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Element Coordinate System align?

Valued Contributor
Valued Contributor

Hello,

 

I am still a beginner in FEMAP and have a question regarding element coordinate system.

 

I created a 2D Quad mesh and when I display the element coordinate orientation for each element, the X & Y axes are all over the place for each element.

 

However when I open a FEMAP supplied example and do the above, I see that the X & Y axes are beautifully aligned respectively in same direction for all elements.

 

Question is, is there a feature to modify the elementa coordinate system in FEMAP once the mesh has been created.

 

Also, any tips on how I can ensure that all elements have the same local coordiante system while meshing.

 

Thanks & Regards,

- Nagaraj

 

 

5 REPLIES

Re: Element Coordinate System align?

Phenom
Phenom

Hi,

 

Yes there is a way to align 2D elements' coordinate systems: go to Modify > Update Elements > Orient Plate Normal/First Edge.

By orienting the first edge (right part of the window) the element csys is switched.

 

However the real question is what is the use? the element csys is used for output orientation, but you can use alternatives such as material orientation and parameters such as OMID (=> f06 output will be oriented in the material axes). In other words making sure that element csys are perfectly aligned can be unnecessary, there are other ways to control output alignement.

 

Plus as models grow and become more complex, ensuring csys alignement quickly becomes a tedious task which is not recommended.

 

AP

Re: Element Coordinate System align?

Valued Contributor
Valued Contributor

Thanks for the response Sir.

 

Yep, I'd agree with you the utility of aligning 2D elements coordinate systems. I needed directional normal stress output and I was getting erroneous results and later found out that it was due to each element having different local axes orientation. Like you have mentioned, I also discovered the work around i.e. to make all elements have the same material coordinate system and transform elemental stress output to matl coordinate.

 

My question came more from knowing the procedure.

 

I do have a follow up question. Is there any way to "add" or combine two elements (quad and/or tria) together in FEMAP? I come from Patran world and Patran has such one feature and I have found it pretty useful at times especially when dealing with elements which have failed quality checks.

Re: Element Coordinate System align?

Phenom
Phenom

Hi,

 

Here's a macro that might help, wrote it a while back. The idea was to combine 2 elements by a common face, by I quickly realised that a fully robust code would be difficult (longer) to do.

 

So here's what the macro WILL do:

- tria+tria => quad

- quad+quad => quad

ONLY LINEAR ELEMENTS

 

Here's what the macro WON'T do:

- parabolic elements

- tria+quad => quad IF 2 edges are aligned

- penta+penta => hexa

- hexa+hexa => hexa (feCheckElemFixup doesn't completely untwist solids...)

 

The thing is that it did not prove to be that useful. For your quality check concerns FEMAP has many alternative functions, such as the Mesh > Smooth command or the manual Mesh Locate feature in the Meshing Toolbox, for which you can activate element quality plots and see them change as you move nodes around.

 

AP

 

Re: Element Coordinate System align?

Phenom
Phenom

better with the file

Re: Element Coordinate System align?

Valued Contributor
Valued Contributor

Hi,

Thanks for the macro.

 

Also can you please recommend any good tutorial on Mesh clean up in FEMAP? Apart from splitting tool, I am finding cleaning up bad elements tedious in FEMAP. I am sure there are easier ways...would apprecaite the response.

 

Thanks for the reply again. Appreciate it.

 

Regards