Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.

Large deformation issue

Please login with a confirmed email address before reporting spam

Hello,

I'm facing a few problems while attempting electrostatic actuation of a fixed-fixed membrane.

But let's start with the most puzzling issue:

Consider a 2D model (plane stress + moving mesh) with a thin and long membrane (1µmx300µm) fixed at both extremities and surrounded by air. I apply a load to the lower boundary of the membrane so that it deforms no more than 4µm vertically (maximum total displacement).

Well, I obtain very different results when the "Large Deformation" option is ON or OFF.
When ON, I observe a linear increase of max displacement with load, and when OFF the displacement is much smaller and more asymptotic.
I would think that a displacement of max 4µm for a 300µm long film is consistent with a small deformation and in that case, I really don't understand why the difference!! I can't find how this option affects the equations...

Moreover if then I want to introduce "initial stresses" in the membrane, then the amount of stress has absolutely no effect on the maximum displacement in the OFF case, and a huge effect in the ON case!

If anyone can provide an explanation, it would really help, because otherwise I'm stuck!
Thank you

Elodie

0 Replies Last Post Apr 27, 2010, 8:06 a.m. EDT
COMSOL Moderator

Hello elodie leveugle

Your Discussion has gone 30 days without a reply. If you still need help with COMSOL and have an on-subscription license, please visit our Support Center for help.

If you do not hold an on-subscription license, you may find an answer in another Discussion or in the Knowledge Base.

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.