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Department of Engineering
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| University of Cambridge > Engineering Department > MMD |
Principal Investigator:
Norman Fleck
Project Details:
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.
Funding Source:
Engineering and Physical Sciences Research Council (EPSRC) studentship.
Research Groups Involved:
Application Deadline:
Open
For further information and to apply contact:
| Professor N A Fleck Cambridge University Engineering Dept Trumpington Street Cambridge, CB2 1PZ United Kingdom |
Phone: +44 (0)1223 332650 Fax: +44 (0)1223 332662 email: div-c@eng.cam.ac.uk |
Initial letters of application and CVs should be sent to Professor Fleck.
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