Fatigue of two contacting wires of the ACSR Ibis 397.5 MCM conductor: Experiments and life prediction

Fatigue damage of overhead conductors is a major problem in the transmission line industry. The damage process, which typically takes place at the contact between the conductor and components or between contacting wires of adjacent layers, occurs under a severe stress concentration and high stress gradients. In this paper, a fatigue life prediction model for two contacting wires of an overhead conductor is developed. To account for the high stress gradient beneath the contact surface, an average of the stress distribution in a damage zone is considered. The characteristic length of the damage zone is determined by fitting the model to test data from notched specimens having high stress gradients. The evaluation of the fatigue model is carried out using 1350-H19 aluminum alloy wires taken from the ACSR (Aluminum Conductor Steel Reinforced) Ibis 397.5 MCM conductor. Fatigue test data of two contacting wires are obtained for a crossing angle of 29 degrees and normal loads equal to 250 N and 500 N. To calibrate the model, experimental data obtained by testing plain wires, circumferentially V-notched wires, and wires with a transverse hole under fully reversed axial loading are used. The model is found to give fatigue life predictions within factor-of-three boundaries, which is a range similar to the scatter of the calibration data. It is also found that predicted lives are not significantly altered by the data set used to calibrate the fatigue model.