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Conference Article: Cumulative fatigue damage on HTGR graphite

Ishiyama, S.; Eto, M. (Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Dept. of High Temperature Engineering)

Abstract

To investigate the effect of cyclic ratio and stress history on cumulative fatigue damage on fine-grained isotropic nuclear graphite, two step fatigue tests were performed by the loading patterns in which peak load was changed from high level to low one (High-Low mode) and low level to high one (Low-High mode). From those results, the following conclusions were derived:

  1. In High-Low mode, remarkable regeneration of stress history of first step loading to fatigue damage of second step were observed at first cyclic ratio of 0.1.
  2. Cumulative fatigue damage of High-Low mode was well expressed as the following equations: D1+D2=1, D1=n1/Nf1, D2=n2/(Nf1+Nf2(A(n1/Nf1)B) where A and B are constants.
  3. Cumulative fatigue damage of Low-High mode was well expressed as the following equations: D1+D2=1, D1=n1/Nf1, D2=n2/(Nf2+Nf1(C(n2/Nf2)D) where C and D are constants.

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key words: failures; fatigue; graphite; htgr type reactors; mathematical models; stresses; carbon; gas cooled reactors; graphite moderated reactors; mechanical properties
Reference:
Specialists' meeting on the status of graphite development for gas cooled reactors. Tokai, Ibaraki (Japan). 9-12 Sep 1991
International Atomic Energy Agency, Vienna (Austria)
IAEA-TECDOC--690, pp:248-255