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|  MIL-R-60040C (PA)
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).
The rack with ejector set assembly shall be subjected
to the following cycling tests at room temperature in addi-
tion to the frequency scan and resonance endurance tests.
The equipment as mounted for the resonance tests shall be
vibrated at the displacements and accelerations defined by
the attached test curve with the frequency in a cycle con-
tinuously varied between the limits of the applicable curve
of approximately 15 minutes. The rate of change of frequency
shall be proportional to the frequency. The total test time
shall be 1-1/2 hours. This test shall be repeated with
vibration along each of three mutually perpendicular axes.
The cycling test may be broken into convenient ranges, pro-
vided the cycling rates and test times for each range are
not change. Testing shall be performed in accordance with
9200445 and 9200050.
4.5.4 Moisture content. (packing material). - The
moisture content shall be determined in accordance with
Method 240 of Specification UU-P-31 except that a 50 gram
sample shall be used.
4.5 .5 Continuity of strapping. - The test shall be as
specified in 4.501.
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