ABSTRACT
Abstract The fatigue crack growth rate for short cracks in zirconia toughened ceramics (ZTC) is described by a Paris-type law as a function of the local stress intensity factor at the crack tip. Allowance is made for crack tip damage during the unloading cycle. The toughening of ZTC is primarily controlled by the presence of transformable precipitates in the brittle matrix and unlike in PSZ is a result of not only the phase transformation in the precipitates, but also because the precipitates impede the progress of the macrocrack and trap it. The combined effect of these two mechanisms in the bridged zone ahead of the open macrocrack is modelled by a distribution of springs whose stiffness is determined from the transformation and geometrical characteristics of the precipitates. The reduction in the shielding effect on unloading is modelled by a constant stress preventing the closure of a part of the crack close to its tip.
