13th International Conference on Fracture June 16–21, 2013, Beijing, China -10- Figure 11. Influence of water concentration R.H. by its dependence with n 0 (R.H.) and U0 (R.H.) on the prediction of the V-KI curves and K0 for Polycrystals of Zirconia with G = 0.8 m. 3. Conclusion We have presented a calibration of the cohesive zone parameters for zirconia single crystal based on the cohesive zone description of Romero de la Osa et al. [3-4] for SCG in ceramics. The cohesive model is shown able to capture realistic experimental data of SCG in a single crystal. This calibration is then used to simulate intergranular failure in a 2D polycrystal. We have pointed on the influence of the stress threshold n 0 for the reaction-rupture to be triggered on the prediction of the threshold load of SCG in a polycrystal. We have shown the influence of the initial thermal stresses related to processing on the kinetics of SCG and the magnitude of K0. We also examined the influence of the water concentration on the prediction of the regime I and K0 of SCG and showed that the water concentration can be accounted for with a dependence of the activation energy and traction threshold with the amount of water. References [1] K. Wan, S. Lathabai and B. Lawn, Crack velocity functions and thresholds in brittle solids in J. Am. Ceram.Soc., 1990, 6 259-68. [2] J. Chevalier, C. Olagnon and G. Fantozzi, Subcritical crack propagation in 3y-tzp ceramics : static and cyclic fatigue, J. Am. Ceram. Soc., 1999, 82(11) :3129-3138. [3] M. Romero de la Osa, R. Estevez, J. Chevalier, C. Olagnon, Y. Charles, L. Vignoud ,C. Tallaron, Cohesive zone model and slow crack growth in ceramic polycrystals, Int. J. Fract, 2009, 158(2) 157-167. [4] M. Romero de la Osa, R. Estevez, J. Chevalier, C. Olagnon, Y. Charles, L. Vignoud ,C. Tallaron, Cohesive zone model for intergranular slow crack growth in ceramics : influence of the process and microstructure, Modell. Simul. Mat. Sci. Engng., 2011, 19:074009. [5] T. A. Mischalske and S. W. Freiman, A molecular Mechanism for Stress Corrosion in Vitreous Silica, J. Am. Ceram. Soc., 66 284-8. [6] T. Zhu and J. Li, X. Lin, S. Yip, Stress-Dependent Molecular Pathways of Silica-Water Reaction. J. Mech. Phys. Slolids, 2005, 53 1597-623. [7] J. Chevalier and G. Fantozzi, Slow crack propagation in ceramics at the nano- and microscale : effect of the microstructure, Proceedings of the 8th Internaional Symposium on Fracture Mechanics of ceramics, held February 25 28, 2003, at the University of Houston, Texas. [8] S. N. Zhurkov, Kinetics Concept of the Strength of Solids, J. Fract. Mech., 1965, 1 311-23. [9] R. P. Ingel, D. Lewis, Elastic Anisotropy in Zirconia Single Crystals, J. Am. Soc., 1988, 74(4) 265-71.
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