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Inducing torque at the ends of a deformed, imported 3D beam geometry
Posted 27 gen 2017, 11:48 GMT-5 Heat Transfer & Phase Change, Geometry, Mesh, Structural Mechanics Version 5.2 11 Replies
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This is unfortunately quite sloppy since the beam is deformed - I have lots of overlap and it's difficult to clean up for meshing. I am currently just reducing repair tolerance and using virtual operations to clean it up but I'm not sure exactly which virtual operations are needed. Typical error messages when trying to mesh this are "overlapping faces" and "failed to insert point".
If anyone has any ideas on how to do induce the moments C_1 and C_2 more gracefully or implement the arms without overlap or any tips on which virtual operations could best be employed here, I would be extremely grateful. Thank you very much!
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Have you considered applying a spatially-dependent load on each end of your beam?
A load that's positive at the top, same magnitude but negative at the bottom, and varies linearly in between will apply a torque without applying a net force. From a Saint-Venant's principle perspective it is the same as a concentrated torque.
Best,
Jeff
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Hi Nicholas,
Have you considered applying a spatially-dependent load on each end of your beam?
A load that's positive at the top, same magnitude but negative at the bottom, and varies linearly in between will apply a torque without applying a net force. From a Saint-Venant's principle perspective it is the same as a concentrated torque.
Best,
Jeff
I did not consider this, it sounds great! Do you mean applying the loads on the the upper and lower edges of the beam in the longitudinal direction?
Also, what sort of boundary conditions could I use for this? In some cases this beam will be deformed asymmetrically and I will want to apply moments/torques asymmetrically. The advantage of using the arms was that I could apply my constraints mostly to them without having to place any non-physical constraints on the beam. Right now the only constraint on the beam is an x,y-fixed-point on the bottom-center so it is free to move vertically which will be necessary in the asymmetric cases. I can't find a way to hold the beam in three dimensions without interfering with this asymmetric bending somehow.
Thanks a ton for your reply.
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Note that imposing no displacement at a single point is not enough constraints to remove all three rigid body motions in 2D: the rotation around the fixed point remains unchecked. Ultimately, how you constrain the structure needs to be decided based on the physical reality you're modeling.
Best,
Jeff
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See the attached file.
Note that imposing no displacement at a single point is not enough constraints to remove all three rigid body motions in 2D: the rotation around the fixed point remains unchecked. Ultimately, how you constrain the structure needs to be decided based on the physical reality you're modeling.
Best,
Jeff
Awesome, I'll check this out first thing Tuesday. Thanks so much for putting that together for me. I do understand that the model needs to be constrained in three dimensions - it's just the case that I don't want to impose a vertical constraint on the beam itself because the study is based on vertical bending in order to correct vertical deformation. If the deformations were always symmetric, then I could feasibly constrain some center part of the beam in all 3 dimensions. At any rate, I will look in to it further next week; Have a great weekend!
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See the attached file.
Note that imposing no displacement at a single point is not enough constraints to remove all three rigid body motions in 2D: the rotation around the fixed point remains unchecked. Ultimately, how you constrain the structure needs to be decided based on the physical reality you're modeling.
Best,
Jeff
Hi Jeff, would it be possible to get a version of that file that I can open up with version 5.2? Thank you!
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I still would strongly recommend you upgrade to 5.2a if you can. The name does not necessarily suggest it but there are many valuable additional features in 5.2a compared to 5.2, see www.comsol.com/release/5.2a .
Best,
Jeff
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Here you go!
I still would strongly recommend you upgrade to 5.2a if you can. The name does not necessarily suggest it but there are many valuable additional features in 5.2a compared to 5.2, see www.comsol.com/release/5.2a .
Best,
Jeff
Great, I really appreciate it!
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I invite you to contact our tech support team if we can be of further help.
Jeff
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Jeff
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