error during job analysis in ABAQUS

[cdeepakroy]

hello everybody,

I imported a VRML mesh model ( of a female human body ) into abaqus.

I applied a downward body force to a few regions in the model.

When i perform stress analysis, ABAQUS gives the following error:

- The area of 1605 elements is zero, small, or negative. Check coordinates or node numbering, or modify the mesh seed. The elements have been identified in element set errelemareasmallnegzero.

- Solver input file processor exited with an error - please see the data file for possible error messages if the file exists.

I am a newbie to abaqus and I cant figure out where the error is and what it means.

What should i do to get rid of this error ?

Please help me.

Deepak

 

[corus]

You're probably using tet elements and have a poor element shape. View the set of elements with the zero volume in Viewer and remesh it.

corus

 

[cdeepakroy]

hello,

Thanks for the prompt and informative reply corus.

I dont understand one thing, how can i view the elements in the ABAQUS Viewer( Visualization ) mode before the job analysis succeeds. If i try opening the visualization module, abaqus doesnt show anything and keeps complaining the no output database is created. But output database is created only if the Job analysis step succeeds.

My problem now is, i am getting errors during analysis and job analysis completely fails - so no output database is created.

Now how can i get rid of the errors i mentioned in the previous posting, bcos ABAQUS doesnt show anything in the viewer unless job analysis succeeds.

Please help.

Deepak

 

[harry123456]

ABAQUS will show you in visualisation the deformed shape, contours etc. for every increment by default. In othe rwords you can visualize as the job proceeds and not wait until completion In your case though since its happening in the first increment itself you are not seeing anything. Maybe just try it with a more refined mesh and then see if it runs.
harry

 

[corus]

Generally if Abaqus identifies a set then it does that so you can see it in Viewer. The job doesn't need to succeed for it to create an odb file, it's just that there will be no results to see. Check again to see if there is an odb file there.
If I'm wrong then you can always use the element verification check in CAE to identify bad element shapes. This will also identify those elements that will cause the analysis to fail.

corus

 

[cdeepakroy]

Hello,

Thanks for the informative reply harry.

I tried decimating my VRML model and imported it again into abaqus, but still the same error comes up when i execute job analysis. Below is the error:

"The area of 385 elements is zero, small, or negative. Check coordinates or node numbering, or modify the mesh seed. The elements have been identified in element set ErrElemAreaSmallNegZero."

I am wondering how to solve this problem.

The first problem i faced is to import the VRML geometry. Since abaqus does not support this directly, i am using Roshaz software to convert it into Abaqus input file format.

Now when i succeeded in importing the meshes, there are some analysis problems.

What is the best way i can refine the mesh, enough for the abaqus to complete analysis successfully, rather than the trial and error process.

Deepak

 

[harry123456]

When you import the model can you look at the elements and then get an idea as to where the elements might be bad? I guess the problem is arising when you import the model. Can you refine it more before you read it in?
harry

 

[cdeepakroy]

hello,

thank you very much for the informative reply harry.

What do you exatcly mean refining the mesh. should i increase or decrease the mesh density by subdivision or decimation.

At the first place, i dont understand what the error means.

Can anyone tell me, what the error tentatively means and what are the possible causes ?

Deepak

 

[harry123456]

Like corus said use the abaqus mesh checking to see which elements are bad and in that area refine the mesh increase the elements by increasing the mesh density and then import it in

 

[cdeepakroy]

hello,

Thanks for all the useful reply.

As you all suggested, i refined the mesh in the areas of high curvature but still it didnt help.

Then i cutted out mesh portions with normals in the negative direction.

Now it worked ! thanks to you all.

Analysis succeeded now.

but now there is a new problem.

When i import the 3D mesh of the human body into abaqus, it is imported as a 2D deformable part in ABAQUS part module.

I realised this when i saw the result of the analysis step, since the output seems like some 2D projection of it, mostly the depth projection.

What is the reason for this behaviour ?

How do i get rid of this ?

 

[cdeepakroy]

Hello,

Thanks for all the usefule replies.

Whenever i try to import a vrml 3D surface mesh into abaqus, it gets imported as a 2D deformable part.

I want it to be imported as a 3D deformable shell ?

How do i do this ?

Should i change anything in the ABAQUS input file ( *.inp )....

Please Help

Deepak