Menu

Discussion Forum

New Discussion
Filter

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 The information provided may be out of date.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.

Boundary conditions for identity pairs

Posted Mar 23, 2011, 4:18 a.m. EDT Materials, Parameters, Variables, & Functions, Structural Mechanics Version 4.1 2 Replies

PerD
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Hi

I'm trying to use an idendity pair to connect to parts in an assembly but can't get it to work as intended.

To illustrate the concept I've included a simple model. The model consists of a simple-simple supported beam with a evenly distrubuted load that consist of two "layers". I want the boundary between the two "layers" to transfer loads in the z-direction only and not to transfer shear forces in the plane.

In other words i want the moment of inertia of the beam to be I=1/12*w*(h1^3+h2^3) and not I=1/12*w*(h1+h2)^3 which is the case if a union is formed of the two parts.

Initially I thought I could use a "Roller" boundary condition but it seems to be fixed in a non deformed coordinate system.

If anybody has any suggestions please let me know.

Best regards,

Per


Attachments:

2 Replies Last Post Mar 24, 2011, 2:36 a.m. EDT
Nagi Elabbasi Facebook Reality Labs
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Mar 23, 2011, 10:11 a.m. EDT
My experience with the Roller boundary condition is that it applies to each surface individually (even when applied to an identify pair). That means that both your surfaces will be constrained in the normal direction. What you really need is to constrain the relative motion between the two surfaces instead. You should try using a contact pair instead.

Nagi Elabbasi
Veryst Engineering
My experience with the Roller boundary condition is that it applies to each surface individually (even when applied to an identify pair). That means that both your surfaces will be constrained in the normal direction. What you really need is to constrain the relative motion between the two surfaces instead. You should try using a contact pair instead. Nagi Elabbasi Veryst Engineering
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Mar 24, 2011, 2:36 a.m. EDT
Hi

I havent used these new features in V4 yet, but you should notice the the roller condition has sub-nodes. Study the equations underlaying, you might get around by adding a sub-node roller, but I haven't tried this out, it would indeed need further investigations, but I expect it to be possible to get the two surfaces to "roll" one upon each other and not w.r.t. a external absolute frame

--
Good luck
Ivar
Hi I havent used these new features in V4 yet, but you should notice the the roller condition has sub-nodes. Study the equations underlaying, you might get around by adding a sub-node roller, but I haven't tried this out, it would indeed need further investigations, but I expect it to be possible to get the two surfaces to "roll" one upon each other and not w.r.t. a external absolute frame -- 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