MIL-DTL-49104C
maintained at a temperature of 95±1 °C for one hour +5, -0, minutes. The specimen shall then be
removed from the oven and the insulation examined for strains or cracks under a magnification of at least
three diameters (focal distance of 8 centimeters).
4.5.4 Deformation. A gage used for this measurement shall consist of a dial micrometer graduated
to read in increments of .001 inch (.03 mm) and equipped with a flat anvil not less than .375 inch
(9.53 mm) in diameter and a flat pressure foot .375 inch in diameter attached to a plunger. The anvil and
pressure foot shall be parallel to within .0001 inch (.00 mm). The plunger shall support a weight of
250 grams. The gage shall be placed in an oven maintained at a temperature of 95±1 °C for a period of
1 hour +5, -0, minutes. A specimen of finished cable at room temperature shall then be placed on the
platform, centrally located under the foot, and its diameter shall be read exactly 5 seconds after being so
placed. The gage and specimen shall then remain in the oven for a period of 1 hour +5, -0, minutes at
the above temperature and the diameter of the specimen again read without disturbing the specimen or
gage.
4.5.5 Cold bend. A specimen of finished cable and a mandrel of .080 ±.003 inch (2.03±.08 mm)
diameter shall be placed in a cold chamber maintained at a temperature of -40±1 °C for a period of
24 +1, -0, hours. At the end of this time, while still in the cold chamber, the specimen shall be wound
around the mandrel for five close turns at the rate of approximately one turn per second. The specimen
shall then be examined under a magnifying glass of at least three diameters magnification (focal distance
of 8 cm) for visible evidence of cracking of the insulation. During the above processing, no object having
a temperature higher than -40±1 °C shall come within 12 inches (304.80 mm) of the part of the specimen
being examined.
4.5.5.1 Aging. A specimen of finished cable shall be dried in an air oven for a period of at least 24
hours at 80±1 °C and then transferred directly (within 5 minutes) from the air oven to an oxygen bomb
containing an atmosphere of oxygen at 300±10 psi at a temperature of 70±1 °C and held there for a
period of 96 +2, -0 hours. Alternately, the specimen may be transferred directly to a desiccator containing
a drying agent to preclude re-absorption of water and then to the oxygen bomb when the bomb is
available. After 96 +2, -0 hours in the oxygen bomb, the specimen shall be transferred directly to a
desiccator containing a drying agent and held there for at least 24 hours and until such time as the
specimen is transferred directly to a cold chamber. The conditioned specimen shall then be tested as
specified in 4.5.5.
4.5.6 Insulation cutting load. A specimen of finished cable shall be cut in half and the insulation
stripped from one end of each piece. One piece shall be formed into a loop, the ends of which shall be
tightly clamped in one of the grips of a tensile tester. The second piece shall be passed through the loop
and its ends shall be tightly clamped in the other grip of the tensile tester. The two bare ends shall be
connected in series with an electrical alarm circuit and a load shall be applied to the looped conductors by
separation of the grips, at a rate of 2 inches (50.80 mm) per minute, until the grips cut through the
insulation, thus making electrical contact as indicated by the electrical alarm. One of the metal grips of
the tensile machine may have to be electrically insulated from the rest of the machine to avoid false
indications.
4.5.7 Insulation breaking load. The breaking tension (see 3.4.1.5) load or tensile strength of the
finished cable insulation shall be measured using the apparatus and method described in method 3211 of
FED-STD-228.
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