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Non-Linear Static Structural to Explicit Dynamic Environment (Material Properties Issue)

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MechEngineerNT

Mechanical
Dec 13, 2013
25
Hi Guys,

I'm running a Primer crimp simulation. In step one, I'm applying a displacement to a roll die and plastically deforming a crimp on a primer. From there, I want to apply a pressure trace to the internal faces of the primer to see if it holds. I've been running this simulation in the non-linear static environment using tabular data, however, I'm getting very poor results. The primer is essentially popping out of the crimp. We've done testing on the crimped primers and all function as expected in real life. This leads me to believe that applying the pressure in a static environment is way to overly conservative. So essentially, I want to plastically deform the crimp, get those stressed conditions over to an explicit environment, then apply a pressure trace. The only run in i'm having is how do I change material of the crimp from non-linear isotropic to that of an explicit material? I've tried this without success since I need to get strain rate dependent loading data input into the material property for the explicit analysis. Anyone know how to do this?? Any advice would help.

Thank you,

MechengNT
 
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Look into Johnson-Cook material model. It can be implemented in Ansys Mechanical and Explicit STR.
 
In Explicit STR system (Workbench) the above mentioned material model can be found
in Engineering Data. If you want to use an explicit solver instead of implicit,
would not it be better to solve the model there, thus not having to transfer
results between environments?
 
Thanks, L K.

I don't have a good understanding of the Johnson-Cook material model for 7075-T6 (material I'm analyzing). I've done some preliminary research and have found some constants online (attached), but can't seem to find some constants ansys is looking for.

I've found Ansys has some default explicit materials using the Steinberg Guinan strength. This model is actually non-linear, the only downside is I'm trying to find good failure criterion for the model. I did find Johnson Cook failure-- where the Damage constants are available online for a 7075-T6 material. May try this. What do you think?

--Alex
 
 https://files.engineering.com/getfile.aspx?folder=9200c40e-74a0-4336-8fce-e4f26c034c18&file=Material-properties-and-Johnson-Cook-model-parameters-for-aluminium-alloy-7075-T6.png
If you have the time, maybe run with both material models (Johnson-Cook according to your spreadsheet and
Steinberg-Guinan found in Eng. Data).
 
I ran the Johnson cook model in a static environment and the results were a bit weird. I thought it took into account permanent plastic deformation, however, the flange of the crimp popped back after the roll die cold-formed it. The crimp should've clearly been deformed. Johnson cook is meant for more dynamic analyses.
 
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