Wire Ropes Under Tensile Load - Wire Ropes: Tension, Endurance, Reliability - page 103

1,00

0,98

0,96

0,94

0,92

0,90

0 100 200 300 400

N / mm 2

specific tensile force S / d 2

Fig. 2.18 Relative rope diameter d/d 0 of 8-strand ropes with fibre core

2.3 Reduction of the Rope Diameter Due to Rope
Tensile Force

The reduction of the rope diameter due to the rope tensile force is caused by the
lateral contraction of the wires, the strands and, in particular, the cores. The lateral
contraction of the wires caused by its tensile stress is small. Even for a tensile
stress of 670 N/mm 2 the wire contraction is only one per mil of the diameter of the
wire. In comparison, the effect of the relatively low length-related compressive
force of the wires and in particular of the strands on the core is much greater.
The length-related compressive force first results in resetting any loose wires
and strands and then in deforming the rope in a different way. There is also some
minor deformation due to the pressure between wires crossing. As far as fibre-core
wire ropes are concerned, a large diameter reduction occurs and this is mainly due
to the compression of the core. The diameter reduction of steel-core wire ropes, on
the other hand, is normally less than that found with fibre-core wire ropes and this
is mainly caused by the wires of the strands and the core becoming adjusted to one
another.
Measurements were taken of the diameters of a great number of wire ropes
affected by different tensile forces. Figures 2.18 and 2.19 show the diameter
reduction measured as the relative rope diameter d S /d 0 for the first loading. The
diameter for the loaded wire rope is d S and the actual diameter for the not loaded
wire rope is d 0 . Figure 2.18 presents the relative rope diameter of 8-strand fibre-
core wire ropes and Fig. 2.19 those with steel cores. The nominal rope diameter—
which is normally smaller than the actual diameter—of all these ropes is 16 mm.