Switching induced heating at the crack tip in ferroelectric ceramics

The fracture behavior of ferroelectric materials is investigated under cyclic electric fields using a boundary layer approach for small scale switching conditions. By means of a micromechanical ferroelectric material model the coupled thermo-electro-mechanical fields at the crack tip are analyzed. Besides external loading, the internal heat generation due to dissipative domain switching processes is considered. As a result, the shape and size of the formed switching zones during forward and reverse loading are elucidated together with the temperature distribution. The effect of all the internal and external factors on the crack driving energy is described by means of the configurational forces and the electromechanical J-integral. The numerical results show that, under the application of the electric field a shielding effect for the crack tip due to domain switching occurs. However, the crack is more vulnerable to fracture while unloading, because of the residual fields at the crack tip. The temperature increase around the crack tip due to domain switching is determined assuming an adiabatic process. A higher temperature leads to the degeneration of the ferroelectric properties as a result of applied cyclic loading. It is reducing the shielding effect, thus promoting fracture.