Ferroelectric ceramics are broadly used in applications including actuators, sensors and information storage. An understanding of the microstructual evolution and domain dynamics is vital for predicting the performance and reliability of such devices.
The underlying mechanism responsible for ferroelectric constitutive response is
ferroelectric domain wall motion, domain switching and the interactions of domain
walls with other material defects.
In this work, a combined theoretical and numerical modeling framework is
developed to investigate the nucleation and growth of domains in a single crystal of
ferroelectric material. The phase-field approach, applying the material electrical
polarization as the order parameter, is used as the theoretical modeling framework to
allow for a detailed accounting of the electromechanical processes. The finite element
method is used for the numerical solution technique. In order to obtain a better
understanding of the energetics of fracture within the phase-field setting, the J-integral is
modified to include the energies associated with the order parameter. Also, the J-
integral is applied to determine the crack-tip energy release rate for common sets of
electromechanical crack-face boundary conditions. The calculations confirm that only
true equilibrium states exhibit path-independence of J, and that domain structures near
crack tips may be responsible for allowing positive energy release rate during purely
electrical loading.
The small deformation assumption is prevalent in the phase-field modeling
approach, and is used in the previously described calculations. The analysis of large
deformations will introduce the concept of Maxwell stresses, which are assumed to be
higher order effects that can be neglected in the small deformation theory. However, in
order to investigate the material response of soft dielectric elastomers undergoing large
mechanical deformation and electric field, which are employed in electrically driven
actuator devices, manipulators and energy harvesters, a finite deformation theory is
incorporated in the phase-field model. To describe the material free energy,
compressible Neo-Hookean and Gent models are used. The Jaumann rate of the
polarization is used as the objective polarization rate to make the description of the dissipation frame indifferent. To illustrate the theory, electromechanical instabilities in composite materials with different inclusions will be studied using the finite element
methods. / text
| Identifer | oai:union.ndltd.org:UTEXAS/oai:repositories.lib.utexas.edu:2152/ETD-UT-2011-12-4705 |
| Date | 01 February 2012 |
| Creators | Li, Wenyuan, 1982- |
| Source Sets | University of Texas |
| Language | English |
| Detected Language | English |
| Type | thesis |
| Format | application/pdf |
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