Cancel
Showing results for 
Search instead for 
Did you mean: 

Validation of automatic coupling

Hi there,

 

because i have to use the feature "automatic coupling" i have to know how this feature works. So i read the NASTRAN user's guide and found this (26-16):

cyclic symmetry.png

 

Like on this picture it seems to be the software will couple the nodes on side 1 with the nodes on side 2 so the displacement on side 1 should be the same as side 2. But sadly i can't read this anywhere. My question: is this statement true -> u2 = u1 ?

 

Another question: If i apply loads to the part i coupled the nodes for cyclic symmetry will the loads also simulated like they would applied over the whole perimeter? Or is the automatic coupling feature only limited to centrifugal inertia load? Cause i compared the different situations but only with centrifugal inertia load i get the same results like on the entire model.

cyclic symmetry force.PNG

 

Thank you for your help Smiley Happy

15 REPLIES

Re: Validation of automatic coupling

Siemens Creator Siemens Creator
Siemens Creator

This is an example of "Cyclic Symmetry."  It is explained in the NX Help documents. The displacements are matched by the software at each of the symmetry boundaries. Loads applied to the mesh will obey those symmetry conditions.

 

If you have a force applied to the mesh and all your boundaries have symmetric boundary conditions (BCs), then the "complete" part is subject to that entire force; the sum of all the forces.

 

The applied force can be "mirrored" in the plus-to-minus direction using the planes of symmetry and their boundary conditions. If one of the boundaries has symmetric BCs applied and the other is anti-symmetric, then you will have loaded the part with one segment loaded in the positive direction, and the other (the invisible mirrored one) in the negative direction.

Re: Validation of automatic coupling

Hi,

 

thank you for your help. I know the example in nx help document but there is nowhere written that the displacements are the same on side 1 as on side 2.

 

you mean this document?

automatic coupling

 

sorry it's maybe in german i don't know how to display this in englisch.

 

thank you Smiley Happy

Re: Validation of automatic coupling

Siemens Creator Siemens Creator
Siemens Creator

Yes the automatic coupling will enforce displacments from one boundary plane to match another, just as the Help article says.

Re: Validation of automatic coupling

I have done a simple model to test this feature on the right side we see that the displacements are the same on the cut surfaces. Thats what automatic coupling do. But the displacements are very differ compared to the whole model.

couplingtest.PNG

 

loads as on the follow:

loadacright.PNG

 

only if i load the models with centrifugal inertia the displacements are the same.

 

Thank you very much

Re: Validation of automatic coupling

Siemens Creator Siemens Creator
Siemens Creator

If the nodes on the boundaries are the same radial distance along the edges then the displacments will be the same under a symmetric loading, such as a centifugal load.

Re: Validation of automatic coupling

i found the problem. I forgot to choose total per object for the loads. Now the displacements are the same.

Thank you for your help

Re: Validation of automatic coupling

Siemens Creator Siemens Creator
Siemens Creator

I am glad you found the problem. Loads and boundary condiitons can be difficult to resolve sometimes.

Re: Validation of automatic coupling

Hi there,

 

sadly it's not a solution Smiley Sad If i load the model over the whole scope the displacements are not the same. Also while loading the model with centrifgual inertia the displacements in tangential direction doesn't matching.

I added the model. Maybe you have the time to look into these. I already tried everything but no luck.

 

Models

 

Thank you very much for your help

Re: Validation of automatic coupling

Siemens Creator Siemens Creator
Siemens Creator

Do you have access to the on-line Siemens PLM Training - Learning Advantage?

 

In "Learning Advantage Pre/Post Tutorials" we have activities to teach you how to use this feature properly. They are named "Creating a 2D Dependent Mesh" and "Applying Coupling and Rotation."

 

It is possible that in your model you have not properly set up the dependent mesh properly and therefore the coupling (or nodal displacement mapping) is incorrectly matching nodal displacements.