MIL-DTL-83420M
4.4.5.1 Endurance testing at 65°F (-54°C) for type II, composition A and B. An
endurance test at -65°F (-54°C) shall be conducted for each type II, composition A and B, wire
rope diameter and construction specified in table IV. The number of reversals and tension loads
shall be as indicated in table IV. After the endurance test at -65°F (-54°C), a test specimen that
is that portion of the nylon jacketed wire rope that passes over the test sheave during the
endurance test shall be selected for breaking strength tests. From this specimen, two samples
representing the top and bottom sheave of the specimen shall be subjected to a breaking strength
determination as specified in 4.4.5, except the breaking strength of each sample shall be equal to
or greater than that specified in table IV.
4.4.5.2 Endurance test at room temperature for type II, composition A and B. An
endurance test at room temperature shall be conducted for each type II, composition A and B,
wire rope diameter and construction as specified in table IV. The number of reversals and
tension loads shall be as indicated in table IV. After the endurance test at room temperature, a
test specimen that is that portion of the nylon jacketed wire rope that passes over the test sheave
during the endurance test shall be selected for breaking strength tests. From this specimen, two
samples representing the top and bottom sheave of the specimen shall be subjected to a breaking
strength determination as specified in table IV, except the breaking strength of each sample shall
be equal to or greater than that specified in table IV.
4.4.6 Stretch test for type I, composition A and B. One specimen from each sample of
wire rope selected as specified in 4.4.3 shall be tested to determine the percent stretch. The total
length of the wire rope specimen to be tested shall not be less than 24 inches. Where necessary,
swaged terminals and accompanying hardware may be used to facilitate installation of the
specimen in the jaws of the test machine. The amount of stretch shall be determined on a tension
testing machine in accordance with ASTM E 8. The specimen shall be loaded to one percent
MBS shown in table I to straighten the wire rope and, while the specimen is under tension, a
gauge length not less than 10 inches shall be marked on the wire rope between the end fittings of
the testing specimen. The specimen shall then be loaded to 60 percent of MBS and measured for
elongation under load. From these data, the percent stretch can be calculated using the formula
below:
Elongation of gauge length under load
Percent stretch = -------------------------------------------------- x 100 ≤1.5%
Original gauge length
4.4.7 Test load for type I, composition A and B. The following test shall be conducted
using the same wire rope specimen used in stretch test, or similarly prepared specimen. Load the
specimen to one percent of breaking strength and then increase the loading to 80 percent of the
minimum required breaking strength of the wire rope specified in table I. The load shall be
applied for five seconds. At the end of the test, the entire wire rope shall be completely
unwound and every wire inspected. A suitable electronic device capable of detecting the
breaking of individual wires during testing may be used instead of unwinding the wire rope. The
failure of any wire shall be cause for rejection (see 4.4.7.1).
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