Defining values for predefined field variables

You can define the initial value and the magnitude and time variation of a field variable over a selected region for each analysis step; Abaqus interpolates the values to the material points.

Related Topics
Understanding symbols that represent prescribed conditions
Creating predefined fields
Using analytical expression fields
Creating expression fields
Creating discrete fields
In Other Guides
Predefined field variables

  1. Display the predefined field variable editor using one of the following methods:

    • To create a new predefined field variable, follow the procedure outlined in Creating predefined fields (Category: Other; Types for Selected Step: Field).

      Note:

      If you want to specify the field variable variation directly in the editor, in user subroutine UFIELD or VUFIELD, or using an analytical field or discrete field, you must select a region for the field variable. If you want to specify any other field distribution, you can click Done in the prompt area to use calculated fields.

    • To edit an existing field variable using menus or managers, see Editing step-dependent objects.

  2. If you are editing a field variable in any general analysis step other than the one in which the field variable was created, click the arrow to the right of the Status field, and select the option of your choice from the list that appears:

    • Select Propagated to indicate that the field variable is active in the current step with field variable values held constant from the previous step. No data can be specified; click OK to exit the editor. If you change the status of the current step from Modified to Propagated and click OK, all modifications to the current step are removed.

    • Select Modified to edit the field variable definition for the current step. Continue with Step 3.

    • Select Reset to initial to reset the field variable definition to the one that was prescribed in the initial step. No data can be specified; click OK to reset the field and to exit the editor.

  3. If you are creating a new field variable, click the arrow to the right of the Distribution field, and select the option of your choice from the list that appears.

    Note:

    If you are creating a field variable in the initial step, only the Direct specification, From results or output database file, analytical field, and discrete field distribution options are available.

    • Select Direct specification to specify the field variable variation over the selected region in the field editor.

    • Select From results or output database file to read field variable values from the results or output database file of a previous Abaqus analysis.

    • Select User-defined to define field variable values in user subroutine UFIELD for Abaqus/Standard analyses or user subroutine VUFIELD for Abaqus/Explicit analyses. See Specifying general job settings for more information.

    • Select From results or output database file and user-defined to read field variable values from the results or output database file of a previous Abaqus analysis and modify them in user subroutine UFIELD or VUFIELD.

    • Select an analytical field, labeled with an (A), or a discrete field, labeled with a (D), to define a spatially varying field variable. The selection list contains all analytical fields and only discrete fields that are valid for the field variable.

      Alternatively, you can click to create a new analytical field. (See The Analytical Field toolset for more information.)

  4. If you selected the Direct specification, analytical field, or discrete field distribution option, perform the following steps:

    1. Click the arrows to right of the Field variable number field to indicate the number of the field variable you are defining.
    2. Click the arrow to the right of the Section variation field, and select an option from the list that appears. Only options that are valid for the selected region appear in the list. Beam and shell gradient values are not affected by an analytical field or a discrete field. You should select an option that is consistent with the field variable variation method defined in the section definition associated with the region selected for this field variable as follows:

      • Select Constant through region to define a constant field variable value over a section.

        In the Magnitude text field, enter the magnitude of the field variable across the section.

      • Select Gradient through beam section to define the field variable variation through a beam section. (This method is not available for axisymmetric models.)

        In the Reference magnitude text field, enter the magnitude of the field variable at the cross-section origin. In the N2 gradient text field, enter the field variable gradients through the section in the n2-direction of the beam.

      • Select Defined at shell/beam field points to define a piecewise linear field variable variation through a shell or beam section.

        Select the number of field points to be specified by either typing an integer in the Field points text field or using the arrows to the right of the text field to select a number, and enter the magnitude of the field variable at each point in the Section Data table. The number of values in the section definition should be less than or equal to the number of field variable data points given for this field. If the number of values is less, the last value will be repeated to match the number of field variable data points.

    3. If desired (for all steps other than the initial step), click the arrow to the right of the Amplitude text field, and select the amplitude of your choice from the list that appears. Alternatively, you can click to create a new amplitude. (See The Amplitude toolset for more information.) Beam and shell gradient values will be modified by the amplitude definition.
    4. Click OK to save your data and to exit the editor.

  5. If you selected the From results or output database file distribution option, perform the following steps:

    1. Click the arrows to the right of the Field variable number field to indicate the number of the field variable you are defining. The default is field variable number 1. To define more than one field variable, you can create additional predefined fields. You must number the field variables consecutively starting from 1.
    2. In the File name text field, enter the name of the results or output database file from which field variable data are to be read; or click to display the Select Results or Output Database File dialog box and select the file of your choice. (See Using file selection dialog boxes for more information.)
    3. If you are reading results from an output database in an Abaqus/Standard analysis, you can specify a scalar nodal output variable to be read and used to initialize the field variable.
    4. If you are creating a field variable in the initial step:

      • In the Step text field, enter the step number of the analysis whose results or output database file is being used as input from which the field variable data should be read.

      • In the Increment text field, enter the increment number of the analysis whose results or output database file is being used as input from which the field variable data should be read.

    5. Optionally, if you are creating a field variable in an analysis step other than the initial step:

      • In the Begin step text field, enter the step number of the analysis whose results or output database file is being used as input that begins the field variable data to be read. By default, the first step available in the results or output database file is used.

      • In the Begin increment text field, enter the increment number of the analysis whose results or output database file is being used as input that begins the field variable data to be read. By default, the first increment available in the results or output database file is used.

      • In the End step text field, enter the step number of the analysis whose results or output database file is being used as input that ends the field variable data to be read. By default, the Begin step value is used.

      • In the End increment text field, enter the increment number of the analysis whose results or output database file is being used as input that ends the field variable data to be read. By default, the last increment available for the End step value in the results or output database file is used.

    6. Choose the Mesh compatibility.

      • Select Compatible if the meshes in the original analysis and the current analysis are the same or differ only in the element order.

      • Select Incompatible if the meshes in the original analysis and the current analysis are dissimilar. This option is valid only if the field variable values are being read from an output database file.

    7. Click OK to save your data and to exit the editor.

  6. If you selected the User-defined distribution option, perform the following steps:

    1. Click OK to exit the editor.
    2. Enter the Job module, and display the job editor for the analysis job of interest. (For more information, see Creating, editing, and manipulating jobs.)
    3. In the job editor, click the General tab, and specify the file containing the user subroutine that defines the field variable values. For more information, see Specifying general job settings.

      Note:

      You can specify only one user subroutine file in the job editor; if your analysis involves more than one user subroutine, you must combine the user subroutines into one file and then specify that file.

  7. If you selected the From results or output database file and user-defined distribution option, follow the procedures outlined in Steps 5 and 6 for the From results or output database file and User-defined distribution options.