• Title/Summary/Keyword: 탄성추종계수

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Method to Determine Elastic Follow-Up Factors to Predict C(t) for Elevated Temperature Structures (이차하중을 받는 고온 구조물의 C(t) 예측을 위한 탄성추종 계수 결정법)

  • Lee, Kuk-Hee;Kim, Yun-Jae
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.36 no.7
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    • pp.759-768
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    • 2012
  • This paper proposes a method to determine the elastic follow-up factors for the $C(t)$-integral under secondary stress. The rate of creep crack growth for transient creep is correlated with the $C(t)$-integral. Elastic follow-up behavior, which occurs in structures under secondary loading, prevents a relaxation of stress during transient creep. Thus, both the values of $C(t)$ and creep crack growth increase as increasing elastic follow-up. An estimation solution for $C(t)$ was proposed by Ainsworth and Dean based on the reference stress method. To predict the value of $C(t)$ using this solution, an independent method to determine the elastic follow-up factors for cracked bodies is needed. This paper proposed that the elastic follow-up factors for $C(t)$ can be determined by elastic-plastic analyses using the plastic-creep analogy. Finite element analyses were performed to verify this method.

Prediction of Creep Stress in High Temperature Piping System Using Elastic Follow-up Factor (탄성추종계수를 이용한 고온 배관계의 크리프 응력 예측)

  • Seo, Jun-Min;Youn, Gyo-Geun;Lee, Hyun-Jae;Oh, Young-Jin;Kim, Yun-Jae
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.14 no.1
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    • pp.32-37
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    • 2018
  • When designing high temperature piping system, creep phenomena must be considered. Since ASME code does not provide detailed methods of design by rule (DBR) for high temperature piping, Finite element analysis should be performed. However, In the case of piping system with frequent design changes, creep analysis of the entire piping system for every change is ineffective and practically impossible. Therefore, based on elastic and elastic-plastic analysis, which takes a relatively short time, the creep stress is predicted by using elastic follow-up factor method provided in R5 code and plastic-creep analogy presented by Hoff. The predicted creep stress for a virtual piping system was compared with the creep analysis result and the two results showed similar stress relaxation tendency in time.

A Study on Sliding Mode Control of EHA System for Robust Control (견실한 추종 제어를 위한 EHA 시스템의 슬라이딩 모드제어에 관한 연구)

  • Park, Yong-Ho;Park, Sung-Hwan
    • Journal of Advanced Marine Engineering and Technology
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    • v.33 no.1
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    • pp.71-80
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    • 2009
  • The response characteristics of EHA systems are sensitive to the temperature change of working fluid because the temperature of working fluid causes the variation of system parameters such as effective bulk modulus and viscous friction coefficient. In this paper, a precise position control of EHA system using the adaptive sliding mode control system is suggested. The adapted system parameters such as effective bulk modulus and viscous friction coefficient can be used for monitoring failures in the EHA system which has potential applications in the industrial fields. Not only the accuracy of adapted system parameters but also the improved performance and robustness in a given reference position of the cylinder are verified by computer simulation using AMESim software.