The residual strain of polycrystalline graphite. II

Studies on the relationships between the residual strain and the energy dissipated during the compressive loading and unloading cycles are carried out for nuclear and other commercial graphites. It is also investigated whether there are correlations between the fracture energy and mechanical properties such as the compressive strength of these materials. The results show that for needle coke and fine-grained isotropic graphites the residual strain epsilon0 = K1Esup(1/2), while for Gilsocarbon graphites epsilon0 = K2Esup(1/3). Here, E is the dissipated energy and K1 and K2 are constants dependent on the kind of graphite and the specimen orientation. These relationships can be derived on some assumptions concerning the mechanisms for deformation of needle coke or Gilsocarbon graphite. It is also found that both the compressive strength and the fracture strain, are proportional to the square root of the fracture energy for various polygraphites. (Auth.)