The role of autocatalysis and transformation shear in crack tip zone shape and toughening of zirconia ceramics

The effect of autocatalysis and transformation induced shear strain on the stationary crack tip zone shape and toughening is studied by the finite element method. The numerical analysis is based on the rnicromechanics constitutive model of transformation plasticity proposed by Sun et al. (J. Mech. Phys. Solids 39, 1991). This model is capable of describing the autocatalytic transformation and is used as the foundation for the theoretical and numerical study of the autocatalytic phenomenon during martensitic transformation in ceramics. The results demonstrate that autocatalysis and transformation shear strain play an important role in the anomalous crack tip zone morphology and transformation zone shielding. The "negative shielding effect" for the stationary mode I crack in plane stress is discovered and the narrow elongated crack tip zone shape is first simulated by the constitutive model of Sun et al. (1991). © 1997 Elsevier Science Ltd