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|  MIL-T-26025E (USAF)
i
High stress areas of the frame assembly shall be coated with brittle lacquer. The
4.5.19.2
tractor shall be driven over the test course at a speed of 8 MPH and 4 MPH, it shall perform a maximum
stop from 15 MPH, and perform a drawbar pull of 10,000 miles for 1/2 mile.
4.5.19.3 Strain recording Strain gauge rosettm shall be positioned in locations of high stress
concentrations. The locations should be determined as indicated by the brittle lacquer patterning and a
minimum of 30 strain gauges shall be used. Strains shall be recorded for each of the three following tests:
Four round trips over the test course.
a.
b. Five maximum stops from 15 MPH.
Twenty miles under load as follows:
c.
One mile at 10,000 pound drawbar pull.
(1)
(2)
Five miles at 9,000 pound drawbar pull.
Eight miles at 8,000 pound drawbar pull.
(3)
Four miles at 6,000 pound drawbar pull,
(4)
Two miles at 4,000 pound drawbar pull.
(5)
Strain/occurrence histograms shall be supplied for each gauge for each test cycle. The actual test course
shall be recorded on the histogram. A picture of each gauge indicating its position shall be provided.
.
valuation< The minimum ultimate tensile and yield strengths of the gauge components shall
4.5.19.4
be documented. Any strain recorded indicating stresses greater than 50 percent of the material minimum
yield strength shall be cause for rejection. Fatigue calculations shall project a vehicle life as follows: _
a.
One thousand miles over test course.
b. Ten thousand maximum brake stops.
Ten thousand miles under loads as tested.
c.
eliab ilitv/durability te sting Compliance with the quantitative reliability requirements of
4.5.20
3.1.3.1 shall be demonstrated by the following tests. Apparent failures that are caused by some unintended
factor external to the equipment (e.g. test equipment failure) shall not be counted as reliability failures if
the cause is substantiated to the satisfaction of the procuring activity. Any test resulting in a failure shall
be fully documented. Servicing, preventive maintenance, or adjustments authorized by this specification
or the procuring activity shall not be counted as failures.
4.5.20.1 Vehicle durability test. The tractor shall be driven 2,000 miles under load as follows. During
the tests, tractor shall be stopped by the service brakes at least once in each five miles.
a.
One hundred miles at 10,000 pounds drawbar pull.
Five hundred miles at 9,000 pounds drawbar pull.
b.
c.
Eight hundred miles at 8,000 pounds drawbar pull.
Four hundred miles at 6,000 pounds drawbar pull.
d.
e.
Two hundred miles at 4,000 pounds drawbar pull.
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