CNVTOL, Lab, VALUE, TOLER, NORM, MINREF
Sets convergence values for nonlinear analyses.
LabValid convergence labels.
| Discipline | Displacement Convergence | Force Convergence | ||
|---|---|---|---|---|
| Label | Label Description | Label | Label Description | |
| Structural | U | Displacements | F | Forces |
| ROT | Rotations | M | Moments | |
| HDSP | Hydrostatic Pressure | DVOL | Volume | |
| JOINT [1] | Joint Element Constraint Check | |||
| COMP [2] | Volumetric Compatibility Check | |||
| Thermal | TEMP | Temperature | HEAT | Heat Flow |
| Fluid | PRES | Pressures | FLOW | Fluid Flow |
| V | Velocity | VF | Fluid Force | |
| Electric | VOLT | Voltage | AMPS or CHRG | Current Flow or Charge |
| EMF | Electromotive Force | CURT | Current Flow | |
| Magnetic | MAG | Scalar Potential | FLUX | Scalar Flux |
| A | Vector Potential | CSG | Current Segments | |
| Diffusion | CONC | Concentration | RATE | Diffusion Flow Rate |
JOINT specifies a tolerance for
the joint element constraint check and is applicable to MPC184 joint elements. It is a nonlinear element convergence
status value, not a displacement convergence value. TOLER is the only other valid argument when Lab = JOINT.
COMP specifies a tolerance for
the volumetric compatibility check in current-technology plane
and solid elements (18x elements). It is a nonlinear element convergence
status value, not a displacement convergence value. TOLER is the only other valid argument when Lab = COMP
VALUETypical reference value for the specified convergence
label (Lab).
VALUE defaults to the maximum of a program calculated
reference or MINREF. For degrees of freedom,
the reference is based upon the selected NORM and the current total DOF value. For forcing quantities, the reference
is based upon the selected NORM and the
applied loads.
If VALUE is negative, the convergence
criterion based on the specified label is removed, including the default
convergence criterion value. The convergence criterion for all other
labels remain as they were (either a default value or a previously
specified value).
TOLERTolerance; defaults to 0.005 (0.5%) for force and moment, 1.0E-4 (0.01%) for DVOL, 0.05 (5%) for displacement when rotational DOFs are not present, and 0.05 (5%) for HDSP.
If Lab = JOINT, TOLER must be a positive value; defaults to 1.0E-7.
This value rarely needs to be changed. A loose tolerance value may
lead to inaccurate or incorrect solutions. VALUE, NORM, and MINREF are ignored.
If Lab = COMP, TOLER must be greater than zero and less than one;
defaults to 1.0E-3. VALUE, NORM, and MINREF are ignored.
NORMSpecifies norm selection:
2 | — | L2 norm (check
SRSS value). Default, except for |
1 | — | L1 norm (check absolute value sum). |
0 | — | Infinite norm
(check each DOF separately). Default for |
MINREFThe minimum value allowed for the program calculated
reference value. If negative, no minimum is enforced. Used only if VALUE is blank. Defaults to 0.01 for force, moment,
and volume convergence, 1.0E-6 for heat flow, 1.0E-12 for VLTG and
CHRG, 1.0E-6 for HDSP, and 0.0 otherwise.
For static or transient analysis, check
the out-of-balance load for any active DOF using the default VALUE, TOLER, NORM, and MINREF. Also check
the translational displacement convergence in most cases. For harmonic
magnetic analysis, check the out-of-balance of the degrees of freedom.
This command is usually not needed because the default convergence criteria are sufficient for most nonlinear analyses. In rare cases, you may need to use this command to diagnose convergence difficulties.
Values may be set for the degrees of freedom (DOF) and/or the out-of-balance load for the corresponding forcing quantities.
Issuing CNVTOL to set
a convergence criterion for a specific convergence label (Lab) does not affect the convergence criterion for
any other label. All other convergence criteria will remain at their
default setting or at the value set by a previous CNVTOL command.
When the GUI is on, if a "Delete" operation in a Nonlinear Convergence Criteria dialog box writes this
command to a log file (Jobname.LOG or Jobname.LGW), you will observe that Lab is blank, VALUE = -1, and TOLER is an integer number. In this case, the GUI
has assigned a value of TOLER that corresponds
to the location of a chosen convergence label in the dialog box's
list. It is not intended that
you type in such a location value for TOLER in an ANSYS session. However, a file that contains a GUI-generated CNVTOL command of this form can be used for batch input
or with the /INPUT command.
Convergence norms specified with CNVTOL may be graphically tracked while the solution is in process using the ANSYS program's Graphical Solution Tracking (GST) feature. Use the /GST command to turn GST on or off. By default, GST is ON for interactive sessions and OFF for batch runs.
At the first iteration of a substep, the reference value uref (see Convergence in the Mechanical APDL Theory Reference) for the displacement convergence check is calculated from the total displacement at the current time step since the current incremental displacement is not yet available. At the second iteration and higher, uref is calculated from the current incremental displacement. Therefore, if your analysis only takes one iteration within a substep to converge, the displacement check may not be sufficiently stringent. In this case, you should tighten your displacement convergence tolerance.
This command is also valid in PREP7.