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Boundary conditions for identity pairs

Posted 2011年3月23日 GMT-4 04:18 Materials, Parameters, Variables, & Functions, Structural Mechanics Version 4.1 2 Replies

PerD
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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


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2 Replies Last Post 2011年3月24日 GMT-4 02:36
Nagi Elabbasi Facebook Reality Labs
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Posted: 1 decade ago 2011年3月23日 GMT-4 10:11
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)
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Posted: 1 decade ago 2011年3月24日 GMT-4 02:36
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

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