Simple hyperlasticity
Simple hyperlasticity
(OP)
Hi,
I am trying to model an intervertebral disc, in compression.
So for now it's just a rod with 2 thin endplates on both edges, one is fixed and one has a pressure load compressing everything.
I am heading towards making it more realistic in terms of geometry and ideally it will porohyperelastic.
But for now Im just getting familiar with ABAQUS and want to make it just hyperelastic. I am using Mooney Rivlin equations and putting the coefficients into ABAQUS. My question is, when I put elastic properties the job is completed, no problem. But when I put hyperelasticity, the job is aborted but gives results anyway (negative eigenvalues, and excessive distortion in the msg file). can I solve this? how much can I trust the data of these aborted jobs? I also noticed that if I put a lower pressure load, then the job is completed.
Can anyone help me? I hope I was clear enough.
Thank you very much
Ben
I am trying to model an intervertebral disc, in compression.
So for now it's just a rod with 2 thin endplates on both edges, one is fixed and one has a pressure load compressing everything.
I am heading towards making it more realistic in terms of geometry and ideally it will porohyperelastic.
But for now Im just getting familiar with ABAQUS and want to make it just hyperelastic. I am using Mooney Rivlin equations and putting the coefficients into ABAQUS. My question is, when I put elastic properties the job is completed, no problem. But when I put hyperelasticity, the job is aborted but gives results anyway (negative eigenvalues, and excessive distortion in the msg file). can I solve this? how much can I trust the data of these aborted jobs? I also noticed that if I put a lower pressure load, then the job is completed.
Can anyone help me? I hope I was clear enough.
Thank you very much
Ben





RE: Simple hyperlasticity
Basically, the load is moving the upper plate too quickly and passing through the lower plate before the next time step can be calculated.
Garland E. Borowski, PE
Borowski Engineering & Analytical Services, Inc.
Lower Alabama SolidWorks Users Group
Magnitude The Finite Element Analysis Magazine for the Engineering Community
RE: Simple hyperlasticity
If I apply a load magnitude of 2 it doesnt work, but 1 works....I dont get it.
Thank you anyway
Ben
RE: Simple hyperlasticity
Actually a job of 2 or 30 or anything more would give the same result. So somewhere between 1 and 2 it just stops calculating....
If anybody has an answer that would be great, thank you
Ben
RE: Simple hyperlasticity
RE: Simple hyperlasticity
I tried to put 0.05 and it works also, but the deformation is very very small of course...
RE: Simple hyperlasticity
RE: Simple hyperlasticity
I have tried the tet meshing, the job is completed and does not give any error message. Even if I put a force of 50.
BUT the results show almost no deformation. And if I put a bigger force (100), then it doesnt work. But 50 should be enough to see a big swelling....which is by the way what I see with my aborted jobs and the hex meshing, the results show the cylinder really compressed.
I dont understand why meshing changes everything so much.
Thanks for helping....
Ben
RE: Simple hyperlasticity
Why don't you test it first with some more simple example? In that case, may be you can grasp its behavior before heading to the actual one.