Coupling Effect of Electric Field, Residual Stress and Medium on Propagation of Indentation Cracks in A PZT--5H Ceramic
电场、残余应力和介质对PZT-5H铁电陶瓷压痕裂纹扩展的耦合作用

The experiment of a coupling effect on propagation of unloaded indentation cracks in a PZT--5H ceramic shows that residual stress itself is too small to induce delayed propagation of the indentation crack in silicon oil. If applied constant electric field is larger than 0.2 kV/cm, the coupling of electric field, residual stress and silicon oil can cause delayed propagation of the crack after incubation time, but the crack will arrest after propagating for 10---30 um because of decrease of the stress intensity factor with increasing the crack length. The threshold electric field of delayed propagation of the crack in silicon oil is EDP=0.2 kV/cm. If the field is larger than the critical field of 5.25 kV/cm, coupling of the electric field and residual stress is enough to cause instant propagation of the crack and propagates continuously, then arrests if under the constant electric field. If the applied field is larger than 12.6 kV/cm, even if no residual stress, the electric field itself can make many cracks initiate, grow and connect in a smooth specimen, resulting in delayed failure. The threshold electric field of delayed failure of a smooth specimen in silicon oil is 12.6 kV/cm and the critical electric field for instant failure is EF=19.1 kV/cm.