Create or edit a coupled thermal-electrical procedure
-
Display the Edit Step dialog box following the
procedure outlined in
Creating a step
(Procedure type:
General; Coupled
thermal-electric ), or
Editing a step.
-
On the Basic,
Incrementation, and Other tabbed
pages, configure settings such as the time period for the step, increment size,
and solution technique preferences as described in the following procedures.
Configure settings on the Basic tabbed page
-
In the Edit Step dialog box, display the
Basic tabbed page.
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In the Description field, enter a short
description of the analysis step.
Abaqus
stores the text that you enter in the output database, and the text is
displayed in the state block by the Visualization module.
-
Choose a Response option:
-
Choose Steady-state to omit the internal
energy term (the specific heat term) in the governing heat transfer equation.
Only direct current is considered in the electrical problem, and it is assumed
that the system has negligible capacitance. (Electrical transient effects are
so rapid that they can be neglected.) For more information, see
Steady-State Analysis.
-
Choose Transient to perform time integration
with the same backward Euler method used in uncoupled heat transfer analyses.
This method is unconditionally stable for linear problems. For more
information, see
Transient Analysis.
Note:
After you have selected a Response option, a
message appears informing you that
Abaqus/Standard
has selected the Default load variation with time option
(located on the Other tabbed page) that corresponds to
your Response selection. Click
Dismiss to close the message dialog box.
-
In the Time period field, enter the time period
of the step.
Configure settings on the Incrementation tabbed
page
-
In the Edit Step dialog box, display the
Incrementation tabbed page.
(For information on displaying the Edit Step
dialog box, see
Creating a step,
or
Editing a step.)
-
Choose a Type option:
-
Choose Automatic if you want
Abaqus/Standard
to determine suitable time increment sizes.
-
Choose Fixed to specify direct user control
of the incrementation.
Abaqus/Standard
uses an increment size that you specify as the constant increment size
throughout the step.
-
In the Maximum number of increments field, enter
the upper limit to the number of increments in the step. The analysis stops if
this maximum is exceeded before
Abaqus/Standard
arrives at the complete solution for the step.
-
If you selected Automatic in Step 2, enter values
for Increment size:
-
In the Initial field, enter the initial time
increment.
Abaqus/Standard
modifies this value as required throughout the step.
-
In the Minimum field, enter the minimum time
increment allowed. If
Abaqus/Standard
needs a smaller time increment than this value, it terminates the analysis.
-
In the Maximum field, enter the maximum time
increment allowed.
-
If you selected Fixed in Step 2, enter a value
for the constant time increment in the Increment size
field.
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If you selected Transient analysis on the
Basic tabbed page, do the following:
-
Toggle on End step when temperature change is less than
n if you want the analysis to end when
the temperature at every temperature degree of freedom changes at a rate that
is less than a rate that you specify. If you toggle on this option, enter the
desired temperature change rate in the field provided.
-
If you selected Automatic in Step 2, enter a
value for the Max. allowable temperature change per
increment.
Abaqus/Standard
restricts the time step to ensure that this value is not exceeded at any node
(except nodes with boundary conditions) during any increment of the step.
-
If you selected Automatic in Step 2 and you are
performing a cavity radiation analysis, enter a value for Max.
allowable emissivity change per increment, or accept the default of
0.1. If this value is exceeded,
Abaqus/Standard
cuts back the increment until the maximum change in emissivity is less than the
specified value. See
Cavity Radiation in Abaqus/Standard, for
more information.
Configure settings on the Other tabbed page
-
In the Edit Step dialog box, display the
Other tabbed page.
(For information on displaying the Edit Step
dialog box, see
Creating a step,
or
Editing a step.)
-
Choose a Matrix storage option:
-
Choose Use solver default to allow
Abaqus/Standard
to decide whether a symmetric or unsymmetric matrix storage and solution scheme
is needed.
-
Choose Unsymmetric to restrict
Abaqus/Standard
to the unsymmetric storage and solution scheme. (This is the only matrix
storage option available if you choose the Full Newton
solution technique.)
-
Choose Symmetric to restrict
Abaqus/Standard
to the symmetric storage and solution scheme.
For more information on matrix storage, see
Matrix Storage and Solution Scheme in Abaqus/Standard.
-
Choose a Solution technique:
-
Choose Full Newton to use Newton's method as
a numerical technique for solving nonlinear equilibrium equations. For more
information, see
Nonlinear solution methods in Abaqus/Standard.
-
Choose Separated to specify that linearized
equations for the individual fields in the fully coupled procedure are to be
decoupled and solved separately for each field. This option provides a less
costly solution for an analysis that is fully coupled in the sense that the
electrical and thermal solutions evolve simultaneously, but with a weak
coupling between the two solutions. For more information, see
Approximate Implementation.
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Click the arrow to the right of the Convert severe
discontinuity iterations field, and select an option for dealing
with severe discontinuities during nonlinear analysis:
-
Select Off to force a new iteration if severe
discontinuities occur during an iteration, regardless of the magnitude of the
penetration and force errors. This option also changes some time incrementation
parameters and uses different criteria to determine whether to do another
iteration or to make a new attempt with a smaller increment size.
-
Select On to use local convergence criteria
to determine whether a new iteration is needed.
Abaqus/Standard
will determine the maximum penetration and estimated force errors associated
with severe discontinuities and check whether these errors are within the
tolerances. Hence, a solution may converge if the severe discontinuities are
small.
-
Select Propagate from previous step to use
the value specified in the previous general analysis step. This value appears
in parentheses to the right of the field.
For more information on severe discontinuities, see
Severe Discontinuities in Abaqus/Standard.
-
Abaqus/Standard
automatically selects the Default load variation with time
option that corresponds to your Response selection on the
Basic tabbed page. It is recommended that you leave the
Default load variation with time selection unchanged.
-
Click the arrow to the right of the Extrapolation of
previous state at start of each increment field, and select a method
for determining the first guess to the incremental solution:
-
Select Linear to indicate that the process is
essentially monotonic and
Abaqus/Standard
should use a 100% linear extrapolation, in time, of the previous incremental
solution to begin the nonlinear equation solution for the current increment.
-
Select Parabolic to indicate that the process
should use a quadratic extrapolation, in time, of the previous two incremental
solutions to begin the nonlinear equation solution for the current increment.
-
Select None to suppress any extrapolation.
For more information, see
Extrapolation of the Solution.
When you have finished configuring settings for the step, click
OK to close the Edit Step dialog
box.
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