Ferroelectric crystals are widely used for manufacturing smart actuators owing to their strong electromechanical coupling effect and the prompt response to the applied electric fields. Many ferroelectric actuators are operated under cyclic loading conditions. The cyclic-loading strengths of these materials are, however, substantially lower than their monotonic-loading strengths. It has been observed that the macroscopic properties of these materials deteriorate after a large number of cycles of the applied electric field. This is the so-called electric fatigue. Recent experimental investigations suggest that microcracking may be the major cause of electric fatigue. The authors investigated the interactions of ferroelectric twins with grain boundaries and pre-existing microcracks. They have demonstrated that the stress fields exhibit a power-law singularity at the intersecting points of twinning planes and grain boundaries. This concentration in stresses may initiate microcracks at the intersecting points. They have also shown that the formation of ferroelectric twins at a pre-existing crack tip results in stronger singularities of the stress and electric fields than the common (root)r-singularity. This indicates that the interaction between the ferroelectric twins and the microcracks may promote crack growth.

Date Published: 5 May 1995
PDF: 12 pages
Proc. SPIE 2442, Smart Structures and Materials 1995: Mathematics and Control in Smart Structures, (5 May 1995); doi: 10.1117/12.208856

Published in SPIE Proceedings Vol. 2442:
Smart Structures and Materials 1995: Mathematics and Control in Smart Structures
Vasundara V. Varadan, Editor(s)