Evaluation of Subcritical Crack Growth in Glass Ceramics : Examination by Double Torsion Technique

Abstract

The lifetime prediction of ceramics has been discussed on the basis of the relationship between the stress intensity facter (K₁) and crack velocity (V). In the present work, the effect of environment on this relationship was studied for two kinds of glass ceramics with different grain sizes. The load relaxation method and controlled load method, which are double torsion (DT) techniques, were used for the determination of the K₁-V characteristics under different environments of air and ionexchanged water. The controlled load method, which is simple and reliable, has been proposed by the authors. We also examined the possibility of failure prediction using acoustic emission (AE). As a result, it was found that at high K₁, V is enhanced by diffusion of corrosive species to crack tips and is also dependent on the amount of water. Crack growth resistance significantly increases with increasing grain size. Also, the AE event rate is quantitatively related to V.