|Department of Engineering
|University of Cambridge > Engineering Department > MMD|
Ferroelectric materials (e.g. PZT) are increasingly used in actuators and sensors. For maximum output they operate within the non-linear regime, and transformation from one crystal variant to the next is by domain wall motion. The design, manufacture and use of these devices are not optimal as they are based on simple empirical constitutive models. We propose to develop a robust constitutive model for the non-linear behaviour of ferroelectrics under general mechanical and electrical loading, based on the underlying switching mechanism. The first steps to achieve this ambitious goal have already been taken: the recent self-consistent crystal plasticity model of Fleck, McMeeking and Huber can predict the progressive switching and hysteresis of PZT. Further, it predicts the development of a 'yield surface' in combined stress-electric field space with a corner at the loading point; the yield surface partitions the elastic regime from the non-linear switching regime. We propose to develop the model further by performing a number of non-linear homogenisation calculations based on new variational bounds and estimates. The accuracy of the predictions will be assessed by performing experiments on soft, hard and relaxor PZTs. Proportional loading experiments will be performed to simulate the response of typical ferroelectric actuators, and non-proportional loading experiments will be performed to probe the 'yield surface' for the possible existence of corners. A simplified version of the constitutive model will be implemented with a finite element code and used to estimate the deformation state within a stack actuator under a combination of residual stress (from manufacture) and in-service loading. Potential failure mechanisms will be explored.
Engineering and Physical Sciences Research Council (EPSRC) studentship.
Research Groups Involved:
For further information and to apply contact:
|Professor N A Fleck
Cambridge University Engineering Dept
Cambridge, CB2 1PZ
|Phone: +44 (0)1223 332650
Fax: +44 (0)1223 332662
Initial letters of application and CVs should be sent to Professor Fleck.
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