Using HYPERFOAM to model foam compression

General Questions
1

I am working on setting up a simple disk to be compressed using *HYPERFOAM model. When I activate the hyperforam model with these coefficients

*HYPERFOAM,N=1
37000.0,2.944,0.0404,0.0

for some reason the disk compression looks unusual and the edge nodes of the tope face where it is pushed down falls behind where this is not the case if a simple linear material model is used, I have attached the image of the case for you to see,
I appreciate your comment on it

Thanks
Amir

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P.S. I tried to upload my case here however this platform says the new users are not able to upload file. Happy to share my file in any other ways!
disk-compression_nonLinear_pie.zip (8.0 MB)

2

Try again. Now you should be able to upload the file.

1 Like
3

Thanks, the zip file of the pie with the hyperfoam activated is uploaded now

4

It seems to be a problem with CalculiX. Abaqus runs this input file normally. I would do a single element test for now. I also checked the stability of this material definition in Abaqus and it’s ok.

5

Thanks for looking into it. I was hoping there was a way to fix this but perhaps not. I tried to mesh the same pie with the lowest number of elements which turned it into 8 tet elements and one main node at each corner (total of 25 nodes) and ran it. The displacement seems to have been corrected but the values for stresses and forces are zero, so there is an issue with the solver

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6

Just a quick update that I have been able to solve a case using N=2 Ogden model with generic coefficients I found on a sample on the web, however I am still struggling to solve this case with the coefficient we fit experimentally to the foam we are investigating. The results don’t make sense and I am trying to figure out the problem. Does anyone have experience with HYPERFOAM model and its coefficients?
My questions are:

  • Our fit shows only positive coefficients although the generic model on the web I found shows negative for α_2 (see this example beamhf.inp)
  • Wondering what the units are for µ. Document shows it is shear stress with the unit of stress so if I go metric it will be Pascal however my fit shows something in the range of 450 and 70 kpa for these two however the generic sample value is very small. I have been playing with the order of magnitude of these just in case something is formulated inconsistently and the lower number shows more stable run numerically however the actual kpa range are failing to converge
  • Could the way we load the sample (tension vs compression) change the way we setup the sign of these coefficients? I have also been playing with the sign of µ however no luck yet