Wire Ropes Under Bending and Tensile Stresses - Wire Ropes: Tension, Endurance, Reliability - page 294

Table 3.17 Constants for calculating the Donandt force, ( 3.71 ) and ( 3.72 )

Rope q 0 q 1

Mean Donandt
force

Donandt force that with a certainty of 95 % for at
most 1 % of the ropes will be smaller

s d S D1

sZ zZ sZ zZ

FC 6 9 19 0.787 0.824 0.619 0.656 -4.10

8 9 19 0.796 0.826 0.624 0.654 -4.20

6 9 36 0.781 0.798 0.608 0.625 -4.20

8 9 36 0.782 0.782 0.605 0.605 -4.30

WRC 6 919 0.809 0.849 0.653 0.693 -3.77

8 9 19 0.852 0.886 0.686 0.719 -4.02

6 9 36 0.802 0.821 0.642 0.661 3.86

8 9 36 0.835 0.835 0.664 0.664 -4.12

WSC 18 9 7 0.693 0.492 -3.02

34 9 7 0.715 0.537 -3.34

The constants q i for t he different rope constructions are listed in Table 3.17 for
the mean Donandt force S D and for the Donandt force S D1 where with a certainty
of 95 % it is smaller for at most 1 % of the ropes. As for the simple and the reverse
bendings, for the combined fluctuating tension and bendings, the tensile force S—
and not the equivalent tensile force S equ —should be smaller than the Donandt
force S D1 . The Donandt force S D1 has to be used as the wire rope tensile force
limit, but there is no danger if in a few cases the tensile force reaches the mean
Donandt force.

3.4.5.2 Discarding Limit

(a) Discarding Number of Wire Breaks

The evaluation of the discarding numbers of wire breaks has been presented in
Sect. 3.2.8 , as an example refer to Fig. 3.77 . This discarding number of wire
breaks on a reference rope length L = 30 d is for simple bendings with the con-
stants of Table 3.18

2
g 2

2
g 3

2 2

:

S
d 2

d
D

S
d 2

d
D

B A30 ¼ g 0 g 1 ð 3 : 83 Þ

For reverse bendings the number of wire breaks has to be calculate with a DS/
d 2 = 50 N/mm 2 higher specific tensile force, Jahne ( 1992 ).