![](../icons_C2/common/areference.gif) |
This capability is only available
with the ELFINI Structural Analysis product (except for inserting
a first Frequency Analysis Case).
Inserting a new Frequency Case allows you to create objects sets for
the new environmental specifications, and to implicitly require a
normal modes solution procedure for the computation of the system
vibration frequencies and normal modes for a given non-structural mass
distribution under given restraints.
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Frequency Analysis Case
This task shows you how to insert a
new Frequency Case.
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![](../icons_C2/common/awarning.gif) |
Remember that if you do not have the ELFINI Structural Analysis product license, your Finite Element Model can
simultaneously contain at most one Static Analysis Case and one Frequency
Analysis Case.
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You can use the sample00.CATAnalysis
document from the samples directory
for this task.
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1. Select Insert -> Frequency
Case .
The Frequency Case dialog box is displayed.
![](images/9aPanelInsertFrequency.gif)
For each type of objects set (Restrains, Masses, Static Case Solution), you
can require that your new Frequency Case contains either an empty
objects set or an objects set existing in a previously defined Analysis
Case.
The New and Reference switches for Restrains and
Masses objects sets allow you to choose between these two
options:
![](_themes/v5r5/ul1.gif) | New: the new objects set is empty. |
![](_themes/v5r5/ul1.gif) | Reference: the new objects set is a copy of an objects set existing
in a previously defined Analysis Case. |
The Static Case Solution option allows you to perform a
pre-loaded frequency computation by selecting a static solution. The frequency computation
will then take the corresponding loads into account and generate a (non-linear, load-dependent) pre-loaded frequency computation.
2. Set the switch for each type of objects set
and click OK.
A new Frequency Case template (objects sets set) appears in the Finite Element Model
specification tree template displayed on the left.
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![](images/7gs07Tree.gif)
The new Frequency Analysis Case representation consists of the following (empty) object
sets:
![](_themes/v5r5/ul1.gif) | Restrains |
![](_themes/v5r5/ul1.gif) | Masses |
![](_themes/v5r5/ul1.gif) | Solution |
You can edit the frequency case, by double-clicking on the Frequency
Case Solution
object in the specification tree.
The following dialog box will appear:
![](images/aPanelFrequencyCaseAnalysis.gif)
![](_themes/v5r5/ul1.gif) | Number of modes |
![](_themes/v5r5/ul1.gif) | Method (Iterative subspace, lanczos) (only available
if you have ELFINI Structural Analysis product installed,
otherwise, the default method is Iterative subspace). |
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If you select the lanczos Method, the Shift option
appears: compute the modes beyond a given value: Auto, 1Hz,
2Hz and
so forth. Auto means that the computation is performed on a structure
that is partially free.
![](images/aPanelFrequencyCaseAnalysis01.gif)
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![](_themes/v5r5/ul1.gif) | Dynamic parameters (maximum iteration number, accuracy) |
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![](../icons_C2/common/ainfo.gif)
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By default, the last created (inserted)
Analysis Case is set as current, and the corresponding objects set is
underlined in the analysis features tree.
A right mouse click (key 3) on a
Frequency Case objects set further allows the following action:
![](_themes/v5r5/ul1.gif) | Set as Current: allows you to define the Frequency Analysis Case as
being the currently active one. The Frequency Case is then underlined
in the features tree and all subsequent actions refer to it. |
If you inactivate the Hide Existing
Analysis Cases switch in the Frequency Case dialog box, the symbols of
objects created in previous Analysis Cases will remain displayed.
Once a New Analysis Case has
been inserted, its Definition parameters cannot be changed. To modify the Analysis Case
Definition parameters you can only replace it (Delete followed by
Insert)
in the analysis specification tree.
To compute free vibration modes, you need a Frequency Analysis Case
containing no Restraints objects set. This means that you must insert a
new Frequency Analysis Case without Restraints.
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![](../icons_C2/common/amethod.gif)
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To compute free vibration modes, you need a Frequency Analysis Case
containing no Restraints objects set. This means that you must first
delete the existing Frequency Analysis Case and insert a new Frequency
Analysis Case without Restraints.
To subsequently compute supported (non-free)
vibration modes, you must delete the previous, Restraints-less (free
vibration modes) Frequency Analysis Case and insert a new (supported)
Frequency Analysis Case with Restraints.
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