Cyclic plasticity behavior of 90° back-to-back pipe bends under cyclic bending and steady pressure

Nak-Kyun Cho, Haofeng Chen

Research output: Chapter in Book/Report/Conference proceedingConference contribution book

1 Citation (Scopus)
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Back-to-back pipe bends are widely adopted applications in many industries including nuclear sectors. Evaluation of their load bearing capability under complex cyclic loading is very important. Recently, a couple of research reported shakedown boundary of a 90° back-to-back pipe bends by adopting a conservative approach but no comprehensive post yield structural behaviors have been dealt with. In this research the concerning pipe bends subjected to cyclic opening in-plane (IP)/out-of-plane (OP) bending and steady internal pressures are analyzed to construct shakedown and ratchet limit boundary by means of the Linear Matching Method. Analyzed results present that the concerning pipe bends under out-of-plane bending has higher resistance to cyclic bending than under in-plane bending. In additions, the out-of-plane bending causes very small alternating plasticity areas, unlike the in-plane bending. Full cyclic incremental analyses known as step-by-step analysis are performed to verify the structural responses either side of each boundary and confirm correct responses. Parametric studies are carried out with respect to changes in geometry of the concerning pipe bends subjected to the same loading, and semiempirical equations are derived from relationships of the reverse plasticity limit and the limit pressure with the bend characteristic. This paper offers broad understandings of structural responses of the 90° back-to-back pipe bends under the complex cyclic loading as well as providing key points to be considered for the life assessment of the piping system.
Original languageEnglish
Title of host publication2018 26th International Conference on Nuclear Engineering
Place of PublicationNew York
Number of pages9
Publication statusPublished - 24 Oct 2018
Event26th International Conference on Nuclear Engineering - London, United Kingdom
Duration: 22 Jul 201826 Jul 2018


Conference26th International Conference on Nuclear Engineering
Country/TerritoryUnited Kingdom


  • pipe bends
  • cyclic bending
  • plasticity
  • pressure
  • Akiyama Medal

    CHO, N. (Recipient), 24 Jul 2018

    Prize: Prize (including medals and awards)


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