Low and ultra-low-cycle fatigue behavior of X52 piping steel based on theory of critical distances

João C. R. Pereira, Abilio M. P. de Jesus, José Xavier, José António Fonseca De Oliveira Correia, Luca Susmel, António Augusto Fernandes

Research output: Contribution to journalConference articlepeer-review

8 Citations (Scopus)


The cyclic failure observed in structural components such as pipelines subjected to extreme loading conditions highlights some limitations concerning the application of existing fatigue damage models. The evaluation and prediction of this type of failure in these steel components under large-scale plastic yielding associated with high levels of stress triaxiality are not sufficiently known nor explored. This fatigue domain is conventionally called ultra-low-cycle fatigue (ULCF) and damage features are representative of both low-cycle fatigue (LCF) and monotonic ductile fracture. Thus, in order to understand the ULCF damage mechanisms both monotonic and LCF tests are required to get representative bounding damage information to model the material damage behaviour under such extreme loading conditions. This paper aims at exploring the Theory of Critical Distances (TCD) in the LCF and ULCF fatigue regimes, including the application of the point, line and area methods. The application of the TCD theories has not been explored so far in the ULCF fatigue regimes, despite its promising results in the LCF and high-cycle fatigue. An experimental program was carried out on several specimens’ geometries made of X52 piping steel. In detail, smooth plane specimens and notched plane specimens were cyclic loaded under tension/compression loading in order to obtain fatigue lives within the range of 101–104 cycles. In addition, cyclic bending tests on notched plane specimens were also incorporated in this study. Finite element simulations of all small-scale tests were conducted allowing to derive elastoplastic stress/strain fields along the potential crack paths. The numerical data were subjected to a post-processing in order to find characteristic lengths that can be treated as a fatigue property according to the TCD. A unified strain-life relation is proposed for the X52 piping steel together with a characteristic material length, consisting of a practical relation for pipeline strain-based design under extreme cyclic loading conditions.

Original languageEnglish
Article number105482
JournalInternational journal of fatigue
Publication statusPublished - 1 May 2020
Event19th International Colloquium on Mechanical Fatigue of Metals (ICMFM) - Faculdade de Engenharia da Universidade do Porto (FEUP), Porto, Portugal
Duration: 5 Sep 20187 Sep 2018


  • Cyclic plasticity
  • LCF
  • Piping steel
  • Theory of critical distances
  • ULCF


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