FED-STD-228A
4.1.2 The specimen shall be prepared by means of a die described in method 3021. The shape of the
specimen shall be as described on figure 3111. It shall be cut with the grain running the long way of the
specimen. To facilitate cutting, the piece of material from which the specimen is to be cut, and the edge
of the die may be lubricated with water containing a wetting agent and a corrosion inhibitor. The
specimen shall be 2 inches long, the reduced portion ¼ inch wide, and the enlarged portion ½ inch wide.
Using a sharp blade, a slit shall be cut along the center of the constricted portion, extending to within 0.15
inch of the end of the enlarged part of the specimen. The slit shall be cut approximately 90° to the flat
surface of the specimen.
4.2 Measurement of specimen. The thickness of the specimen shall be measured as described in
method 1124 before cutting the slit, except that three measurements shall be made at the enlarged end
and not more than 0.25 inch from the end of the piece. The median of the three measurements shall be
recorded for use in calculating the tearing strength.
4.3 Determination of tearing strength. One end of the split portion of the specimen shall be clamped in
the lower grip of the tensile machine. The force shall then be applied with a lower jaw speed of 20 ± 1
inch per minute. The maximum force in pounds registered on the dial recorder or scale shall be recorded
in calculating the tearing strength.
5. RESULTS
5.1 Calculation. The tearing strength of the specimen shall be calculated as follows:
Tearing strength, pounds per inch of thickness = __F__
T
where:
F = tearing force in pounds
T = thickness, inch
5.2 Unless otherwise specified in the detail specification, five specimens from each inspection unit shall
be tested except that under the following conditions seven specimens shall be tested:
5.2.1 If the tearing strength of one or more specimens does not meet the specified requirement for
tearing strength in the detail specification.
5.2.2 If referee tests are being made.
5.3 The tearing strength of the sheath of the inspection unit shall be the median of the results obtained
from the specimens tested.
5.4 The tearing strength of the sheath of the inspection unit shall be recorded to the nearest 1 pound per
inch of thickness.
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