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NX Nastran Surface to Surface Contact in Joint

Hello Community,

 

At the moment i'm trying to calculate an assembly FEM.

4 weeks ago i began with it and i had also some good experiences, but there are still problems.

 

I did the solution in the first step with a completely glued assembly, that was no problem and i had good results.

 

Now i try to built the joint with surface to surface contact, but the joint now always flies apart.

 

My Questions:

 

1. Is it possible to fix the joint with spring elements?

2. I have also some mesh problems between the contact surfaces, is there any option, which helps to clear interferences?

 

 

Thank you for your help!

 

 

4 REPLIES

Re: NX Nastran Surface to Surface Contact in Joint

[ Edited ]

Suface to surface Gluing is particularly used in Nastran to Join the mesh of two contact parts in an assembly (in case if the mesh on those mating face is dissimilar).

 

Gluing will automatically establish stiff spring or weld joint (according to the setup) to prevent relative motion in all direction of the contact region, and thus your parts will not flies away.

 

So, if your mating face mesh distribution is not coincident, you have to use Gluing Functionality.

 

Moreover, if you want to give surface to surface contact on the same FEM (which have not mating mesh coincident) you also have to apply Surface to surface gluing.

 

Thanks

Rahul Patni

Re: NX Nastran Surface to Surface Contact in Joint

To define surface/surface contatct, you can use the exact same regoins as you used for glue joint.  You DO NOT need both glue joint and suface contact definitiion, this would not work.  Glue joint fuses surfaces together while contact let them slide on each other...

 

If the parts are flying off, this means there is at least one massless mechanism, i.e. the model is missing some BCs to hold it togehther or the contact definitions are not created properly...  Could be a region definition, a search distance or simply the contact definitions are not in the solution...  Is there something you can post, it's difficult to debug otherwise...

Re: NX Nastran Surface to Surface Contact in Joint

Quite incorrect, Rahul.  Surface Contact allow for sliding of surfaces on each other, including friction.  

 

Glue Joint does not allow relative movement, but rather fuses meshes together.  There is absolutely no need for coincident mesh distribution and certainly no reason foradding a glue joint definition on the same surfaces.  What would be the point of adding a surface contact onto an already fused set of surfaces?

Re: NX Nastran Surface to Surface Contact in Joint

Thank You,TENTECHLLC
 
I was wrong in explaining contact definition.
Now after reading your reply, things must goes well.