Non-rotating wire ropes are an important part of the lifting and transportation system of port cranes. Major ports have strict maintenance requirements for non-rotating wire ropes used to lift cranes. However, in recent years, although all ports have strengthened the maintenance of non-rotating wire ropes in strict accordance with relevant requirements, accidents of broken ropes still occur every year.
Failure phenomenon of non-rotating wire rope
A crane company recently scrapped non-rotating steel wire ropes. After dismantling and analysis, more than 90% of the steel wire ropes had wear spots to varying degrees. The obvious spots were accompanied by cracks, and the long ones extended to more than 1/3 of the steel wires. The wear spots on the inner strands were particularly obvious. .
1) Fretting wear of non-rotating wire rope: Fretting wear is a compound form of wear caused by relatively small vibrations of contact objects. The process is: the contact pressure causes the micro-protrusions actually carried on the bonding surface to plastically deform and adhere, and the micro-vibration causes the adhesion points to be sheared off. The exfoliated particles and the newly exposed metal surface react with the oxygen in the atmosphere to form oxides, and the oxide particles act as abrasive particles on the bonding surface to form abrasive wear. Therefore, fretting wear is the joint effect of adhesion, corrosion and wear, and it often occurs on the tight contact surfaces that are relatively static in name but relatively worn in fact.
2) Fatigue wear of non-rotating
Steel Wire Rope: Under the action of alternating contact stress, fatigue cracks are formed on the friction surface, and the phenomenon that metal particles fall off is called fatigue wear. The mechanism of fatigue wear is: under the action of high alternating contact stress, fatigue cracks will be generated on the friction surface, and the cracks will continue to expand, causing metal particles to fall off from the metal surface to form many pitting corrosion, thus causing fatigue wear (or fatigue pitting)
During the use of the non-rotating wire rope, each working cycle includes linear lifting, passing through pulleys or guide wheels, winding drums and no-load descending. Therefore, what the non-rotating wire rope is actually subjected to is a fatigue load, and the force acting on each wire in the wire rope is essentially an alternating stress. The strands in the non-rotating steel wire rope are intertwined with each other. Under the action of axial force, the deformation of the steel wires in the steel strand can be considered to be synchronous, but there is a slight misalignment between the steel strands. Therefore, the wires in the wire rope are actually in a fretting wear environment.
