FED-STD-228A
4.4 Exposure of specimen.
4.4.1 Unless otherwise specified in the detail specification, the total dosage of radiation shall be 1.16 x
104 mg. per square decimeter with a plus or minus tolerance of 2 percent. Approximately 50 hours
exposure should be sufficient for this dosage.
4.4.2 Unless otherwise specified in the detail specification, tensile strength and elongation tests, methods
3021 and 3031, and the nature and degree of cracking and checking, 4.4.5 shall be used to determine the
deterioration of the material due to aging.
4.4.3 Unless otherwise specified in the detail specification, the specimen, mounted in the holder, shall be
stretched to an elongation of 10 percent within 3 hours after it has been buffed. The specimen shall be
held in the stretched position for 16 to 24 hours at a temperature of 38° ± 1°C (100° ± 2°F) to aid in the
blooming of the protective waxes.
4.4.4 Within 1 hour after the preconditioning period, the stretched specimen mounted in the holder shall
be placed in the aging container in such a position as to receive full radiation from the arc. It shall be
exposed to the light until the total exposure is equivalent to that required to decompose the specified
quantity of oxalic acid (4.4.1). At least one measurement of intensity of radiation shall be made, as
described in 4.3, at the start and the end of each exposure and at intervals of not more than 24 hours
during the period of exposure. The temperature of the air in the vicinity of the specimen shall be
maintained at 45° ± 5°C (118° ± 9°F) during the exposure period, by controlling the temperature of the
room and the ventilation of the space surrounding the specimen. The filters or other enclosure shall be
cleaned at least once every 24 hours during the exposure period.
4.4.5 At the end of the exposure period, the holder with specimen shall be removed and the specimen
examined immediately by means of binocular microscope for cracking and checking. The specimen shall
be removed from the holder and set aside on a flat surface to rest for not less than 16 hours nor more
than 96 hours at room temperature before physical tests are made.
4.4.6 At the end of the rest period, unless otherwise specified in the detail specification, 4.4.2, tensile
strength and elongation shall also be determined of the specimen as described in methods 3021 and
3031. If other properties are required the specimen shall be tested as described in the specified method.
The same physical tests shall be conducted on aged and unaged specimens for the purpose of
comparison in determining the degree of deterioration of the aged material. The dimensions of the
specimens for use in calculating the tensile strength and elongation shall be determined after exposure.
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
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.
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