SINGLE WIRE FRETTING FATIGUE TESTS FOR ELECTRICAL CONDUCTOR BENDING FATIGUE EVALUATION

Overhead electrical conductors are often subjected to aeolian vibrations which may induce fretting fatigue damage of individual aluminium wires in suspension clamp regions. Many bending fatigue tests have been performed on electrical conductors. Depending on the test conditions, wire fracture may be found to occur in the external as well as internal layers. Individual wire fretting fatigue is very difficult to predict due to a conductor complex structure and dynamic mechanical behaviour. The main objective of this work is to present experimental results obtained from tests on single wires under conditions simulating a typical conductor-clamp contact. A fretting fatigue test bench specifically designed for such simulation has been used on single H19 aluminium wires. They have been subjected to an initial minimal axial stress of 59 MPa. At the fretting point, a transverse compressive load of 130 N to 4000 N has been imposed, as well as an alternating displacement of 100 to 900 mu m displacement amplitude. Cycling frequency has been kept at 10 Hz and test duration went up to 1.6X10(7) cycles. All tests were performed in the stick-slip regime occurring in the plastically deformed contact zone. No global slip was allowed. Subsequent examination of the fretting scars at the contact surface and through the cross-section have been carried out by optical microscopy and scanning electron microscopy. The mechanical parameters influence is studied and comparison with results from complete conductor fatigue tests is discussed.