Learning Forum

[b.j.v.leeuwen]

Hi all,

I am trying to implement pre-stress on a tube in LS Dyna. I am using the CONTROL_REFERENCE_CONFIGURATION keyword, with settings for the Rausch method. However, I am not sure what the targetfile is that I need to choose.
Currently, I have 3 k-files: main.k, set_nodes.k, set_mesh.k . Set_nodes contains sets of nodes, without their x, y, z coordinates. Set_mesh specifies the elements.
I was able to run the simulation with the target set_nodes.k, however, the results of the simulation are the same as when no CONTROL_REFERENCE_CONFIGURATION was added. Do you have any idea whether the targetfile I chose is correct, and/or why the results remain the same?

Best,

Babette

[Alex R.]

 

Hello,

Purpose of *CONTROL_REFERENCE_CONFIGURATION is to find an approximate reference geometry (stress free) given a measured/known deformed geometry. A solution to this inverse problem is found iteratively by means of an optimization method. This keyword needs to be in the main keyword file, not in any of the include files. case must be used on the command line (see Remark 2).

Target file contain the nodes subjected to optimization and has the same simple structure:

Please read the keyword description in Keyword Manual I: https://lsdyna.ansys.com/manuals/

References for *CONTROL_REFERENCE_CONFIGURATION might be also helpful:

1] Sellier, M, “An iterative method for the inverse elasto-static problem,” Journal of Fluids and Structures, Volume 27, issue 8, (2011)

[2] Rausch, M.K., Genet M., and Humphrey J.D, “An augmented iterative method for identifying a stress-free reference configuration in image-based biomechanical modeling” Journal of Biomechanics 58 (2017) 227-231.

Please let me know if that helps,

Thank you,

Alex

 

[b.j.v.leeuwen]

Hello Alex,

Thank you for your response! I still do have some questions though.
Even if I set the number of iterations to 4, still only one iteration takes place. What could be the problem? What is the outputfile with the reference geometry, is that the iter1.guess file? Is the pressure curve applied the pressure due to which the stressfree geometry was deformed? Hope to hear from you!

Best,

Babette