- Large Deformation Effects (NLGEOM)
- Large Displacement Transient (if using the Solution Controls dialog box to set analysis type)
- Apply loads and specify load step options in the same manner as you would for a linear full transient
dynamic analysis. A transient load history usually requires multiple load steps, with the first load step
typically used to establish initial conditions (see the Basic Analysis Guide). The general, nonlinear, birth
and death, and output control options available for a nonlinear static analysis are also available for a
nonlinear transient analysis.
In a nonlinear transient analysis, time must be greater than zero. See Transient Dynamic Analys-
is (p. 107) for procedures for defining nonzero initial conditions.
For a nonlinear transient analysis, you must specify whether you want stepped or ramped loads
(KBC). See the Basic Analysis Guide for further discussion about ramped vs. stepped loads.
You can also specify dynamics options: alpha and beta damping, time-integration effects, and tran-
sient integration parameters.
Command(s): ALPHAD,BETAD,TIMINT,TINTP
GUI: Main Menu> Solution> Analysis Type> Sol'n Control ( :Transient Tab)
Main Menu> Solution> Unabridged Menu> Load Step Opts> Time/Frequenc> Damping
Main Menu> Solution> Unabridged Menu> Load Step Opts> Time/Frequenc> Time Integration
An explanation of the dynamics options follows.
Rayleigh damping constants are defined using the constant mass (ALPHAD) and stiffness (BETAD)
matrix multipliers. In a nonlinear analysis the stiffness may change drastically - do not use BETAD,
except with care. See Damping (p. 2) for details about damping.
- Time-Integration Effects (TIMINT)
Time-integration effects are ON by default in a transient analysis. For creep, viscoelasticity, visco-
plasticity, or swelling, you should turn the time-integration effects off (that is, use a static analysis).
These time-dependent effects are usually not included in dynamic analyses because the transient
dynamic time step sizes are often too short for any significant amount of long-term deformation
to occur.
Except in kinematic (rigid-body motion) analyses, you rarely need to adjust the transient integration
parameters (TINTP), which provide numerical damping to the Newmark and HHT methods. (See
your Mechanical APDL Theory Reference for more information about these parameters.)
Automatic solution control sets the defaults to a new time-integration scheme for use by first
order transient equations. This is typically used for unsteady state thermal problems where θ =
1.0 (set by SOLCONTROL, ON); this is the backward Euler scheme. It is unconditionally stable and
more robust for highly nonlinear thermal problems such as phase changes. The oscillation limit
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Performing a Nonlinear Transient Analysis
