In order to clarify the property of internal damage of IWRC (independent wire rope core) wire ropes widely used for cranes, S-type bending fatigue tests were carried out on IWRC 6×Fi(29) wire ropes, under the condition of bending ratio (ratio of sheave diameter to rope diameter)
D/d=16 and 12.8, and their wire breaking damages were quantitatively analyzed.
It was shown that even under the condition of
D/d=16 allowed for various cranes by the Crane Structural Standard, the internal wire breaks occur at the bottom and the nip portions of strands preferentially to the external wire breaks, that is, the visible ones. This preferentiality of internal wire-breaks was more distinct for the case of smaller
D/d value of 12.8.
Both the number of visible wire breaks and the total number of real wire breaks in strands can be approximated by power functions of the number of cycles
N of reciprocally repeated S-bending. The number of internal wire breaks, therefore, can also be approximated by a simple function of
N. These functional relations seem very useful for precise damage evaluation of this kind of wire ropes.
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