원자력급 흑연의 파괴인성 평가

Abstract

Fracture toughness of the fine grain isotropic graphite IG-11 was evaluated. Fracture toughness value, K<SUB>IC</SUB> was obtained by 3-point bending test using SENB specimen. To determine the optimum loading rate, the effects of loading rate on fracture toughness were investigated. The crack initiation point was determined by DCPD method. Weibull modulus of IG-11 graphite was determined by two parameter Weibull equation using test results of 30 SENE specimens. Crack lengths estimated by DCPD method were lower than real crack length because of leakage of current through contacting and non-broken regions within the specimens. Fraction of those area on the cracked surfaces can be inferred from the difference between the crack lengths measured by DCPD and dye penetration method. Contacting and non-broken regions which are mainly induced by shear cracking and crack bridging increase fracture toughness of graphite.