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|  MIL-F-48673 (AR)
4. 8.1.4.4 Vibration test procedur. .
.e
..
4. 8.1.4.4.1 Resonance search. Resonant frequencies of the
equipment shall be determined by varying the frequency of applied
vibration slowly through the specified range at reduced test levels
but with sufficient amplitude to excite the item. Sinusoidal
resonance search may be performed using the test level and cycling
time specified for sinusoidal cycling test, provided the resonance
search time is included in the required cycling test time. Vibrate
per Table XIII one cycle in each of the three axes.
4.8.1.4.4.2 Resonance dwell. The test item shall be vibrated
along each axis at the most severe resonant frequencies determined
Test levels, frequency ranges, and test
in the resonance search.
If more than four
times shall be in accordance with Table XIII.
significant resonant frequencies are found for any one axis, the
four most severe resonant frequencies shall be chosen for the dwell
If a change in the resonance frequencies occurs during the
test.
test, its time of occurrence shall be recorded and immediately the
frequency shall be adjusted to maintain the peak resonance
condition. The final resonant frequency shall be recorded on the
..
Test Data sheet.
TABLE XIII.
Resonance dwell
)
Survey Time Resonance
Sweep Time
Frequency
Dwell
per increment* per Axis `
Vibratory Level
Increments
(minutes)
(minutes)
(minutes)
(Inches Peak-to-Peak)
Hz
I
15
10
10
0.025 inches (0.635mm)
5 to 25
5
0.020 inches (0.508mm)
25 to 55
*Note: Sweep times specified shall be for a low frequency to high
frequency to lot frequency variation for the applicable increment.
4.8.1.4.4.3 Sinusoidal cyclinq. The test item shall be
vibrated thru one cycle alonq each axis in accordance with the
displacement levels; frequency range (5-55 Hz) and time (15 min.).
I
The accumulated minimum vibration test time per axis shall be 45
minutes. The specified sweep time (15 min.) is that of an ascending
sweep only. Record test results on data sheets.
49
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