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 MIL-HDBK-419A
Table 7-1
DC Resistance of Direct Bonds Between Selected Metals
Resistance (Micro-ohms)
Bond Composition
Brass-Brass
6
Aluminum-Aluminum
25
Brass-Aluminum
50
150
Brass-Steel
Aluminum-Steel
300
Steel-Steel
1500
Notes: Apparent Bond Area:
Fastener Torque: 100 in -lb
Source: Adapted from Reference (7-5)
7.4.1.4 Bond Area.
Smaller bond areas with the same loadings would produce higher contact pressure which would decrease the
resistance. However, as shown in Figure 7-4, an increase in pressure over 1500 psi for steel and 1200 psi for
aluminum produces relatively slight changes in bond resistance. Further, the improvement in resistance due to
increased pressure is offset by the smaller overall bond area. In a similar fashion, a larger bond area (with no
change in fastener size) under the same torque results in a lowered pressure at the bond surfaces. The reduced
pressure would be counterbalanced to some extent by the increased bond area, but the net effect can be
expected to be an increase in bond resistance. Thus, when larger bond areas are used, larger bolts at
correspondingly higher torques should be used for fastening. (See Para 7.4.2.4)
7-8
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