Axial corrosion fatigue tests were conducted to compare the fatigue strength of foam-filled with unfilled one-inch diameter, 6x36, IWRC wire rope, both galvanized and bright, in air and in substitute ocean water. The results of the tests showed that the axial corrosion fatigue lives in substitute ocean water of foam-filled and unfilled wire ropes manufactured from the same wires were similar. However, the galvanized ropes showed a smaller loss in fatigue resistance in. substitute ocean water than the foam-filled ropes. Also, the results of the tests showed that S0cket-related failures of the ropes, which were observed in 40% of the specimens tested, resulted in fatigue lives that were ½to 1/9 of the lives of similar ropes that failed in the body. When socket-related failures were encountered, the effects of corrosion on fatigue life were negligible compared to the stress concentration effects of the socket.
Many applications of wire ropes and strands are in environments that promote corrosion. Such applications include bridge cables and suspenders, crane boom-pendants, mooring systems, and riser tensioners. While some of the applications are subject only to rain, others are subjected to harsh marine environments. Because many wire ropes are subjected to cyclic loading, the environment interacts with the cyclic loads to cause corrosion fatigue of the ropes.
Rope continues to be an important item in the marine environment; the need to understand its response to such an environment and to protect it against corrosion has been recognized for a long time. Sharp f1] reviewed the application of rope in marine environment and listed:
the requirements for ropes in marine applications, and
the characteristics of wire ropes used to meet these needs.
Matanzo [2] studied the axial corrosion fatigue of wire rope to compare the effects of loading factors and rope construction on its fatigue in air and sea water. Unfortunately, high temperatures (because of the high test-frequency) affected the in-air fatigue life, and the relative effects of sea water can not be evaluated. Lucht and Donecker [3] discussed the factors affecting wire rope life in a marine environment. Their study included a report of in-air axial fatigue tests and an estimation of the effects of sea water by extrapolation from data obtained for statically loaded wire ropes exposed to a marine environment. While these data provide general information on the effects of the environment, Thorpe and Rance [4] showed that the important factor in the corrosion fatigue life of wire rope is fretting concomitant with cyclic loading. Thus the conclusions of Lucht and Donecker [3] may not be applicable to the corrosion fatigue of wire rope.
