Chapter 4: Smart Stop Criterion

A smart stop criterion can be specified via the NLHIST command. The STOP_VALUE, STOP_COND and STOP_TOL arguments allow you to automatically terminate an analysis based on the value of a tracked result. The solution can be tailored to stop at the specified value of a solution tracking variable, using bisections and correction.

The optional STOP_TOL argument is available as a beta feature. It halts the solution when the smart stop value (STOP_VALUE) is within the percentage tolerance you specify.

Smart Stop Options for NLHIST Command

NLHIST specifies results items to track during the solution.

NLHIST, Key, Name, Item, Comp, NODE, ELEM, SHELL, LAYER, STOP_VALUE, STOP_COND, STOP_TOL

The following smart stop options are available as beta features:

STOP_COND

Specifies the conditional relationship between the variable being tracked and the values for STOP_VALUE and STOP_TOL upon which the analysis is terminated.

-1

Terminate the solution when the tracked variable is less than or equal to STOP_VALUE.

0

Terminate the solution when the tracked variable equals STOP_VALUE.

1

Terminate the solution when the tracked variable is greater than or equal to STOP_VALUE.

2

Terminate the solution when the tracked variable is within the percentage tolerance specified by STOP_TOL.

STOP_TOL

Terminate the solution when the tracked variable is within the specified percentage tolerance of the STOP_VALUE, entered as a decimal value. If you do not specify a STOP_TOL, the NLHIST command uses the default value of 0.025 (2.5%).

Notes

The STOP_VALUE, STOP_COND, and STOP_TOL arguments automatically terminate the analysis when a tracked contact result or section result either reaches the desired value or is within the specified percentage tolerance of the desired value. To accurately control the solution, request a smart stop criterion at each sub-step.

Smart stop is intended for nonlinear analyses. Auto time stepping must be activated via the AUTOTS,ON command. To use smart stop for linear analyses, issue the NROPT,FULL command to force Mechanical APDL to generate a nonlinear solution using the full Newton-Raphson method.