Crack-growth resistance in transformation-toughened ceramics

Micromechanical approach to transformation toughening in zirconia-enriched multiphase composites

“…For the sake of completeness of this paper a brief introduction of the continuum model of transformation toughening [Stump and Budiansky 1989] will be presented next. Assume that a transformation zone surrounding the crack tip has undergone an irreversible transformation dilatation of strength f (1) θ where f (1) is the zirconia particle volume fraction and θ is the unconstrained particle dilatation (Figure 1).…”

“…Details can be found in Stump and Budiansky [1989]. The final result of the calculation of the fracture toughening of the composite for a stable and a growing crack is shown in Figure 2.…”

“…The micromechanical model developed above can be directly incorporated into the continuum model [Stump and Budiansky 1989] by replacing the corresponding material constants, dilatation, and critical stress with those derived from the micromechanical model, Equations (22), (23), (28) and (30). Such substitution will not affect the fracture-toughening curve as shown in Figure 2; however the strength of the transformation will be modified as…”

“…The continuum models of the phenomenon were developed by Lange [1982], McMeeking and Evans [1982], Budiansky et al [1983], and Stump and Budiansky [1989]. All of these models are based on the assumption of effectively homogeneous composite material, where only macroscopic aspects of the Keywords: transformation toughening, micromechanics, multiphase composites, crack, zirconia particles, continuum model, dilatant strain.…”

“…In this paper, a micromechanical model is developed and incorporated into the continuum model of transformation toughening of Stump and Budiansky [1989], to investigate the effect of the mismatch of the constituent phases on the transformation toughening mechanism in multiphase composites. This model is based on the mean-field theory of Wakashima and Tsukamoto [1991].…”