Wire Ropes, Elements and Definitions - Wire Ropes: Tension, Endurance, Reliability - page 23

3

new wires, Ziegler et al (2005)
ʴ

wires out of ropes, Wolf (1987)
ʴ

= 0.80mm - R 0 =2160 N/mm 2

= 0.80 - 1.08 mm
rel. FC core mass 70% - 80%

2

1

0
400 500

wire rotary bending strength

600 700 800

˃ Rot

Fig. 1.19 Relative number of rope bending cycles N = N for different rotary bending strengths of

rope wires

The influence of the rotary bending strength of the wires on the endurance of
ropes made from these wires has been evaluated by Wolf ( 1987 ) and Ziegler et al.
( 2005 ). Wolf ( 1987 ) evaluated the rotary bending strength r Rot of wires taken out
of the wire ropes tested. The nominal tensile strength of these wires is
R 0 = 1,570-2,160 N/mm 2 . Because of the enormous influence of the fibre core
mass on rope endurance N, he only used the results of ropes with a relative fibre
core mass between 70 and 80 %. This relative mass is related to the required core
mass for ropes used for rope ways, BO-Seil, 1982. The wires used by Ziegler et al.
( 2005 ) all have the nominal tensile strength R 0 = 2,160 N/mm 2 . The rotary
bending strength r Rot for these wires has been evaluated before the wires have
been twisted into ropes. The three Seale 6 9 19-FC test ropes were manufactured
with the same fibre core and as far as possible in the same way.
The effect of the rotary bending strength r Rot of the wires used on the rope's
number of bending cycles N can be seen in Fig. 1.19 . The results of Ziegler et al.
( 2005 ) have been inserted into th is diagram drawn by Wolf ( 1987 ). The increase of
the relative rope endurance N = N with the rotary bending strength r Rot of the wires
from both series of tests is practically the same.

1.2 Strands

1.2.1 Round Strands

Lay length, lay angle. In the simplest case, the strand consists of three or four
twisted wires. The first wire rope made in 1834 by Albert ( 1837 ) has three of these
simple strands with four wires each. In practice, however, such simple strands are
no longer used. Nowadays the simplest strand has one layer of wires laid helically