Volume 22, Issue 5 (September 1994)
Wear-Related Fatigue in a Wire Rope Failure
The fatigue failure of a nonrotating wire rope used on a skip hoist in an underground mine has been studied as part of the ongoing research by the U.S. Bureau of Mines into haulage and materials handling hazards in mines. Correlation of individual wire failures within two segments of the failed rope were used to gain an understanding of the progression of degradation leading to rope failure. Wire failures occurred predominantly at locations of wear between adjacent strands. These interstrand wear sites are identifiable by a large reduction in diameter; however, reduction in area is not responsible for the location of failure. Fractography revealed crack initiation sites to be located opposite the characteristic wear site or at other less noticeable wear sites. The primary failure mechanism of individual wires within the rope is believed to be a function of contact stress at the interstrand wear sites. Axially loading and unloading the rope produces high compressive stresses at the contact sites, which in turn produce large alternating tensile stresses on the opposite side of the wire. This mechanism has been termed “contact stress-accelerated fatigue.” This mechanism and the affiliated wear pattern both are consequences of interstrand contact.