In studying crack problems in a piezoelectric material, many crack models have been proposed and some fracture criteria have been established. The author of 1 presented a new permeable crack model. That is, a permeable crack is modeled as a rectangular hole having height The first-order perturbation solution in terms of small parameter is derived, and asymptotic electroelastic field, together with field intensity factors, local and global energy release rates are further determined. The obtained theoretical prediction agrees basically with experimental observation. Here, we would like to make some discussions on 1.
In addition it is seen from (81)–(83)) that the height of a rectangular crack has been taken into account. However, for such a rectangular crack, (or strictly speaking a rectangular hole), and should have no singularity near the points since the points are not the crack tips Instead, the electromechanical field near the apexes of the rectangle exhibits a singularity. Moreover, the singularity is no longer an inverse square-root singularity. The classical definition of field intensity factors is therefore employed directly except for the case of