MIDTOL, KEY, TOLERB, RESFQ
Sets midstep residual criterion values for structural transient
analyses.
KEYMidstep residual criterion activation key.
ON or 1 | — | Activate midstep residual criterion in a structural transient analysis (default). |
OFF or 0 | — | Deactivate midstep residual criterion in a structural transient analysis. |
STAT | — | List the current midstep residual criterion setting. |
TOLERBMidstep residual tolerance or reference value for bisection.
Defaults to 100 times the TOLER setting of the CNVTOL command.
If TOLERB > 0, it is used as a tolerance
about the typical force and/or moment to compare midstep residual force and/or
moment for convergence.
If TOLERB < 0, it is used as a reference
force value against which the midstep residual force is compared for convergence.
The reference force value is used to compute a reference moment value for
midstep residual moment comparison.
If midstep residual force and/or moment has not converged and AUTOTS,ON
is used, then TOLERB is also used to predict time
step size for bisection.
RESFQKey to use response frequency computation along with midstep residual criterion for automatic time stepping (AUTOTS,ON).
OFF or 0 | — | Do not calculate response frequency and do not consider it in the automatic time stepping (default). |
ON or 1 | — | Calculate response frequency and consider it in the automatic time stepping. |
When TOLERB is input as a tolerance value
(TOLERB > 0), the typical force and/or moment from
the regular time step is used in the midstep residual force and/or moment
comparison.
In a structural transient analysis, the suggested tolerance range of TOLERB (TOLERB >
0) is as follows:
TOLERB = 1 to 10 times the TOLER setting
of the CNVTOL command for high accuracy solution. |
TOLERB = 10 to 100 times the TOLER setting
of the CNVTOL command for medium accuracy solution. |
TOLERB = more than 100 times the TOLER setting
of the CNVTOL command for low accuracy solution. |
If the structural transient analysis is elastic and linear, and
the load is constant or changes slowly, use a smaller value of TOLERB to
achieve an accurate solution. If the analysis involves large amounts of energy
dissipation, such as elastic-plastic material, TOLERB can
be larger. If the analysis includes contact or rapidly varying loads, a smaller
value of TOLERB should be used if high frequency
response is important; otherwise, a larger value of TOLERB may
be used to enable faster convergence with larger time step sizes.
For more information on how the midstep criterion is used by the program, see Midstep Residual for Structural Dynamic Analysis in the Mechanical APDL Theory Reference.
This command is also valid in PREP7.