FED-STD-228A
4.7.1 Thickness. The thickness of the specimen shall be determined as described in method 1124
except that a dumbbell tensile strength specimen shall be subjected to three measurements, one at the
center and one near each end of the reduced section. If the specimen is narrower than the diameter of
the foot, measurements shall be made with the center of the micrometer foot coinciding with the
longitudinal center line of the specimen so that there will be an equal overlap of the foot on each side.
The median of the three measurements shall be used as the thickness in calculating the cross-sectional
area of the specimen except that specimens for which the difference between maximum and minimum
thickness exceeds 0.003 inch shall be discarded.
4.7.2 Width. The width of the specimen shall be determined with the apparatus described in method
1018 or any device which is accurate to 0.0001 inch and which can be used in such a manner that
compression of the specimen is negligible. A dumbbell tensile strength specimen shall be measured at
three places, one at the center and one near each end of the reduced section. The median of the three
measurements shall be used as the width in calculating the cross-sectional area of the specimen.
4.7.3 Cross-sectional area. The cross-sectional area shall be calculated or determined as described in
method 3021.
4.8 Unless otherwise specified in the detail specification, tensile strength and elongation shall be
determined on the aged specimen as described in methods 3021 and 3031 respectively. If other
properties are required, the specimen shall be tested as described in the specified method. The same
tests shall be conducted on aged and unaged specimens for the purpose of comparison in determining
the degree of deterioration of the aged material.
5. RESULTS
5.1 Calculation. The change in tensile strength, elongation, or other characteristic of the insulation or
sheath of the inspection unit due to aging shall be calculated as follows:
Change in characteristic, percent=O-E x 100
O
where:
O=the value obtained on the unaged insulation or sheath of the inspection unit
E=the value obtained on the aged insulation or sheath of the inspection unit
5.2 Unless otherwise specified in the detail specification, the number of specimens tested from each
inspection unit shall be as required in the method of test, 4.2, used for determining the deterioration of the
insulation or sheath.
5.3 The change in the characteristic of the insulation or sheath of the inspection unit shall be recorded to
the nearest 1 percent.
5.4 The temperature and time of exposure and time of recovery shall be recorded.
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