Learning Forum

[Richard Sousa]

I want to use a Prony series to model a viscoelastic material with LS-DYNA in Workbench. When I have my analysis system set as LS-DYNA and I filter the engineering data, I am able to select and edit the Prony series option in Workbench. However, when I try to run the simulation in Mechanical, I get these errors:

I'm not sure why the properties would not be supported. It also seems like I do not have the solver for LS-DYNA with my version of ANSYS. I have a free student version of it. I also have LS-DYNA separately installed, so I have been able to export a keyword file to run the simulation in LS-Run, but the viscoelastic portion of my material model does not get transferred over, just the elastic part. Is there any way I can get LS-DYNA to run a simulation with a Prony series?

[Armin]

Hi Richard,

I checked the 2024R2 version and I had a similar experience: the Prony Shear Relaxation option under Viscoelastic group of Engineering Data is not supported in Workbench LS-DYNA.
In Engineering Data application, if you open the LSDYNA External Model – MAT group in the Toolbox, the MAT_GENERAL_VISCOEASTIC option is available which supports Prony series; however, the current implementation in Engineering Data is limited and does not allow for accessing the cards associated with Prony series.
So, I suppose the best approach is to use Command Snippets in Workbench LS-DYNA (in Project Outline, right-click on your model under the Geometry branch and select insert, commands) to implement the model. Other possible approaches are editing the input file directly to add the material card or using LS-PrePost. 
You can obtain more information about this material model, MAT_076, and its format using the keyword manual, on page 581:   https://www.dynasupport.com/manuals/ls-dyna-manuals/ls-dyna_manual_volume_ii_r13.pdf