You can define a complex frequency step to perform eigenvalue extractions that
calculate the complex eigenvalues and the corresponding complex mode shapes of a
system.
A complex frequency step is a linear perturbation procedure that uses the Lanczos method. It
must be preceded by a frequency step so that eigenfrequencies are extracted prior to the
complex eigenvalue extraction.
From the Procedures section of the action bar,
click Complex Frequency Step.
Optional:
Enter a descriptive Name.
Select the Modes using one of the following methods:
Option
Description
All in frequency range
Evaluate all the eigenvalues from the minimum frequency of interest up to the
maximum frequency of interest.
Specify
Indicate the number of eigenvalues to be calculated.
If you are using Specify for modes, enter the Number
of modes to specify the number of eigenvalues to be calculated.
In the Minimum frequency field, enter the minimum eigenvalue
frequency of interest.
In the Maximum frequency field, enter the maximum eigenvalue
frequency of interest.
Minimum and maximum frequency values are mandatory when you specify modes using the
All in frequency range method.
Enter the Shift point in squared cycles per time (positive or
negative).
Optional:
Expand Advanced to further configure the step.
Select Include friction-induced damping effects to add
friction-induced contributions to the damping matrix.
In the Evaluate dependent properties at frequency field,
enter a frequency at which the solver will evaluate frequency-dependent material
properties.
If you do not specify a frequency, the solver evaluates the stiffness associated
with frequency-dependent springs and dashpots at zero frequency and does not consider
the stiffness contributions from frequency domain viscoelasticity.
Enter a Cutoff frequency value for complex mode output to
have the solver process output only for complex modes where the real part of the
eigenvalue is higher than the cutoff.
Select an option for the Matrix storage method.
Option
Description
Solver default
The Abaqus solvers chooses a matrix storage and solution scheme based on the
model.
Symmetric
Uses the symmetric matrix storage and solution scheme.
Unsymmetric
Uses the unsymmetric matrix storage and solution scheme
.