MIL-DTL-18375H
table IV. The application of lubricant to the endurance test sample, in addition to the lubricant
applied during the manufacture of wire rope, shall not be permitted either before or during the
endurance test. The breaking strength of the wire rope specimen after the endurance test shall be
determined by the method specified. The test specimen shall be that portion of the wire rope that
passes over one of the test sheaves during the endurance test. The breaking strength shall be
equal to or greater than the corresponding MBS specified in table II.
4.5.4 Stretch test. The total length of the wire rope specimen to be tested shall not be
less than 24 inches. When 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 1 percent of applicable MBS shown in table I to straighten the wire
rope. While the specimen is under the 1 percent preload, a gauge length of not less than 10
inches shall be marked on the wire rope between the end fittings of the test specimen. The
specimen shall then be loaded to 60 percent of the wire rope's MBS and measured for elongation
under this load. The percent stretch shall be calculated using the formula below.
Elongation of gauge length under load
Percent stretch = -------------------------------------------------- x 100 ≤1.5%
Original gauge length
4.5.5 Ductility of steel. The wire shall be wrapped in a way that does not cause
indenting. The wire shall be wrapped around a cylindrical mandrel for 2 complete turns in a
close helix at a rate not exceeding 15 turns per minute. The cylindrical mandrel diameter shall
be equal to the nominal wire diameter being tested.
4.5.6 Test load. The following test shall be made using the same wire rope specimen
used in the 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 5 seconds. At the end
of the test, the entire 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 4.5.6.1).
4.5.6.1 Use of acoustic, electronic device for wire break test. The load shall be increased
to 80 percent on the test specimen. If no ping (see 6.4.8) is heard, the specimen has passed the
test. If one or more pings are heard, the wire rope specimens shall be unraveled and the broken
wires shall confirm failure of the specimen. If no broken wires are found, the specimen has
passed the test.
4.5.7 Magnetic permeability. Each sample selected shall be inspected with the
permeability indicator specified in ASTM A 342/A 342M. All indications shall establish that the
permeability of the material does not exceed 1.5.
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