異なる環境下でのグラスセラミックスの混合モード破壊 : 圧裂引張試験法による検討

概要

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Mixed-mode fracture of two glass ceramics with different grain sizes and soda-lime glass due to inclined knoop indentation flaws was studied in diametral compression tests. These tests were carried out under various environments of vacuum, air, and water. Mode I and mode II stress intensity factors at fracture and the directions of crack extension were analyzed. Fracture envelopes obtained from experiments under vacuum atmosphere indicated less sensitivity to mode II loading than those in existing theories, and less sensitivity to mode II loading of the glass ceramics than the soda-lime glass. It was considered that differences in the relative sensitivity to mode II of the glass ceramics and soda-lime glass are attributed to microstructure effects on shear resistance on the crack tip faces. The maximum stress theory modified by considering the shear resistance on the crack tip faces explained the experimental results well. In fracture under corrosive environments, both mode I and mode II stress intensity factors at fracture became lower in the order of vacuum, air, water, due to subcritical crack growth. However the sensitivity to mode II loading in glass ceramics was somewhat larger in a water environment than a vacuum environment due to the decrease of the shear resistance by crack tip blunting.
社団法人日本機械学会の論文
1994-03-25