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mikel_29_mikel
Posts: 13
Registered: ‎03-20-2013

Problem with meshing options in Autodesk Mechanical

232 Views, 5 Replies
05-22-2013 07:03 AM

Hello everybody,

 

Well, the question is this: I have Autodesk Simulation Mechanical installed on my PC. I do analysis of a boiler and I use the Model Mesh Settings->Solid->Options->Solid->Bricks and Tetrahedra option in the meshing process, but I read on Wikihelp that this option was not very good/ helpful. For my design that has 3mm of tickness, Wikihelp says that it is better to use the Bricks and wedges (layered mesh of thin parts) option.

 

Well, I try to do this kind of analysis and it is impossible, it never finishes with a correct mesh. It always does a meshing but leaves some parts in black or grey without meshing them. Then I start the analysis and the software advises me that a problem occured and it finishes without analysis.

 

I checked with the same design on a different PC and it works just fine. My question is, What happen to my first PC? is it possible that there might be a corrupted file or something like that?

I look forward to your answer because this issue is very important/ urgent for me, I need a solution to continue with my work.

Thank you, my best regards.

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*Expert Elite*
punisher
Posts: 299
Registered: ‎10-13-2008

Re: Problem with meshing options in Autodesk Mechanical

05-22-2013 07:55 AM in reply to: mikel_29_mikel

What type analysis are you performing? Static Stress, Thermal, etc?

Which element types used would depend on what you are trying to achieve.

 

 

John Evans
Autodesk Certified Professional

http://designandmotion.net
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*Expert Elite*
punisher
Posts: 299
Registered: ‎10-13-2008

Re: Problem with meshing options in Autodesk Mechanical

05-22-2013 12:12 PM in reply to: mikel_29_mikel

As for the second PC, I would take the successful simulation and archive it (.ach file). Copy that to the problem machine as a new simulation project, and run it. 

Try that and let us know if it still fails.

 

 

John Evans
Autodesk Certified Professional

http://designandmotion.net
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Contributor
mikel_29_mikel
Posts: 13
Registered: ‎03-20-2013

Re: Problem with meshing options in Autodesk Mechanical

05-22-2013 11:42 PM in reply to: punisher

OK, I am doing a Stress analysis of a boiler. My boiler is a .iam

I draw on Inventor and I did a Thermal and Flow analysis with Autodesk Simulation CFD. When it finished I start a Stress analysis with the thermal loads of CFD.

 

I did a mesh with option Bricks and Tetrahedra and the analysis finished, now I try to do a analysis with Bricks and wedges and the result is bad because it doesn't finish.

 

I tested with a simple face extruded (a rectangle) and with this geometry I get to do a Stress analysis with Bricks and wedges. I try to do the same with a cube and the analysis with Bricks and wedges doesn't work.
 What is it the problem? Why sometimes is good and sometimes is bad?

 

The second simulation with my second PC, I can't try it because I am travelling in this moment and I only have my laptop, I am going to travel one or two weeks. Do you have other solution?

 

 

Thank you.

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Contributor
mikel_29_mikel
Posts: 13
Registered: ‎03-20-2013

Re: Problem with meshing options in Autodesk Mechanical

05-23-2013 02:26 AM in reply to: punisher

When this fail occures, a message appears  and it says: Problem with zero jacobian... I don't remember the text exactly. What is it the meaning of this?? Why does it happen??

 

If I change my size mesh from 100% to 110% this error disappears but this size is bad because it isn't very exact.

I need your help.

 

Thanks!!

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*Expert Elite*
AstroJohnPE
Posts: 570
Registered: ‎08-30-2012

Re: Problem with meshing options in Autodesk Mechanical

05-23-2013 11:42 AM in reply to: mikel_29_mikel

As much as we would like to think, "One plus One does not equal Two" on all computers. Okay, maybe that simple equation is Two on all computers, but when the computations involve thousands of calculations to create a mesh and thousands of calculations to solve the analysis, different computers will give different results. It can depend on the type of processor, the amount of RAM, maybe even the operating system. So it is not surprising that one computer fails while another works okay.

 

Am I understanding correctly that the "thin layer mesh of brick and wedges" is giving a jacobian error? I think that would be unusual, but something must be getting distorted by the way the method works. If the part is thin, you may want to consider using plate elements for the analysis so that you so not need to worry about the number of elements through the thickness.

 

Otherwise, search the wiki help for the word Jacobian and follow the suggestions to eliminate the problem.

John Holtz, PE
Mechanical Engineer
Pittsburgh, PA

Simulation Mechanical user since Dec 1997
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