Effect of short-term data on predicted creep rupture life: Pivoting effect and optimized censoring

Stefan Holmström, Pertti Auerkari

    Research output: Contribution to journalArticleScientificpeer-review

    4 Citations (Scopus)

    Abstract

    Fitting data to classical creep rupture models can result in unrealistically high extrapolated long-term strength. As a consequence, the standard strength values for new steel grades have frequently needed downward correction after obtaining more long-term test data. The reasons for non-conservative extrapolation include the influence of short-term data, which are easiest to produce but tend to pivot upwards the extrapolated values of creep rupture strength. Improvement in extrapolation could be expected by reducing this effect through model rigidity correction and censoring of very short-term data, but it may not be immediately clear how to justify the correction of particular models or censoring.

    Analogously to the instability parameter in the minimum commitment model for creep rupture, a rigidity parameter correction (RPC) is introduced to assess the pivoting effect of creep rupture models for the purpose of reducing potential to non-conservativeness in extrapolation. The RPC approach can be used with any creep rupture model for comparing the model rigidity and the potential benefit from censoring short-term data. The correction itself will never introduce non-conservatism, regardless of the model. The RPC approach is demonstrated by analyzing an ECCC data set for cross-welded 9%Cr steel (E911).
    Original languageEnglish
    Pages (from-to)103-109
    Number of pages7
    JournalMaterials at High Temperatures
    Volume25
    Issue number3
    DOIs
    Publication statusPublished - 2008
    MoE publication typeA1 Journal article-refereed

    Fingerprint

    Creep
    rigidity
    Rigidity
    Extrapolation
    extrapolation
    Steel
    creep rupture strength
    steels
    pivots
    grade

    Keywords

    • Creep rupture life
    • Optimized censoring
    • Pivoting effect
    • Short-term data

    Cite this

    @article{c39965a5d05241c3aec21d86d57b2af5,
    title = "Effect of short-term data on predicted creep rupture life: Pivoting effect and optimized censoring",
    abstract = "Fitting data to classical creep rupture models can result in unrealistically high extrapolated long-term strength. As a consequence, the standard strength values for new steel grades have frequently needed downward correction after obtaining more long-term test data. The reasons for non-conservative extrapolation include the influence of short-term data, which are easiest to produce but tend to pivot upwards the extrapolated values of creep rupture strength. Improvement in extrapolation could be expected by reducing this effect through model rigidity correction and censoring of very short-term data, but it may not be immediately clear how to justify the correction of particular models or censoring.Analogously to the instability parameter in the minimum commitment model for creep rupture, a rigidity parameter correction (RPC) is introduced to assess the pivoting effect of creep rupture models for the purpose of reducing potential to non-conservativeness in extrapolation. The RPC approach can be used with any creep rupture model for comparing the model rigidity and the potential benefit from censoring short-term data. The correction itself will never introduce non-conservatism, regardless of the model. The RPC approach is demonstrated by analyzing an ECCC data set for cross-welded 9{\%}Cr steel (E911).",
    keywords = "Creep rupture life, Optimized censoring, Pivoting effect, Short-term data",
    author = "Stefan Holmstr{\"o}m and Pertti Auerkari",
    year = "2008",
    doi = "10.3184/096034008X354747",
    language = "English",
    volume = "25",
    pages = "103--109",
    journal = "Materials at High Temperatures",
    issn = "0960-3409",
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    Effect of short-term data on predicted creep rupture life : Pivoting effect and optimized censoring. / Holmström, Stefan; Auerkari, Pertti.

    In: Materials at High Temperatures, Vol. 25, No. 3, 2008, p. 103-109.

    Research output: Contribution to journalArticleScientificpeer-review

    TY - JOUR

    T1 - Effect of short-term data on predicted creep rupture life

    T2 - Pivoting effect and optimized censoring

    AU - Holmström, Stefan

    AU - Auerkari, Pertti

    PY - 2008

    Y1 - 2008

    N2 - Fitting data to classical creep rupture models can result in unrealistically high extrapolated long-term strength. As a consequence, the standard strength values for new steel grades have frequently needed downward correction after obtaining more long-term test data. The reasons for non-conservative extrapolation include the influence of short-term data, which are easiest to produce but tend to pivot upwards the extrapolated values of creep rupture strength. Improvement in extrapolation could be expected by reducing this effect through model rigidity correction and censoring of very short-term data, but it may not be immediately clear how to justify the correction of particular models or censoring.Analogously to the instability parameter in the minimum commitment model for creep rupture, a rigidity parameter correction (RPC) is introduced to assess the pivoting effect of creep rupture models for the purpose of reducing potential to non-conservativeness in extrapolation. The RPC approach can be used with any creep rupture model for comparing the model rigidity and the potential benefit from censoring short-term data. The correction itself will never introduce non-conservatism, regardless of the model. The RPC approach is demonstrated by analyzing an ECCC data set for cross-welded 9%Cr steel (E911).

    AB - Fitting data to classical creep rupture models can result in unrealistically high extrapolated long-term strength. As a consequence, the standard strength values for new steel grades have frequently needed downward correction after obtaining more long-term test data. The reasons for non-conservative extrapolation include the influence of short-term data, which are easiest to produce but tend to pivot upwards the extrapolated values of creep rupture strength. Improvement in extrapolation could be expected by reducing this effect through model rigidity correction and censoring of very short-term data, but it may not be immediately clear how to justify the correction of particular models or censoring.Analogously to the instability parameter in the minimum commitment model for creep rupture, a rigidity parameter correction (RPC) is introduced to assess the pivoting effect of creep rupture models for the purpose of reducing potential to non-conservativeness in extrapolation. The RPC approach can be used with any creep rupture model for comparing the model rigidity and the potential benefit from censoring short-term data. The correction itself will never introduce non-conservatism, regardless of the model. The RPC approach is demonstrated by analyzing an ECCC data set for cross-welded 9%Cr steel (E911).

    KW - Creep rupture life

    KW - Optimized censoring

    KW - Pivoting effect

    KW - Short-term data

    U2 - 10.3184/096034008X354747

    DO - 10.3184/096034008X354747

    M3 - Article

    VL - 25

    SP - 103

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    JO - Materials at High Temperatures

    JF - Materials at High Temperatures

    SN - 0960-3409

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    ER -