ProductsAbaqus/StandardAbaqus/CAEAbaqus/AMS TypeHistory data
LevelStep Abaqus/CAEStep module
Optional parameters
 ACOUSTIC COUPLING

For the AMS eigensolver and Lanczos
eigensolver, set ACOUSTIC COUPLING=ON to include the effect of acousticstructural coupling during
the natural frequency extraction procedure in models with acoustic and
structural elements coupled using the
TIE option or in models with ASItype elements. This is the default option for the Lanczos
eigensolver.
For the AMS eigensolver and Lanczos
eigensolver based on the SIM architecture, set ACOUSTIC COUPLING=PROJECTION to extract the uncoupled acoustic and structural modes and
project the acousticstructural coupling operator during the natural frequency
extraction procedure in models with acoustic and structural elements coupled
using the
TIE option. This is the default option for the
AMS eigensolver.
Set ACOUSTIC COUPLING=OFF to omit the projection of the acousticstructural coupling
operator and to ignore the effect of acousticstructural coupling during
natural frequency extraction in models with acoustic and structural elements
coupled using the
TIE option or in models with ASItype elements.
This parameter is not relevant for the subspace iteration eigensolver.
 DAMPING PROJECTION

This parameter is relevant only for the AMS
eigensolver or for the Lanczos eigensolver used in conjunction with the SIM parameter.
Set DAMPING PROJECTION=ON (default) to project the viscous and structural damping
operators during the natural frequency extraction procedure. If there is no
damping defined in the model, the projection is not performed.
Set DAMPING PROJECTION=OFF to omit the projection of damping operators.
 EIGENSOLVER

Set EIGENSOLVER=LANCZOS (default) to invoke the Lanczos eigensolver.
Set EIGENSOLVER=AMS to invoke the automatic multilevel substructuring (AMS) eigensolver.
Set EIGENSOLVER=SUBSPACE to invoke the subspace iteration eigensolver.
 NORMALIZATION

Set NORMALIZATION=DISPLACEMENT to normalize the eigenvectors so that the largest
displacement, rotation, or acoustic pressure (in coupled acousticstructural
extractions) entry in each vector is unity. Displacement normalization is the
default for both the subspace iteration eignensolver and for the Lanczos
eigensolver when they are used without the SIM parameter.
Set NORMALIZATION=MASS to normalize the eigenvectors with respect to the structure's
mass matrix (the eigenvectors are scaled so that the generalized mass for each
vector is unity). Mass normalization is the default and only available option
for the AMS eigensolver. Mass normalization is switched on for both the
Lanczos eigensolver and the subspace iteration eigensolver when they are used
in conjunction with the default SIM parameter.
 PROPERTY EVALUATION

Set this parameter equal to the frequency at which to evaluate
frequencydependent properties for viscoelasticity, springs, and dashpots
during the eigenvalue extraction. If this parameter is omitted,
Abaqus/Standard
will evaluate the stiffness associated with frequencydependent springs and
dashpots at zero frequency and will not consider the stiffness contributions
from frequency domain viscoelasticity in the
FREQUENCY step.
 RESIDUAL MODES

This parameter is relevant only for the Lanczos and AMS eigensolvers.
Include this parameter to indicate that residual modes are to be computed.
 SIM

This parameter is relevant only for the Lanczos and subspace iteration
eigensolvers.
Set the value of this parameter equal to NO if the nonSIM architecture is required for the Lanczos or subspace iteration
eigensolvers.
Set the value of this parameter equal to YES (default) if the SIM architecture is required.
The SIM architecture is the only option if the AMS eigensolver is activated.
Optional parameter when EIGENSOLVER=AMS
 NSET

Set this parameter equal to the name of the node set or include the
parameter with no value to allow Abaqus/Standard to
automatically select the nodes at which eigenvectors will be computed. If this
parameter is omitted, eigenvectors will be computed at all nodes.
Data line for a
natural frequency extraction when EIGENSOLVER=LANCZOS First (and
only) line

Number of eigenvalues to be calculated. This field can be left blank if the
maximum frequency of interest is provided and the evaluation of all the
eigenvalues in the given range is desired. The number of requested eigenmodes
must be provided in a cyclic symmetry analysis or if the analysis includes more
than one natural frequency extraction step.

