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Conference Article: Fracture behavior of nuclear graphites under compressive impact loading

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

Abstract

Compressive impact fracture behavior of two kinds of nuclear grade graphites, fine-grained isotropic IG-11 graphite and coarse-grained near-isotropic PGX graphite, have been investigated as a function of various strain rates up to more than 100 (1/s) at room temperature. Two types of cylindrical specimens, 12.5 mm in diameter with 25 mm length and 25 mm in diameter with 50 mm length, were employed to investigate the volume effect on compressive impact strength. Compressive fracture load, longitudinal and circumferential strains were measured in this test. The effect of strain rate up to 100(1/s) on compressive strength and deformation behavior of these graphites are discussed and the following conclusions were derived:

  1. Compressive strength of graphites increased with increasing of strain rate up to 100(1/S) and is well expressed by the following equation: sigmaC=AepsilonB where sigmaC, epsilon are compressive strength and strain rate and A and B are constants respectively.
  2. Compressive strength decreased drastically with increasing of strain rate over 100(1/S).
  3. Specimen volume effect on impact compressive strength and deformation behavior was not found.

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key words: compression strength; cylindrical configuration; fracture properties; graphite; mathematical models; sampling; strain rate; carbon
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:256-261