MIL-DTL-11891G(AT)
APPENDIX A
A.3.3.9 Cyclic torsional deflection load. Simultaneous cyclic torsional deflection load
shall be from +15° to -15° (+l°) at a frequency of 256 cpm +4 cpm (see figure 9). Cyclic torsional
deflection load frequency shall be maintained at four (4) times the cyclic compression load
frequency by positive mechanical means.
A.3.3.10 Testing duration. Testing will be continuous (24 hours per day) until bushing
failure, defined by the deflection exceeding 0.144 inches (0.145 inches of deflection). Radial load,
deflection, ambient temperature, bushing temperature, number of cycles, and time shall be
continuously monitored and recorded on a floppy disk using a Daytronic data acquisition system
(or equivalent) for future reference as required. A one-time lapse of up to 30 minutes from the
requirement of continuous operation of the test machine is permitted.
A.3.3.11 Test machine failure. In the event of a test machine failure, KRC shall discard
the bushing undergoing the endurance test and any data pertaining to it, and will randomly select a
new bushing specimen for testing.
A.3.3.12 Qualification requirements. Qualification requirements are determined by
eliminating the highest bushing test cycle result and averaging the remaining eight (8) bushing test
cycles. The average shall be a minimum of 130 000 compression load cycles. No single bushing of
the nine (9) tested shall be less than 110 000 cycles. If, at any time during the test, a test sample
fails to attain the minimum 110 000 cycles, KRC shall notify TACOM, AMSTA-TR-E/BLUE
(810) 574-8745 for disposition and direction.
A.3.3.13 Test completion. Following completion of the test, a report containing all test
data shall be provided to TACOM, AMSTA-TR-MTT and AMSTA-TR-E/BLUE. This report shall
also include the results of the thermogravimetric analysis. All test information and reports will be
released by TACOM personnel only. KRC personnel will not release any test information to
manufacturers.
A.3.3.14 Sample disposition. All samples shall be retained by the test site until receipt of
official Government approval to release the samples to the contractor. All remaining samples
shall then be returned to the contractor supplying parts for qualification.
A.3.4 Monitoring and certification. The test shall be monitored and results certified by
the local Government Quality Assurance Representative (QAR) . Monitoring will be conducted to
ensure proper machine calibration and that the test is conducted in accordance with the
established procedures. At a minimum, the QAR will visit KRC at the beginning of the test of a
contractor's supplied bushings (at the installation of the first 3 bushings) and near the mid-point of
the test (test initiation of bushing # 5). At the conclusion of all bushing tests, the QAR will make
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