MIL-DTL-24643C
4.8.31.1 Specimen. Each specimen shall consist of a single insulated conductor (including insulation covering)
of a length not less than that specified in table XV. Specimens shall be removed from completed cable as follows:
a. Cables containing four or fewer conductors - one conductor shall be removed from each insulated
conductor.
b. Cables containing more than four but fewer than 21 different insulated conductors (a total of four
specimens).
c. Cables containing 21 or more conductors - the number of specimens removed shall be equal to the square
foot (rounded to the nearest whole number) of the total number of conductors. Each specimen shall be removed
from a different insulated conductor.
An additional specimen, which shall consist of a piece of insulated conductor (including insulation covering) of not
less than 10 feet in length, may be required (see 4.8.31.5)
TABLE XV. Specimen and mandrel dimensions for crack resistance
test.
Conductor size
Min. specimen
Mandrel diameter
(AWG)
length (inches)
(inches)
1½±1/16
7
24
1±1/16
9
18
½±1/32
10
12
½±1/32
14
12
⅓±1/64
16
8
⅓±1/64
18
8
¼±1/64
Greater than 18
6
4.8.31.2 Special apparatus. Apparatus shall include the following:
a. Mandrel shall be a rigid, smooth cylinder, of the diameter specified in table XV and the length and
construction for the specimen wrapping as specified in 4.8.31.3.
b. An aqueous solution of gentian violet, of a quantity and concentration for staining as specified in 4.8.31.3
or 4.8.31.5, as applicable.
4.8.31.3 Procedure. Each specimen shall be tightly hand wrapped, for not fewer than three circumferential and
continuous, 360-degree turns around the mandrel. Following this, each specimen shall be removed from the
mandrel and continuous 360-degree turns in the opposite lateral direction. Each specimen shall next be removed
from the mandrel and straightened to the extent that the specimen is nowhere bent along a radius of less than 12
times the maximum measured specimen diameter. Each straightened specimen shall then be submerged, except for
the extreme ends (which shall remain exposed to the air), in the gentian violet for a period of not less than 30
minutes. The specimen shall then be removed from the gentian violet and visually inspected for defects.
4.8.31.4 Observation. Specimen failure shall be construed if the insulation covering of any specimen exhibits
visible cracking or peeling which allows penetration of the gentian violet. If the insulation covering of any
specimen exhibits an average of more than one pinhole, which allows penetration of the gentian violet for each 12
inches of length, then the further procedure as specified in 4.8.31.5 shall be performed.
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