Microstructural damage mechanics-based model for creep fracture of 9%Cr steel under prior fatigue loading

Wei Zhang, Xiaowei Wang, Haofeng Chen, Tianyu Zhang, Jianming Gong

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Predicting the remnant creep fracture life precisely is crucial for ensuring safety of high temperature components. This study presents a microstructural damage mechanics-based model for creep fracture of 9%Cr steel under prior fatigue loading. Microstructure observation reveals that the decrease of dislocation density and the growth of martensite lath width occurred during prior fatigue process contribute to the degradation of creep strength. Particularly, coarsening of martensite lath width plays the dominated role. To take into account the effect of the prior fatigue loading, kinematic damage equations that represent the evolution of dislocation density and martensite lath are proposed in the developed model. With the proposed model, creep fracture life and creep failure strain at various lifetime factions, strain amplitudes and hold times of prior fatigue loading can be satisfactorily predicted, which manifests that the proposed model is robust in capturing the effects of various prior fatigue loadings. The proposed model is also shown to be able to accurately predict prolonged creep deformation of other similar steel after different prior fatigue loadings.
Original languageEnglish
Article number102269
Number of pages25
JournalTheoretical and Applied Fracture Mechanics
Early online date10 Jun 2019
Publication statusPublished - 1 Oct 2019


  • prior fatigue loading
  • microstructure damage model
  • creep fracture
  • lath width
  • dislocation density

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