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Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.

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Frequency response of a structure with residual stress

Posted 20.07.2012, 16:16 GMT-4 Structural Mechanics Version 3.5a 3 Replies

T Cheng
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I would like to run a frequency response analysis on a silicon nitride membrane under tensile stress. I followed the instructions in the version 3.5a manual for "Residual stress in a thin-film resonator" to get the eigenfrequencies of the stressed structure. Do I follow the exact same procedure for harmonic analysis, ie, solve for the static solution with stress and then run a harmonic analysis?

In particular, do I keep the "include thermal expansion" box checked on the subdomain properties when running the frequency response? I'm wondering if that stress load becomes a harmonic load in the frequency response analysis. That does not seem desireable to me, since I only want the membrane to be statically stressed and to be used as a starting point for the frequency response.

Thanks in advance.
3 Replies Last Post 28.07.2012, 23:13 GMT-4
Nagi Elabbasi Facebook Reality Labs
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Posted: 1 decade ago 21.07.2012, 23:11 GMT-4
The stress load in the initial static analysis should not become a harmonic load in the second analysis if the settings are done correctly. In the latest COMSOL version you can do that by setting the Study type to “Prestressed Analysis, Frequency Domain”. Then when defining the loads right click on the load nodes and select “Harmonic Perturbation” only for the harmonic loads. There is a basic COMSOL example that shows these settings in “Introduction to the Stuctural Mechanics Module. Model ID: 10314”.

Nagi Elabbasi
Veryst Engineering
The stress load in the initial static analysis should not become a harmonic load in the second analysis if the settings are done correctly. In the latest COMSOL version you can do that by setting the Study type to “Prestressed Analysis, Frequency Domain”. Then when defining the loads right click on the load nodes and select “Harmonic Perturbation” only for the harmonic loads. There is a basic COMSOL example that shows these settings in “Introduction to the Stuctural Mechanics Module. Model ID: 10314”. Nagi Elabbasi Veryst Engineering
T Cheng
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Posted: 1 decade ago 28.07.2012, 16:19 GMT-4
Nagi, thank you for your reply. Is there a way to do what you described in version 3.5a?

Thanks!
Nagi, thank you for your reply. Is there a way to do what you described in version 3.5a? Thanks!
Nagi Elabbasi Facebook Reality Labs
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Posted: 1 decade ago 28.07.2012, 23:13 GMT-4
It most probably can be done in 3.5a but requires some manual setup.
It most probably can be done in 3.5a but requires some manual setup.

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