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Modeling anisotropic hyperelastic material

Submitted by A.Jabary on
research

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

Zaoyang Guo

 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

Mon, 12/29/2008 - 18:49 Permalink
Sugeng Waluyo

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

 

Wed, 01/07/2009 - 07:41 Permalink
Zaoyang Guo

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 

 

 

Thu, 01/15/2009 - 12:01 Permalink