The technique of birefringence imaging was exploited to observe the evolution of creeping strain fields in transparent PLZT 8/65/35 samples. PLZT samples with features that produce non-uniform fields were loaded with constant voltage boundary conditions. The resulting birefringence contours evolve with time and can be related to strain measurements. Three experimental arrangements are reported: partial surface electrodes producing intense fields near an electrode tip, a round insulating hole producing local concentration of electric field, and a thin, sharp crack producing crack tip fields. In each case, material was initially in the as-sintered (unpoled) state, and was loaded with nominal electric field strengths that were well below the coercive field. However, the birefringence imaging indicates significant remanent strain evolving over a time period of order 10³s. The resulting mean electric displacements are greatly enhanced relative to uniform field conditions at the same mean field strength. The measurements show only weak interaction between thin cracks and the applied electric field, suggesting that the thin cracks are effectively permeable. The results are of potential use in calibrating multi-axial and time dependent material models.

Date Published: 2 April 2008
PDF: 8 pages
Proc. SPIE 6929, Behavior and Mechanics of Multifunctional and Composite Materials 2008, 69290B (2 April 2008); doi: 10.1117/12.774385

Published in SPIE Proceedings Vol. 6929:
Behavior and Mechanics of Multifunctional and Composite Materials 2008
Marcelo J. Dapino; Zoubeida Ounaies, Editor(s)