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Impact of initial stress induced deformation on eigenfrequencies
Posted Jul 6, 2012, 9:32 a.m. EDT MEMS & Nanotechnology, MEMS & Piezoelectric Devices, Structural Mechanics Version 4.1 0 Replies
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working with COMSOL 4.1 I am trying to solve the problem of the initial stress/strain induced deformation in the unimorph bridges.
Doubly calmped rectangular beam consists of three layers:
1. doped semicondoctur (top electrode)
2. piezoelectric layer
3. metall layer (bottom electrode)
The aim is to look what is the dependence of the eigenfrequencies upon changes of the compressive strain in the thick top electrode.
I am following the procedure described below
1. I am taking the Piezoelectric Devices model
2. I am defining Initial Stress & Strain (in-plane, isotropic) in the Linear Elastic Material Model applied
to the top and bottom electrodes (piezoelectric in pzd. model remains unstressed)
s0 =
|144e6 0 0|
|0 144e6 0|
|0 0 0|
3. In Stationary Study I am getting the deformation defined by pre-stress
4. In the same Study I am performing the calculations of Eigenfrequencies
and see no changes comparing to the non-prestressed case.
Is it bug, or I did something wrong?
From experiments and analytical calculations I know the results. The shift is enourmous.
Unfortunatelly, the formulas are not quite applicable in the case of more complex geometries.
Can anybody give me an advice? I would be very thankful indeed.
the model file is attached
Regards, Vadim
Attachments:
Hello Vadim Lebedev
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