Random Vibration VS Sine Vibration?

Question

Which vibration is more severe: 1G @50Hz or 1G @ 500Hz (linear sine)? Rather than area under the curve is there other computional method? For random vibration, the amplitude is typically lower at higher frequency hence, for same amplitude at 50Hz and 500Hz which is more severe? How do one compute?

Answer 1

1G @ 50 Hz is a greater amplitude vibration than 1G at 500 Hz. They are both the same in terms of force applied. The 500 Hz signal cause more load reversals per unit time, which is not an issue if the loaded structure is designed to keep the resultant stresses below the endurance limit for the materials of the structure. There is alot more engergy in your 500 Hz signal.

For random vibrations, use an RMS method to determine the relative magnitude and energy of the loading signature. This can be accomplished fairly simply using a frequency to voltage converter.

My company has a device that we are able to mount to rotating machinery to detect bearing failure before it happens (this maintenance can be scheduled, as opposed to reacting to a machine going out of production). It uses an algorithm of sampling the machine vibration (using multi-axis accelerometers) and then comparing the "signature" of this signal to a known signature of impending bearing failure. If there is a close enough match, an alarm signal is sent.

Answer 2

Wouldn't the severity be a function of the structure's response you're analyzing?

What's your structure's response - deflection vs frequency?