Mechanical APDL Structural Analysis Guide

deformation for which you may be interested. For these reasons, a high parameter value is not recom-
mended.

The following example input listing shows a typical use of the Ogden foam option with two parameters:

TB,HYPER,1,,2,FOAM !Activate 2 parameter Ogden foam data table

TBDATA,1,1.85 !Define μ 1

TBDATA,2,4.5 !Define α 1

TBDATA,3,-9.20 !Define μ 2

TBDATA,4,-4.5 !Define α 2

TBDATA,5,0.92 !Define first compressibility parameter

TBDATA,6,0.92 !Define second compressibility parameter

Refer to Ogden Compressible Foam Hyperelastic Material Constants for a description of the material
constants required for this option.

8.4.1.2.10. Response Function Hyperelastic Option (TB,HYPER,,,,RESPONSE)

The response function hyperelastic option (TB,HYPER,,,,RESPONSE) works with experimental data
(TB,EXPE).

The TB,HYPER command's NPTS argument defines the number of terms in the volumetric potential
function. The data table includes entries for the deformation limit cutoff for the stiffness matrix as the
first entry, and the volumetric potential function incompressibility parameters starting in the third pos-
ition. ( The second position in the data table is unused.)

The following example input shows the use of the response function option with two terms in the
volumetric potential function:

TB,HYPER,1,,2,RESPONSE! Activate Response Function data table

TBDATA,1,1E-4! Define deformation limit cutoff

TBDATA,3,0.002! Define first incompressibility parameter

TBDATA,4,0.00001! Define second incompressibility parameter

For a description of the material constants required for this option, see Response Function Hyperelasticity
in the Material Reference. For detailed information about response functions determined via experimental
data, see Experimental Response Functions in the Mechanical APDL Theory Reference.

Experimental data for the model is entered via the TB,EXPE command, where the TBOPT argument
specifies the type of data to be input:

• Uniaxial tension is input via TBOPT = UNITENSION.


• Uniaxial compression is input via TBOPT = UNICOMPRESSION.


• Equibiaxial tension is input via TBOPT = BIAXIAL.


• Planar shear is input via TBOPT = SHEAR


• Combined uniaxial tension and compression is input via TBOPT = UNIAXIAL.

The response function hyperelastic model must include experimental data for at least one of the listed
deformations.

Any combination of uniaxial tension, equibiaxial tension, or planar shear is also valid. For incompressible
and nearly incompressible materials, uniaxial compression can be used in place of equibiaxial tension.

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Nonlinear Structural Analysis