Learning Forum

[st161532]

Hi,

I'm new to ls-dyna and simulation as a whole and am getting an error where I don't understand whats wrong. I hope this is the right forum to ask questions about the use of keywords.

In my dummy simulation I'm only doing a themal analysis of a simple cube and I'm trying to apply a user load through *USER_LOADING_SET:

*USER_LOADING

       1.0       0.0       0.0       0.0       0.0       0.0       0.0       0.0

*USER_LOADING_SET

         1TEMPTN             1         0       0.0       0.0       0.0         0

A simulation with these Parameters result in a Error message:

*** Error 20680 (STR+680)

    unexpected end-of-file

This is only the case when USER_LOADING_SET is used and not for only USER_LOADING but I need both.

I know I need to modify the code in dyn21.f and I did but it doesn't even reach the function and it seems to me that there is a keyword missing that is not named in the manual? If I use the option FORCEN instead of TEMPTN and do a stress analysis, it calls the load function.

The keyword check in LS-PrePost has no errors and these are the control keywords for the TEMPTN case:

*CONTROL_SOLUTION

         1         0         0       100         0         1

*CONTROL_TERMINATION

       1.0         0       0.0       0.01.000000E8         0

*CONTROL_THERMAL_SOLVER

         1         0        111.00000E-4         8       1.0       1.0       0.0

         0       5001.0000E-101.00000E-4       1.0                           1.0

         0       0.0         0

*CONTROL_THERMAL_TIMESTEP

         1       0.5      0.011.00000E-4       0.1       1.0       0.5         0

Is there a additional keyword that I need to place for USER_LOADING_SET to work?

Thank you for taking a look!

[tslavik]

Hello Please understand that we are not permitted to download any files from the Forum, but we can provide guidance and links to informative material.
Please visit this website which will take you to a relevant paper : https://www.dynalook.com/conferences/european-conf-2003/examples-manual-for-user-loading-option.pdf/view
Also, use Google to search for "user_defined_materials.faq" which should take you to some pertinent FAQs on an LSTC FTP site. Also, use Google to search for "user-material-notes"
We don't have examples of thermal loading and suggest you test out the custom executable you compiled ...
1/ run a simple example input file , e.g., any of the many examples available here: https://www.dynaexamples.com
2/ in your model with user-defined thermal loads, eliminate all references to *USER commands - run a simulation
3/ add some similar "standard" thermal loads and run it again
4/ add some of user-defined features to see which command is causing the problem

[st161532]

Hi tslavik Thank you for your answer, sadly it doesn't solve my problem.
The paper that you mentioned revolves around the USER_LOADING keyword, which as far as I can tell is not the Problem here. When I ran the simulation without *USER_LOADING_SET it ran just fine and even when I changed the input file from:
*USER_LOADING_SET
1TEMPTN100.00.00.00
to
*USER_LOADING_SET
1FORCEN100.00.00.00
there was no error running the code. I know its not because of my changed code, because I also ran it on a unchanged ls-dyna version and the Error appears before the Simulation is even started so its not a runtime Error. (I think it is during interpretation of the keyword file, but this is just a guess)
Thank you however for the faq's. Even though they don't solve this problem, I think there are a few things I can take away from these sites.

[tslavik]

What was the setting of SOLN in *CONTROL_SOLUTION when you ran with "FORCEN"? Have you tried running a simple thermal-only model with your executable? What version of LS-DYNA was used to build your executable?

[st161532]

I tried all options, structural, thermal and coupled structural and thermal analysis. Where its not surprising that SOLN=1 worked because the method didn't get called. But a coupled structural and thermal analysis allowed me to even set flux boundary conditions using the usrflux subroutine.
Yes thermal-only models work fine with the executable, and at this point a coupled simulation with multiple thermal boundary conditions.
The version built is LS-DYNA 9.3.1 on a CentOS 6 cluster but I also ran the model with the current student version of LS-DYNA on windows which resulted in the same error.