HYPERELASTIC MATERIAL MODELS

Nancy Jewel Mcdonie

Hi all experts,

I'm dealing with hyperelastic material models and I'm really stuck in this. I have some questions, hope you guy can help me.

1.  What is the difference between Uniaxial test versus Planar test?

2. Why do we need to calibrate hyperelastic material model? What happen if I only use curve data (uniaxial, biaxial, planar) or only use hyperelastic material model's parameters? Which is more accurate? 

3. When I do a curve fiting test (example on ABOYCE model, Uniaxial curve data), then OptiStruct give me these coefficient in out file:

So, how can I deal with these coefficients? Are these parameters use for next simulation without curve data?  

4. What is homogenous deformation? Is it good or bad for calibrating hyperelastic material?

Thanks all.

Alberto Campagna

Hello Nancy,

a planar test is done to estimate shear resistance of the material. With hyperelastic materials you can proceed in 2 ways:

1) inserting C# coefficients directly into the MATHE card if you have them or

2) providing at least 1 of 3 test curves (uni/biaxial/planar). In this case OS will fit these curves and computes for you the strain energy coefficients of the law you are using. These coefficients are the "Hyperelastic  Material Constants" that are printed in the .out file and are automatically used by OS solver.

Method 1 and 2 are equivalent, it is just a matter of the data you possess.

Hope this helps.

Alberto