Strength:

Wire rope strength is usually measured in tons of 2,000 lbs. In published material, wire rope strength is shown as minimum breaking force. Minimum breaking force refers to calculated strength figures that have been accepted by the wire rope industry.

When placed under tension on a test device, a new rope should break at a figure equal to—or higher than - the minimum breaking force shown for that rope.

The minimum breaking force applies to new, unused rope. A rope should never operate at—or near—the minimum breaking force. During its useful life, a rope loses strength gradually due to natural causes such as surface wear and metal fatigue.

Fatigue
    Resistance:

Fatigue resistance involves metal fatigue of the wires that make up a rope. To have high fatigue resistance, wires must be capable of bending repeatedly under stress—for example, a rope passing over a sheave.

Increased fatigue resistance is achieved in a rope design by using a large number of wires, It involves both the basic metallurgy and the diameters of wires.

In general, a rope made of many wires will have greater fatigue resistance than a same-size rope made of fewer, larger wires because smaller wires have greater ability to bend as the rope passes over sheaves or around drums. To overcome the effects of fatigue, ropes must never bend over sheaves or drums with a diameter so small as to bend wires excessively. There are precise recommendations for sheave and drum sizes to properly accommodate all sizes and types of ropes.

Every rope is subject to metal fatigue from bending stress while in operation, and therefore the rope's strength gradually diminishes as the rope is used.

Crushing
    Resistance:

Crushing is the effect of external pressure on a rope, which damages it by distorting the cross-section shape of the rope, its strands or core or all three.

Crushing resistance therefore is a rope's ability to withstand or resist external forces, and is a term generally used to express comparison between ropes.

When a rope is damaged by crushing, the wires, strands and core are prevented from moving and adjusting normally during operation.

In general, IWRC ropes are more crush resistant than fiber core ropes. Regular lay ropes are more crush resistant than Lang lay ropes. 6 strand ropes have greater crush resistance than 8 strand ropes or i9 strand ropes. Flex-X ropes are more resistant than standard round-strand ropes.

Resistance to
    metal loss and

    Deformation:

Metal loss refers to the actual wearing away of metal from the outer wires of a rope, and metal deformation is the changing of the shape of outer wires of a rope.

In general, resistance to metal loss by abrasion (usually called "abrasion resistance") refers to a rope's ability to withstand metal being worn away along its exterior. This reduces strength of a rope.

The most common form of metal deformation is generally called "peening"—since outside wires of a peened rope appear to have been "hammered" along their exposed surface.

Peening usually occurs on drums, caused by rope-to-rope contact during spooling of the rope on the drum. It may also occur on sheaves. Peening causes metal fatigue, which in turn may

cause wire failure. The hammering—which causes the metal of the wire to flow into a new shape—realigns the grain structure of the metal, thereby affecting its fatigue resistance. The out-of-round shape also impairs wire movement when the rope bends.

Stability:

The word "stability" is most often used to describe handling and working characteristics of a rope. It is not a precise term since the idea expressed is to some degree a matter of opinion, and is more nearly a "personality" trait than any other rope feature.

For example, a rope is called stable when it spools smoothly on and off a drum—or doesn't tend to tangle when a multi-part reeving system is relaxed.

Strand and rope construction contribute mostly to stability. Preformed rope is usually more stable than non preformed, and lang lay rope tends to be less stable than regular lay. A rope made of simple seven-wire strands will usually be more stable than a more complicated construction with many wires per strand.

There is no specific measurement of rope stability.

Bendability:

Bendability relates a rope's ability to bend easily in an arc. Four primary factors affect this capability:

1. Diameters of wires that make up the rope.

2. Rope and strand construction.

3. Metal composition of wires and finish such as galvanizing.

4. Type of rope core—fiber core or IWRC.

Some rope constructions are by nature more bendable than others. Small ropes are more bendable than big ones. Fiber core ropes bend more easily than comparable IWRC ropes. As a general rule, ropes of many wires are more bendable than same-size ropes made with fewer, larger wires.

Reverse
    Strength:

Reserve strength of a rope is that percentage of its minimum breaking force which is represented by its inner wires. This recognizes that outer wires should be the first to be damaged or worn away.

Usually, the more wires there are in each strand of rope, the greater will be its reserve strength. This is true because of the geometry of a circle—since increasing the number of outer wires in a strand also increases the cross-sectional area occupied by inner wires.

Rotation-resistant ropes, due to their construction, can experience different modes of wear and failure than standard ropes. Therefore, their reserve strength is based on the percentage of the metallic area represented by the core strand plus the inner wires of the strands of both the outer and inner layers.

Reserve strength is especially important where the consequences of rope failure are great.