where B is the proportionality constant and n is the exponent. The values of the constants a and n depend on the joint configuration, type of lubricant and coating used. The values of n for bare, coated and lubricated aluminum-to-aluminum and aluminum-to-copper connections were found to vary between 0.1 and 1.0. The effect of contact load on the contact resistance of aluminum bus bar connections is shown in Figure 5.75 [143]. For practical purposes, the problem of adequate contact force for a joint of satisfactorily low initial resistance can be simplified by considering the applied force as uniformly distributed over the apparent contact area. Naybour and Farrell [71] have shown that, provided the initial stress at 20°C is less than 60 N/mm ...

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