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 The information provided may be out of date.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.
Importing a CAD Model that is an assembly.
Posted 28 juil. 2010, 20:27 UTC−4 Version 3.5a 6 Replies
Please login with a confirmed email address before reporting spam
They are in contact. And one parts sticks to another parts on one of the surfaces.
When I import this assembly CAD model to Comsol, comsol understands it as "one body", not "two body with a contact surface" ( I had to convert them to STL since comsol cannot import ProE file. )
For example, if you click on subdomain setting, on the subdomain selection menu on the left, there is only one body.
I need to input differents materials properties for different parts.
Anybody has any idea how to go about this problem.
Thanks in advance !
and sorry if my questions is something dumb. I am a bigginer in CAD and simulation
by the way Im using comsol 3.5a
Thanks!
Please login with a confirmed email address before reporting spam
Please login with a confirmed email address before reporting spam
Thanks and Regards
Please login with a confirmed email address before reporting spam
you should learn the diferences of asembled (two bodies in contact but with each it's own boundary overalapping) and union mode where both bodies have a common boundary.
The latter is mostly the default, as it means you have continuity of flux over this boundary, once you have "geomanalysed" your geometry, you have two bodies but one common boundary with "continuity".
If you want to add specific physics on the boundary depends on te physics or application modes mostly you must use assembly mode to define the two boundary surfaces, each with opposed normals.
In particular if you are working with contact surfaces, with our without sliding, then you should use assembly mode, if not normal union mode is easier and the model is simpler.
Assembly mode means also that you will mesh each of the two boundary surfaces independently
Hope this helps
--
Good luck
Ivar
Please login with a confirmed email address before reporting spam
The attached images give an idea of the example problem I'm running. I'm doing an example stress analysis of a small screw inside of a larger structure (mainly just to make sure this problem is indeed running OK). I did not apply any contact pairs or identity pairs where the threads meet inside.
The puzzle is that the model appears to run fine when I am applying a distributed positively-directed z load on the top surface of the little screw; I fix the boundaries of most of the bottom of the outside structure into which the small screw is placed. On the one hand, the ex strains look reasonable for the bending of the small screw's shaft as expected, e.g., tension on the one side and compression on the other. HOWEVER, here is the very odd result: note that the deformed shape and the z displacement output seem to be saying that the screw bends toward the negative z direction! And note the scale for the displacements -- in the balpark of 1 e12 !! What is wrong? Am I missing something very basic in the model setup, leading to this absurd result?
Thanks very much.
Hi
you should learn the diferences of asembled (two bodies in contact but with each it's own boundary overalapping) and union mode where both bodies have a common boundary.
The latter is mostly the default, as it means you have continuity of flux over this boundary, once you have "geomanalysed" your geometry, you have two bodies but one common boundary with "continuity".
If you want to add specific physics on the boundary depends on te physics or application modes mostly you must use assembly mode to define the two boundary surfaces, each with opposed normals.
In particular if you are working with contact surfaces, with our without sliding, then you should use assembly mode, if not normal union mode is easier and the model is simpler.
Assembly mode means also that you will mesh each of the two boundary surfaces independently
Hope this helps
--
Good luck
Ivar
Attachments:
Please login with a confirmed email address before reporting spam
well its difficult to undertand your volume, from the smll items, are they really one volume or many assembled ?
if you have such a displacement, are you sure youre part is "fixed" or sufficient constrined somewhere, it's just as if it hase translated freely by 1E12 m
--
Good luck
Ivar
Please login with a confirmed email address before reporting spam
Hi
well its difficult to undertand your volume, from the smll items, are they really one volume or many assembled ?
if you have such a displacement, are you sure youre part is "fixed" or sufficient constrined somewhere, it's just as if it hase translated freely by 1E12 m
--
Good luck
Ivar
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
- FORUM How to select all surfaces outside a complex assembly at once?
- KNOWLEDGE BASE Resolving Gaps and Intersections in Imported CAD Assemblies
- FORUM Could not obtain license for CAD Import Module.
- BLOG Working with Imported CAD Designs
- FORUM How to create a contact pair though import dxf model generated by CAD?