Characterization of the effects of applied electric fields on fracture toughness and cyclic electric field induced fatigue crack growth for piezoceramic PIC 151

The influence of applied electric field on fracture toughness and cyclic electric field induced fatigue crack growth behaviour was characterized for an actuator piezoelectric ceramic under the combined loading of a high electric field and a mechanical stress. Results show that there exists a strong anisotropic effect on fracture toughness and electric field induced fatigue crack growth in polarized PZT. It is found that the apparent fracture toughness in the orientation parallel to the polarization direction is much higher than that in the transverse orientation. Under a positive electric field, increasing the electric field intensity reduces the fracture toughness in the transverse orientation but enhances that in the parallel orientation. However, the reverse is true under a negative electric field. A sphere cavity model in dielectrics was employed to characterize the effect of the external applied electric field on the evolution of cracking in an indentation. The results also show that low electric field intensity does not result in fatigue crack growth in PZT. For a relatively high applied electric field, the cracks initially grow quickly and then are arrested. This result is very significant for the long-term durability of PZT actuators.