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 The information provided may be out of date.

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.

Eigenfrequency shift due to thermal expansion

Please login with a confirmed email address before reporting spam

Hi,

I'm new to Comsol and the Comsol I'm using is 4.3. I would like to study the eigenfrequency shift of a solid cylinder over the time when an infrared laser is heating one of its surface. The heating will cause thermal stress and expansion change inside the material thus changing the eigenfrequency. So I use "Joule Heating and Thermal Expansion" physics. First, I run a time dependent study and then run a new study of eigenfrequency to find resonant frequencies around 15,000 Hz. I want to use the result of the time-dependent study as the initial parameters of the eigenfrequency study. So in "Values of variables not solved for" of eigenfrequency study, I choose the time dependent solution at a certain time. However, no matter which time I choose, from the "Mode Shape" in the Results the Comsol always give me the same eigenfrequencies. I also tried to use "Initial Values of Variables Solved for" but it doesn't work either. Can anyone suggest which points I missed in order to do it properly? I have attached my file but I deleted the solver configurations in order to save space (I used the default solvers).


1 Reply Last Post 2 juil. 2015, 08:38 UTC−4
Henrik Sönnerlind COMSOL Employee

Please login with a confirmed email address before reporting spam

Posted: 9 years ago 2 juil. 2015, 08:38 UTC−4
Hi,

There are different effects which may cause a change of eigenfrequnecies with temperature:

a) Changes in material data with temperature
b) Changes in geometry (usually small)
c) Stress stiffening caused by thermal stresses

Of course, it can also be a combination.

There are different things you need to consider here, so first you need to state which effects you are looking for. There are several discussions about this in the forum, see for example

www.comsol.com/community/forums/general/thread/47241
www.comsol.com/community/forums/general/thread/34427

Regards,
Henrik
Hi, There are different effects which may cause a change of eigenfrequnecies with temperature: a) Changes in material data with temperature b) Changes in geometry (usually small) c) Stress stiffening caused by thermal stresses Of course, it can also be a combination. There are different things you need to consider here, so first you need to state which effects you are looking for. There are several discussions about this in the forum, see for example http://www.comsol.com/community/forums/general/thread/47241 http://www.comsol.com/community/forums/general/thread/34427 Regards, Henrik

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.