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|  MIL-R-60040C (PA)
flare cartridge during vibration be impaired. In all cases,
the flare rack with ejector set assembly shall be attached
either directly or through the airplane mounting brackets,
if feasible, to a test fixture of maximum rigidity. The
test fixture should be designed to eliminate or minimize
fixture resonances in the test frequency range. The test
configuration shall be such that rotational motion of the
test fixture is not induced due to any unsymmetrical weight
or stiffness distribution of the equipment item or
mounting brackets.
Measurements of vibratory accelerations or displacements
shall be made adjacent to the mounting points or the equipment
item. All frequency measurements shall be accurate within
plus or minus 5 percent. All displacement or acceleration
measurements shall be accurate within plus or minus 10 percent.
The motion of the vibrator table shall be simple harmonic motion
with not more than 20 percent distortion. The monitoring
control signal from the accelerometers shall be unfiltered.
The rack with ejector set assembly shall vibrate with'
essentially simple harmonic motion in each of three mutually
perpendicular directions to explore for resonant frequencies
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 a stated speed). This time shall be deducted
from the specified test frequency scan.
The test report must contain complete description 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.
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