*SELECT EIGENMODES

Select the modes to be used in a modal dynamic, complex eigenvalue extraction, or substructure generation analysis.

This option selects the modes to be used in a dynamic analysis based on modes, in a complex eigenvalue extraction analysis, or in a substructure generation analysis. Only one option per step can be used. If this option is omitted in a dynamic analysis based on modes or in a complex eigenvalue extraction analysis, all modes extracted in the prior FREQUENCY step will be used, including residual modes if they were activated.

If this option is omitted in a substructure generation analysis, none of the modes extracted in the prior FREQUENCY step will be used, including residual modes if they were activated.

This page discusses:

See Also
*MODAL DAMPING
In Other Guides
Implicit Dynamic Analysis Using Direct Integration
Complex Eigenvalue Extraction
Transient Modal Dynamic Analysis
Mode-Based Steady-State Dynamic Analysis
Subspace-Based Steady-State Dynamic Analysis
Generating Substructures
Response Spectrum Analysis
Random Response Analysis

ProductsAbaqus/StandardAbaqus/CAE

TypeHistory data

LevelStep

Abaqus/CAESupported in the Step module only for substructure generation.

Optional parameters

DEFINITION

Set DEFINITION=MODE NUMBERS (default) to indicate that the selected modes are given as a collection of mode numbers.

Set DEFINITION= FREQUENCY RANGE to indicate that the modes are selected from the specified frequency ranges including frequency boundaries. Frequency ranges can be discontinuous.

If both the MODAL DAMPING and SELECT EIGENMODES options are used in the same step, the DEFINITION parameter must be set equal to the same value in both options.

GENERATE

If this parameter is included, each data line should give a first mode, n1; a last mode, n2; and the increment in mode numbers between these modes, i. Then all modes going from n1 to n2 in steps of i will be added to the set. i must be an integer such that (n2-n1)/i is a whole number (not a fraction).

This parameter can be used only with DEFINITION=MODE NUMBERS.

Data lines if DEFINITION=MODE NUMBERS and the GENERATE parameter is omitted

First line

  1. List of modes to be used.

Repeat this data line as often as necessary. Up to 16 entries are allowed per line.

Data lines if DEFINITION=MODE NUMBERS and the GENERATE parameter is included

First line

  1. First mode number.

  2. Last mode number.

  3. Increment in mode numbers between modes. The default is 1.

Repeat this data line as often as necessary.

Data lines if DEFINITION=FREQUENCY RANGE

First line

  1. Lower boundary of the frequency range (in cycles/time).

  2. Upper boundary of the frequency range (in cycles/time).

Repeat this data line as often as necessary.