FATIGUE BEHAVIOUR OF LARGE DIAMETER WIRE ROPES.

This report presents information on the changes in stiffness and length that were observed to take place during the tensile fatigue testing of wire ropes 40 mm, 70 mm and 127 mm diameter. The presence of wire breaks is the most likely cause of these changes, particularly as the test progresses, but relative movement of the strands and wires during testing is also thought to play a role. The results suggest that measurement of rope stiffness may provide a means of estimating rope endurance during fatigue testing. Examination of tested sections of rope was carried out and this revealed the presence of very large numbers of wire breaks, particularly in the independent wire rope core. The results also indicate that outer strand wire breaks occur relatively late on in the test, thus under tensile fatigue conditions visual inspection for broken wires is not necessarily an accurate guide to the condition of a rope.