• 제목/요약/키워드: creep life

검색결과 270건 처리시간 0.036초

증기 터빈축 강재의 장시간 크리프 수명 예측법 개선 (Improvement of long-time creep life prediction of steam turbine rotor steel)

  • 오세규;정순억;전태언
    • 한국해양공학회지
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    • 제10권1호
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    • pp.47-52
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    • 1996
  • This paper deals with a study on improvement of long-time creep life prediction of steam turbine rotor steels by using initial strain method as a new approach at high temperatures of 500 to 70$0^{\circ}C$ . The main result shows that the inital strain method could be reliably utilized to predict and evaluate the long-time creep life as creep rupture strength and that the predicting equation for long-time creep life under a certain creep stress at a certain high temperature could be empirically derived out from each initial instantaneous strain measured.

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스테인리스 강의 단시간 크리프 파단시간의 변동성과 수명예측 (Variability of Short Term Creep Rupture Time and Life Prediction in Stainless Steels)

  • 정원택;공유식;김선진
    • 한국해양공학회지
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    • 제24권6호
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    • pp.97-102
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    • 2010
  • This paper deals with the variability of short term creep rupture time based on previous creep rupture tests and the statistical methodology of the creep life prediction. The results of creep tests performed using constant uniaxial stresses at 600, 650, and $700^{\circ}C$ elevated temperatures were used for a statistical analysis of the inter-specimen variability of the short term creep rupture time. Even under carefully controlled identical testing conditions, the observed short-term creep rupture time showed obvious inter-specimen variability. The statistical aspect of the short term creep rupture time was analyzed using a Weibull statistical analysis. The effect of creep stress on the variability of the creep rupture time was decreased with an increase in the stress level. The effect of the temperature on the variability also decreased with increasing temperature. A long term creep life prediction method that considers this statistical variability is presented. The presented method is in good agreement with the Lason-Miller Parameter (LMP) life prediction method.

크리프 파단 데이터의 변동성에 대한 새로운 고찰과 수명예측 (New Considerations on Variability of Creep Rupture Data and Life Prediction)

  • 정원택;공유식;김선진
    • 대한기계학회논문집A
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    • 제33권10호
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    • pp.1119-1124
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    • 2009
  • This paper deals with the variability analysis of short term creep rupture test data based on the previous creep rupture tests and the possibility of the creep life prediction. From creep tests performed by constant uniaxial stresses at 600, 650 and $700^{\circ}C$ elevated temperature, in order to investigate the variability of short-term creep rupture data, the creep curves were analyzed for normalized creep strain divided by initial strain. There are some variability in the creep rupture data. And, the difference between general creep curves and normalized creep curves were obtained. The effects of the creep rupture time (RT) and steady state creep rate (SSCR) on the Weibull distribution parameters were investigated. There were good relation between normal Weibull parameters and normalized Weibull parameters. Finally, the predicted creep life were compared with the Monkman-Grant model.

박판 크리프 수명평가에 마찰계수의 영향 (Effects of Friction Coefficient on Creep Life Assessment of Sheet)

  • 정지용;임지우;금영탁
    • 소성∙가공
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    • 제19권7호
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    • pp.435-440
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    • 2010
  • The creep life of 9Cr1MoVNb steel, in terms of Larson-Miller parameter(LMP), was evaluated by small punch(SP) creep simulation and verified by uniaxial creep test. By employing the elastoplastic FEM(finite element method), the small punch creep behaviors associated with various friction coefficients were simulated to identify a real friction phenomena. The friction coefficient, ${\mu}$=0.7, determined by comparing deflection history was used in the small punch creep simulation to find the equivalent stresses with which the relationship between punch load and uniaxial creep stress was found. The creep life was then predicted by the LMP, which was the relationship among the rupture time, temperature, and stress. Finally, the LMP calculated by SP-creep simulation was compared with that had computed by the uniaxial creep test and fairly matched LMPs were found.

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

  • 이상국;정민화;오세규;송정근
    • 한국해양공학회지
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    • 제12권2호통권28호
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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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소형펀치-크리프 시험에 의한 9Cr1MoVNb강의 고온 크리프 특성 평가 연구 (A Study on Evaluation of High Temperature Creep Properties of 9Cr1MoVNb Steel by Small Punch-Creep test)

  • 유효선;나성훈;백승세;권일현;안병국;나의균
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2000년도 추계학술대회논문집A
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    • pp.99-104
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    • 2000
  • This paper describes the high temperature creep characteristics for virgin material of 9Cr1MoVNb steel using small punch creep(SP-Creep) test technique which is developing recently. In addition, the several results of SP-Creep test are compared with that of 2.25Cr- 1Mo steel which is widely used as boiler materials and that of conventional uniaxial creep test. The obtained SP-Creep curves show the creep behaviors of three regimes like that obtained from conventional uniaxial creep test, and SP-Creep properties are definitely depended on applied load and test temperature. The correlation of SP-Creep rate and creep rupture life with applied load has been determined like the correlation between creep rate/rupture life and stress in uniaxial creep test, and also is satisfied with Power law. The creep rupture times of newly 9Cr1MoVNb steel are higher than those of 2.25Cr1Mo steel at the same creep temperature and applied loading condition, and the decrease extent of creep rupture life with loads is very lower compared with 2.25Cr1Mo steel.

