A Simplified Treatise on the Effect of Wear in Cables

Cables and wire ropes are known to both elongate and reduce diametrically during their lifetime. The relationship between cable elongation and cable life has been observed for many years and includes three distinct stages. The first, the constructional stretch stage, occurs early in the cable’s use and is mostly the result of the core compressing and the cable elements fitting closely together. The second stage of the cable’s life is referred to as the normal life stretch stage and is a much more gradual occurrence in which wear is the most dominant mechanism. The third stage includes a rapid elongation and indicates impending failure. The current study offers a simplified explanation on the effect of wear in cables. This work utilizes the recently developed theory for wire ropes and cables in which the cable is considered to be a collection of thin helical wires and the equations of equilibrium for bending and twisting of thin rods are applied. A simple cable cross section is considered and the effects of wear on cable stiffness, diameter reduction and individual wire strains are evaluated. It is determined that cable stiffness can actually increase for small amounts of wire wear due to the disparity between the changes in the geometric and elastic stiffness components with wear.