Mechanical APDL Structural Analysis Guide

To help you understand when to use either method, the following table compares both methods and
their applications:

Nonlinear Stabilization vs. Arc-Length

Analysis Problem Nonlinear Stabilization Arc-Length

Local instability or local buckling Yes Yes

Global instability or global buckling Yes Yes

Cannot detect this part of Yes

the curve, but other parts

Negative slope of load-vs.-displacement curve

can be simulated for deform-

ation-history-independent

materials, and the preceding

part can be simulated for

deformation- history-depend-

ent materials

Rate-dependent materials and creep Yes Yes

Line search Yes No

Substep predictor (PRED,ON) Yes ( 1 ) Different algorithm

Automatic time stepping Yes Different algorithm

Displacements as load Yes Yes

Activate/deactivate from load step to load Yes Limited

step, or within a load step

Linear solver use No restrictions Sparse solver only

Time at converged substep Positive Positive or negative

No (except for bonded

contact)

Nonlinear contact Yes

1. Solid elements only.

8.12. Guidelines for Nonlinear Analysis

This section provides information to help you perform a successful nonlinear analysis.

ANSYS, Inc. recommends using current-technology elements for nonlinear analyses.

The following topics are available:

8.12.1. Setting Up a Nonlinear Analysis

8.12.2. Overcoming Convergence Problems

8.12.1. Setting Up a Nonlinear Analysis

By taking your time and proceeding carefully, you can avoid many difficulties commonly associated
with nonlinear analyses.

Consider these suggestions:
8.12.1.1. Understand Your Program and Structure Behavior
8.12.1.2. Simplify Your Model
8.12.1.3. Use an Adequate Mesh Density
8.12.1.4. Apply Loading Gradually

Release 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information

Guidelines for Nonlinear Analysis