Imagine you've been acquiring vibration data all day... while analyzing, your boss suggests animating an operational deflection shape with the data.
The only problem is that you did not use the same naming convention on the geometry as you did with the test data. Or even worse, the data was stored without suitable names and directions for a geometry animation.
Previously, if these names did not match, either the geometry names or the data names would have to be altered to match. That’s a lot of renaming just to animate a shape, especially if a lot of different runs and configurations were tested!
As of LMS Test.Lab Version 17, an alias table (similar to a lookup table) has been introduced so that mapping can be done between the geometry and the modal data. This makes it possible to animate shapes without altering node names.
Example of using alias table: modal analysis of a golf club
Imagine conducting an impact test on a golf club. Data is taken in the X and Y directions at eleven points along the physical club. FRFs are calculated for all the runs and it is now desired to animate mode shapes in LMS Test.Lab.
A simple geometry is created in LMS Test.Lab that matches the accelerometer locations on the physical object in Figure 2 above.
The node names between the geometry and the modal data do not match. Rather than renaming all of the nodes in the geometry or in the data, an alias table is created. The alias table links the node names in the geometry to the node names from the modal data. This way the software can animate nodes on the geometry with the appropriate data (despite the geometry name and the data name not matching).
In the Navigator worksheet of LMS Test.Lab, open the alias mapping table by right clicking on the project name in the project tree and selecting "Add/Edit Alias Mapping".
The alias data and the original data must both be selected and mapped.
First, from the upper left, choose the "Active Project Geometry" as the alias data. The test measurement data will be mapped onto the selected geometry nodes.
Select the directions that need to be alias mapped. In this case, only the X, Y, and Z directions are of interest. Click “Replace”. This will import all of the geometry nodes and selected directions.
Next, import the source measurement data that the geometry is to be mapped to. Using the selections in the upper right of the menu, this can either be from the active project or from the input basket. In this case, all the runs from a section in the active project are imported.
Now the mapping must be completed. In this case, only the +X and +Y directions must be mapped (because data was only taken in the +X and +Y directions).
So, in the “Quick find” filter, search for +X in both the alias data and the original data.
Knowing that “golfclub1:+x” in the geometry is equivalent to “club1:0+X” in the test data, these two nodes can be matched. Enter the nodes into the alias table by selecting the node from the list and then clicking the “Add” button. Repeat this for both the alias data and the original source data.
Repeat this process until all necessary nodes are mapped.
NOTE: It is possible to copy and paste the alias table to / from excel. This would allows saving and restoring different configurations.To de-activate the alias table, highlight all the filled cells, right click, and choose "Clear".
When the status is green and "Everything OK" message appears, press the "OK" button to continue.
Once all the nodes are mapped, it is possible to continue with the operational deflection shape or modal analysis and successfully animate shapes.
NOTE: ALWAYS create the alias table before doing any modal analysis processing. The alias table will not override existing processing, it will only work for new processing.
The alias table makes linking the data names to the geometry names easier than ever!
Questions? Contact us.