Stretch is apparent in all wire ropes, initially as permanent stretch when the load is first applied and the individual wires bed down, and then as conventional elastic stretch within the wires. Where stretch is critical to the application, initial stretch can be accounted for with cables pretensioned or pre-stressed during swaging and cable manufacturing.
Elastic stretch can be calculated by the following formula:
Elastic Stretch (mm) = (W × L )/ (E × A)
W= Applied Load (kN)
L = Cable Length (mm)
E = Strand Modulas (kN/mm² )
A = Area of Cable = (D2 × ) / 4
1 x 19 107.5kN/mm² 15.59 × 10 exp 6 P.S.I.
7 x 7 57.3kN/mm² 8.31 × 10 exp 6 P.S.I.
7 x 19 47.5.5kN/mm² 6.89 × 10 exp 6 P.S.I.