13th International Conference on Fracture June 16–21, 2013, Beijing, China -2- Table 1 Material properties of C-91 Elastic compliance （10-12 m2/N） Piezoelectric constant （10-12m/V） Dielectric permittivity （10-10 C/Vm） s11 s33 s44 s12 s13 d31 d33 d15 T 11 T 33 17.1 18.6 41.4 -6.3 -7.3 -340 645 836 395 490 Figure 1. SEPB specimen and testing set up fatigue fracture surfaces. 3. Analysis Mechanical equilibrium and Gauss’ law are given by 0 , ji j (1) 0 , i i D (2) where ij and Di are the stress tensor and electric displacement vector, and a comma denotes partial differentiation with respect to the coordinates xi (i = 1, 2, 3). We have employed Cartesian tensor notation and the summation convention for repeated tensor indices. In a ferroelectric material, domain switching leads to changes in remanent strain r ij and remanent polarization P r i . Constitutive relations are described by r ij kij k kl ijkl ij s d E (3) r i k ik kl ikl i E P D d T (4)
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