MIL-DTL-87104C
4.6.2.4.2.2.7 Frequency and amplitude. The frequency and amplitude of all critical resonant frequencies and
resonant frequencies below 13 cycles shall be recorded on a data sheet.
4.6.4.2.2.3 Resonance endurance tests.
4.6.4.2.2.3.1 Critical resonance. If a critical resonance is detected during the frequency range scans, the test
sample shall be vibrated at the critical resonant frequency (see 6.4.7) in accordance with the following conditions:
a.
If all three temperature counterparts of a critical resonance are determined, two-thirds of each resonance
endurance test shall be conducted at room ambient temperature, one-sixth of each test shall be conducted
at -53.8°C, and one-sixth of each test shall be conducted at +71.1°C. The total dwell time shall be 30
minutes at each critical resonance.
b.
If all three temperature counterparts of a critical resonance are not determined and the amplitude of the
resonance is less than 4:1, the amount of dwell time shall be: Twenty minutes if the critical resonance
point was recorded at room ambient temperature; 5 minutes if the critical resonance point was recorded at
-53.8°C; and 5 minutes if the critical resonance point was recorded at +71.1°C.
c.
If all three temperature counterparts of a critical resonance are not determined and the amplitude of the
resonance is greater than 4:1, the dwell time of the missing temperature(s) shall be distributed on the
remaining resonance in the normal ratio of temperature-time distribution, with the total dwell time being
30 minutes.
4.6.4.2.2.3.2 Resonant frequencies. Resonant frequencies (see 6.4.8) shall be determined by the use of
accelerometers capable of detecting 10 percent difference in relative amplitude between the points and the sample
under tests. The location of the accelerometers shall be specified in the detailed test procedure.
4.6.4.2.2.3.3 Recording of data. The frequency, duration, amplitude, axis, and temperature of each resonant
endurance run shall be recorded on a data sheet.
4.6.4.2.2.4 Test sample. At the termination of the vibration test, the test sample shall be subjected to examination
of product, procedures II and III (see 4.6.1.2 and 4.6.1.3); leakage, procedure III (see 4.6.4.13.3); VSWR, procedure
II (see 4.6.2.1.2); and RF insertion loss, procedures I and II (see 4.6.2.3.2 and 4.6.2.3.3) in the sequence listed.
4.6.4.2.3 Accept-reject criteria (see 3.5.3.4). The test sample shall be considered to have failed to pass the
vibration test if: resonance occurs below 13 cycles; the test sample fails to satisfy the accept-reject criteria specified
in 4.6.1.2.2, 4.6.1.3.1, 4.6.2.1.2.5, 4.6.2.3.2.1 and 4.6.2.3.3.1; or there was evidence of bubbles coming from within
the equipment while being subjected to the leakage test (see 4.6.4.13.3.3).
4.6.4.3 Shock test (see 3.5.3.5). The shock test shall determine the structural integrity of the equipment and
determine if the equipment can perform satisfactorily after being subjected to mechanical shocks that might be
encountered in in-service and maintenance periods.
4.6.4.3.1 Test setup.
4.6.4.3.1.1 Test equipment. The test equipment shall consist of:
A shock machine as specified in MIL-STD-810, method 516.6.
a.
b.
Apparatus as shown on figures 2 and 3 herein.
4.6.4.3.1.2 Test conditions. The test conditions shall be as specified in MIL-STD-810, method 516.6, procedure I,
and herein.
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