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Change element orientation - Not normal?

Gears Phenom Gears Phenom
Gears Phenom

Is it possible to change the element co-ordinate system orientation? Not the normal!

 

I am doing a test with rms value (from a response simulation module). I want to look at stress component Sxx

As you can see from the attached picture, the Sxx plot is misleading which is easily explained when looking at the material orientation (I think)

 

Thanks

Production: NX.CAE 9.0.3.4, NX.CAE 10.0.2.6
Development: VB.NET (amateur level !)
11 REPLIES

Re: Change element orientation - Not normal?

Gears Phenom Gears Phenom
Gears Phenom

Hi selex_ct,

native orientation in 2D-elements depends on (said simplified) position of first and second grid point in element. If you try to modify that native CSYS, as I remember, there is no way to redefine it without modifying material definition CSYS. In your special case where you have a flat structure, it's easy to do. But it's associated with mesh and not with property or mesh collector. It's more complicate to find an appropriate co-ordinate system for a whole structure in 3D-space. 

 

Additionally, you can select another result co-ordinate system at the result dialog "Set Result". Keep in mind that the co-ordinate system has to be selected by use of "Simulation Navigator" not in "Post Processing Navigator".

 

Edit: As stresses are tensor results it's not necessary to define element specific CSYS in pre processor, except you need specific orientation in definition of material. You can transform it to any co-ordinate system in post processor as well.

 

AND, to see the orientation of stress components you can use visualization as tensor component in post processing.

Best wishes, Michael

| Production: NX10; Development: VB, TCL/TK, FORTRAN; Testing: NX11 | engelke engineering art GmbH, Germany
| Kudos for good posts! And if my post answers your question, please mark it as an "Accepted Solution".

Re: Change element orientation - Not normal?

Gears Phenom Gears Phenom
Gears Phenom

If one calculates an RMS stress using the NX Resp. Sim module one can only select 'Element CSYS' or 'Material CSYS'

Did a test with a dummy model where  elements co-ordinate where not consistent. By forcing a "Material CSYS' then one can get "consistent" results. See attached plot of an XX rms stress

Production: NX.CAE 9.0.3.4, NX.CAE 10.0.2.6
Development: VB.NET (amateur level !)

Re: Change element orientation - Not normal?

Gears Phenom Gears Phenom
Gears Phenom

Hi selex_ct,

then you have to define material co-ordinate systems or orientation definitions for all of your meshes, right? - Is it the way that you did identify? The problem is that complex models can't deliver a consistent set of co-ordinate systems or orientation definitions for the whole structure. Mostly there will be problems e.g. on weld seam edges or so in double bended shells. A local co-ordinate system in post processing would a good improvement here. But if I understand you right, that's not usable. That's bad.

Best wishes, Michael

| Production: NX10; Development: VB, TCL/TK, FORTRAN; Testing: NX11 | engelke engineering art GmbH, Germany
| Kudos for good posts! And if my post answers your question, please mark it as an "Accepted Solution".

Re: Change element orientation - Not normal?

Gears Phenom Gears Phenom
Gears Phenom

That's what I did but on would only do it for the area(s) of interest I guess

There must be a way of specifying/changing the element co-ordinate sytem orientation (apart from the normal - z direction)

Production: NX.CAE 9.0.3.4, NX.CAE 10.0.2.6
Development: VB.NET (amateur level !)

Re: Change element orientation - Not normal?

Siemens Phenom Siemens Phenom
Siemens Phenom

As @MiDi1791 stated above, the element csys is a function of the element formulation and is not user definable or modifiable.

 

As you have found, defining a material orientation is an appropriate method to achieve what you are looking for.

Re: Change element orientation - Not normal?

Gears Phenom Gears Phenom
Gears Phenom

true that the element csys is a function of the element formulation but pre/post processor like Patran has the option to "rotate" the said csys. Very handy when you want to make sure that for example "all" the elements have the x-axis in the same direction!

Production: NX.CAE 9.0.3.4, NX.CAE 10.0.2.6
Development: VB.NET (amateur level !)

Re: Change element orientation - Not normal?

Siemens Phenom Siemens Phenom
Siemens Phenom

Again, the element csys cannot be modified. What you describe (a rotation of some angle about element Z) is exactly what THETA does and is the definition of the material coordinate system:

 

https://docs.plm.automation.siemens.com/tdoc/nxnastran/12/help#uid:index_QRG:id511476:id507676

Re: Change element orientation - Not normal?

Pioneer
Pioneer

I am not sure it is correct to use a post-processor to transform RMS results.

Re: Change element orientation - Not normal?

Pioneer
Pioneer

JimB

Do you maybe have the answer to

https://community.plm.automation.siemens.com/t5/CAE-Simulation-NX-Nastran-Forum/PARAM-OMID-and-RMS-S...

if PARAM, OMID, YES is set to output stresses/strains in the material coordinate system?

Thanks