A common use of Frequency Analyses are to compare the
natural, or resonant, frequencies of a part or assembly to the
input frequencies. The example I like to use is a grinding wheel in
the shop. It usually sits on a steel frame bolted to the floor.
Most people have noticed that after turning the motor on and as the
wheel accelerates to operating speed, the stand shutters and
vibrates, then settles down. The wheel speed (RPM) just passed thru
the first natural frequency of the stand, causing it to resonante
and vibrate. When the wheel speed increased past that natural
frequency, the stand stops shaking. It would be important from a
desinger standpoint, to make sure that the 1st natural frequency of
ths stand wasn't the operating speed instead of some intermediate
speed since the stand wouldn't be usable and would shake itself to
death.
Does this make more sense?
