The electrical boundary conditions on the crack faces and their applicability in piezoelectric materials are discussed. A slit crack and a notch of ?nite thickness in piezoelectric materials subjected to combined mechanical and electrical loads is considered. Here, a crack is de?ned as a notch without thickness, which is ?lled with air or vacuum. The crack or notch is perpendicular to the poling direction of the medium. The ideal crack face electrical boundary conditions, i.e., the electrically permeable crack and the electrically impermeable crack, are in- vestigated ?rst. Then dependence of the ?eld intensity factors on notch thickness at the notch tips is analyzed to obtain a closed-form. The results are compared with the ideal crack solutions. Some useful results are found.
