抄録
The graphite components in HTR (High Temperature gas-cooled Reactor) are subjected to impact force when an earthquake occurs. It is important from a viewpoint of seismic safety design to investigate the difference between impact and nonimpact strengths.
Both bending strength and bending fatigue strength tests, therefore, were carried out under impact and nonimpact loads on two kinds of graphite materials, that is, isotropic and near-isotropic ones. The impact response analyses, in which a beam model was used by taking account of the contact behavior between the specimen and a tap, were performed to evaluate the relationships among impact energy, impact force and impact stress.
The main conclusions obtained are summarized as follows;
(1) A beam model taking account of the contact behavior through the Hertzian theory is applicable to describe the impact behavior.
(2) The bending strength of graphite is independent of strain rate in the range 10-6 to 5l/s.
(3) The strength of graphite is lower in impact fatigue than in nonimpact fatigue, irrespective of kind of graphite and specimen volume.
