快削性セラミックスのき裂進展特性に及ぼす水環境の影響

概要

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The fatigue behavior of ceramics has been discussed on the basis of the relation between stress intensity facter (K_I) and crack velocity (V). In this paper, the effect of environment on the relation between K_I and V was studied on machinable ceramics (mica glass ceramics) and two kinds of glass ceramics with different grain sizes. The double torsion (DT) technique was used for the determination of the K_I-Vcharacteristics under different environments of air and ion-exchanged water. The characteristics of acoustic emission (AE) during stress corrosion cracking of mica glass ceramics was also examined. In water environment, the region II in the K_I-V curve, in which crack velocity varies slowly with K_I, disappeared. From this experimental fact, it was considered that at high K_I, the crack velocity is encouraged by diffusion of the corrosive species to the crack and thus depended on the amount of water. SEM fractography revealed that mica single crystals in the material caused crack arrest and deflection to occur. It is also found that AE event rate is quantitatively related to the crack velocity. AE measurement can be used in studying the crack propagation behavior of mica glass ceramics.
社団法人日本材料学会の論文
1997-06-15