ABSTRACT
There is increasing evidence in recent times to suggest that the same toughening mechanisms that give rise to the R-curve characteristic are also responsible for the mechanical fatigue suffered by many advanced ceramics when subjected to cyclic stresses. It is commonly believed that the degradation of the toughening mechanisms when repeated loading is applied is the main reason for this effect. For example, for a coarse-grained alumina, it has been experimentally observed that the cracktoughening obtained from grain-bridging is substantially reduced in this situation (Lathabai, Rodel and Lawn, 1991). However, for many Z r 0 2 bearing ceramics including Mg-PSZ, Ce-TZP, Y-TZP and ZTA, the mechanical fatigue mechanisms have not yet been convincingly revealed though an attempt is made to establish the relation between cyclic fatigue crack growth and the degradation of fracture resistance (Mai et al., 1992; Duan, Mai and Cotterell, 1992; Hu and Mai, 1992a).
