enforced displacemnt in a local csys with NLGEOM - possible bug

sbalazs

Hi,

 

I tried to model the pretension for a NLGEOM analysis with enforced displacements in a local csys. If the pretension is not followed by an another loadcase, the results are OK, if there is a follower loadcase the results are not the same as before and wrong.

 

Attached you can find a test model (with pretension with and without an additional loadstep). Nodes id. 1 and 2 are the ones with enforced displacements in the local csys id 4. Please take a look at the displacements for the pretension in both cases.

 

Is this problem known? Is there a workaround for this problem?

 

Thank you.

 

Best regards,

Szilard Balazs

 

 

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Rahul Rajan_21763

Can you try this in the latest version OptiStruct 2018.0.Lot of new feature has been changed since version 14.0.We now solve Nlgeom with large displacement analysis.

Please request free eBook on OptiStruct Nonlinear analysis with below link.

https://altairuniversity.com/free-ebook-introduction-to-nonlinear-finite-element-analysis-using-optistruct/

sbalazs

Hi,

 

thanks for your answer, I tried to solve with Optistruct 2017, unfortunately occours the same problem....We don't use Optistruct 2018 at the moment.

 

Regards,

Szilard

Rahul Rajan_21763

can you share the files of 2017 version.

sbalazs

Hi Rahoul,

 

here are the results when I run the same input files under Optistruct 2017.

 

My problem is that the same pretension lodcase (enforced displacements in a local csys) produces different results whether there is a follower loadcase or not.....

 

Regards,

Szilard

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Rahul Rajan_21763

can you share the .fem file setup using 2017 version.

sbalazs

Hi,

 

I used the same fem file which I used for the Optistruct 14 run (see atached files from my first post), I only used the Optistruct 2017 solver (since I want to do the same analysis ) .... Is it wrong doing so ?

 

Regards,

Szilard

 

sbalazs

Hi Rahoul,

 

did you find out something about this Optistruct bug? Is there really no solution for this problem? How can I perform this analysis in an another way?

 

Regards,

Szilard Balazs

Rahul Rajan_21763

You can refer attached sample deck from OS example guide. OS-E: 0135 Contacts and Pretensioning of Bolts

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sbalazs

Hi Rahul,

 

thank's a lot for your help!

 

Reagrds,

Szilard Balazs