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Prestressed piezoelectric analysis in frequency domain
Posted 10.01.2015, 04:46 GMT-5 Structural Mechanics Version 4.4 6 Replies
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I'm trying to simulate the prestress effect on the resonance frequency of a piezoelectric material using the "piezoelectric devices" physics.
I'm trying to do it in two steps :
1. Apply the static force to the structure and solve the problem using a stationary study and store the solution.
2. I use the stored solution to initialize the variables of the frequency domain step. I disable the "boundary load" condition and apply voltage to the piezoelectric material.
The result seems not good. when i look at the 3D stress for different values of the prestress the result remain unchanged.
I believe i'm missing something here, in particular the transition from step 1 to step 2.
Could you please help ?
thank you
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In order to get any prestress effects, you must enable geometric nonlinearity in the second study step.
Using the new piezoelectic coupling feature available in version 5.0 will make this type of modeling significantly easier. You will then have access to the predefined study type 'Prestressed Analysis, Frequency Domain'. You will also have access to 'Harmonic Perturbation' settings for loads and boundary conditions both for mechanical and electrical features.
Regards,
Henrik
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Thank you for your valuable feedback.
I will try to install the 5th release of COMSOL.
It is "impossible" or just "complicated" to do this kind of piezoelectric study with Comsol 4.4 ?
Thank you,
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You can do the analysis in version 4.4 too. It is just that you are a bit more on your own in setting up the analysis.
Essentially there are three things that you should pay attention to:
1. Enable geometric nonlinearity in at least the frequency domain analysis
2. Manually add the linper() operator to the harmonic perturbation loads (I guess that wold be the electric potential in your case).
3. Set up the frequency domain solver to do a linear perturbation analysis.
You should not use the enable/disable functionality. The separation between prestress and perturbation should be made using the linper() operator.
Regards,
Henrik
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Thank you for your help, it works when following the steps you mention in your reply.
However i have a question, what is the difference between enabling the geometric nonlinearity and adding a moving mesh node ?
Thank you
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However i have a question, what is the difference between enabling the geometric nonlinearity and adding a moving mesh node ?
These are different things. Typically you would use a moving mesh to model a non-solid domain with a changing shape, such as the fluid domain in a fluid-structure interaction problem. The boundary of a moving mesh domain is then controlled by an adjacent Solid Mechanics domain. Solid Mechanics is formulated on the 'Material Frame' (search for it in the documentation).
Regards,
Henrik
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I am trying to perform pre-stressed analysis on piezoelectric model as well - would it be possible to see your model settings ? My results are strange with the settings I use now and I am not sure if they are correct.
thanks
Oskar