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Visual examination results from unassembled bundles were also reviewed to determine the
amount of damage that the wires sustained from the straps and lacing string. (A summary of the
results is provided in appendix C, table C-5.)
The results indicate that all the wire types displayed little or no wear at the straps, whether the
bundles were nonmixed or mixed wire types. The PI wire (code 2) had a little wear when mixed
with PTFE/glass (code 9), whereas there was none in the PI nonmixed bundle. The XLETFE
alloy wire (code 5) had a little wear with the XPI, PTFE, and PI/PTFE wire type (codes 3, 6, and
10, respectively), but none in the nonmixed. The PI/PTFE wire (code 10) had a little wear with
the XPI, XLETFE, XLETFE alloy, and MF-PTFE wire types (codes 3, 4, 5, and 7,respectively),
but none in the nonmixed.
Only the PI, MF-PTFE, and PI/PTFE alloy wire types (codes 2, 7, and 11, respectively) showed
any wear from the lacing string, and this was just in one case each in a mixed wire bundle.
Overall, within the subjectivity of the visual examinations performed, the results indicate no
significant wire wear occurred from the straps or lacing string in group I.
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5.1.6 Wire Wear From Vibration Fixture Plate.
A number of wire types suffered abrasion from the aluminum test fixture during vibration, which
may have contributed to electrical failures. Figures 1 through 10 provide a graphical
representation of the wire wear from the plate for each wire type in the mixed and nonmixed
configurations.
The two electrical failures detected on the XLETFE alloy wire (code 5) in the nonmixed bundle
were attributed to the severe wire wear from rubbing against the vibration fixture (see appendix
D, figure D-9). A little wire-to-wire wear was also observed on this wire type in the nonmixed
configuration.
One electrical failure was also detected on the XLETFE alloy wire (code 5) in a bundle mixed
with MF-PTFE (code 7), but visual examination of the bundle indicated that the failure was
caused by wire wear from the plate or clamps since no wire-to-wire wear was noted.
5.1.7 Wear of Support Components.
The clamps were the only support components (clamps, straps, and lacing string) that exhibited
moderate wear. In these cases, either PVC/glass/nylon or PTFE/glass wires were in the bundles
(see figures 18 and 19). This might be explained by the abrasive nature of the glass component
within the PTFE/glass insulation and the slightly harder outer coating of the PVC/glass/nylon
wire.
FIGURE 18. MODERATE WEAR ON
CLAMP FROM PVC/GLASS/NYLON
AND MF-PTFE GROUP I BUNDLE
FIGURE 19. MODERATE WEAR OF
CLAMP FROM NONMIXED
PTFE/GLASS BUNDLE IN GROUP I
5.1.8 Wear of Single Wires vs Twisted Pairs.
It was noted that nearly twice as many wet electrical failures were detected on twisted pairs than
single wires in group I. This was likely due to the high points of the twisted pairs being
subjected to concentrated frictional forces from wires rubbing against each other.
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5.2 GROUP II TEST RESULTS.
5.2.1 Visual Observations.
Upon completion of 100 and 250 hours of vibration exposure, the wire bundles were visually
inspected while still mounted on the test fixtures. General observations after 100 hours of
vibration included rotation of the heads of the straps; twisted pairs separating from the bundles;
wear marks on the fixtures from wires, straps, and lacing string; the presence of residue on the
bundles from the clamp or wire insulation; slippage of bundles in the cushion clamps; and
splatter marks on bundles from the fluid contamination. After 250 hours of vibration, additional
observations included lacing string cutting into insulation and wearing of the black wire stripe
marking. The results from the inspection are shown in appendix C, table C-7.
5.2.2 Electrical Testing.
No dry insulation resistance or DWV failures were detected after 100 hours of vibration
conditioning in group II. Furthermore, no dry DWV failures were observed following 250 hours
of vibration exposure. However, some wires failed to meet the IR pass/fail threshold selected for
the program. As in group I, a wire was not considered to have failed if it passed the DWV test,
even if IR did not exceed the selected pass/fail threshold. Electrical failures were detected on the
PTFE/glass and PI/PTFE wires only (codes 7 and 10, respectively). (A complete summary of the
dry and wet IR and DWV failures is provided in appendix C, tables C-8 and C-9. Specific
electrical failures are discussed in conjunction with the wire wear paragraphs.)
Only one dry DWV test failure was confirmed by wet testing; however, all wet DWV failures
were confirmed through visual examination of the test bundles. For this reason, the dry electrical
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