Creating field output by operating on fields

You can create field output by computing new results using the field output available in the output database. For example, you might create new field output variables to show the differences in the stress fields between two increments. For detailed examples, see Building valid field output expressions.

Related Topics
Selecting a specific results step and frame
Building valid field output expressions
Using operations on field output
Creating coordinate systems during postprocessing
Understanding how results are computed
Transforming results into a new coordinate system
Saving field output created during the session

Context:

You create new field output variables from fields by operating on analysis results found in the output database. You can display field output variables that you have created in the same ways as output database field output variables: in the form of a deformed, contour, or symbol plot; by probing any model or X–Y plot; as X–Y data obtained along a path through your model; or in a tabular report. Field output variables that you have created are saved in the session step until you end the session or close the output database from which the field output originates. You can also save the field output to the output database, in which case you must open the output database with write privileges.

Note: Field output created using complex results will contain only the real portion of the data. You cannot create field output that includes the imaginary part of complex results.

If you create field output that extracts an invariant scalar component of a tensor variable, such as the tensor variable's Mises stress or one of its principal stresses, contour plots of the resulting field output may be different than the original contour plots of the invariant. This difference occurs because these contours are calculated differently. Abaqus/CAE calculates the original invariant by first extrapolating the tensor to the nodes, calculating the invariant values, and averaging the values at the nodes. For the field output, Abaqus/CAE extrapolates the invariant values to the element nodes and averages them, which can result in a different contour plot.

Note: Some field output variables like PEEQ and PEMAG always have positive values at the integration points. For these variables extrapolation of the results from integration points to element nodes can result in negative values at some nodes. To avoid these negative value results, Abaqus/CAE clamps the element nodal values of such fields internally at 0.0 and resets negative values to 0.0. If you operate on these field output variables to create new field output, Abaqus/CAE does not clamp the values at 0.0 for the new resulting field output and the contour plot may show some negative values.

  1. Locate the options for creating field output from fields.

    From the main menu bar, select ToolsField OutputCreate From Fields.

    The Create Field Output dialog box appears.

    Tip: You can also specify field output by using the tool in the toolbox.

  2. The default name for the new field output variable appears in the Name text field. To provide a more meaningful name, replace this default with the name of your choice (including blank spaces if you wish).

  3. Build your expression in the expression text field using a combination of the following procedures:

    1. Select a function from the menu on the right side of the Create Field Output dialog box.

      • Select Operators to apply a built-in arithmetic operator to the selected field output.

      • Select Transformation to apply a coordinate system transformation to the selected field output.

      • Select Scalar to extract a scalar component from the selected field output.

      The list below the menu changes to reflect your selection.

    2. Select field output variables from the list on the left side of the Create Field Output dialog box. You can select field output for any step and frame in the analysis.

      Tip: Place your cursor over the vertical lines separating each column in the output variable table, and enlarge the column widths to see the complete text.

      The field output variable appears in the expression text field.

    3. Select operators, transformations, or scalars from the list on the right side of the Create Field Output dialog box.

      The selected function appears in the expression text field.

      Note:

      If you select a dynamic coordinate system (a system that follows nodes in your model) from the list of transformations, deformationField= appears in the expression text field inside the transform function. You must select a deformation field output variable that Abaqus/CAE will use to compute the position of the coordinate system.

    4. Use standard mouse and keyboard editing techniques in the expression text field to position the cursor and configure your expression.
    5. Adjust the syntax of your expression if necessary: parentheses may be needed.
    6. If you make a mistake and wish to start over, click Clear Expression.

    For more information, see Building valid field output expressions.

  4. Click OK to create your new field output variable and to dismiss the dialog box.

    Abaqus creates a new field output variable that is contained in a frame of the session step and available from the Field Output dialog box. Current results plots, if any, are not affected.