Wire Ropes Under Tensile Load - Wire Ropes: Tension, Endurance, Reliability - page 168

300

N/mm 2

IWRC
nominal strength R o = 1770 N/d 2
number of load cycles N = 2 000 000

Warr.-Seale 6 36

−

250

200

150

d = 30 mm

100

d = 40 mm

permissible
according to
DIN 15018
load group B6

50

0

N/mm 2 0 100 200 300 400

lower spec. force S lower /d 2

Fig. 2.50 Allowed range of specific force of Warrington-Seale ropes after DIN 15018 and from
tests, Wehking and Klöpfer ( 2000 )

2.7.2 Fluctuating Forces

2.7.2.1 Technical Rules-Test Results

In the existing technical regulations, the larger the lower stress is, the smaller the
stress range that is allowed. This restriction of the stress range for large lower
stresses cannot be explained at all by the test results. On the contrary, the test
results show that for a certain number of load cycles the stress range tends to
increase with the lower stress up to the allowed maximum stress. As an example,
Fig. 2.50 from Wehking and Klöpfer ( 2000 ) shows the range of the specific rope
force allowed after DIN 15018 compared with the test results. The comparison was
made for Warrington-Seale ropes 6 9 36-IWRC-sZ with rope diameters 30 and
40 mm. The specific force range allowed in the DIN loading group B6 for a strong
load collective is compared with test results where the ropes are loaded with the
full force range for all load cycles (full load cycles) and where only 10 % of the
ropes break before 2 9 10 6 load cycles have been reached.
In future technical regulations, the range of the specific force found for the
lower force 0 can simply be allowed for all lower forces, or, taking the influence of
the lower forces into consideration, the allowed range of specific forces (stress)
can be calculated for a given lower specific force and for a given number of load
cycles. That is possible at this time for open spiral ropes zinc coated and lubricated
and for ordinary lay Warrington-Seale ropes, bright or zinc coated and lubricated.