*TRS

Optional parameters

DEFINITION

Set DEFINITION=WLF (default) to define the shift function by the Williams-Landel-Ferry approximation.

Set DEFINITION=ARRHENIUS to define the shift function by the Arrhenius approximation.

Set DEFINITION=USER to define the shift function in user subroutines. In Abaqus/Standard analyses define the shift function in user subroutine UTRS for the linear viscoelastic model (see Time Domain Viscoelasticity) or in user subroutine UTRSNETWORK for the nonlinear viscoelastic model defined using the parallel rheological framework (see Parallel Rheological Framework). In Abaqus/Explicit analyses define the shift function in user subroutine VUTRS for the linear viscoelastic model.

Set DEFINITION=TNM to define the shift and response functions for the Tool-Narayanaswamy-Moynihan model.

Set DEFINITION=TABULAR to define the shift function in tabular form.

DEPENDENCIES

This parameter is relevant only for DEFINITION=TABULAR.

Set this parameter equal to the number of field variables included in the specification of the shift function.

If this parameter is omitted, it is assumed that the shift function is constant or depends only on temperature. For more information, see Material Data Definition.

PROPERTIES

This parameter applies only to Abaqus/Explicit analyses and to Abaqus/Standard analyses if user subroutine UTRSNETWORK is used to define the shift function.

Set this parameter equal to the number of properties being entered. The properties are available for use in user subroutines VUTRS or UTRSNETWORK.

Data line to define the shift function by the Williams-Landel-Ferry approximation

First (and only) line

Reference temperature, $θ_{0}$ .
Calibration constant, $C_{1}$ .
Calibration constant, $C_{2}$ .

Data line to define the shift function by the Arrhenius approximation by specifying the reference temperature and the activation energy

First (and only) line

Reference temperature, $θ_{0}$ .
Activation energy, $E_{0}$ .

In addition, you need to specify the universal gas constant and absolute zero using the PHYSICAL CONSTANTS option.

Data line to define the shift function by the Arrhenius approximation by specifying the reference temperature and the ratio of the activation energy to the universal gas constant

First (and only) line

Reference temperature, $θ_{0}$ .
Blank space.
Ratio of the activation energy to the universal gas constant, $E_{0} / R$ .

In addition, you need to specify absolute zero using the PHYSICAL CONSTANTS option.

Data lines to define material properties for a user-defined shift function (DEFINITION=USER)

No data lines are needed if the PROPERTIES parameter is omitted or set to 0. Otherwise, first line

Enter the material properties, eight per line.

Repeat this data line as often as necessary to define all material properties.

Data lines to define the shift and response functions for the TNM model

First line

Reference temperature, $θ_{R}$ .
Activation energy, $E_{0}$ .
Material parameter, $χ$ .
Initial fictive temperature, $θ_{f i c t}^{0}$ .
Number of terms in the response function.

Second line

Coefficient, $C_{1}$ , in the first term of the response function.
Relaxation time, $τ_{1}$ , in the first term of the response function.

In addition, you need to specify the universal gas constant and absolute zero using the PHYSICAL CONSTANTS option.

Repeat this data line as often as necessary to define the second, third, etc. terms of the response function. There is no restriction on the number of terms in the response function.

Data lines to define the shift function in tabular form

First line

Logarithm to base 10 of the shift function, $\log_{10} (A)$ .
Temperature, $θ$ .
First field variable.
Second field variable.
Etc., up to six field variables.

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

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

Repeat this set of data lines as often as necessary to define the logarithm of the shift function as a function of temperature and other predefined field variables.