Fatigue Properties of Reactor Pressure Vessel Steel and Damage Evaluation

Tetsuo Shoji, Yuji Kawamori, Yutaka Watanabe, Juichi Fukakura

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)

Abstract

Low-cycle fatigue tests were carried out on a reactor pressure vessel steel at 290°C in order to investigate an evaluation method for fatigue damage and fatigue straining histories. The initiation behavior of surface microcracks was examined, and the following results were obtained. (1) The initiation of surface cracks begins from the early stage of fatigue life and the crack density (number of cracks per unit surface area) continues to increase throughout the fatigue life. (2) The increasing behavior of the crack density can be correlated with the Coffin-Manson type parameter ΔεP · N0.6 irrespective of an applied strain range (Δεt). Therefore, fatigue straining histories represented by ΔεP · N0.6 can be estimated from the measurement of surface crack density. (3) The grain boundary is one of the preferential sites of crack initiation, and micro-cracks which just initiated have a tendency to propagate along the grain boundary. The electrochemical etching was performed at a midplane of the fatigue damaged specimens where no geometrical damage could be expected. Etching properties of fatigue damaged specimens were also studied and were found to change with damage accumulation. The results obtained can be summarized as follows. (4) Many random-shape pits appeared only on the surface of the fatigue damaged material by the electrochemical etching. These random-shape pits initiated mainly at the triple point of grain boundaries and grew preferentially along the grain boundaries. These pits can be considered as a result from degradation of corrosion resistance of the demaged material caused by microstructural changes at or near grain boundaries during fatigue. (5) The area fraction of corroded region on the electrochemically etched surface shows a single correlation with ΔεP · N0.6 and quantitative evaluation of fatigue damage accumulation can be made nondestructively by the electrochemical etching.

Original languageEnglish
Pages (from-to)1558-1564
Number of pages7
JournalJournal of the Society of Materials Science, Japan
Volume41
Issue number469
DOIs
Publication statusPublished - 1992 Oct

Keywords

  • Crack density
  • Electrochemical etching
  • Fatigue damage
  • Low-cycle fatigue
  • Reactor pressure vessel steel
  • Surface cracks

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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