MIL-DTL-24640C
4.8.9.1 Cable sample preparation. The individual shields of shielded components, when present, shall be
connected to the conductors and the connected conductors and shields shall be the conductor as specified in NEMA
WC 61.
4.8.9.2 Determination of EMP response. The surface transfer impedance determined as specified shall be
known over the frequency range DC to 100 MHz. It shall be assumed constant in the frequency range DC to 0.1
MHz. The EMP response in dB shall be determined as follows:
1. 10
8
Zt . ( f)
2
10. log
EMP response = (
185)
df
f . β
2
2
2
2
α
f
0
The integral expression may be approximated by a summation if at least 100 points per decade of frequency are
used.
4.8.9.3 Observation. Specimen failure shall be construed if the surface transfer impedance is greater than
specified (see 3.1) or if the calculated EMP response of the overall cable shield is less than specified (see 3.1).
4.8.10 Armor. Cable armor performance shall be determined as specified in 4.8.10.1 through 4.8.10.4.
4.8.10.1 Specimen. Each specimen shall consist of a single piece of armor wire, of not less than 6 inches in
length, which has been removed from a spool of armor wire prior to cable armoring. Each specimen shall be
removed from a different spool. Ten specimens shall be required.
4.8.10.2 Special apparatus. Apparatus shall include the following:
a. Mandrel. A ¼±1/64 inch diameter steel cylinder, of length and construction for the springiness test as
specified in 4.8.10.3.
b. Scale. A spring or other type scale, the measurement error of which shall not exceed ±5 percent for use in
the springiness and toughness tests specified in 4.8.10.3.
c. Special vise. A special vise, with 2 parallel edges of 0.030±0.001 inch radius between which a specimen
may be clamped to perform the toughness test as specified in 4.8.10.3.
4.8.10.3 Procedure. The two following tests shall be performed using not fewer than five specimens. The
specimen shall be tested one at a time for each test. The same specimen shall not be used for more than one test.
a. Springiness. One specimen shall be selected and secured by one end to the mandrel such that it is both in
contact with the curved surface of the mandrel and perpendicular to the mandrel axis. The opposite end of the
specimen shall be attached to the scale. The specimen shall be wrapped circumferentially around the mandrel, by
handling the scale only, for not fewer than four complete turns, while maintaining a specimen tension of not less
than 100 nor more than 125 grams. Care should be taken to pull the scale in such a direction that it accurately
indicates the specimen tension. The specimen shall then be released from the scale and allowed to uncoil. Any
specimen which is kinked at any place other than the attachment points at either end shall be considered an invalid
specimen. The test shall be repeated using a different specimen. This test shall be successfully repeated four more
times (five times total) using a different specimen each time.
b. Toughness. One specimen shall be selected and secured by one end between the rounded, horizontal, and
parallel vise edges, such that not less than 2 inches of the specimen extends vertically above the vise. The scale
shall then be attached to the free end of the specimen and a specimen tension of 100±10 grams shall be established
by handling the scale only. The specimen shall be bent 90+15, -0 degrees alternately in both directions
perpendicular to the vise edges, while maintaining the specified vise tension. Not fewer than ten 90 degree bends
shall be made unless the specimen breaks sooner. The bending rate shall not exceed fifty 90 degree bends per
minute. This test shall be repeated four more times (five times total), using different specimens each time.
4.8.10.4 Observation. Either of the following shall constitute specimen failure:
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