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|  MIL-F-60037C (PA)
Frequency scans shall be conducted very slowly and care-
fully . The recommended speed shall be half (1/2) the stated
cyclical rate from five (5) Hz to 1500 (Hz) (eg. if the time
spread to cycle is fifteen (15) minutes it shall be accomplished
in 30 minutes, or at stated speed). This time shall be deducted
from the specified test frequency scan.
The test report must contain complete descriptions of all
resonances, including the resonant frequencies, parts in res-
onance, and the effects on the functioning of the test Item.
Scans shall be conducted at room temperature, and also at -60
degrees F. and plus 150 degrees F.
After completion of the frequency scan, resonance en-
durance tests shall be conducted at all resonant frequencies
of the components, with the applied force adjusted as neces-
sary to obtain the applicable fixture displacements or accel-
erations specified by the test curve. The vibrator and power
supply must be capable of producing the prescribed fixture
motions at all frequencies. Endurance tests shall not be
conducted at any resonant frequency of the fixture. Endurance
test shall be performed in fifteen (15) minute intervals.
The delay interval shall be a minimum of ten (10) minutes
for safety considerations.
If a change in resonant frequency occurs during endurance
testing at resonance, the frequency of vibration shall be
adjusted to follow the resonance. However, if large or
abrupt resonant frequency shifts occur, the item shall be
examined for component failures or excessive wear, etc.
Resonance endurance tests shall be conducted for one
million hertz each or 8 hours, whichever occurs first, for
the total of all resonances. Two-thirds of each endurance test
shall be conducted at room temperature. One-sixth of each test
shall be conducted at -60 degrees F, and one-sixth of each test
shall be conducted at plus 150 degrees F. If the same resonance
is excited by vibration applied in more than one direction,
the endurance test for that resonance shall be accomplished
with vibration applied to the direction which produces the
greatest response. If no resonances are found, the item shall
be vibrated at 100 Hertz (Hz) and the corresponding amplitude
of the applicable test curve for one million Hertz In each of
three mutually perpendicular directions (see figure 1).
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