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Modeling anisotropic hyperelastic material
Recently I work on Finite Element Modeling of human eye . And focus on cornea .( the outer transparent layer of human eye) . Based on Its structure which consist of collagen fibers I have to use the Anisotopic hyperelastic model . And I derived the coefficients of
strain energy function which divided into three terms of : volumetric,isotropic and anisotropic
But I have some troubles to modeling this material in Ansys v.10 Beacause I have to use UMAT subroutine and I have not enough information about how to define material with macro in Ansys. So would you mind introduce me usefull links about predefined UMAT in Ansys
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volumetric decomposition of anisotropic materials
Dear Jabary,
You mentioned the volumetric decomposition of anisotropic hyperelastic material. Recently we find that, if the material is anisotropic (in our case, it is compressible transversely isotropic), the volumetric decoupling decomposition cannot be applied because it will lead to wrong response of the material under hydrostatic compression. The details can be found in our recent paper:
http://www.mech.gla.ac.uk/~zguo/Publications/J014.pdf
We also developed several soft tissue models to consider the reinforcement of collagen fibres and you can find related papers on my website.
Hope that helps,
Zaoyang
Re: volumetric decomposition of anisotropic materials
Dear Zaoyang,
I read your paper in http://www.mech.gla.ac.uk/~zguo/Publications/J014.pdf briefly. I am wondering in which situations a "pure" hydrostatic compression are exist in practice, thus your mathematical argument can be meaningful.
Thanks a lot for the answers.
Best regards,
Sugeng
Dear Sugeng, For example,
Dear Sugeng,
For example, when the solid is in some fluid. The key is, if the model is not correct in dydrostatic compression when the compressibility is quite significant to the material, the model will have problems because the response of the material is continuous.
If you check new version (6.8) of ABAQUS, you may find that they provide an isotropic compression term for anisotropic hyperelastic material, and this is also questionable when the material is not just "nearly incompressible".
Best,
Zaoyang
anisotropic hyperelastic FE for biological materials
You might also consider trying the open source code "FEBio", this works well for hyperelastic anisotropic materials without having to write a UMAT--this sort of material model is built in directly.
Support for anisotropic hyperelastic model in ABAQUS v6.8
Dear Michelle,
ABAQUS v6.8 now also supports anisotropic hyperelastic models, you need only supply the strain energy functions and the derivatives and don't need work out the stiffness matrix, which is usually very complex like in UMAT.
Dear Michellel,
Dear Michellel,
I am now trying to study hyperelastic anisotropic materials.
I clicked your "FEBio" for getting the open source code, but the link is "
This Page Could Not Be Found!
So where can I find the code else?
Thank you very much!!!
"