Vibration Testing Requirements

50 cycles per second Peak to Peak displacement = 0.060"

Displacement measurement is not the best measurement of vibration, velocity measurement is, in most cases. Vibration Velocity indicates the amount of energy transferred to the bearing and is the degree of severity.

50 cycles per second with 0.060 inches peak to peak looks like 2 x 0.060 per cycle (round trip travel) x 50 trips per second with peak speed about 1.4 x average speed (square root of 2) for a result of about 9 inches per second. This is a huge vibration velocity. Expected machine vibration velocities are about 0.7 inches per second so the reported vibration is very large.

The 9 inches per second is actually 9.425 in/s peak or 18.850 in/s p-p (6.664 in/s rms). The 50 Hz frequency with .060 in p-p displacement results in 3000 RPM and requires acceleration of 7.669 g peak or 15.338 g p-p (5.423 g rms).

Looking at it another way, this frequency matches the AC electric power frequency of many countries.

Hello, it has been a long time since I had any involvement with vibratons. But first the 50 cps at a double amplitude of 0.060 inches contains a lot of information. First, how big is your test article? The thing you want/need to shake? That will govern the size of the shaker. Also since the vibrations specifially call for 50 hz then you want to make sure your test fixture has no fundamantal resonances at 50 Hz. If so it might go into resonance and cause even more loading of the TA. And for sure you want to make sure your TA design has no resonances at that frequency. Otherwise it will probably disassemble itself right there on the shaker test stand (been there done that, lol). One of the critical things will be to prove that you stroked the TA at the requierd frequency and at the stated displacement. If this is in a single axis then a single accelerometer can help in determining the displacement (double integration). You will need an analysis tool such as a structural analyzer to make sense of your data. You will need some sort of accelerometers on the TA as well to show that the input is correlated to the output in TA response. My best though it that if you are new to this game and are bidding on a proposal, then you get a company like Wyle LAbs involved. They do this for a living.

mayf