Taking torsional data with LMS Test.Lab? Here are three tips that will save you time!
TIP 1: Acquisition: Change the channel group from Tacho to Vibration
With this trick, there is no need to split the tacho channel and route it into both a dynamic channel and a tacho channel. Both a tachometer and vibration channel are calculated.
When the tacho channel is set to vibration, it is possible to create order cuts and FFTs from the throughput data.
TIP 2: Display vibration in angle, RMS, peak, or peak-to-peak
An example of a torsional order is below. The x-axis represents the overall RPM level and the y-axis represents the fluctuation in RPM (torsional vibration).
To view the torsional vibration in rotational displacement rather than rotational speed:
The graph will then appear as below in Figure 5.
Want to display the maximum angular displacement?
To change whether the axis is represented in Peak, RMS, or Peak-to-Peak values:
The graph will then appear as shown below in Figure 7.
TIP 3: Torsional Vibration Animation
Create an operational deflection shape of your torsional vibration:
3. Click on “Add Disc…”. The “Add disc” window will appear (Figure 9).
4. Type in the node name, the radius of the rotating component, and the orientation in which you want to create the disc.
5. Click apply and then click close.
The torsional node will appear in the Geometry Display as shown below (Figure 10).
Once all the desired nodes and torsional nodes are created, it is possible to animate the nodes with spectrums, orders, and time histories of the nodes (Figure 11), just as you would animate any geometry.
Figure 11: An animation of the torsional nodes shows the fluctuation in the shaft as it rotates.
Both translational and rotational vibration can be displayed simultaneously.
Enjoy these tips when working with torsional vibration.
Questions? Contact us!
Rotating machinery dynamics:
LMS Test.Lab Tips: