| EXPERTNL |
<YES,
NO, AUTO, or
CNTSTB> Default = AUTO (For
Small Displacement Analysis)
For both Small and Large
Displacement Analysis, Contact Stabilization is inactive by
default.
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PARAM,EXPERTNL has two functionalities
embedded within it:
- Automatic Time-stepping Schema
(YES/AUTO/NO).
This is applicable only for Small Displacement Nonlinear
Analysis.
- Contact Stabilization (CNTSTB). This is
applicable to both Small and Large Displacement
Analysis.
For Automatic Time-stepping Schema:
- YES
- Activates a nonlinear "expert system" that aids in
the convergence of small displacement nonlinear
problems. This version is designed to facilitate
obtaining converged, high accuracy solutions without
much concern for computational time. The system
monitors the convergence of nonlinear processes and,
if needed, implements measures designed to improve
convergence for poorly converging cases. These
measures include performing additional iterations,
under-relaxation, automatic adjustment of the load
increment, as well as backing off to the last
convergent solution and retrying. This may lead to a
large number of nonlinear iterations for poorly
converging problems.
- NO
- Deactivates the nonlinear expert system.
- AUTO
- Activates a "light" version of the expert system,
which is designed to facilitate converging nonlinear
process in reasonably close to minimum number of
iterations. In particular, this version may adjust
the time step, including increasing the time step
beyond that prescribed on the
NLPARM card.
For Contact Stabilization:
- CNTSTB
- Additionally introduces temporary stabilization on
contact interfaces (CONTACT or
GAP(G) elements) that may
improve nonlinear convergence, especially in cases
where individual parts lack full support and are
supported only by contact. The stabilization is
applied only during incremental loading and is not
present in the final solution for the respective
nonlinear subcase. (Refer to the CNTSTB Bulk Data
Entry for default and priority information).
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