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Hinge model

Posted 08.07.2019, 05:30 GMT-4 Structural & Acoustics, General, Structural Mechanics Version 5.4 3 Replies

Sherry
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Hi all,

I need to model a hinge with structural mechanics module. Is it possible to achieve large rotations? Or it will just work for small rotations? I want to see if its necessary to buy Multibody dynamics module..

Thanks

Shaghayegh

3 Replies Last Post 09.07.2019, 11:24 GMT-4
Henrik Sönnerlind COMSOL Employee

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Posted: 5 years ago 08.07.2019, 10:56 GMT-4
Updated: 5 years ago 08.07.2019, 10:56 GMT-4

Hi,

As long as you can formulate the appropriate set of coupling equations for finite rotations, there is no limitation as such for creating a hinge coupling which works for large rotations. If the axis of the hinge has a fixed orientation, it should not be that difficult. If the hinge axis orientation can rotate, it is a bit trickier, but not impossible.

The only built-in support for various mechanisms is in the Multibody Dynamics module though.

Regards,
Henrik

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Henrik Sönnerlind
COMSOL
Hi, As long as you can formulate the appropriate set of coupling equations for finite rotations, there is no limitation as such for creating a hinge coupling which works for large rotations. If the axis of the hinge has a fixed orientation, it should not be that difficult. If the hinge axis orientation can rotate, it is a bit trickier, but not impossible. The only built-in support for various mechanisms is in the Multibody Dynamics module though. Regards, Henrik
Sherry
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Posted: 5 years ago 09.07.2019, 05:09 GMT-4
Updated: 5 years ago 10.07.2019, 05:09 GMT-4

Dear Henrik,

Thank you very much for your reply. The hinge which I want to model has a fixed orientation (Y axis). At first I used Form Assembly, then performed following procedures to couple displacements and rotations:

  1. Displacements at Rigid Connector 2 are linked to those of Rigid Connector 1

  2. x- and z- relative rotations are set to be zero, so that only the relative y-rotation is permitted. To express these conditions, I used two Global Constraint(s) nodes.

Rot_x (RC2) = Rot_x (RC1) , and

Rot_z (RC2) = Rot_z (RC1)

Then I apllied boundary load to rotate it. Even with very large forces I only received very small rotations. Can I kindly ask you to check my file as I really need your help.

Best regards,

Shaghayegh

Dear Henrik, Thank you very much for your reply. The hinge which I want to model has a fixed orientation (Y axis). At first I used Form Assembly, then performed following procedures to couple displacements and rotations: 1. Displacements at Rigid Connector 2 are linked to those of Rigid Connector 1 2. x- and z- relative rotations are set to be zero, so that only the relative y-rotation is permitted. To express these conditions, I used two Global Constraint(s) nodes. Rot_x (RC2) = Rot_x (RC1) , and Rot_z (RC2) = Rot_z (RC1) Then I apllied boundary load to rotate it. Even with very large forces I only received very small rotations. Can I kindly ask you to check my file as I really need your help. Best regards, Shaghayegh
Henrik Sönnerlind COMSOL Employee

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Posted: 5 years ago 09.07.2019, 11:24 GMT-4
Updated: 5 years ago 09.07.2019, 11:23 GMT-4

Dear Shaghayegh,

Even though we sometimes post a quick answer here on the User Forum to questions which have some general interest, I hope that you understand that you cannot expect support from COMSOL staff when it involves debugging specific models. For that you would have to turn to the standard support channels.

The modeling you describe above does however make sense. Since the axis orientation is fixed, it would also be possible to constrain the rotations individually rather than just the relative difference.

Hopefully somone in the user community can help you out here. By the way, if you post a few screenshots, the probablility of getting an answer increases.

Regards,
Henrik

-------------------
Henrik Sönnerlind
COMSOL
Dear Shaghayegh, Even though we sometimes post a quick answer here on the User Forum to questions which have some general interest, I hope that you understand that you cannot expect support from COMSOL staff when it involves debugging specific models. For that you would have to turn to the standard support channels. The modeling you describe above does however make sense. Since the axis orientation is fixed, it would also be possible to constrain the rotations individually rather than just the relative difference. Hopefully somone in the user community can help you out here. By the way, if you post a few screenshots, the probablility of getting an answer increases. Regards, Henrik

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