Criteria for Small Scale Creep Testing Condition and Estimation of Ct

    Volume 39, Issue 3 (May 2011)

    ISSN: 0090-3973

    CODEN: JTEOAD

    Published Online: 18 October 2010

    Page Count: 7


    Wha Ma, Young
    Research Associate, Dept. of Mechanical Engineering, Chung Ang Univ., Seoul,

    Yoon, Kee Bong
    Professor, Dept. of Mechanical Engineering, Chung Ang Univ., Seoul,

    (Received 16 December 2009; accepted 9 September 2010)

    Abstract

    As new creep resistant materials are developed for the temperature range of 800–1100°C, the improved creep properties sometimes require the modification of the conventional approaches in high temperature life assessment procedures which have been applied for low alloy steels and chromium steels usually used in the temperature range of 500–650°C. In this study, finite element analyses were carried out by using the creep properties of a gas turbine material to establish the small scale creep testing requirements and to propose a corrected Ct estimation scheme. The maximum allowable creep zone size was estimated through the analogy between the small scale yielding conditions and the small scale creep conditions. The maximum time during which the small scale creep condition holds was also defined. The creep zone boundary with the definition of εce was more suitable for Ct estimation than that with the definition of εc=0.002, since it was easy to find a proper correction function by applying the former definition. The newly estimated value of βr̃c=1/7=1/12 was derived for determining Ct instead of the conventional value of βr̃c=1/7.5. Excellent correlations were shown between the estimated Ct values obtained with the new βr̃c and the finite element calculated Ct values in all creep condition ranges. This result strongly supports the validity of the suggested small scale creep criterion and the new correction value βr̃c=1/12 proposed in this study.


    Paper ID: JTE102920

    DOI: 10.1520/JTE102920

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    Author
    Title Criteria for Small Scale Creep Testing Condition and Estimation of Ct
    Symposium , 0000-00-00
    Committee E08