Creep-fatigue interaction models for grade 91 steel

Stefan Holmström, Rami Pohja, W. Payten

    Research output: Contribution to journalArticleScientificpeer-review

    3 Citations (Scopus)

    Abstract

    Different approaches for modelling creep-fatigue (CF) interaction are used on strain controlled creep fatigue data of 9Cr-1Mo-VNb (P91) steel and assessed with the target of finding suitable candidates for use in design rules. The assessed models include time, ductility and strain energy based creep-fatigue interaction methods and two simplified models. For the interaction diagram based models the challenge of acquiring representative creep damage fractions from the dynamic material response, i.e. cyclic softening with changing relaxation behaviour is addressed. Also, the interaction diagram approaches are discussed in the light of known (fatigue) material scatter and defining representative cycles for CF data. The performance of the model are presented and also compared against the RCC-MR design code methodology. It is shown that the fitting accuracy of the complex interaction models vary significantly and that modified ductility based models seem to be less susceptible to changes in supporting creep and relaxation models. Successful and also superior prediction of the CF number of cycles to failure for Grade 91steel was accomplished by simplified methods with much less fitting parameters. The practicality in using interaction diagram methods for design purposes, where simplicity is a key issue, is questioned.
    Original languageEnglish
    Article numberMPC20130054
    Pages (from-to)156-181
    Number of pages25
    JournalMaterials Performance and Characterization
    Volume3
    Issue number2
    DOIs
    Publication statusPublished - 2014
    MoE publication typeA1 Journal article-refereed

    Fingerprint

    Steel
    Creep
    Fatigue of materials
    Ductility
    Strain energy

    Keywords

    • creep-fatigue
    • modeling
    • P91 steel

    Cite this

    Holmström, Stefan ; Pohja, Rami ; Payten, W. / Creep-fatigue interaction models for grade 91 steel. In: Materials Performance and Characterization. 2014 ; Vol. 3, No. 2. pp. 156-181.
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    abstract = "Different approaches for modelling creep-fatigue (CF) interaction are used on strain controlled creep fatigue data of 9Cr-1Mo-VNb (P91) steel and assessed with the target of finding suitable candidates for use in design rules. The assessed models include time, ductility and strain energy based creep-fatigue interaction methods and two simplified models. For the interaction diagram based models the challenge of acquiring representative creep damage fractions from the dynamic material response, i.e. cyclic softening with changing relaxation behaviour is addressed. Also, the interaction diagram approaches are discussed in the light of known (fatigue) material scatter and defining representative cycles for CF data. The performance of the model are presented and also compared against the RCC-MR design code methodology. It is shown that the fitting accuracy of the complex interaction models vary significantly and that modified ductility based models seem to be less susceptible to changes in supporting creep and relaxation models. Successful and also superior prediction of the CF number of cycles to failure for Grade 91steel was accomplished by simplified methods with much less fitting parameters. The practicality in using interaction diagram methods for design purposes, where simplicity is a key issue, is questioned.",
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    Creep-fatigue interaction models for grade 91 steel. / Holmström, Stefan; Pohja, Rami; Payten, W.

    In: Materials Performance and Characterization, Vol. 3, No. 2, MPC20130054, 2014, p. 156-181.

    Research output: Contribution to journalArticleScientificpeer-review

    TY - JOUR

    T1 - Creep-fatigue interaction models for grade 91 steel

    AU - Holmström, Stefan

    AU - Pohja, Rami

    AU - Payten, W.

    N1 - Project code: 71951

    PY - 2014

    Y1 - 2014

    N2 - Different approaches for modelling creep-fatigue (CF) interaction are used on strain controlled creep fatigue data of 9Cr-1Mo-VNb (P91) steel and assessed with the target of finding suitable candidates for use in design rules. The assessed models include time, ductility and strain energy based creep-fatigue interaction methods and two simplified models. For the interaction diagram based models the challenge of acquiring representative creep damage fractions from the dynamic material response, i.e. cyclic softening with changing relaxation behaviour is addressed. Also, the interaction diagram approaches are discussed in the light of known (fatigue) material scatter and defining representative cycles for CF data. The performance of the model are presented and also compared against the RCC-MR design code methodology. It is shown that the fitting accuracy of the complex interaction models vary significantly and that modified ductility based models seem to be less susceptible to changes in supporting creep and relaxation models. Successful and also superior prediction of the CF number of cycles to failure for Grade 91steel was accomplished by simplified methods with much less fitting parameters. The practicality in using interaction diagram methods for design purposes, where simplicity is a key issue, is questioned.

    AB - Different approaches for modelling creep-fatigue (CF) interaction are used on strain controlled creep fatigue data of 9Cr-1Mo-VNb (P91) steel and assessed with the target of finding suitable candidates for use in design rules. The assessed models include time, ductility and strain energy based creep-fatigue interaction methods and two simplified models. For the interaction diagram based models the challenge of acquiring representative creep damage fractions from the dynamic material response, i.e. cyclic softening with changing relaxation behaviour is addressed. Also, the interaction diagram approaches are discussed in the light of known (fatigue) material scatter and defining representative cycles for CF data. The performance of the model are presented and also compared against the RCC-MR design code methodology. It is shown that the fitting accuracy of the complex interaction models vary significantly and that modified ductility based models seem to be less susceptible to changes in supporting creep and relaxation models. Successful and also superior prediction of the CF number of cycles to failure for Grade 91steel was accomplished by simplified methods with much less fitting parameters. The practicality in using interaction diagram methods for design purposes, where simplicity is a key issue, is questioned.

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