13th International Conference on Fracture June 16–21, 2013, Beijing, China -7- Table 2 Number of cycles to failure under electric fields Electric field, E0 (MV/m) -0.2 -0.04 0 Number of cycles to failure, N 385 494645 38994 Table 3 Energy release rate under electric fields for Cases 1 and 2 without polarization switching effect Electric field, E0 (MV/m) -0.2 -0.04 0 Energy release rate, G (J/m2) Case 1 Case 2 5.5 4.3 5.5 4.3 5.5 4.3 C-91 under Pmax = 110 N (R = 0.5, f = 50 Hz) and E0 = 0, -0.04, -0.2 MV/m. The value of average number of cycles to failure increases by about 12 times due to the electric field of -0.04 MV/m, but decreases to less than about 0.01 times due to the electric field of -0.2 MV/m. Although the results are not shown here, the fracture surface of the PZT ceramics under E0 = 0 V/m shows intergranular and transgranular regions, and the micrograph of the PZT ceramics under E0 = -0.04 MV/m reveals a predominantly intergranular fracture. On the other hand, crack paths in the fracture for PZT ceramics under E0 = -0.2 MV/m are predominantly transgrannular. Table 3 lists the energy release rate G for SEPB C-91 ceramics with a crack of length a = 0.5 mm under load Pmax = 110 N and E0 = 0, -0.04, -0.2 MV/m for Cases 1 and 2 without polarization switching effect. The energy release rates for Cases 1 and 2 are independent of the electric field, Figure 3. Energy release rate vs electric field for Case 1 with and without polarization switching effect
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