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How do I get Simulation to calculate the number of natural frequencies?

Question asked by David Maxham on Oct 22, 2009
Latest reply on Oct 23, 2009 by Anthony Botting

I've been running a random vibration model where I have Random Vibration/Properties/Frequency Options set to Upper bound frequency.  But now when I run the model, the random vibration status window indicates that there is a predefined(?) number of natural frequencies = 120. Initially I had run the model with the option of Number of Frequencies = 120, but that box is now grayed out, since I've chosen the Upper bound frequency option.


Under global damping, options is set to Modal damping with the first mode = 0 and the last mode = 120.  I've had this setting all along, so I don't understand how the model is now indicating a predefined number of natural frequencies?  I don't think I've changed anything that would cause the software not to calculate the number of natural frequencies instead of setting the number equal to 120.