Stress relaxation of aluminum wire conductors

Published experimental evidence and various reports of trouble in service suggest that the contact stability of aluminum wire connections is sometimes inadequate. Among a number of factors affecting the contact stability is a rather rapid stress relaxation of aluminum which can significantly reduce the contact stability. Stress relaxation behaviour of EC-1350 H12 and NUAL-H12 grade wire conductors was evaluated at 100/spl deg/C and under current-cycling conditions. In addition, the contact resistance behavior of these wire conductors in a binding-head screw under the influence of electrical current was also investigated. It was shown that the stress relaxation of EC-1350 grade aluminum wire and its contact resistance behaviour in a binding-head screw configuration is inferior to that of the NUAL wire conductor. Current-cycling carried out at room temperature at was found to produce as much stress relaxation as that carried out at 100/spl deg/C and much higher initial contact loads.