Wire Rope Elastic Stretch Under Load

dL = P L / (A_m E_r), with the metallic area A_m = F d^2 (fill factor F ~ 0.40 for 6x19/6x37 IWRC) and the effective rope modulus E_r ~ 12,000,000 psi (a seated rope, below solid steel because it is a bundle of helixes). A 1/2 in rope 100 ft long under 10,000 lb stretches 10 in (0.83%) - nearly a foot. A brand-NEW rope also seats ~0.5-0.75% (permanent, one-time) as the strands nest, which is separate. Thermal, rotation, and the true per-construction modulus/fill are the maker's. Never exceed the rated load. A rigging estimate; the wire rope maker and the qualified rigger govern.

A_m = F d^2 (F ~ 0.40 for 6x19/6x37 IWRC); dL = P L / (A_m E_r), L in inches, E_r ~ 12e6 psi seated rope; stretch % = dL/L.

The wire-rope elastic elongation dL = P L / (A_m E_r) with the metallic area A_m = F d^2 and the effective rope modulus (Wire Rope Users Manual), by name.

The elastic-elongation relation is a standard published wire-rope result; the effective modulus and fill factor are the maker's data. An ESTIMATE - the manufacturer's rope data governs.

Estimate. Head rigger and manufacturer working-load-limit charts govern. Inspect every piece of hardware before the show.

Field names used by the API: load_lb, length_ft, rope_diameter_in, effective_modulus_psi, metallic_area_factor, stretch_in, stretch_pct

• Elastic elongation dL = P L / (A_m E_r), recoverable stretch onlyWire Rope Users Manual
• Rope constants A_m = F d^2 (F ~ 0.40 IWRC); E_r ~ 12e6 psi seated rope - use the maker's per-construction valuesWire Rope Users Manual
• Constructional stretch a new rope seats another ~0.5-0.75% (permanent), separate from the elastic stretchrope construction