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MIL-S-52506D(ME)
A test specimen 2,50 inches long by 0.50 inch
4.5.2.1.3 Transverse strength.
square shall be used for this test.  The test specimen shall be supported on two
The knife edges shall be 2.0
knife edged rounded on a radius of 0.062 inch.
The stress shall be
inches apart and shall be equidistant from the specimen ends.
applied by a third knife edge, midway between the support knife edges and in the
The force shall be applied at a steady rate not
direction of molding pressure.
The total net force in pounds at which the
exceeding 2 pounds per second.
Transverse strength shall then be
specimen ruptures shall be noted and recorded.
calculated in accordance with the following formula:
3LF
Transverse strength in pounds per square inch =
2WT2
F
=
total force in pounds at the instant of rupture.
where:
w
=
width of specimen in inches.
T
=
thickness of specimen in inches.
L
=
distance between supporting knife edges.
A transverse strength of less than 10,000 psi shall constitute failure of this
test.
4.5.2.1.4 Tensile strength.
Tensile strength shall be determined in accordance
with ASTM E 8.
A tensile strength less than 2900 psi shall constitute failure of
this test.
4.5.2.1.5 Specific gravity.
Specific gravity shall be determined in accordance
A specific gravity of less than 1.75 or more than 3.20 shall
with ASTM C 135.
constitute failure of this test.
4.5.2.1.6 Coefficient of linear thermal expansion.
The coefficient of linear
thermal expansion shall be determined in accordance with ASTM E 228. A
(1/F) shall
coefficient of linear thermal expansion greater than 2.95 X
constitute failure of this test..
4.5.2.1.7 High-temperature test.
One carbon sealing washer shall be placed in
(149
for
a circulating-hot-air oven and maintained for 4 hours at 300
(260
for washers containing resin.
washers containing babbitt and at 500
The washer shall then be removed from the oven and allowed to cool in air until it
The washer shall be examined for evidence of cracks,
returns to room temperature.
Any evidence of cracks, spalling, or surface
spalling, or surface deterioration.
deterioration shall constitute failure of this test.
4.5.2.2  Flatness.
The flatness of the sealing surfaces of a carbon sealing
washer and its corresponding seat shall be determined under a monochromatic light
using an optical flat.
The monochromatic light shall be transmitted as a strong
near-one-color light of 11.6 millionths of an inch per dark interference band.
The optical flat shall be highly-transparent,  abrasion-resistant quartz with good
wear characteristics and thermal stability.
The optical flat shall be produced to
a standard of 0.10 of a light band (0.00000116-inch) and 0.20 of a light band
(0.00000232-inch) across the diameter.
A flatness not within 4 light bands for
the softer surface or a flatness not within 3 light bands for the harder surface
shall constitute failure of this test.
8

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