STABILIZE
STABILIZE,
Key, Method,
VALUE, SubStpOpt,
FORCELIMIT,
RECALCDAMP
Activates stabilization for all elements that support nonlinear
stabilization.
KeyKey for controlling nonlinear stabilization:
OFF
—
Deactivate stabilization (default).
CONSTANT
—
Activate stabilization. The energy-dissipation ratio or damping factor remains constant during the load step.
REDUCE
—
Activate stabilization. The energy-dissipation ratio or damping factor is reduced linearly to zero at the end of the load step from the specified or calculated value.
MethodThe stabilization-control method:
ENERGY
—
Use the energy-dissipation ratio as the control. This value is the default when
Key≠ OFF.DAMPING
—
Use the damping factor as the control.
VALUEThe energy-dissipation ratio (
Method= ENERGY) or damping factor (Method= DAMPING). This value must be greater than 0 whenMethod= ENERGY orMethod= DAMPING. WhenMethod= ENERGY, this value is usually a number between 0 and 1.SubStpOptOption for the first substep of the load step:
NO
—
Stabilization is not activated for the first substep even when it does not converge after the minimal allowed time increment is reached. This value is the default when
Key≠ OFF.MINTIME
—
Stabilization is activated for the first substep if it still does not converge after the minimal allowed time increment is reached.
ANYTIME
—
Stabilization is activated for the first substep. Use this option if stabilization was active for the previous load step via
Key= CONSTANT.FORCELIMITThe stabilization force limit coefficient, such that 0 <
FORCELIMIT< 1. The default value is 0.2. To omit a stabilization force check, set this value to 0.RECALCDAMPKey for controlling damping recalculation:
0 – No recalculation of the damping factor (default). 1 – Recalculate the damping factor for the energy-based stabilization-control method.
Command Default
Once issued, the stabilization effects of the command remain until you issue either a STABILIZE command (with no arguments) or a STABILIZE,OFF command. If you issue the command with no arguments, the effect is to deactivate stabilization.
Notes
Once issued, a STABILIZE command remains in effect until you reissue the command.
For the energy dissipation ratio, specify VALUE = 1.0e-4 if you have no prior experience with the current model;
if convergence problems are still an issue, increase the value gradually.
The damping factor is mesh-, material-, and time-step-dependent; an
initial reference value from the previous run (such as a run with
the energy-dissipation ratio as input) should suggest itself.
Exercise caution when specifying SubStpOpt = MINTIME or ANYTIME for the first load step; Ansys, Inc. recommends this
option only for experienced users. If stabilization was active for
the previous load step via Key = CONSTANT
and convergence is an issue for the first substep, specify SubStpOpt = ANYTIME.
When the L2-norm of the stabilization force (CSRSS value) exceeds the L2-norm of the internal
force multiplied by the stabilization force coefficient, the program issues a message
displaying both the stabilization force norm and the internal force norm. The
FORCELIMIT argument enables you to change the default
stabilization force coefficient (normally 20 percent).
When using the energy-based stabilization-control method and
RECALCDAMP = 1, the damping factor is recalculated in the
following cases:
In an analysis restart.
In a nonlinear adaptivity analysis in the substep following the remeshing substep.
This command stabilizes the degrees of freedom for current-technology elements only. Other elements can be included in the FE model, but their degrees of freedom are not stabilized.
For more information about nonlinear stabilization, see Unstable Structures in the Structural Analysis Guide. For additional tips that can help you to achieve a stable final model, see Simplify Your Model in the Structural Analysis Guide.