Computing Frequency Solutions

The Compute command is most often applied to Analysis Case Solutions (which are particular types of objects sets). In this case, it generates the analysis case solution, along with partial results for all objects involved in the definition of the Analysis Case.

The primary Frequency Solution Computation result consists of a set of frequencies and associated modal vibration shape vectors whose components represent the values of the system dof for various vibration modes.

The program can compute simultaneously several Solution objects sets, with optimal parallel computation whenever applicable.

Avoid having CATAnalysis documents automatically saved. For this, go to Tools->Options->General (menu bar) and de-activate the Automatic save every xx minutes option. Otherwise, on some models, each computation will be followed by a Save, thus making temporary data become persistent data.

This task shows how to compute a Frequency Case Solution.

You can use the sample16.CATAnalysis document from the samples directory for this task.

1. Click the Compute icon

.
The Compute dialog box is displayed.

The combo box allows you to choose between several options for the set of objects to be updated:

All: all objects defined in the analysis features tree will be computed.

Mesh Only: the preprocessing parts and connections will be meshed. The preprocessing data (loads, restraints and so forth) will be applied onto the mesh.
Capability is only available with the ELFINI Structural Analysis product: for your information, in case the Mesh only option was previously activated, you will then be able to visualize the applied data on the mesh by using the Visualization on Mesh option (contextual menu)

Analysis Case Solution Selection: only a selection of user-specified Analysis Case Solutions will be computed, with an optimal parallel computation strategy. This capability is only available with the ELFINI Structural Analysis product
.

Selection by Restraint: only the selected characteristics will be computed (Properties, restraints, Loads, Masses).

The Preview switch allows you to obtain an estimate of the Time and Memory required to perform the computation, prior to triggering the actual computation.

2. Select All (or Analysis Case Solution Selection).

In this case, the program will compute by default all objects up to (and including) the Frequency Case Solution in the analysis features tree.

3. Activate the Preview option from the Compute dialog box.

4. Click OK in the Compute dialog box.

The estimations are displayed in the Computation Resources Estimation dialog box. You can proceed with the computation or choose to postpone it.

5. To launch the computation, click Yes.

The Computation Status dialog box provides a series of status messages (Meshing, Factorization, Solution) that inform you of the degree of advancement of the computation process.

The Frequency Analysis Solution is computed and can be visualized.

Upon successful completion of the computation, the FE mesh is visualized on your part, and the status of all objects in the analysis features tree up to the Frequency Case Solution objects set is changed to valid. You can now:

analyze the report of the computation

visualize images for various results

Products Available in Analysis Workbench

The ELFINI Structural Analysis product offers the following additional feature:

	If several Frequency Analysis Cases have been defined, you can compute them simultaneously by following the same procedure. You can also compute only a selection of cases by selecting Analysis Cases Solution Selection. You can then specify the cases in the Compute dialog box.
	You can compute vibration modes either for the free system or for the system subjected to supports. In the first case there are no restraints so your Analysis Case must contain no Restraints objects set.
	To display CPU time and memory requirement estimates prior to launching any computations, activate the Estimates switch in the Update dialog box.
	The status and results of intermediate pre-processor computations necessary to perform this translation are reported in HTML format. For more detail see the basic global Report capability .
	The Definition parameters of an Analysis Case, (available, in the ELFINI Structural Analysis product, in the New Case dialog box at the time of a Case Insertion) cannot be modified once the Case has been created. These must not be confused with the Computation parameters of a Case Solution, which are proposed by default at creation, and are editable afterwards.
	To edit the default values of the Computation parameters of a Case Solution, double-click the Solution objects set in the analysis specification tree (or right-click, then click `.Object -> Definition` ) to display the Definition par...dialog box.

The Frequency Solution Parameters dialog box contains the following parameters:

Number of modes

Method (Interative subspace or lanczos)

Dynamic parameters (Maximum iteration number and Accuracy)

which can all be modified in the dialog box.

The ELFINI product offers the following additional features with a right mouse click (key 3):

on a Static Case Solution objects set:

Generate Image: proposes to generate the various images available along with the Static Solution objects set. The image can be edited to include part or all of the options available.

Right-click the Mass object and then click the Generate Image option from the displayed contextual menu (on the condition you previously computed a solution using the Compute icon ).

The Image Choice dialog box is displayed. You can select images by clicking them in the list.

Report: the global status and results of all computations are reported in HTML format.

Click the Basic Analysis Report icon on the bottom toolbar (on the condition you previously computed a solution using the Compute icon ).

The .html partial report file is displayed. It contains a summary of the modal computation results, including the values of the rigid body modal participation factors for the computed modes.