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3.5Ni-Cr-Mo-V 강의 크리프 수명예측에 재질열화 및 오스테나이트 결정립 조대화가 미치는 영향 (Effect of Material Degradation and Austenite Grain Coarsening on the Creep life Prediction in 3.5 Ni-Cr-Mo-V Steel)

  • 홍성호;조현춘
    • 대한기계학회논문집
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    • 제18권11호
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    • pp.2837-2845
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    • 1994
  • Several methods have been developed to predict on the remaining life of the old power plants. However, Larson-Miller parameter, one of existing creep life prediction methods, has not reflected the effect of material degradatioin and grain size. So this study has been carried out to research the effects of material degradation and austenite grain coarsening on the life prediction of 3.5Ni-Cr-Mo-V steel. An experimental result shows that carbide coarsening has no significant effects on the creep rupture life and the Larson-Miller parameter, but grain coarsening has an important influence on the creep ruptrure life and the Larson-Miller parameter. Therefore Larson-Miller constant, K should be determined to consider on the chemical composition and the grain size of materials.

인공 신경망을 이용한 크리프-피로 상호작용시 수명예측기법에 관한 연구 (A Study on the Life Prediction Method using Artificial Neural Network under Creep-Fatigue Interaction)

  • 권영일;김범준;임병수
    • 한국자동차공학회논문집
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    • 제9권6호
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    • pp.135-142
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    • 2001
  • The effect of tensile hold time on the creep-fatigue interaction in AISI 316 stainless steel was investigated. To study the fatigue characteristics of the material, strain controlled low cycle fatigue(LCF) tests were carried out under the continuous triangular waveshape with three different total strain ranges of 1.0%, 1.5% and 2.0%. To study the creep-fatigue interaction, 5min., 10min., and 30min. of tensile hold times were applied to the continuous triangular waveshape with the same three total strain ranges. The creep-fatigue life was found to be the longest when the 5min. tensile hold time was applied and was the shortest when the 30min. tensile hold time was applied. The cause fur the shortest creep-fatigue life under the 30min. tensile hold time is believed to be the effect of the increased creep damage per cycle as the hold time increases. The creep-fatigue life prediction using artificial neural network(ANN) showed closer prediction values to the experimental values than by the modified Coffin-Manson method.

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STS 316L 스테인리스강의 크리프 수명예측 (Creep Life Prediction of SUS 316L Stainless Steel)

  • 윤종호;황경충
    • 한국자동차공학회논문집
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    • 제14권2호
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    • pp.16-22
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    • 2006
  • Stainless steel has widely been used in various industrial fields because it has high corrosion resistance. But, we have little design data about the creep life prediction of SUS316L stainless steel. Therefore, in this study, a series of creep tests and study on them under 16 constant stress and temperature combined conditions have been performed to get the creep design data and life prediction of SUS316L stainless steels and we have gotten the following results. First, the stress exponents decrease as the test temperatures increase. Secondly, the creep activation energy gradually decreases as the stresses become bigger. Thirdly, the constant of Larson-Miller parameters on this alloy is estimated about 10. And last, the creep rupture fractographs show the intergranular ductile fracture with many dimples.

최소구속법을 이용한 Type 316LN 강의 크리프 수명 예측 (Creep Life Prediction of Type 316LN Steel Using Minimum Commitment Method)

  • 김우곤;윤송남;류우석;이원
    • 한국정밀공학회:학술대회논문집
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    • 한국정밀공학회 2005년도 추계학술대회 논문집
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    • pp.295-298
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    • 2005
  • A minimum commitment method (MCM) was applied to predict the creep rupture life of type 316LN SS. For this purpose, a number of the creep rupture data for the type 316LN SS were collected through literature survey and experimental data of KAERl, Using the short-term creep rupture data under 2000 hr, the long-term creep rupture life above $10^5$ hour was predicted by means of the MCM. An optimum value of A, P and G function, used in the MCM equation, was determined respectively, and the creep rupture life with the A values in different temperatures was compared with the experimental data and the predicted curves.

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