Anisotopic hyperelastic Ansys subroutine...help please!!

[adrianita]

Recently I work on Finite Element Modeling of a human vertebral body, and focus on intervertebral disc.
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.
But I have some troubles to modeling this material in Ansys v.10 or v.12
Beacause I have to use user material subroutine and I have not enough
information about how to define material with macro in Ansys.
Please can someone help me with this routine, I read the help but i dont understand anything. thanks!

[Jobie.Gerken]

adrianita,

There are 2 major parts to writing your own constitutive model for use in the ANSYS MAPDL software.

First you must write the Fortran (or other language) subroutine(s) to calculate the stress and stiffness and return them as required by the interface of the MAPDL subroutine usermat3d(). I have posted an example for the NeoHookean material in this thread
http://polymerfem.com/showthread.php...tep-derivation

The next part is you have to figure out how to compile and link the subroutine to give you a customized executable that calls your modified subroutine. Sheldon Imaoka has some step-by-step details on this process posted here
http://ansys.net/tips_sheldon/STI090...iling_UPFs.pdf

Jobie