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Twisted mesh element.

Pioneer
Pioneer

Hi Experts,

I am importing .nas file from ANSYS and associating it with .stp geometry file.

 

When i import mesh in nastran it says:

-Twisted elements 2244.

and association with geomtry also says that:

-0 geomtry association with 2244 elements.

can someone plz help me out and tell me that how can i refine my imported mesh or how can i refine my  imported mesh element quality in nx nastran? so that i can associate it with geomtry and run analysis with no fatal errors.

 

Regards,

Sheheryar Khan

7 REPLIES

Re: Twisted mesh element.

Solution Partner Pioneer Solution Partner Pioneer
Solution Partner Pioneer

Hello Aero-Design,

Could you please clarify what you mean by: Associating your NAS file to your STP geometry file?

 

If your NAS file only contains element, you can import it, then, in the FEM, use the "Face from Mesh" Command. This will allow you to remesh that area. You can do so for your problematic regions (show the bad elements using the "Element Quality" command. Make sure you have NO elements with negative or zero jacobians.

 

Cheers,

Jacques

 

 

Re: Twisted mesh element.

Pioneer
Pioneer

Hi @JacquesL,

Thnx for replying.

I mean when i import mesh with elements and nodes from ANSYS then NASTRAN says twisted elements(some element numbers). 

and when i try to associate my same errored mesh with geomtry using Modify>Associativity>Automatic command then it says no geometry association with element(numbers same as twisted elements). 

and i am using version 11.4.1 of NX Nastran.

is there any way that when i import mesh then i can refine my elements in nx nastran? 

 

Regards,

Sheheryar Khan

Re: Twisted mesh element.

Valued Contributor
Valued Contributor
Hi Aero

Just trying to get a grasp of what you are trying to achieve here - what is the need to associate your mesh with the stp. geometry.

Are you trying to update the mesh after importing?

Can you not run the analysis directly after an import?

& how badly twisted are your elements?

Re: Twisted mesh element.

Siemens Phenom Siemens Phenom
Siemens Phenom

People do have existing meshes, and existing geoemtry, and with Modify - Associativity - Automatic, can associated an orphan mesh with its geometry.  Then, one can use all the meshing toolbox, mesh updates, and geometric loading and boundary conditions FEMAP has to offer.

 

Regarding the twisted element message, FEMAP runs all imported elements through a quality check.  Coming from ANSYS, there may be a case where the node ordering on an element was ok for ANSYS, but not ok for NASTRAN, FEMAP lets you know when it finds a problem element.  I would make a group with just that element and see what is going on.

 

If the imported mesh does not fully associate after the automatic associativity command, I'd undo, and run it again at a looser tolerance.

 

If you get really stuck, post the data here, and myself or another member of the FEMAP team can advise.

 

Mark.

Re: Twisted mesh element.

Pioneer
Pioneer

Hi @Stuart_S,

I am performing flutter analysis for this analysis when i contraint my model then it says which type of contraint you want? NODAL, NODAL on FACE, Equation?

in case of mesh only i cant selct whole surface and selecting nodes 1 by 1 is hard.

that is why i mesh my geomtry in hypermesh or ANSYS then import geomtry and mesh independently and then associate them. SOmtimes i import .STP and sometimes i import parasolid file for geomtry.

as i am new to NX NASTRAN if you have other better way in which i can run analysis by using mesh only. Can you plz guide me to it? this will be very helpful.

 

Regards,

Sheheryar Khan

Re: Twisted mesh element.

Pioneer
Pioneer

Hi @masherman,

Thnx for your reply.

i will try your suggestion then if this works then its ok. If not then i will upload model so that you can chck yourself.


Regards,

Sheheryar Khan

Re: Twisted mesh element.

Siemens Phenom Siemens Phenom
Siemens Phenom

Nodal on Face allows you to quickly pick nodes on connected faces of elements controlled by a break angle.  This is in addition to standard box, circle, and polygon picking that should make it possible tp choose constrained nodes without the benefit of geometry.