MIL-DTL-44419A
4.5 Methods of inspection.
4.5.1 Stiffness test.
a) Degree of Stiffness before soaking. Tested according to ASTM D 2821 except the specimens
shall be pre-flexed as follows:
1. Loosen knob (G). Using knob (H) slowly rotate the top dial (K) in a counterclockwise
direction until the specimen clamp indicator (I) shows that the specimen has been twisted 90°.
Use a uniform rate of rotation that will take 4 to 5 seconds to twist the specimen through 90°.
2. Reverse rotation to the clockwise direction and continue rotating slowly until the specimen
clamp indicator (I) has passed the original reference line indicated on the lower dial (J) by
approximately 45°. Again reverse the direction of rotation and slowly realign the specimen clamp
indicator (I) with the original reference line indicated on the lower dial (J).
3. Lock top dial (K) by turning knob (G) until tight, then reset dial (K) to read 270°.
4. Repeat the flexing operation by following steps 1, 2, and 3. When the second flexing cycle
is completed, loosen knob (G), turn upper dial (K) slowly (4 to 5 seconds for 90° rotation) in a
counterclockwise direction, using knob (H), until the specimen clamp indicator (I) shows 90°
twist. Read the angle of torsion from the upper dial (K) and record the value to the nearest
5 degrees. The angle of torsion of each specimen shall be reported to the nearest 5 degrees.
b.) Degree of Stiffness after soaking. If the stiffness requirements specified for before soaking are
not met, then do not test for stiffness after soaking. Any individual specimen exceeding the
maximum stiffness values specified for before soaking shall not be tested for stiffness after
soaking. The specimens shall be immersed in 1,000 mL of distilled water at 140 °F + 5 °F for
20 hours + 2 hours. Complete immersion of the specimens shall be accomplished by placing a
floating cover on the vessel used for the immersion of the specimens. After the required
immersion period, the specimens shall be removed from the water and reconditioned in
accordance with standard atmospheric conditions as specified in ASTM D 2821. The
reconditioned specimens shall be placed flesh side down on a rule graduated in decimal inches and
the distance between the bench marks shall be measured to the nearest 0.05 inch. If the distance is
3.4 to 3.6 inches, test the specimen in accordance with ASTM D 2821 and the exceptions.
If the distance is 3.2 inches or less, the specimen shall be reported as a test failure. If the distance
between benchmarks is 3.25 to 3.35 inches, the specimen shall be stretched before testing. To
stretch the specimen, place the specimen on the rule and align one of the benchmarks with a
division line on the rule. Hold the specimen against the rule by placing the fingertip of one hand
on the aligned benchmark. With the thumb and index finger of the other hand, lightly grip the
specimen near the aligned bench mark, then slide the finger and thumb along the specimen to the
other bench mark while exerting pressure on the specimen that is sufficient to obtain the required
distance between the bench marks. If the required distance between the benchmarks has been
obtained (3.4 inches to 3.6 inches), test the specimen in accordance with ASTM D 2821 and the
exceptions (see Footnote 3). If the distance between the benchmarks is greater than 3.6 inches
discard the specimen and test a new specimen selected from the same 12 x 12 inch test sample of
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