MIL-DTL-14824C(AR)
4.4.2.2 Yield strength and elongation. Two final heat
treated projectiles from a heat treated inspection lot shall be
selected for the tension test. The projectiles selected shall be
those which have the highest and the lowest hardness reading from
4.4.2.1. From each of these projectiles two specimens shall be
tested in accordance with 4.4.2.2.1. In the event of rejection,
new samples of higher or lower hardness values or both, as
applicable, may be selected and tested in order to establish an
acceptable hardness range. Once this range has been established
all projectiles whose hardness values fall outside the range
shall be rejected or subjected to re-temper or heat treat cycle
if approved by the Contracting Officer. An acceptable hardness
range is one which will provide acceptable yield and elongation
results.
4.4.2.2.1 Yield strength and elongation method. The two
projectiles selected for testing shall have two specimens taken
from each and tested. Two longitudinal specimens shall be taken
0
180 apart from the sidewall. Location shall be centered under
the rotating band seat and in the middle of the wall thickness in
that area. Failure of any specimen to comply with the applicable
drawing requirement shall be cause for rejection of the heat
treated inspection lot. Testing shall be conducted in accordance
with ASTM E8 with the largest substandard size round specimen
possible.
4.4.2.3 Miscellaneous lots. Miscellaneous heat treatment
lots shall be subjected to a hardness test in accordance with
4.4.2.1.1.
4.4.3 Rotating Band.
4.4.3.1 Mechanical properties of rotating band blank. The
band shall be cut from front to rear and flattened, without
hammering which may further cold work the materiel, and the
largest obtainable flat type specimen shall be cut from the band,
the length of which shall provide a one inch gage length, plus
adequate material at each end to accommodate the grips of the
tensile testing machine. This method should yield a .500 inch
gage width. In any event, the gage cross section shall be
determined to the nearest .001 square inch and utilized to
calculate the tensile strength, and elongation. Testing shall be
conducted in accordance with ASTM E8.
4.4.3.2 Mechanical properties of disassembled rotating
bands. One body assembly shall be randomly selected from each
regular production shift or fraction thereof per banding machine
in operation and subjected to this test to determine compliance
with 3.4.1. Failure to comply shall be cause for rejection of
the assemblies represented by the sample. The sample provide
shall have the rotating band removed and carefully flattened so
as to hold a minimum to any additional cold working. The
specimen blank shall be machined so that all serration marks from
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