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1、Wire rope is a type of rope which consists of several strands of metal wire laid (or twisted) into a helix. Initially wrought iron wires were used, but today steel is the main material used for wire ropes.Historically wire rope evolved from steel chains which had a record of mechanical failure. Whil
2、e flaws in chain links or solid steel bars can lead to catastrophic failure, flaws in the wires making up a steel cable are less critical as the other wires easily take up the load. Friction between the individual wires and strands, as a consequence of their twist, further compensates for any flaws.
3、 This method of minimising the effect of flaws may also be seen in Damascus steel, employing multiple folding or laminations.History and materialsModern wire rope was invented by the German mining engineer Wilhelm Albert in the years between 1831 and 1834 for use in mining in the Harz Mountains in C
4、lausthal, Lower Saxony, Germany. It was quickly accepted because it proved superior to ropes made of hemp or to metal chains, such as had been used before.Wilhelm Alberts first ropes consisted of wires twisted about a hemp rope core, six such strands then being twisted around another hemp rope core
5、in alternating directions for extra stability. Earlier forms of wire rope had been made by covering a bundle of wires with hemp.In America wire rope was later manufactured by John A. Roebling, forming the basis for his success in suspension bridge building. Roebling introduced a number of innovation
6、s in the design, materials and manufacture of wire rope.Manufacturing a wire rope is similar to making one from natural fibres. The individual wires are first twisted into a strand, then six or so such strands again twisted around a core. This core may consist of steel, but also of natural fibres su
7、ch as sisal, manila, henequen, jute, or hemp. This is used to cushion off stress forces when bending the rope.This flexibility is particularly vital in ropes used in machinery such as cranes or elevators as well as ropes used in transportation modes such as cable cars, cable railways, funiculars and
8、 aerial lifts. It is not quite so essential in suspension bridges and similar uses.Wire rope is often sold with vinyl and nylon coatings. This increases weather resistance and overall durability, however it can lead to weak joints if the coating is not removed correctly underneath joints and connect
9、ions.Lay of wire ropeLeft-hand ordinary lay (LHOL) wire rope (close-up). Right-hand lay strands are laid into a left-hand lay rope.Right-hand Langs lay (RHLL) wire rope (close-up). Right-hand lay strands are laid into a right-hand lay rope.The lay of a wire rope describes the manner in which either
10、the wires in a strand, or the strands in the rope, are laid in a helixLeft and right hand layLeft hand lay or right hand lay describe the manner in which the strands are laid to form the rope. To determine the lay of strands in the rope, a viewer looks at the rope as it points away from them. If the
11、 strands appear to turn in a clockwise direction, or like a right-hand thread, as the strands progress away from the viewer, the rope has a right hand lay. The picture of steel wire rope on this page shows a rope with right hand lay. If the strands appear to turn in an anti-clockwise direction, or l
12、ike a left-hand thread, as the strands progress away from the viewer, the rope has a left hand lay. (The rope in the left hand lay photo shows one left hand lay rope from left to right and top to bottom, with 5 right hand lay strands, and part of a sixth in the upper left. It is not 5 right hand lay
13、 ropes adjacent to each other.)Ordinary, Langs and alternate layOrdinary and Langs lay describe the manner in which the wires are laid to form a strand of the wire rope. To determine which has been used, first identify if left or right hand lay has been used to make the rope. Then identify if a righ
14、t or left hand lay has been used to twist the wires in each strand. (On ordinary lay, the outer wires approximately follow the alignment of the rope: with Langs lay they are cross at an angle of about 45.) Langs laid rope is able to flex over sheaves easier (with less damage) but it has the disadvan
15、tage of having a high torque tendency (it tends to untwist when tension load is applied) compared with ordinary laid rope. Untwisting can be dangerous with a steel-cored rope: load is shed from the strands and may cause the core to fail as it becomes higher loaded. For this reason, swivel termination units can be dangerous.
