Learning Forum

[AhmetKaya]

Dear ANSYS community,

I am currently engaged in modeling a quasi-static compression analysis on structures constructed from paperboard. In my pursuit of precise design, I recognized the value of commencing with a simplified plate model to proactively identify potential errors. My material of choice is orthotropic elastic with multilinear isotropic hardening and the Hill yield criterion. I initially created the composite part using ACP and subsequently transferred the shell composite data to Static Structural, LS-DYNA, and Explicit Dynamics.

For your reference, I have included a visual representation of my workflow and a related case study in the form of an image, which can be viewed in this YouTube video: [insert link here].

However, I am encountering a significant issue in my simulation. Specifically, when I enable the multilinear isotropic hardening and Hill yield criterion in the material definition, LS-DYNA produces an error (*** Error 40724 (SOL+724) routine eigab fails to obtain eigenvalues), and Explicit Dynamics also fails with the error message stating, "Could not transfer material Sheet A 190 gsm to the solver. Error reading in the CAERep from Simulation."

Curiously, when I suppress the multilinear isotropic hardening and Hill yield criterion in the material definition, both LS-DYNA and Explicit Dynamics perform as expected without errors. I am seeking guidance to diagnose and address the root cause of this simulation problem.

Any insights or assistance from the community would be greatly appreciated.

Thank you.

[Reno Genest]

Hello Ahmet,

I don't think multilinear isotropic hardening and Hill yield combined with orthotropic elasticity is supported in Explicit Dynamics and LS-DYNA. In LS-DYNA, you can open the input.k file in a text editor to check what material model that is used.

At Ansys 2023R2, there is a new orthotropic strength material model for Explicit Dynamics:

https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v232/en/exd_ag/adyn_ortho_yield_model.html



You can define orthotropic strength coefficients (A11 - A66) along with a master Stress-Plastic strain curve. See image above.

You will find  more information here:

https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v232/en/adyn_comp/adyn_comp_str_hard.html

There is information on how to obtain and calculate the coefficients here:

https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v232/en/adyn_comp/adyn_comp_plasticity_params.html

This information is in the Composite modelling guide for Autodyn:

https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v232/en/adyn_comp/adyn_comp.html

This model can be combined with orthotropic elasticity.

 

In LS-DYNA, *MAT_PAPER (*MAT_274) could be used. Here is an excerpt from the LS-DYNA User Manual Vol II:

 

You can download the LS-DYNA manuals here:

https://lsdyna.ansys.com/manuals/

Note that *MAT_PAPER is not available in Ansys WB yet, but you can include it in your model using a command snippet or using the Keyword Manager. You can use *PART_COMPOSITE to build the composite layup with *MAT_PAPER using a command snippet as well.

Let me know how it goes.

 

Reno.