Crack propagation in a four-parameter piezoelectric medium

The simplified three-parameter formulation of a piezoelectric medium proposed by Gao et al. [Gao, H.J., Zhang, T.Y., Tong, P., 1997. Local and global energy release rates for an electrically yielded crack in a piezoelectric ceramic. J. Mech. Phys. Solids 45, 491–510] is extended to a four-parameter modified model in order to point out the features of a steadily propagating Griffith crack. It is assumed that the crack is electro-elastically free and the medium is subjected to a generalized electro-mechanical loading applied at infinity. The complete solution is provided under impermeable and permeable boundary conditions and results are presented in order to show the main dynamical features.