CPD Dynamics Ltd
Assess your understanding of Vibration Testing
- The peak to peak displacement of an item attached to a shaker system is 1mm at a sinusoidal frequency of 100 Hertz.
The rms acceleration of the item is approximately:
(a) 14 ms-2 (b) 28 ms-2 (c) 14.2 gn (d) 44.4 gn
- A 2 kg weight suspended from a helical spring produces a static deflection of 4 cm.
The natural frequency of this system is:
(a) 3.86 Hz (b) 5.11 Hz (c) 1.37 Hz (d) 2.49 Hz
- A vibration test system conducts a logarithmic sine sweep test at 1.2 octaves per minute.
How long will it take to traverse the frequency range from 25 Hz to 2000 Hz?
(a) 10.44 mins (b) 7.19 mins. (c) 5.27 mins. (d) 3.82 mins.
- A flat vibration spectrum has an amplitude of 0.3 g2n/Hz over the frequency range 20 to 800 Hz.
This represents a total gnrms value of:
(a) 15.3 gnrms (b) 42.3 gnrms (c) 3.3 gnrms (d) 28.3 gnrms
- An electromagnetic shaker has a peak to peak displacement of 0.1 inches at a frequency of 55 Hertz.
(Yes, the US and some UK engineers still work in Imperial units!!). The peak acceleration is:
(a) 3.4 gn (b) 11.3 gn (c) 8.8 gn (d) 15.5 gn
And the force required to achieve the above acceleration for an armature mass of 25 lb will be (1 kg = 2.205 lb):
(a) 1120 N (b) 1720 N (c) 960 N (d) 1270 N
- An electromagnetic shaker is rated at 16000 N vector force. Its armature mass is 35 kg. The rated “no load” acceleration is
(a) 46.6 gn (b) 29.5 gn (c) 57.8 gn (d) 66.0 gn
A test load of 484 kg is attached. The new rated acceleration will be:
(a) 7.6 gn (b) 1.5 gn (c) 18.2 gn (d) 3.1 gn
The maximum load capable of being tested at 10 gn peak will be:
(a) 31 kg (b) 128 kg (c) 272 kg (d) 57 kg