Mechanical APDL Structural Analysis Guide

Tools are available to help you determine the coefficients for all of the hyperelastic options defined by
TB,HYPER. The TBFT command allows you to compare your experimental data with existing material
data curves and visually fit your curve for use in the TB command. All of the TBFT command capability
(except for plotting) is available via batch and interactive (GUI) mode. See Material Curve Fitting for
more information.

The following topics describing each of the hyperelastic options (TB,HYPER,,,,TBOPT) are available:

8.4.1.2.1. Mooney-Rivlin Hyperelastic Option (TB,HYPER,,,,MOONEY )

8.4.1.2.2. Ogden Hyperelastic Option (TB,HYPER,,,,OGDEN)

8.4.1.2.3. Neo-Hookean Hyperelastic Option ( TB,HYPER,,,,NEO)

8.4.1.2.4. Polynomial Form Hyperelastic Option ( TB,HYPER,,,,POLY )

8.4.1.2.5. Arruda-Boyce Hyperelastic Option ( TB,HYPER,,,,BOYCE)

8.4.1.2.6. Gent Hyperelastic Option ( TB,HYPER,,,,GENT )

8.4.1.2.7. Yeoh Hyperelastic Option ( TB,HYPER,,,,YEOH)

8.4.1.2.8. Blatz-Ko Foam Hyperelastic Option ( TB,HYPER,,,,BLATZ)

8.4.1.2.9. Ogden Compressible Foam Hyperelastic Option ( TB,HYPER,,,,FOAM)

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

8.4.1.2.11. User-Defined Hyperelastic Option ( TB,HYPER,,,,USER)

8.4.1.2.1. Mooney-Rivlin Hyperelastic Option (TB,HYPER,,,,MOONEY)

The Mooney-Rivlin option (TB,HYPER,,,,MOONEY ), which is the default, allows you to define 2, 3, 5, or
9 parameters through the NPTS argument of the TB command. For example, to define a 5 parameter
model you would issue TB,HYPER,1,,5,MOONEY.

The 2 parameter Mooney-Rivlin option has an applicable strain of about 100% in tension and 30% in
compression. Compared to the other options, higher orders of the Mooney-Rivlin option may provide
better approximation to a solution at higher strain.

The following example input listing shows a typical use of the Mooney-Rivlin option with 3 parameters:

TB,HYPER,1,,3,MOONEY !Activate 3 parameter Mooney-Rivlin data table

TBDATA,1,0.163498 !Define c 10

TBDATA,2,0.125076 !Define c 01

TBDATA,3,0.014719 !Define c 11

TBDATA,4,6.93063E-5 !Define incompressibility parameter

!(as 2/K, K is the bulk modulus)

Refer to Mooney-Rivlin Hyperelastic Material (TB,HYPER) for a description of the material constants re-
quired for this option.

8.4.1.2.2. Ogden Hyperelastic Option (TB,HYPER,,,,OGDEN)

The Ogden option (TB,HYPER,,,,OGDEN) allows you to define an unlimited number of parameters via
the NPTS argument of the TB command. For example, to define a three-parameter model, use TB,HY-
PER,1,,3,OGDEN.

Compared to the other options, the Ogden option usually provides the best approximation to a solution
at larger strain levels. The applicable strain level can be up to 700 percent. A higher parameter value
can provide a better fit to the exact solution. It may however cause numerical difficulties in fitting the
material constants, and it requires enough data to cover the whole range of deformation for which you
may be interested. For these reasons, a high parameter value is not recommended.

The following example input listing shows a typical use of the Ogden option with 2 parameters:

TB,HYPER,1,,2,OGDEN !Activate 2 parameter Ogden data table

TBDATA,1,0.326996 !Define μ 1

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Modeling Material Nonlinearities