The present work reviews our theoretical and experimental studiesof the fracture behavior of piezoelectric ceramics. The theoreticalresults show that for an insulating crack, the energy release rate isindependent of the applied electric field either perpendicular orparallel to the crack when the electric field inside the crack istaken into account. For a conducting crack, the applied electricfield parallel to the crack drives the crack to propagate. Whenelectric yielding occurs at a crack tip, the global energy releaserate is the same as that derived from linear fracture mechanics,while the local energy release rate shows a linear relationshipbetween the fracture toughness and the applied electric field. Theexperimental results illustrate that for PZT-84l and PZT-4 ceramics,the scattering degree of measured data is considerably enhanced by anapplied electric field. Either a positive or a negative electricfield reduces the bending strength as well as the fracture toughness.For the PZT-84l ceramics, a two-peak distribution of the bendingstrength seems to appear under combined mechanical-electricalloading. The experimental results also confirm that there existmechanical- and electrical-fracture toughness for PZT-4 ceramics andboth are material properties. The mechanical and electrical criticalenergy release rates are respectively 8.7(±l.l) and 223.7(±45.5)N/m. The electrical fracture toughness is 25 times higher than themechanical one because more energy dissipation such as electricdischarging and domain switching accompanies with crack propagationunder purely electrical loading.
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