FED-STD-228A
Method 2131.1
18 APRIL 2014
TOUGHNESS, ARMOR WIRE
1. SCOPE
1.1 This method is intended for use in determining the ability of armor wire to resist breaking from
repeated flexing.
2. SPECIMEN
2.1 The specimen should be a 6-inch length of the wire taken from the armor of the inspection unit.
3. APPARATUS
3.1 The apparatus shall be as follows:
3.1.1 Flexing machine with a power driven oscillating head and equipment for holding the specimen
under constant tension.
3.1.1.1 Two supports each with a radius of curvature of 0.030 inch shall be mounted on the head. With
the head at its mid-point of travel, the pins shall be in the horizontal plane through the center of the head
and normal to the plane of oscillation. The position of the pins shall be adjustable to accommodate wire
of various diameters and the pins shall be spaced equidistant from the center of oscillation. With a
specimen in the machine, the head shall oscillate through an angle of 180° and bend the specimen, while
under tension, back and forth over the pins. The head shall oscillate at a uniform speed of 25 cycles per
minute (50 oscillations per minute).
3.1.1.2 The machine shall be equipped with a counter to indicate the number of oscillations.
4. PROCEDURE
4.1 The constant tension applied to the specimen shall be as specified in the detail specification.
4.2 The specimen shall be free from mechanical damage, shall show no surface cracks or other defects
visible to the unaided eye, and shall be free from surface oxide. The specimen shall be placed in the
testing machine under the required tension and the machine started. The test shall continue with
frequent observations until the wire has broken. At this point the number of oscillations required to break
the specimen shall be read from the counter and the value recorded.
5. RESULTS
5.1 Unless otherwise specified in the detail specification, three specimens from each inspection unit shall
be tested.
5.2 The toughness of the armor wire of the inspection unit shall be the average of the results obtained
from the specimens tested.
5.3 The toughness of the armor wire of the inspection unit shall be recorded to the nearest cycle.
5.4 The tension applied to the specimen shall be recorded.
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