Mapdl.midtol(key='', tolerb='', resfq='', **kwargs)

Sets midstep residual criterion values for structural transient

APDL Command: MIDTOL analyses.


Midstep residual criterion activation key.

ON or 1 - Activate midstep residual criterion in a structural transient analysis


OFF or 0 - Deactivate midstep residual criterion in a structural transient analysis.

STAT - List the current midstep residual criterion setting.


Midstep residual tolerance or reference value for bisection. Defaults to 100 times the TOLER setting of the CNVTOL command.


Key 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:

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.