Figure 2.2:Transient Load History Curve (p. 23) shows a load history curve that requires three load steps
- the first load step for the ramped load, the second load step for the constant portion of the load, and
the third load step for load removal.
Figure 2.2:Transient Load History Curve
1 23TimeLoad
LoadstepSubsteps are points within a load step at which solutions are calculated. You use them for different
reasons:
- In a nonlinear static or steady-state analysis, use substeps to apply the loads gradually so that an
accurate solution can be obtained. - In a linear or nonlinear transient analysis, use substeps to satisfy transient time integration rules
(which usually dictate a minimum integration time step for an accurat e solution). - In a harmonic analysis, use substeps to obtain solutions at several frequencies within the harmonic
frequency range.
Equilibrium iterations are additional solutions calculated at a given substep for convergence purposes.
They are iterative corrections used only in nonlinear analyses (static or transient), where convergence
plays an important role.
Consider, for example, a 2-D, nonlinear static magnetic analysis. To obtain an accurat e solution, two
load steps are commonly used. (Figure 2.3: Load Steps, Substeps, and Equilibrium Iterations (p. 24) illus-
trates this.)
- The first load step applies the loads gradually over five to 10 substeps, each with just one equilibrium
iteration. - The second load step obtains a final, converged solution with just one substep that uses 15 to 25
equilibrium iterations.
Release 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential informationLoad Steps, Substeps, and Equilibrium Iterations