Learning Forum

[Dmytro Fedin]

Hello all,

I'm trying to model the pre-stressed impact of a composite structure in Ansys Workbench LS-Dyna. I use ACP to model plies and transfer data to the LS-Dyna system to model the pre-stressed state of the structure (see first workflow row in Figure 1). The 'History Variables' option of 'Output Control' is turned on and this data appeared in LS-Dyna results. The 'Stress File for the Flexible Parts' option is also turned on to make it possible to transfer stresses to subsequent analysis.

figure 1 - Workflows to get pre-stressed impact of composite structure with history variables

Then I transfer data to the LS-Dyna Restart system with the Full Restart setting in its Analysis Settings and 'History Variables' option of 'Output Control' turned on. The solution is completed successfully with pre-stress and impact sequential processes but the history variables aren't accessible! These items are in the Soution's worksheet but I get the error message: "An error occurred when the post-processor attempted to load a specific result. Please review all messages." (see Figure 2) when I try to obtain them!

Figure 2 - Error message during history variables evaluation in LS-Dyna Restart system

There are no relevant extra messages on this matter in UI!

 

The second workflow (see second workflow row in Figure 1) was created using dynain file to avoid the use of Full Restart. However, there are no history variables at all(

 

I'm wondering what is the reason for the issue. Is it possible to get history variables in subsequent analysis? Maybe there is a more reasonable workflow for this purpose?

 

I'll be thankful for any help

[Reno Genest]

Hello Dmytro,

Can you post-process the history variables using LS-PrePost?

Did you set NSHV on *INTERFACE_SPRINGBACK_LSDYNA to a large value? Here is more information from the LS-DYNA User Manual Vol I:

NSHV Number of shell or solid history variables (beyond the six stresses
and effective plastic strain) to be initialized in the interface file. For
solids, LS-DYNA writes one additional state variable (initial volume).
If NSHV is nonzero, the element formulations, unit system,
and constitutive models should not change between runs. If NHSV
exceeds the number of integration point history variables required
by the constitutive model, LS-DYNA only writes the number required.
Thus, if in doubt, set NHSV to a large number, such as 100.

Which version of Ansys Workbench are you using?

If you are a commercial customer, please create a support case on ACSS and we will have a look at your model:

customer.ansys.com

 

Reno.

[Dmytro Fedin]

Hello Reno,

I can't explain why but now, maybe after I reopened and resolved the solution, the history variables are shown in both systems)

By the way, the option to show extra history variables is controlled by *DATABASE_EXTENT_BINARY card. NEIPS field of the *DATABASE_EXTENT_BINARY card set to 16 (number of extra variables for *MAT_ORTHOTROPIC_ELASTIC, shell case) in both LS-Dyna and subsequent LS-Dyna Restart systems. This field value is set by the 'History Variables' option of 'Output Control' turned on.

Thanks for Your thoughts!

[Reno Genest]

Hello Dmytro,

I am glad it now works for you! Thanks for letting us know.

 

Have a great day!

 

Reno.