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

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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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title = "Creep-fatigue interaction models for grade 91 steel",
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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