FED-STD-228A
4. PROCEDURE
4.1 The elongation or distance between the bench marks of the stretched specimen shall be as specified
in the detail specification. If no elongation is specified, the specimen shall be stretched an amount equal
to three-fourths of the ultimate elongation as determined by method 3031.
4.2 Unless otherwise specified in the detail specification, the specimen shall be held at the specified
elongation for 2 minutes.
4.3 Unless otherwise specified in the detail specification, the specimen shall be allowed to rest for 2
minutes after release before the set is measured.
4.4 Preparation of specimen. The specimen shall be prepared as described in methods 3021 and 3031.
4.5 Determination of set. The specimen shall be placed in the grips of the testing apparatus in the same
manner as described in method 3021. The grips shall be separated at an approximately uniform rate of
speed such as to require about 15 seconds to reach the required elongation.
4.5.1 The specimen shall be held at the required elongation for the required time, then released
immediately without being allowed to snap back, and allowed to rest for the required time.
4.5.2 After the rest period, the distance between the bench marks shall be measured to the nearest 0.01
inch.
4.5.3 In stretching the specimen it has been found convenient to use a measured rod of a length equal to
the exact distance required between the two bench marks on the stretched specimen. Holding the rod
beside the test specimen while it is being stretched simplifies the operation and reduces the chance of
stretching the specimen more than the required amount. A stop watch shall be used for recording the
time required for the various operations.
5. RESULTS
5.1 Calculation. The tension set of the specimen shall be calculated as follows:
Tension set, percent, = L2-L1 x 100
L2
where:
L1=the distance between bench marks of the unstretched specimen, inches
L2=the distance between bench marks of the specimen at the end of the rest period
5.2 Unless otherwise specified in the detail specification, three specimens from each inspection unit shall
be tested except that under the following conditions five specimens shall be tested:
5.2.1 If the tension set of one or more specimens does not meet the specified requirement for tension set
in the detail specification.
5.2.2 If referee tests are being made.
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