MIL-DTL-3849C
APPENDIX
A.3.2 Calculation of percent change in values. The calculation of percent change in tensile strength,
elongation, etc., after specified conditioning or aging period shall be made for each individual specimen.
When unaged specimens are destroyed during testing, the basis for percent change shall be the
arithmetic mean (average) value of the unaged specimens, which meet the qualifying value.
A.4 Tensile stress. Apparatus and procedure shall be as specified in method 3041 of FED-STD-228.
Tensile strength shall be determined in accordance with method 3021 of FED-STD-228, except that flat,
smooth, steel grips of the self-aligning type may be used.
A.4.1 Sample size. For a conductor smaller then AWG size 6, the insulation test specimen may be
an entire section of the insulation, 6.000 inches long. When the full cross section is used, the specimen
shall not be cut longitudinally unless necessary to remove the conductor. The preferred specimen of the
jacket is a 6.000 inches (152.4 mm) length with a die-cut reduced section 2.313 inches (58.75 mm) long
by .250 inches (6.35 mm) wide. Gage marks shall be applied before conditioning.
A.5 Elongation. Elongation shall be determined in accordance with method 3030 of FED-STD- 228,
except that bench marks shall be 2 inches (50.8 mm) apart, and flat, smooth, steel grips of the self-
aligning type may be used. The elongation after aging shall be based on the bench marks applied before
aging.
A.6 Set. Set shall be determined in accordance with method 3161 of FED-STD-228, the following
details shall apply:
a. Bench marks shall be 2 inches (50.8 mm) apart.
b. The test specimens shall be stretched so that the distance between bench marks is 6 inches (152
mm); They shall then be released within 5 seconds.
c. Set shall be determined 1 minute after the beginning of the release.
d. Flat, smooth, steel grips of the self-aligning type may be used.
A.7 Oxygen bomb aging. Specimens shall be subjected to oxygen-bomb aging requirements
specified in FED-STD-228, method 4011. The required conditions of time and temperature shall be as
specified in table A1. Specimens of insulation shall remain on the wire during aging.
A.8 Ozone resistance. The test for ozone resistance shall be performed in accordance with the
procedures prescribed in ASTM D1149 except as indicated below for ozone concentration and test
temperature. After testing in accordance with A.4, the rubber test specimen shall exhibit no visible cracks
when examined under a seven power optical magnifier.
A.8.1 Selection of sample units. The number of sample units required for inspection shall be chosen
by selecting one spool, reel, or coil for each sample unit. Samples shall be selected at random intervals
throughout the lot. After which the selected spool, reel, or coil shall be treated as the sample unit for
purposes of inspection.
A.8.2 Test specimens. The test specimen shall be a length of completed cable for jacket evaluation
or a length of insulated wire taken from a completed cable. Not less than six specimens each of jacketed
cable and six specimens each of all color insulation shall be tested (see A.8.2).
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