Difference between revisions of "Modal practical"

Remove the line between point 18 and 19 by clicking on `select lines<nowiki>’</nowiki> in the toolbar Select the line 18-19 and delete it.

Rename the point 18 in point 1.

Create the points 4, 5 and 6 with the grid and add lines to link them.

* Experimental coordinates systems

In the `Config review<nowiki>’</nowiki> select the nodes of line 2. Right click and select `Assign Coord.<nowiki>’</nowiki> Enter the following parameters

Results

For  this  demo,  use  the  data  file  `CANTILEVER  HAMMER  DATA.uff<nowiki>’</nowiki>  containing  the  Frequency Response Functions acquired with one impact hammer and 2 accelerometers.

In the File menu, click on Import/Data files (UFF). The following window is displayed.

Select `acceleration<nowiki>’</nowiki> for response type,

Here all the data will be used, so click on OK. The FRFs are directly displayed in the software.

All the FRFs can be visualized.

By using the Control Panel (Series select), all the FRFs can be displayed. For each result, there is information about the DOFs (node, direction).

By  right  clicking  on  the  graph  and  selecting  `Showed  Series…<nowiki>’</nowiki>, you  can  display  several  FRFs on the same graph for comparison.

On the left, the Modal Indication Function (MIF) shows the modes in the frequency band. Position the cursor on the peaks and visualize the corresponding mode shapes on the right.

'''''What is the MIF?'''''

Two separated modes

Weak modes

Two pairs of repeated modes

Sometimes we should note the cross modes. For example, in the below figure, the peak in the second MIF curve doesn<nowiki>’</nowiki>t indicate a mode. It<nowiki>’</nowiki>s formed by the cross of two modes.

In the operation tree: