor series equation. The model parameters were accurately determined by a statistical technique of maximum likelihood estimation, and this model was applied to the creep data of alloy 617. The T-S model results showed better agreement with the experimental data than other models such as the Eno, exponential, and L-M models. In particular, the T-S model was converted into an isothermal Taylor series (IT-S) model that can predict the creep strength at a given temperature. It was identified that the estimations obtained using the converted ITS model was better than that obtained using the T-S model for predicting the long-term creep life of alloy 617.