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Stent with geometry error

Hi everyone. 

 

I've been trying to simulate a stent under bending conditions, with shape memory materials. Although I've been having all kind of errors, now Femap show me this one for each node of the model:

 

error.PNG

 

 

Can anybody please help me in what can I do to solve this? The gemetry itself is imported from an abaqus model so there's not much more I can do (as far as I know). 

 

I'd be really grateful if you could help me since I'm doing this for a project to my master thesis.

 

Thanks in advance,

Regards 

 

Andreia Santos

9 REPLIES

Re: Stent with geometry error

Creator
Creator

Well it would be helpful if you showed us picture of the model. Usualy small edges are hard to mesh so you could use command:SOLID CLEANUP > ADVANCED.

 

Here is the youtube link for manipulating geometry in Femap so maybe this will be of some use to you;

https://www.youtube.com/watch?v=VZD7vu6-0to
Other reasons that I could think of could be that your model is deformed too much so try to decrease load or look up do you have correct  units or look up the mesh quality by command TOOLS-CHECK-ELEMENT QUALITY.

That would be my first intuitive things to do but picture would help.

Re: Stent with geometry error

Hey thank you for your answer!

 

Here's a picture of the part of the model I was trying to simluate. (Note that the model itself is a repetition of this part I'm showing you). 

small.PNG

 

This shows what's happening when I get that error I showed you before. Basically I tried to do what you said but I wasn't capable of because I don't have a geometry assigned on the model, I can only edit the mesh (remove elements mostly) due to the fact that it's an imported model from Abaqus.

 

Can you still help me? 

 

Thanks 

 

 

Re: Stent with geometry error

Creator
Creator

Hi Andreia

Well it doesnt help a lot but if I understood you this is the deformed view after the analysis(obviously for the last step that FEMAP could calculate until error)?

So did you checked boundary conditions and loads on that deformed part beacuse if I understand correctly it stent can be seen as symmetrical structure with symmetrical loading and boundary condition? If you can and want you can upload the model here so I could check and maybe help you more.

Re: Stent with geometry error

Pioneer
Pioneer

To help with some of the element handling take a look at this function:

Solids from elements.png

 

It is designed for your exact scenario; you get a FEA model with no supporting geometry.  Be sure to hit "F1" to get the help file info to use the command.  There is an option to tell FEMAP you've got internal voids.

 

 

Re: Stent with geometry error

Pioneer
Pioneer

Could also turn off all NASTRAN GEOMCHECK as part of the debugging.  If not explcitly turned off, I've had NASTRAN runs end due to poor element quality.  

 

GEOMCHECK.png

 

Located Here:

GEOMCHECK - Location.png

 

 

Re: Stent with geometry error

The boundary conditions are okay as so are the loads applied (in this case a displacement) because I already simulated for an elastic material and it went well. But now, same model different material - Shape Memory Alloy - it won't let me pass a this step. Which is really far from what I expected, and obviously not a convergence.
I'm sorry, I cannot upload the model here once it's not mine. :/

Re: Stent with geometry error

Ei thanks a lot for your answer!

 

I was trying to do what you said but then I noticed I'd always get an error saying that it wasn't possible to  "establish seed element for mesh", even after going to the help page and trying different options. Then I did a little research and I found an answer here in this forum about this tool and it says:

 

"The Mesh-->Geometry-->Solid from Elements command is for making a solid mesh from planar or 2D elements.  It is not for making a geometric solid from a solid mesh.  I do not believe Femap currently has a direct method for creating solids from a mesh."

 

I believe that my mesh already has 3D elements as you can see in this picture.

 

Capturar.PNG

 

 

 

 

Re: Stent with geometry error

Pioneer
Pioneer

Hmm...let me look a bit more.  I remember seeing one of the latest release promos that included a "how to make some geometry when all you have is elements".

Re: Stent with geometry error

Pioneer
Pioneer

Arg...I mis-led you.  The command I'm thinking of only gives sheet-solids (i.e. surfaces) from plates...not solid geometry from solid elements.

 

Surface from Plates.png

 

It'd be a bit more bothersome but you could:

- Plate or Plot-Planar from the solids you have

- Surfaces from those Plate/Plot only

- Stich or thicken those sufaces

- Make a solid from stitched surfaces

 

The bummer is FEMAP doesn't have the strongest geometry editing engine.  Again, sorry to mid-lead you.  

 

Unfortunately I don't have much experience with the memory alloys so I can't help there