Ball Joint Constraint - FEMAP/NASTRAN 2

[MegaStructures]

what is the best way to simulate a pinned joint on a solid model? I am analyzing a ball joint and need to set a constraint that will allow the solid to rotate, but not translate. If I set a pinned constraint by surface the solid will not be able to rotate. I would like to do this without using linear contact. Any help is appreciated.

Edit the image shown is an example only. The ball joint I have cannot be constrained on the shaft as it is part of a larger model and it needs to be constrained at the correct interface.

 

[ThomasH]

Hi
I don't think I have ever done it. But I think a local spherical coordinate system and then the appropriate constraints should solve it.

Thomas

 

[BlasMolero]

Hello!,
Simply the use RBE2+CBUSH+RBE2 will do the job perfectly. The problem can not be solved using external constraints, this is an internal problem.
You need to do the following:
• Select the nodes of the surface of the ball and create an RBE2 element, with the INDEPENDENT node in the center of the sphere ball.
• Run the same way with the nodes of the external surface of the other component.
• Finally the key is the CBUSH element: create a 2-NODE CBUSH element with the 2-nodes being coincident located the the center of the sphere ball, one node is the INDEPENDENT node of the RBE2 element of the ball surface and the other is the independent node of the other RBE2 element of the surface nodes in the other part. Edit the CBUSH property values of stiffness and enter values like 1e6 N/mm per DOF 1, 2 & 3, letting zero for rotational 4, 5 & 6 DOF

And you are done!.
Best regards,
Blas.

~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director

IBERISA
48004 BILBAO (SPAIN)
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http://www.iberisa.com

Blog de FEMAP & NX Nastran:

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[MegaStructures]

Wow great advice Blas thank you!

 

[ThomasH]

Hi
My first impression was that you wanted to simulatee the constraints on the ball joint, the blue part. I did not include the yellow part in the model.

My mistake.

Thomas

 

[MegaStructures]

You are correct Thomas I will only use part of Blas’s advice above. I will fix a center node with RBE2 connected to the surface. Your advice might work too, I just don’t have the experience to pull it off.