Wire Ropes Under Bending and Tensile Stresses - Wire Ropes: Tension, Endurance, Reliability - page 232

4

s=30kN

d = 16 mm, R 0 = 1270 - 2450 N/mm 2
well lubricated
diameter ratio D/d = 25, r = 0.53 d, cast iron

3

D

2

N 90

10 5

8

_

6
5
4

N

6
3

16
4

15
3

37 ropes
6 ropes makers

3

N 10

2

zinc
lang lay

bright zinc coat. bright

ordinary lay

10 4

0 20 40 60 80 100

number of bending tests

Fig. 3.43 Number of bending cycles N, N 10 and N 90 for wire ropes with bright or zinc coated
wires from the results of Woernle and Müller

3.2.3.2 Lubrication

The lubrication of the wire rope exerts a great influence on the endurance of running
ropes. To evaluate this influence, Müller ( 1966 ) carried out bending tests with two
parallel strand ropes, one with fibre core and one with steel core, to compare the
endurance of lubricated and degreased ropes. The results of these tests are shown in
Fig. 3.44 . In the tests, the endurance of the degreased rope only attained 15-20 % of
that found for the lubricated rope. For rope lubrication see Sect. 1.4 .

3.2.3.3 Re-Lubrication

The lubricant put in the rope during manufacturing is only fully effective for a time
or for a certain number of bending cycles. Normally, running wire ropes are only
lubricated during manufacturing. However, long life wire ropes need re-

lubricating.
Figure 3.45 shows, as an example, the effect of re-lubrication in fatigue bending
tests with specimens of one Warrington rope. Six specimens were lubricated
before and nine specimens were lubricated before and during the bending fatigue