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Electrostatic force on cantilever beam
Posted 22 feb 2011, 10:16 GMT-5 2 Replies
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Hi,
I'm modelling a CNT cantilever beam with above a silicon substrate. I've used the assemble mode to use the contact pair. The problem is that when I define some potencial over the beam It does distribute the electric charge but when I apply the structural mechanics module to compute the electrostatic force the beam does not deform.
I've tried with a pure mechanical load and the model works perfectly. I don't know if the BC or the pairs might be affecting this.
I'll attach the model.
Hope somebody can help me.
Thank you
I'm modelling a CNT cantilever beam with above a silicon substrate. I've used the assemble mode to use the contact pair. The problem is that when I define some potencial over the beam It does distribute the electric charge but when I apply the structural mechanics module to compute the electrostatic force the beam does not deform.
I've tried with a pure mechanical load and the model works perfectly. I don't know if the BC or the pairs might be affecting this.
I'll attach the model.
Hope somebody can help me.
Thank you
Attachments:
2 Replies Last Post 23 feb 2011, 22:01 GMT-5
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Posted:
1 decade ago
Hi
I have a few other comments:
- Check your materials, I do not believe the beam should be of "air" (domain 4) or is the beam only domain "5" ?
- Check your structural physics: if you use ALE you should not define the air as a "solid", and the bottom electrode is probably also to be fixed
- Check your ES physics, by default in union mode you have continuity so you do not need the pairs and continuity
Your overall air domain is very large and not symmetric, your electric field will be influenced by these close boundaries, while you loose a lot of mesh volume. I use mostly round circle/sphere air domains to minimise the edges and to not disturb the fields by square shapes, then I add a thin "infinite element layer
in your example when you come to a contact you will change the topology, the ALE mash must locally wanish which is not acceptable, so you must use an offset >0 to leave some volume for the ALE mesh
Anyhow you will also face the difficulty of the bifurcation of the pull in voltage, but leave that to later when your model solves at least up to a given voltage
--
Good luck
Ivar
I have a few other comments:
- Check your materials, I do not believe the beam should be of "air" (domain 4) or is the beam only domain "5" ?
- Check your structural physics: if you use ALE you should not define the air as a "solid", and the bottom electrode is probably also to be fixed
- Check your ES physics, by default in union mode you have continuity so you do not need the pairs and continuity
Your overall air domain is very large and not symmetric, your electric field will be influenced by these close boundaries, while you loose a lot of mesh volume. I use mostly round circle/sphere air domains to minimise the edges and to not disturb the fields by square shapes, then I add a thin "infinite element layer
in your example when you come to a contact you will change the topology, the ALE mash must locally wanish which is not acceptable, so you must use an offset >0 to leave some volume for the ALE mesh
Anyhow you will also face the difficulty of the bifurcation of the pull in voltage, but leave that to later when your model solves at least up to a given voltage
--
Good luck
Ivar
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Posted:
1 decade ago
Hello,
thanks for your advice Ivan,
I've followed your advice, but there's a thing I can't get done yet.
My model is in assembly mode but I just used the union operation in the air boundaries. The beam is only the boundary 5. Now I get a inverted mesh warning and my model does not find any solution. I'm still thinking that there must be some kind of problem with the BC.
Thanks for your help.
I'm attanching a modified model
thanks for your advice Ivan,
I've followed your advice, but there's a thing I can't get done yet.
My model is in assembly mode but I just used the union operation in the air boundaries. The beam is only the boundary 5. Now I get a inverted mesh warning and my model does not find any solution. I'm still thinking that there must be some kind of problem with the BC.
Thanks for your help.
I'm attanching a modified model
Attachments: