Learning Forum

[serene7wings]

Do UDF allows modification of anisotropic hyperelastic material property? UserHyper    seems to be for hyperelastic ,not sure whether it works for anisotropic hyperelastic. 

 

 

[jpasquerell]

The two UPF (User programmable features) for hyperelasticity are UserHyper and UserMat. 

The UserHyper routine is only used for defining isotropic hyperelastic constitutive models in which the potential is a function of I1, I2 and J. It can't be used for defining a model that is formulated in terms of any other set of invariants - including the anisotropic invariants.

The only method to program a user defined anisotropic hyperelastic model is through the usermat() routine. 

[ansysuser]

Hello jpasquerell,

I need to develop an hyperelastic material model following the strain energy function of Holzapfel and Ogden found in https://royalsocietypublishing.org/doi/full/10.1098/rsta.2009.0091 equation 5.38.  This is an anisotropic hyperelastic material model.  I was hoping to use UserHyper.F, but I discovered your comment above which indicates that this is not feasible (it would be nice if the limitations were described in the documentation rather than by chance in a forum!).

I noticed in the UPF folder for 19.3 there is another file called UserHyperAniso.F but there is no mention of this in the documentation whatsoever. Can this file be adapted for such a use, and will I be able to ask questions about how to use it here? Thanks. 

[kostas95]

Hello ansysuser,

I am also looking to develop a material that follows the Holzapfel/Ogden energy function. Did you manage to do it ? If so, would mind explaining the process you followed? Thank you.