Context:
Note:
If you apply the boundary condition to a two-dimensional planar region,
only the U1, U2, and
UR3 degrees of freedom are available. If you model the
part with generalized plane strain elements, you must use the
Keywords Editor to apply boundary conditions on the active
degrees of freedom (U3, UR1, and
UR2) at the reference node of these elements (see
Adding unsupported keywords to your Abaqus/CAE model).
-
Display the displacement/rotation boundary condition editor using one
of the following methods:
-
If you are creating the boundary condition in a buckling step, select
the Use BC for option that specifies the calculations for
which you want the boundary condition used. For more information, see
“Boundary
conditions,” in
Eigenvalue Buckling Prediction.
-
By default, the global coordinate system is used to define the
boundary condition. To change the coordinate system in which the boundary
condition is applied, click
for the CSYS option and do one of the
following:
-
Select an existing datum coordinate system in the viewport.
-
Select an existing datum coordinate system by name.
-
From the prompt area, click Datum CSYS
List to display a list of datum coordinate systems.
-
Select a name from the list, and click
OK.
-
Click Use Global CSYS from the prompt area
to revert to the global coordinate system.
This coordinate system editing option is available only in the step
in which the boundary condition is created.
-
If a Method field appears toward the top of the
editor, click the arrow to the right of the field, and select one of the
following:
-
Select Specify Constraints if you want to
specify values for particular degrees of freedom.
-
Select Fixed at Current Position if you want
to fix the degrees of freedom at their final values from the previous general
step.
The Method option appears in the editor only if
both methods are valid for the selected step.
-
Click the arrow to the right of the Distribution
field, if available, and do the following:
-
Select Uniform to define a uniform boundary
condition.
-
Select User-defined to define the boundary
condition in user subroutine
DISP. See the following sections for more information:
-
Select an analytical field, labeled with an (A), or a discrete
field, labeled with a (D), to define a spatially varying boundary condition.
Only analytical fields and discrete fields that are valid for this boundary
condition type are displayed in the selection list.
Alternatively, you can click
to create a new analytical field. (See
The Analytical Field toolset
for more information.)
The Distribution option appears in the editor
only if you are creating the boundary condition or editing the boundary
condition in the step in which it was created. This option is unavailable if
you select the Fixed at Current Position method.
-
If you selected the Uniform, analytical field, or
discrete field distribution option, perform the following steps:
-
Use the appropriate method to define the boundary condition:
- If no text fields
appear next to each degree of freedom:
-
-
Toggle on a degree of freedom to fix the value either at zero
(if you are defining a degree of freedom in the initial step) or at its final
value at the end of the previous analysis step (if you are defining the degree
of freedom in the second analysis step or in a later step.)
-
Toggle off a degree of freedom to leave the degree of freedom
unconstrained.
- If
text fields appear next to each degree of freedom:
-
-
Toggle on a degree of freedom to constrain the degree of
freedom. The text field becomes available in which you can specify a value for
the degree of freedom. If you are creating the boundary condition in this step,
a default value of zero appears in the text field. If you are modifying the
boundary condition in this step, the value propagated from the previous step
appears in the text field.
-
Toggle off a degree of freedom to leave the degree of freedom
unconstrained. If you toggle off a degree of freedom after modifying the
default or propagated value in the text field, the modified value is lost. If
you toggle that degree of freedom back on, the default or propagated value
reappears in the text field.
-
If an Amplitude appears at the bottom of
the editor, click the arrow to the right of the 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.)
-
Click OK to save your data and to exit the
editor.
-
If you selected the User-defined distribution
option, perform the following steps:
-
If desired, use the following techniques to define displacement:
-
Toggle on a degree of freedom to constrain the degree of
freedom. If you are in the initial step, that degree of freedom is set to zero.
If you are in any step other than the initial step, a text field becomes
available in which you can specify a value for the degree of freedom.
-
Toggle off a degree of freedom to leave the degree of freedom
unconstrained.
Data that you enter in the editor for particular degrees of
freedom are passed into the user subroutine.
-
Click OK to save your data and to exit the
editor.
-
Enter the
Job module
and display the job editor for the analysis job of interest. (For more
information, see
Creating, editing, and manipulating jobs.)
-
In the job editor, click the General tab, and
specify the file containing the user subroutine that defines the boundary
condition. 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.
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