Menu

Discussion Forum

New Discussion
Filtrer

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 The information provided may be out of date.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.

Confused on modeling thermal expansion in a plastic block

Posted 7 oct. 2013, 20:39 UTC−4 Structural Mechanics Version 4.3b 3 Replies

Jessica Faust
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Hi,

I am new to Comsol and trying to model the thermal expansion of a small plastic cube on a post. I was hoping this would be simple to model, but I am having trouble getting the expansion to act correctly. Hopefully someone can help me troubleshoot this, because I am at a loss.

I am heating and cooling a plastic cube (1cm length/width/height) from one side from -55 degC to 85 degC and I am interested in looking at the total expansion in the x and z directions. I used the "Thermal Stress" module available in Comsol 4.3b to attempt to model this.

Each time I run the program with different thermal expansion coefficients or different temperatures, it still gives me a 1mm expansion in each direction. It's as if the parameters I entered do not influence what the program is calculating for the expansion. On paper, I calculated that the total expansion when heated from room temp (~25degC) to 85degC is roughly 50um, so the 1mm that Comsol is calculating is much too high.

If you have any thoughts, I would greatly appreciate it. I have been struggling with this for days now.

Thanks!

Jessica
3 Replies Last Post 9 oct. 2013, 11:24 UTC−4
Jeff Hiller COMSOL Employee

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 8 oct. 2013, 17:31 UTC−4
Hello Jessica,
When plotting the deformed shape in a structural analysis, COMSOL uses a scaling factor to exaggerate the deformations so they are visible to the naked eye. Perhaps this is what's leading you to believe that the displacements are larger than they actually are. Just a guess.
Jeff
Hello Jessica, When plotting the deformed shape in a structural analysis, COMSOL uses a scaling factor to exaggerate the deformations so they are visible to the naked eye. Perhaps this is what's leading you to believe that the displacements are larger than they actually are. Just a guess. Jeff
Jessica Faust
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 9 oct. 2013, 07:48 UTC−4
Hi Jeff, and thank you for replying. I had not thought of that idea. That does make sense though. Do you know if there a way for me to calculate what the actual expansion is in Comsol even if it is exaggerating the results?
Hi Jeff, and thank you for replying. I had not thought of that idea. That does make sense though. Do you know if there a way for me to calculate what the actual expansion is in Comsol even if it is exaggerating the results?
Jeff Hiller COMSOL Employee

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 9 oct. 2013, 11:24 UTC−4
You could do a surface (or volume) plot of the displacements for instance. The min and max values will then be indicated on the colorbar.
The Reference Manual has extensive information on the many postprocessing options available. You can access that manual through the Help menu.
Jeff
You could do a surface (or volume) plot of the displacements for instance. The min and max values will then be indicated on the colorbar. The Reference Manual has extensive information on the many postprocessing options available. You can access that manual through the Help menu. Jeff

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.

Suggested Content