*VOLUMETRIC TEST DATA

Hyperelastic material model

For hyperelastic materials, you can use the VOLUMETRIC TEST DATA option to provide volumetric loading test data that includes user-defined material compressibility. Alternatively, you can include compressibility by:

using the POISSON parameter on the HYPERELASTIC option, or
in the case of the Marlow and Valanis-Landel models, by specifying the nominal lateral strain under the UNIAXIAL TEST DATA option.

If none of these options is used to specify volumetric behavior, Abaqus/Standard assumes that the material is incompressible, while Abaqus/Explicit selects a default value for the compressibility.

See the discussion in Compressibility before using this option in Abaqus/Explicit.

Optional parameters

SMOOTH

Include this parameter to apply a smoothing filter to the stress-strain data. If the parameter is omitted, no smoothing is performed.

Set this parameter equal to the number n such that $2 n + 1$ is equal to the total number of data points in the moving window through which a cubic polynomial is fit using the least-squares method. n should be larger than 1. The default is SMOOTH=3.

Optional parameter when the VOLUMETRIC TEST DATA option is used in conjunction with the HYPERELASTIC, MARLOW option or the HYPERELASTIC, VALANIS-LANDEL option

DEPENDENCIES: Set this parameter equal to the number of field variable dependencies included in the definition of the test data. If this parameter is omitted, it is assumed that the test data depend only on temperature. See “Using the DEPENDENCIES parameter to define field variable dependence” in Material Data Definition for more information.

Data lines to specify volumetric test data for hyperelasticity other than the Marlow and the Valanis-Landel models (the volume ratios must be arranged in either ascending or descending order if the SMOOTH parameter is used)

First line

Pressure, p.
Volume ratio, J (current volume/original volume).

Repeat this data line as often as necessary.

Data lines to specify volumetric test data for the Marlow and the Valanis-Landel models (the volume ratios must be arranged in descending order if the SMOOTH parameter is used)

First line

Pressure, p.
Volume ratio, J.
Temperature, $θ$ .
First field variable.
Second field variable.
Etc., up to five field variables.

Subsequent lines (only needed if the DEPENDENCIES parameter has a value greater than five)

Sixth field variable.
Etc., up to eight field variables per line.

Repeat this set of data lines as often as necessary to define the test data as a function of temperature and other predefined field variables. The volume ratios must be given in descending order.

Hyperfoam material model

There are no parameters associated with this option.

Data lines to specify volumetric test data for a hyperfoam

First line

Pressure, p.
Volume ratio, J (current volume/original volume).

Repeat this data line as often as necessary.

Viscoelastic material model

Optional parameters

VOLINF

To specify creep test data, set this parameter equal to the value of the long-term, normalized volumetric compliance, $j_{K} (\infty)$ .

To specify relaxation test data, set this parameter equal to the value of the long-term, normalized volumetric modulus $k_{R} (\infty)$ .

The volumetric compliance is related to the volumetric modulus by $j_{K} (\infty) = 1 / k_{R} (\infty)$ . The fitting procedure will use this value in the constraint $1 - \sum_{i = 1}^{N} {\bar{k}}_{i}^{P} = k_{R} (\infty)$ .

Data lines to specify volumetric creep test data for a viscoelastic material

First line

Normalized volumetric (bulk) compliance $j_{K} (t), (j_{K} (t) \geq 1)$ .
Time $t, (t > 0)$ .

Repeat this data line as often as necessary to give the compliance-time data.

Data lines to specify volumetric relaxation test data for a viscoelastic material

First line

Normalized volumetric (bulk) modulus $k_{R} (t), (0 \leq k_{R} (t) \leq 1)$ .
Time $t, (t > 0)$ .

Repeat this data line as often as necessary to give the modulus-time data.