Please help....How to import VRML models into ABAQUS 1

[cdeepakroy]

Hello everyone,

How can i import VRML model geometry as parts into ABAQUS ?

Please suggest if there are any alternatives also.

I spent quite a lot of time on the internet finding an answer to this question and i find no support in this regard.

Please help me.

thanks in advance.

deepak

 

[johnhors]

Deepak

You will have to use a 3rd. party software. Most pre-processors seem to be able to import faceted geometry in the STL format, but very few appear to be able to import VRML. Abaqus/CAE cannot import either of these formats. Of those that can import VRML, some may be able to convert to geometry, others may just convert the facets to shell elements. With a product like Roshaz you can import VRML and export either as a STL file or an Abaqus inp file.

 

[cdeepakroy]

thank you very much for the quick reply john.

But i have a few more questions to ask.

Roshaz is a commercial software and i am not sure if the evaluation version does this.

Can you tell me if there are any free 3rd party tools available for doing this job.

As you might have unserstood, my job at hand is just to convert the VRML model geometry to a format recognized by ABAQUS.

what i guess is just a conversion tool ?

are there any tools that just do this, instead of providing a complete FE Package.

thanks in advance

Deepak

 

[johnhors]

Deepak

You are limited to what Abaqus/CAE can import:-

SAT
IGES
STEP
VDA
CATIA V4
PARASOLID
ELYSIUM for Catia V5, Ideas and ProE

There are freeware packages available that allow you to view various file types including VRML, but I very much doubt if you can find any freeware that will convert VRML into any of the above formats.

Failing that, you can either write your own conversion program or get someone to do it for you. The VRML format is easily understood if just want to extract triangular and quadrilateral facets and output them as Abaqus shell elements into an inp file.

 

[brep]

If you want/need clean geometry, the VRML will need significant processing. This is the realm of applications such as Raindrop Geomagic. If you have the Re-Style module in Pro/E (which actually uses Raindrop Geo components I think), then you can construct nurbs faces on the underlying facet VRML.

On the other hand, the last poster johnhors correctly suggests that it might be feasible to write a conversion program from VRML facet info into a shell mesh.

I would emphasize the "might be feasible" since the chances of the vrml facets being well formed, uniformly normal and "water tight" is extremely low. You'll need to zip a lot of gaps, correct normals, fill holes... Good luck!

 

[johnhors]

brep

You are correct about the possible quality problems with VRML facets (the same also applies to a lesser extent to import of STL files, but at least STL should already be watertight). However as I suggested earlier Roshaz can not only import VRML it also has tools to clean up the facets, i.e. collapse very short edges, split lines at T junctions, sew unconnected edges together, correctly orient surface normals and so on. Facets that lie on a common plane can be automatically stitched together to create one larger surface.

 

[cdeepakroy]

Thanks for the informative reply and help.

I downloaded the evaluation version of Roshaz software. even though Roshaz software imports VRML. It does not export into Abaqus input file format, it only supports export into STL files. And ABAQUS cannot import even STL files as parts.

What should i do now ?

May be questions are two trivial for me, but since i am a newbie to Finite Element Analysis tools and CAD softwares these things are not trivial to me.

Please help me.

Thanks in advance.

Deepak

 

[johnhors]

Deepak

Roshaz will export into an Abaqus inp file. (along with other formats)

Perhaps you haven't meshed your model first?

First create a material property and assign this to your whole model. Then build a surface mesh. You will find that you can export this as a shell mesh to Abaqus. If your imported facets form a closed skin then you should be able to build a solid mesh with tetrahedral elements, and export this also.

 

[cdeepakroy]

Thank yoy very much johnhors.

It works now. Thanks everyone for helping me out.

In any case, please inform me if you find any conversion tool from vrml to cad format so that i dont have to buy the whole Finite Element Analysis Software Tool, just for converting between two file formats.

Thanks in advance

Deepak

 

[cdeepakroy]

hello,

Thanks for the help johnhors.

I could successfully export the VRML model into abaqus input format after building a surface mesh.

but there is one problem. It is being imported in ABAQUS as a 2D deformable part Where in i want it to be imported as a 3D deformable shell in abaqus.

How do i solve this problem ?

Deepak

 

[johnhors]

Deepak

Edit the inp file.

At the element type declaration line change the letters CPS to be M3D

e.g. Change *ELEMENT, TYPE=CPS3 , ELSET=E1
to be *ELEMENT, TYPE=M3D3 , ELSET=E1

Also change *Solid Section, elset=E1 , material=M1
to be *MEMBRANE, elset=E1 , material=M1

This should change the element type from 2D to 3D

 

[cdeepakroy]

Hello,

Thank you very much for the help Johnhors.

Well, the problem of my 3D vrml mesh being imported as 2D deformable aprt in abaqus is solved, by changing the ABAQUS input file as you suggested.

But i have a new problem. The Analysis fails due to the following errors and warnings:

------------------------------------------------------

Error:

"Too many attempts made for this increment: analysis terminated.
Abaqus/standard analysis exited with an error - please see the message file for possible error messages if the file exists."

Warnings:

"The system matrix has 78 negative eigenvalues.

Solver problem. Numerical singularity when processing D.O.F. 1 of 1 nodes. The nodes have been identified in node set warnnodesolvprobnumsing_1_1_1_1_1.

Solver problem. Numerical singularity when processing D.O.F. 2 of 2 nodes. The nodes have been identified in node set warnnodesolvprobnumsing_2_1_1_1_1.

Solver problem. Numerical singularity when processing D.O.F. 3 of 831 nodes. The nodes have been identified in node set warnnodesolvprobnumsing_3_1_1_1_1.

The system matrix has 78 negative eigenvalues.

Explanations are suggested after the first occurrence of this message in the message file for job stress_analysis_job.

Solver problem. Zero pivot when processing D.O.F. 3 of 1 nodes. The nodes have been identified in node set warnnodesolvprobzeropiv_3_1_1_2_1.

Solver problem. Numerical singularity when processing D.O.F. 1 of 1 nodes. The nodes have been identified in node set warnnodesolvprobnumsing_1_1_1_2_1.

Solver problem. Numerical singularity when processing D.O.F. 2 of 2 nodes. The nodes have been identified in node set warnnodesolvprobnumsing_2_1_1_2_1.

Solver problem. Numerical singularity when processing D.O.F. 3 of 831 nodes. The nodes have been identified in node set warnnodesolvprobnumsing_3_1_1_2_1.

The system matrix has 78 negative eigenvalues."

------------------------------------------------------

The solution seems to be diverging.

I verified the mesh using the mesh module - Verify - Analysis checks and there are apparnetly no analysis errors.

My job analysis doesnt even complete one increment, so i cannot use the viewer to figure out what is wrong.


How do i solve this problem and get rid of the errors ??

Please Help

Deepak

 

[johnhors]

Deepak

It sounds like that there are insufficient supports. Or may be check with the Abaqus online help to see what other shell or thick shell elements are available. Else check that your properties have a density value and perform a modal analysis, for each unsupported freedom there will be a zero frequency rigid body mode associated with it.