Page 46 - Shock and Vibration Overview
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Response Spectrums
Figure 27: Transmissibility of 250 Hz SDOF system with the airplane seat input vibration profile is
shown on the left. The corresponding power spectral density of such a system in that
environment is shown on the right.
What about other frequencies besides 250 Hz; how would those systems respond?
That’s where the vibration response spectrum comes in; it calculates the response
acceleration (measured by RMS) for a range of natural frequencies as shown in Figure
28. It also uses a Rayleigh distribution to determine the n-sigma peak to use as a safety
factor during the design process.
Figure 28: The vibration response spectrum for the airplane seat data calculates the response for
different natural frequencies of a candidate system.
From the vibration response spectrum the engineer knows to either us some isolator
mounts with a natural frequency below 100 Hz to dampen the vibrations or a stiff
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