• 제목/요약/키워드: CUF(cumulative fatigue usage factor)

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노즐의 피로해석에 미치는 용접잔류응력의 영향 (Effect of Weld Residual Stress on Fatigue Analysis of Nozzle)

  • 김상철;김만원
    • Journal of Welding and Joining
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    • 제32권1호
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    • pp.71-78
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    • 2014
  • Although the fatigue design curve of ASME Code has enough margin with respect to alternating stress and cycles, the welding residual stress(WRS) should be included in fatigue analysis. In this paper, WRS distribution in a nozzle with dissimilar metal weldment was obtained by finite element analysis and was added in fatigue analysis. The fatigue analysis was performed by following the ASME Code including thermal and stress analysis applying with postulated 30 transient conditions. The calculated results of a cumulative fatigue usage factors(CUF) were compared for the case of the models with or without WRS effects. The results showed that the CUF at weldment and heat affected zone was affected by the WRS.

원자로 직접주입노즐의 피로평가에 미치는 응력집중계수의 영향 (Effect of Stress Concentration Factors on the Fatigue Evaluation of the Direct Vessel Injection Nozzle)

  • 김태순;이재곤
    • 한국안전학회지
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    • 제25권6호
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    • pp.53-59
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    • 2010
  • A fatigue damage caused by cyclic load is considered as one of the important failure mechanisms that threaten the integrity of structures and components in a nuclear power plant. In ASME code section III NB, the fatigue analysis procedure and standard S-N curves for the class 1 components are described and these criteria should be met at the design step of components. As the current ASME S-N curves are based on the very conservative assumptions such as a local stress concentration effect, immoderate transient frequencies and a constant Young's modulus, however, they can not precisely address the fatigue behavior of components. In order to find out the technical solution for these problems, a number of researches and discussion have been carried out continuously at home and abroad over the decades. In this study, detailed fatigue analyses for DVI nozzle with various mesh density of finite elements were performed to evaluate effect of stress concentration factors on the fatigue analysis procedure and the excessive conservatism of stress concentration factors are confirmed through the analysis results.

원전 운전환경을 고려한 주기기 피로 건전성 상세평가 절차개발 및 적용 (Development and Application of Detailed Procedure to Evaluate Fatigue Integrity for Major Components Considering Operating Conditions in the Nuclear Power Plant)

  • 김병섭;김태순
    • 한국안전학회지
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    • 제21권6호
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    • pp.20-25
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    • 2006
  • In the design of class 1 components to apply ASME code section III NB, a fatigue is considered as one of the important failure mechanisms. Fatigue analysis procedure and standard fatigue design curve(S-N curve) is suggested in ASME code, which had to be performed to meet the integrity of components at the design step. As the plant life extension for operating power plants and the long-lived plant design, however, are being progressed, the fact which the existing ASME fatigue design curve can not consider fatigue effects sufficiently comes to the fore. To find the technical solution for these problems, a number of researches and discussion are continued up to now. In this study, the detailed fatigue analyses using the 3 dimensional modeling for the fatigue-weakened components were performed to develop the optimized fatigue analysis procedure and their results are compared with other reference solutions.

운전이력을 고려한 지역난방 열배관의 피로수명 평가 및 최적화 (Fatigue Life Evaluation and Optimization for District Heating Pipes Considering Operating Temperature Transition Data)

  • 안민용;정성욱;이상민;장윤석;최재붕;김영진;김상호;김연홍
    • 한국정밀공학회:학술대회논문집
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    • 한국정밀공학회 2005년도 춘계학술대회 논문집
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    • pp.581-584
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    • 2005
  • A district heating(DH) system supplies environmentally-friend heat and is appropriate for reduction of energy consumption and/or air pollutions. The objectives of this paper are to systematize data processing of transition temperature, investigate its effects on fatigue life of DH pipes and optimization for size of DH pipes. A relational database management system as well as reliable fatigue life evaluation procedures is established for Korean DH pipes. Also, since the prototypal evaluation results satisfied both cycle-based and stress-based fatigue criteria. Through the optimum design process, the cross section diminished 18.64% and the CUF diminished 23.35%. So, it can be used as useful information in the future for optimal design, operation and energy saving via setting of efficient condition and stabilization of water temperature.

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