Effect of electrical polarization saturation on stress intensity factors in a piezoelectric ceramic

The electric-field induced stress intensity factor in a piezoelectric mediu m of limited electrical polarization is evaluated based on a strip-saturati on model of the Dugdale-type. Particular emphasis is placed on the effect o f the saturation condition on the near tip field and the stress intensity f actor. To this end, the general solution is derived in terms of the (unspec ified) normal electrical displacement distribution along the saturated stri p. Since the saturated strip is representative of the unknown saturated zon e, the normal electrical displacement may suffer discontinuity across the s aturated strip. It is found that the crack-tip field and the stress intensi ty factors depend on the discontinuity of the normal electrical displacemen t across the saturated strip although this dependency disappears in some pr actically important cases. A crack perpendicular to the poling axis in a ge neral poled ferroelectric is discussed in detail to illustrate the implicat ions of the strip-saturation model for electric-held induced cracking. The results show that some discrepancies between theory and experiments, for wh ich the classical linear piezoelectric model gives qualitatively incorrect results, can be explained clearly in terms of the stress intensity factor g iven by the strip-saturation model. In particular, these results are indepe ndent of the form of the saturation condition imposed on the saturated stri p. (C) 1998 Elsevier Science Ltd. All rights reserved.