Müller, Ralf ; Gross, Dietmar (2005)
Application of material forces in defect mechanics.
11th International Conference on Fracture 2005. Turin, Italy (20.03.2005-25.03.2005)
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Kurzbeschreibung (Abstract)

Ferroelectric materials are nowadays widely used in sensor and actuator applications. Their applicability in cyclic loading however is limited by the so called ’electric fatigue’ effect. Under this terminology various micro-mechanical phenomena are summarized. On the macroscopic level a reduction of the mechanical output for a fixed electric excitation is observed. One of suspected micro-mechanical mechanisms is the hindering and blocking of domain wall movement within the material. Possible sources of these blocking phenomena are point defects in the material. The point defects interact with the domain wall (inhomogeneity) and the external applied loads. Experimentally observations suggest that these point defects are oxygen vacancies. Their presence and characterization is however an experimentally difficult task. The numerical simulation is intended to provide a qualitative understanding of the interaction of point defects and domain walls. In order to model these inhomogeneities the material forces or driving forces acting on the domain wall are identified. Once the coupled field equations are solved by Finite Elements the material forces are calculated to investigate possible motions of the domain wall. At the present state the work does not incorporate a kinetic law, but is based on quasi-equilibrium considerations. The numerical simulations will demonstrate the effect of point defect position and concentration on the driving force acting on the domain wall. Eventually leading to a possible blocking of the domain wall. In order to overcome these obstacles higher external fields are necessary to move the domain wall again.

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