高温ガス炉用黒鉛材料の破壊じん性特性

概要

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Fracture toughness tests were carried out on nuclear graphite, IG-110 and PGX, and the effects of width, ligament ratio of compact tension specimen and cross-head speed on fracture toughness were examined. Crack extension processes in graphite specimen were observed by acoustic emission technique and optical observation method. From the results, it is concluded that : (1) A knee-point on the electrical potential-load displacement curve indicates macro-cracking in compact tension spesimens. (2) Cracking occurred in the middle part of the noyched surface of compact tension specimen and extended from the middle to the surface of specimen. (3) The value of J_<IC> was constant within the range of ligament ratio from 0.4 to 0.55. (4) The value of J_<IC> was constant within the range of cross-head speed from 0.005 mm/min to 0.05 mm/min. (5) The value of J_<IC> was constant when the specimen width was more than 10 mm for PGX graphite and 20 mm for IG-110 graphite, respectively. However, J_<IC> decreased as the specimen width decreased below the above-mentioned values. It is considered that this phenomenon is due to the formation of process-zone at the crack front of CT specimen.
社団法人日本材料学会の論文
1992-04-15