Minimum frequency of interest, in cycles/time. If this field is left blank,
no minimum is set.

Maximum frequency of interest, in cycles/time. If this field is left blank,
no maximum is set. This value is required if the first field was left blank.

Shift point, in squared cycles per time (positive or negative). The
eigenvalues closest to this point will be extracted.

Block size. If this entry is omitted, a default value, which is usually
appropriate, is created.

Maximum number of block Lanczos steps within each Lanczos run. If this entry
is omitted, a default value, which is usually appropriate, is created.

Acoustic range factor. This factor applies only to structuralacoustic
problems and is used to set the maximum frequency for the acoustic stage of the
uncoupled eigenproblem as a multiple of the nominal maximum frequency of
interest. This factor is supported only when using the SIM architecture, and the maximum frequency of interest is
provided. The acoustic range factor must be greater than 0. The default value
is 1.0.
Data lines for a
natural frequency extraction when EIGENSOLVER=AMS First
line

Number of eigenvalues to be calculated. If this field is left blank,
Abaqus
evaluates all the eigenvalues from the minimum frequency of interest up to the
maximum frequency of interest.

Minimum frequency of interest, in cycles/time. If this field is left blank,
no minimum is set.

Maximum frequency of interest, in cycles/time.

$AM{S}_{{\mathrm{cutoff}}_{1}}$,
the first AMS parameter.
$AM{S}_{{\mathrm{cutoff}}_{1}}$
is a cutoff frequency for substructure eigenproblems, defined as a multiplier
of the maximum frequency of interest. The default value is 5.

$AM{S}_{{\mathrm{cutoff}}_{2}}$,
the second AMS parameter.
$AM{S}_{{\mathrm{cutoff}}_{2}}$
is the first cutoff frequency used to define a starting subspace in the reduced
eigensolution phase, defined as a multiplier of the maximum frequency of
interest. $AM{S}_{{\mathrm{cutoff}}_{2}}<AM{S}_{{\mathrm{cutoff}}_{1}}$.
The default value is 1.7.

$AM{S}_{{\mathrm{cutoff}}_{3}}$,
the third AMS parameter.
$AM{S}_{{\mathrm{cutoff}}_{3}}$
is the second cutoff frequency used to define a starting subspace in the
reduced eigensolution phase, defined as a multiplier of the maximum frequency
of interest.$1.0<AM{S}_{{\mathrm{cutoff}}_{3}}<AM{S}_{{\mathrm{cutoff}}_{1}}$.
The default value is 1.1.

Acoustic range factor. This factor applies only to structuralacoustic
problems and is used to set the maximum frequency for the acoustic stage of the
uncoupled eigenproblem as a multiple of the nominal maximum frequency of
interest. The acoustic range factor must be greater than 0. The default value
is 1.0.
 No additional data lines are needed if default residual modes
are sufficient or residual modes are not requested. Otherwise, subsequent
lines

Node number or node set label.

First degree of freedom for which residual modes are requested.

Last degree of freedom for which residual modes are requested. This field
can be left blank if residual modes for only one degree of freedom are
requested.
Repeat this line as often as
necessary to request residual
modes.
Data line for a
natural frequency extraction when EIGENSOLVER=SUBSPACE First (and
only) line

Number of eigenvalues to be calculated.

Maximum frequency of interest, in cycles/time. This userspecified maximum
frequency is increased automatically by 12.5% to help capture closelyspaced
modes.
Abaqus/Standard
will also report all eigenvalues that converge in the same iteration as those
in the specified range, even if their frequencies are more than 12.5% above the
maximum frequency specified by the user. If this field is left blank, no
maximum is set.
 Abaqus/Standard
will extract frequencies until either of the above limits is
reached.

Shift point, in squared cycles per time (positive or negative). The
eigenvalues closest to this point will be extracted.

Number of vectors used in the iteration. If this entry is omitted, a default
value, which is usually appropriate, is created. The default number of vectors
used is the minimum of (n+ 8,
2n), where n is the
number of eigenvalues requested (the first data item on this data line). In
general, the convergence is more rapid with more vectors, but the memory
requirement is also larger. Thus, if the user knows that a particular type of
eigenproblem converges slowly, providing more vectors by using this option
might reduce the analysis cost.

Maximum number of iterations. The default is 30.
